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Bai Y, Jiang X, He B, Zhu Y, Zhang Y. Polydimethylsiloxane enabled triple-action water-resistant coating with desirable relaxation rate in clear aligner. J Colloid Interface Sci 2024; 676:701-714. [PMID: 39059277 DOI: 10.1016/j.jcis.2024.07.181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Revised: 07/12/2024] [Accepted: 07/21/2024] [Indexed: 07/28/2024]
Abstract
Clear aligners undergo rapid stress relaxation in warm, moist oral environments, compromising therapeutic effectiveness and longevity of treatment. To develop an innovative multilayer composite material with improved stability and reduced stress release, we have engineered an innovative coating characterized by the surface aggregation of polydimethylsiloxane (PDMS), which imparts a pronounced hydrophobic effect. In addition, the chemically and physically cross-linked structure of the coating reduces the free volume created by molecular chain rearrangement owing to the presence of water molecules, thereby minimizing water penetration into the coating. Concurrently, the coating's internal structure is enriched with numerous polar functional groups to capture water molecules that penetrate into the inside of the coating. Through combination of these mechanisms, water molecules are effectively sequestered, thereby impeding their penetration into the polyethylene terephthalate glycol (PETG) substrate. The impact of the polydimethylsiloxane content on the triple-action water-resistance mechanisms was thoroughly examined using attenuated total reflection (ATR)-Fourier transform infrared (FTIR), water absorption rate, water swelling rate, and X-ray photoelectron spectroscopy. The low surface energy cross-linked polyurethane coating is applied to the polyethylene terephthalate glycol (PETG) substrate to create a novel composite material with specific mechanical properties and reduced stress relaxation. The composite material remains stable in simulated oral environment with linear swelling rate of 0.58 % upon water absorption. Additionally, the stress release rate of the composite material within 336 h is notably lower (23.64 %) than that of PETG (62.29 %).
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Affiliation(s)
- Yun Bai
- School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China
| | - Xiaoli Jiang
- School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China
| | - Bin He
- National Engineering Research Center for Biomaterials, School of Biomedical Engineering, Sichuan University, Chengdu 610064, Sichuan, China
| | - Yabin Zhu
- Biomedical Engineering Research Center, Medical School of Ningbo University, Ningbo 315211, Zhejiang, China
| | - Yagang Zhang
- School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China.
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Zhang Y, Jin X, Savoldi F, Han J, Su RKL, Fok A, Chen J, Tsoi JKH. Validation of a double-semicircular notched configuration for mechanical testing of orthodontic thermoplastic aligner materials. J Mech Behav Biomed Mater 2024; 155:106543. [PMID: 38636445 DOI: 10.1016/j.jmbbm.2024.106543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 04/05/2024] [Accepted: 04/10/2024] [Indexed: 04/20/2024]
Abstract
The potential of using specimens with a double-semicircular-notched configuration for performing tensile tests of orthodontic thermoplastic aligner materials was explored. Unnotched and double-semicircular-notched specimens were loaded in tension using a universal testing machine to determine their tensile strength, while finite element analysis (FEA) and digital image correlation (DIC) were used to estimate stress and strain, respectively. The shape did affect the tensile strength, demonstrating the importance of unifying the form of the specimen. During the elastic phase under tension, double-semicircular-notched specimens showed similar behavior to unnotched specimens. However, great variance was observed in the strain patterns of the unnotched specimens, which exhibited greater chance of end-failure, while the strain patterns of the double-semicircular-notched specimens showed uniformity. Considerable agreement between the theoretical (FEA) and practical models (DIC) further confirmed the validity of the double-semicircular-notched models.
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Affiliation(s)
- Yuqing Zhang
- Fujian Key Laboratory of Oral Diseases, School and Hospital of Stomatology, Fujian Medical University, PR China; Dental Materials Science, Applied Oral Sciences and Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China
| | - Xiaozhuang Jin
- Dental Materials Science, Applied Oral Sciences and Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China
| | - Fabio Savoldi
- Orthodontics, Division of Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China
| | - Jianmin Han
- Central Laboratory, Peking University School and Hospital of Stomatology, Beijing, PR China
| | - Ray Kai Leung Su
- Department of Civil Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong, China
| | - Alex Fok
- Division of Biomaterials, Department of Restorative Sciences, School of Dentistry, University of Minnesota, Minneapolis, USA
| | - Jiang Chen
- Fujian Key Laboratory of Oral Diseases, School and Hospital of Stomatology, Fujian Medical University, PR China.
| | - James Kit-Hon Tsoi
- Dental Materials Science, Applied Oral Sciences and Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
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Elshazly TM, Bourauel C, Ismail AM, Ghoraba O, Chavanne P, Elattar H, Alhotan A. Effect of thermomechanical ageing on force transmission by orthodontic aligners made of different thermoformed materials: An experimental study. Orthod Craniofac Res 2024. [PMID: 38887908 DOI: 10.1111/ocr.12825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/07/2024] [Indexed: 06/20/2024]
Abstract
OBJECTIVES Investigating the impact of thermal and mechanical loading on the force generation of orthodontic aligners made from various thermoplastic materials and different compositions. MATERIALS AND METHODS Five distinct materials were utilized including, three multi-layer (Zendura FLX, Zendura VIVA, CA Pro) and two single-layer (Zendura A and Duran). A total of 50 thermoformed aligners (n = 10) underwent a 48-hour ageing protocol, which involved mechanical loading resulting from a 0.2 mm facial malalignment of the upper right central incisor (Tooth 11) and thermal ageing through storage in warm distilled water at 37°C. The force exerted on Tooth 11 of a resin model was measured both before and after ageing using pressure-sensitive films and a biomechanical setup. RESULTS Before ageing, pressure-sensitive films recorded normal contact forces ranging from 83.1 to 149.7 N, while the biomechanical setup measured resultant forces ranging from 0.1 to 0.5 N, with lingual forces exceeding facial forces. Multi-layer materials exhibited lower force magnitudes compared to single-layer materials. After ageing, a significant reduction in force was observed, with some materials experiencing up to a 50% decrease. Notably, multi-layer materials, especially Zendura VIVA, exhibited lower force decay. CONCLUSIONS The force generated by aligners is influenced by both the aligner material and the direction of movement. Multi-layer materials exhibit superior performance compared to single-layer materials, primarily because of their lower initial force, which enhances patient comfort, and their capability to maintain consistent force application even after undergoing ageing.
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Affiliation(s)
- Tarek M Elshazly
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany
| | | | - Ahmed M Ismail
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany
- Biomaterials Department, Faculty of Dentistry, Ain Shams University, Cairo, Egypt
| | - Omar Ghoraba
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany
| | | | - Hanaa Elattar
- Orthodontic Department, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt
| | - Abdulaziz Alhotan
- Department of Dental Health, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
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Elshazly TM, Keilig L, Nang D, Golkhani B, Weber A, Elattar H, Talaat S, Bourauel C. Effect of thermomechanical aging on force system of orthodontic aligners made of different thermoformed materials : An in vitro study. J Orofac Orthop 2024:10.1007/s00056-024-00527-0. [PMID: 38653792 DOI: 10.1007/s00056-024-00527-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 02/23/2024] [Indexed: 04/25/2024]
Abstract
PURPOSE The aim was to investigate the effect of aging by thermocycling and mechanical loading on forces and moments generated by orthodontic clear aligners made from different thermoplastic materials. METHODS A total of 25 thermoformed aligners made from 5 different materials, i.e., Essix ACE® and Essix® PLUS™ (Dentsply Sirona, Bensheim, Germany), Invisalign® (Align Technology, San Jose, CA, USA), Duran®+ (Iserlohn, Germany), Zendura™ (Fremont, CA, USA), underwent a 14-day aging protocol involving mechanical loading (a 0.2 mm vestibular malalignment of the upper left second premolar [tooth 25]) and thermocycling in deionized water (temperature range 5-55 °C). The 3D forces/moments exerted on tooth 25 of a resin model were measured at three time points: before aging (day 0), after 2 days and after 14 days of aging. RESULTS Before aging, extrusion-intrusion forces were 0.6-3.0 N, orovestibular forces were 1.7-2.3 N, and moments as mesiodistal rotation were 0.3-42.1 Nmm. In all directions, multilayer Invisalign® exhibited the lowest force/moment magnitudes. After aging, all materials showed a significant force/moment decay within the first 2 days, except Invisalign® for orovestibular and vertical translation. However, following thermomechanical aging, Duran®+ and Zendura™ aligners had equivalent or even higher vestibular forces (direction of mechanical load). CONCLUSION Thermomechanical aging significantly reduced forces and moments during the first 48 h. Multilayer aligner materials exhibit lower initial forces and moments than single-layer ones, and were less influenced by aging. Material hardening was observed after subjecting some of the aligner materials to mechanical loading. Thus, orthodontists should be aware of possible deterioration of orthodontic aligners over time. This work also sheds light on how material selection impacts the mechanical behavior of aligners and may provide valuable guidance regarding optimal timing for the aligner changing protocol.
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Affiliation(s)
- Tarek M Elshazly
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany.
- Oral Technology, University Hospital Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.
| | - Ludger Keilig
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany
- Department of Dental Prosthetics, Propaedeutics and Materials Science, Dental School, University Hospital Bonn, Bonn, Germany
| | - Diva Nang
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany
| | - Bijan Golkhani
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany
| | - Anna Weber
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany
| | - Hanaa Elattar
- Orthodontic Department, Faculty of Dentistry, Umm Al-Qura University, Makkah, Saudi Arabia
- Orthodontic Department, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt
| | - Sameh Talaat
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany
- Orthodontic Department, Future University in Egypt, Cairo, Egypt
| | - Christoph Bourauel
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany
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Barile C, Cianci C, Paramsamy Kannan V, Pappalettera G, Pappalettere C, Casavola C, Suriano C, Ciavarella D. Thermoplastic clear dental aligners under cyclic compression loading: A mechanical performance analysis using acoustic emission technique. J Mech Behav Biomed Mater 2024; 152:106451. [PMID: 38310814 DOI: 10.1016/j.jmbbm.2024.106451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 01/26/2024] [Accepted: 01/30/2024] [Indexed: 02/06/2024]
Abstract
The objective of this work is to analyse the performance of clear aligners made of thermoplastic materials. Within this framework, the damage evolution stages and damage states of the aligners at different cycles of the compressive loading are evaluated using the Acoustic Emission (AE) technique. Three different clear aligner systems were prepared: thermoformed PET-g (polyethylene terephthalate glycol) and PU (polyurethane), and additively manufactured PU. Cyclic compression tests are performed to simulate 22500 swallows. The mechanical results show that the energy absorbed by the thermoformed PET-g aligner remains stable around 4 Nmm throughout the test. Although the PU-based aligners show a higher energy absorption of about 7 Nmm during the initial phase of the cyclic loading, this gradually decreases after 12500 cycles. The time-domain based, and frequency-based parameters of the stress wave acoustic signals generated by the aligners under compression loading are used to identify the damage evolution stages. The machine learning-based AE results reveal the initiation and termination of the different damage states in the aligners and the frequency-based results distinguish the different damage sources. Finally, the microscopy results validated the damage occurrences in the aligners identified by the AE results. The mechanical test results indicate that the thermoformed PET-g has the potential to match the performance and requirements of the dentistry of the popular Invisalign (additively manufactured PU). The AE results have the potential to identify at which cycles the aligners may start losing their functionality.
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Affiliation(s)
- Claudia Barile
- Dipartimento di Meccanica, Matematica e Management, Politecnico di Bari, Bari, Italy
| | - Claudia Cianci
- Dipartimento di Meccanica, Matematica e Management, Politecnico di Bari, Bari, Italy
| | | | - Giovanni Pappalettera
- Dipartimento di Meccanica, Matematica e Management, Politecnico di Bari, Bari, Italy.
| | - Carmine Pappalettere
- Dipartimento di Meccanica, Matematica e Management, Politecnico di Bari, Bari, Italy
| | - Caterina Casavola
- Dipartimento di Meccanica, Matematica e Management, Politecnico di Bari, Bari, Italy
| | - Carmela Suriano
- Dipartimento di Medicina Sperimentale e Clinica, Università di Foggia, Foggia, Italy
| | - Domenico Ciavarella
- Dipartimento di Medicina Sperimentale e Clinica, Università di Foggia, Foggia, Italy
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Srinivasan B, Padmanabhan S, Srinivasan S. Comparative evaluation of physical and mechanical properties of clear aligners - a systematic review. Evid Based Dent 2024; 25:53. [PMID: 38017152 DOI: 10.1038/s41432-023-00937-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 09/25/2023] [Indexed: 11/30/2023]
Abstract
INTRODUCTION The clinical effectiveness of clear aligners depends on the material properties both physical and mechanical. The purpose of this systematic review is to evaluate the physical and mechanical properties of different clear aligner materials and changes in the same during and after intra-oral use. METHODS Search was done in five electronic databases: Pubmed, Embase, Scopus, Web of Science and Ovid individually by two reviewers. In vivo, Ex vivo and In vitro studies that evaluated the physical and mechanical properties of clear aligner materials were selected. The risk of bias assessment was performed using a modified Cochrane risk of bias tool. RESULTS From the 24 articles selected, 19 evaluated a single physical property and 23 articles evaluated a single mechanical property of clear aligner materials. All domains in the risk of bias assessment showed low risk of bias except for 'blinding of outcome' which was unclear in almost all the selected studies. Properties such as hardness, optical properties, stiffness, and yield strength were found to be different for different clear aligner materials and were found to change with thermoforming, with intra-oral aging, and in simulated intraoral conditions. Due to heterogenicity in the parameters used to assess physical or mechanical properties a meta-analysis could not be done. CONCLUSIONS Properties like hardness, color, stiffness, stress relaxation and creep behavior were different for various clear aligner materials and were found to deteriorate with thermoforming and intra-oral aging. Polyurethane-based materials have a higher level of hardness and stiffness but exhibit increased creep and stress relaxation properties. PROSPERO REGISTRATION NUMBER CRD42021269597.
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Affiliation(s)
- Bhadrinath Srinivasan
- Department of Orthodontics, Sri Ramchandra Institute of Higher Education and Research, PIN- 600116, Chennai, India
| | - Sridevi Padmanabhan
- Department of Orthodontics, Sri Ramchandra Institute of Higher Education and Research, PIN- 600116, Chennai, India.
| | - Sivakumar Srinivasan
- Department of Applied Mechanics, Indian Institute of Technology (Madras), 600036, Chennai, India
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Wang YG, Zhu GY, Liu JQ, Wang YF, Zhao ZH. Dynamic biomechanical changes of clear aligners during extraction space closure: Finite element analysis. Am J Orthod Dentofacial Orthop 2024; 165:272-284.e3. [PMID: 38108674 DOI: 10.1016/j.ajodo.2023.08.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 08/01/2023] [Accepted: 08/01/2023] [Indexed: 12/19/2023]
Abstract
INTRODUCTION Clear aligners (CAs) have recently become popular and widely used orthodontic appliances. Research on CA biomechanics has become a focal point in orthodontics to improve the efficiency of CA treatment and address challenging issues, such as extraction. The biomechanical characteristics of CAs in space closure have been reported. However, previous studies have mainly focused on static biomechanical analysis that cannot demonstrate the dynamic biomechanical changes in CAs during space-closing. Given that these biomechanical changes can be significant and have considerable clinical value, this study aimed to investigate these characteristics. METHODS Sequential extraction space-closing models were derived from included patient data and refined using modeling and CA design software. A finite element analysis was performed to obtain biomechanical raw data. This study introduced a dual coordinate system and space geometry analysis to demonstrate the biomechanical properties accurately. RESULTS As space closure progressed, the instantaneous tooth displacements increased, indicating an enhanced space closure force because of the increased strain in the CA extraction area. Meanwhile, the central axis of rotation of the anterior teeth continuously moved toward the labial-apical direction, showing a gradually enhanced vertical and torque control effect. CONCLUSIONS During space closure, CAs undergo specific biomechanical changes, including increased contraction and control forces on both sides of the gap. These biomechanical effects are beneficial to alleviate the roller coaster effect gradually. Meanwhile, more reasonable staging design strategies can be proposed on the basis of this biomechanical mechanism.
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Affiliation(s)
- Yi-Gan Wang
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Guan-Yin Zhu
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jun-Qi Liu
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yi-Fan Wang
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Zhi-He Zhao
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
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Nicita F, D'Amico C, Filardi V, Spadaro D, Aquilio E, Mancini M, Fiorillo L. Chemical-Physical Characterization of PET-G-Based Material for Orthodontic Use: Preliminary Evaluation of micro-Raman Analysis. Eur J Dent 2024; 18:228-235. [PMID: 37247624 PMCID: PMC10959632 DOI: 10.1055/s-0043-1764424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023] Open
Abstract
OBJECTIVES Orthodontic treatment with clear thermoplastic aligners is in great demand by patients especially for aesthetics. Any alterations in the chemical composition of the thermoplastic material for aligners, subjected to the oral environment and exposure to various commonly used substances, could influence the desired orthodontic movement decreasing the predictability of the treatment. The objective of this study was to determine the chemical-physical characterization by micro-Raman spectroscopy of a thermoplastic material based on polyethylene terephthalate glycol (PET-G) used for the manufacture of Lineo aligners (Micerium Lab, Avegno, Italy) subjected to different staining beverages and cleaning agents. MATERIALS AND METHODS Twenty-two thermoformed PET-G samples were immersed to various substances of daily use for 10 and 15 days (coffee, tea, Coca-Cola, red wine, colloidal silver disinfectant, nicotine, artificial saliva, cigarette smoke, and different combinations of saliva with some of the previous solutions). Subsequently, the chemical-physical characterization was investigated by micro-Raman spectroscopy. RESULTS The analysis of the spectra acquired for all the specimens showed no difference in the exposure to the different solvents at 10 and 15 days. Furthermore, having ascertained the heterogeneous surface morphology of the PET-G material due to thermoforming, various deposits were present on all the samples whose consistency and concentration depended on the substance used. CONCLUSION The spectroscopic investigations have provided a precise and detailed analysis of the qualitative and structural data of the PET-G material under examination. No significant structural modifications of the thermoplastic polymer were found after immersion in different solutions in the exposure times adopted.
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Affiliation(s)
- Fabiana Nicita
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, via Consolare Valeria, Messina, Italy
| | - Cesare D'Amico
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, via Consolare Valeria, Messina, Italy
| | - Vincenzo Filardi
- D.A. Research and Internationalization, University of Messina, Via Consolato del mare 41, Messina, Italy
| | | | | | - Maura Mancini
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, via Consolare Valeria, Messina, Italy
| | - Luca Fiorillo
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, via Consolare Valeria, Messina, Italy
- Multidisciplinary Department of Medical-Surgical and Dental Specialties, University of Campania Luigi Vanvitelli, Naples, Italy
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Camenisch L, Polychronis G, Panayi N, Makou O, Papageorgiou SN, Zinelis S, Eliades T. Effect of printing orientation on mechanical properties of 3D-printed orthodontic aligners. J Orofac Orthop 2024:10.1007/s00056-023-00511-0. [PMID: 38277054 DOI: 10.1007/s00056-023-00511-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Accepted: 12/07/2023] [Indexed: 01/27/2024]
Abstract
PURPOSE The purpose of this study was to assess differences in the fundamental mechanical properties of resin-made three-dimensional (3D) printed orthodontic aligners according to the printing orientation. METHODS Twenty resin 3D-printed dumbbell-shaped specimens and 20 orthodontic aligners were fabricated and postcured in nitrogen. Half of the specimens and aligners were built in horizontal (H), the other half in vertical (V) directions. The dumbbell-shaped specimens were loaded in a tensile testing machine, while parts of the aligners were embedded in acrylic resin, ground, polished, and then underwent instrumented indentation testing (IIT). Mechanical properties that were assessed included the yield strength (YS), breaking strength (BS), plastic strain (ε), Martens hardness (HM), indentation modulus (EIT), elastic index (ηIT), and indentation relaxation (RIT). Data were analyzed statistically with independent t‑tests or Mann-Whitney tests at α = 5%. RESULTS No significant differences were found between specimens or aligners printed either in a horizontal or a vertical direction (P > 0.05 in all instances). Overall, the 3D-printed aligners showed acceptable mechanical propertied in terms of YS (mean 19.2 MPa; standard deviation [SD] 1.7 MPa), BS (mean 19.6 MPa; SD 1.2 MPa), ε (mean 77%; SD 11%), HM (median 89.0 N/mm2; interquartile range [IQR] 84.5-90.0 NN/m2), EIT (median 2670.5 MPa; IQR 2645.0-2726.0 MPa), ηIT (median 27.5%; IQR 25.9-28.1%), and RIT (mean 65.1%; SD 3.5%). CONCLUSION Printing direction seemed to have no effect on the mechanical properties of 3D-printed resin aligners, which are promising for orthodontic use.
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Affiliation(s)
- Lukas Camenisch
- Clinic of Orthodontics and Pediatric Dentistry, Center for Dental Medicine, University of Zurich, Plattenstr. 11, 8032, Zurich, Switzerland
| | - Georgios Polychronis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Nearchos Panayi
- Department of Dentistry, European University Cyprus, Nicosia, Cyprus
| | - Olga Makou
- Department of Dentistry, European University Cyprus, Nicosia, Cyprus
| | - Spyridon N Papageorgiou
- Clinic of Orthodontics and Pediatric Dentistry, Center for Dental Medicine, University of Zurich, Plattenstr. 11, 8032, Zurich, Switzerland.
| | - Spiros Zinelis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Theodore Eliades
- Clinic of Orthodontics and Pediatric Dentistry, Center for Dental Medicine, University of Zurich, Plattenstr. 11, 8032, Zurich, Switzerland
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Bruni A, Abate A, Maspero C, Castroflorio T. Comparison of Mechanical Behavior of Clear Aligner and Rapid Palatal Expander on Transverse Plane: An In Vitro Study. Bioengineering (Basel) 2024; 11:103. [PMID: 38391589 PMCID: PMC10886082 DOI: 10.3390/bioengineering11020103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/09/2024] [Accepted: 01/19/2024] [Indexed: 02/24/2024] Open
Abstract
(1) Background: This study aims to investigate, within a controlled laboratory environment, the magnitude of the transversal load and the force decay over time produced by clear aligners in comparison to a Rapid Palatal Expander (RPE). (2) Methods: Resin models of a dental maxillary arch, additively manufactured from an intraoral scan, were inserted in a testing machine with uniaxial load cells to measure the force trend over time expressed by RPE and clear aligners. The mechanical load was recorded during a certain timeframe for both appliances. (3) Results: The force expressed by the RPE ranged from 30 to 50 N for each activation, decreasing with a nonlinear pattern over time. The force expressed by the clear aligner ranged from 3 to 5 N, decreasing with a linear pattern over time. In contrast, the force generated by the clear aligner fell within the range of 3 to 5 N, showing a linear reduction in force magnitude over the observed period of time. (4) Conclusions: The RPE exerted a force magnitude approximately ten times greater than that generated by clear aligners. Nevertheless, it is essential to acknowledge that the oral environment can significantly influence these results. These limitations underscore the need for caution when applying these findings to clinical settings.
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Affiliation(s)
- Alessandro Bruni
- Surgical, Medical and Dental Department, University of Modena and Reggio Emilia, 41124 Modena, Italy
| | - Andrea Abate
- Department of Sciences Integrated Surgical and Diagnostic, University of Genova, 16126 Genova, Italy
| | - Cinzia Maspero
- Department of Biomedical Surgical and Dental Sciences, University of Milan, 20142 Milan, Italy
- Fondazione IRCCS Cà Granda, Ospedale Maggiore Policlinico, 20122 Milan, Italy
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Staderini E, Chiusolo G, Guglielmi F, Papi M, Perini G, Tepedino M, Gallenzi P. Effects of Thermoforming on the Mechanical, Optical, Chemical, and Morphological Properties of PET-G: In Vitro Study. Polymers (Basel) 2024; 16:203. [PMID: 38257002 PMCID: PMC10820839 DOI: 10.3390/polym16020203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 12/30/2023] [Accepted: 12/30/2023] [Indexed: 01/24/2024] Open
Abstract
The effectiveness of clear aligners in correcting malocclusions is closely linked to the properties of the materials used to make them. The polymers used in the manufacture of clear aligners have well-established properties. However, the process of manufacturing clear aligners, known as thermoforming, involves thermal and mechanical shocks that may alter these properties. The objective of this study was to evaluate the effects of thermoforming on the mechanical, optical, chemical, and morphological properties of sixty PET-G specimens. The study compared the thickness, weight, absorbance, chemical structure, surface roughness, elastic modulus, yield strength, and breaking load of thirty thermoformed specimens with thirty non-thermoformed specimens. The study introduces a new approach by using standardized samples to analyze both chemical and physical properties. The results showed statistically significant differences in thickness (-15%), weight (-11%), and surface roughness (+1233% in roughness average; +1129% in RMS roughness) of the material. Additionally, a correlation was found between reduction in thickness and increase in opalescence. There was no significant change in the functionality of the aligners after thermoforming, as no significant mechanical changes were found. However, the increase in surface roughness may lead to plaque and fluid accumulation and worsen the fit of the aligners.
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Affiliation(s)
- Edoardo Staderini
- School of Dentistry, Dean: Prof. Massimo Cordaro, Catholic University of the Sacred Heart, IRCCS “A. Gemelli” University Polyclinic Foundation, Largo Agostino Gemelli 8, 00168 Rome, Italy; (E.S.); (G.C.); (P.G.)
- Postgraduate School of Orthodontics–Director: Prof. Massimo Cordaro, Catholic University of the Sacred Heart, Largo Agostino Gemelli 8, 00168 Rome, Italy
| | - Giuseppe Chiusolo
- School of Dentistry, Dean: Prof. Massimo Cordaro, Catholic University of the Sacred Heart, IRCCS “A. Gemelli” University Polyclinic Foundation, Largo Agostino Gemelli 8, 00168 Rome, Italy; (E.S.); (G.C.); (P.G.)
| | - Federica Guglielmi
- School of Dentistry, Dean: Prof. Massimo Cordaro, Catholic University of the Sacred Heart, IRCCS “A. Gemelli” University Polyclinic Foundation, Largo Agostino Gemelli 8, 00168 Rome, Italy; (E.S.); (G.C.); (P.G.)
- Postgraduate School of Orthodontics–Director: Prof. Massimo Cordaro, Catholic University of the Sacred Heart, Largo Agostino Gemelli 8, 00168 Rome, Italy
| | - Massimiliano Papi
- Department of Neurosciences, Catholic University of the Sacred Heart, Largo Francesco Vito 1, 00168 Rome, Italy; (M.P.); (G.P.)
- IRCCS “A. Gemelli” University Polyclinic Foundation, Largo Agostino Gemelli 8, 00168 Rome, Italy
| | - Giordano Perini
- Department of Neurosciences, Catholic University of the Sacred Heart, Largo Francesco Vito 1, 00168 Rome, Italy; (M.P.); (G.P.)
- IRCCS “A. Gemelli” University Polyclinic Foundation, Largo Agostino Gemelli 8, 00168 Rome, Italy
| | - Michele Tepedino
- Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, Piazza Santa Margherita 2, 67100 L’Aquila, Italy
| | - Patrizia Gallenzi
- School of Dentistry, Dean: Prof. Massimo Cordaro, Catholic University of the Sacred Heart, IRCCS “A. Gemelli” University Polyclinic Foundation, Largo Agostino Gemelli 8, 00168 Rome, Italy; (E.S.); (G.C.); (P.G.)
- Postgraduate School of Orthodontics–Director: Prof. Massimo Cordaro, Catholic University of the Sacred Heart, Largo Agostino Gemelli 8, 00168 Rome, Italy
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Sayahpour B, Zinelis S, Polychronis G, Eliades T, Goteni M, Kopp S, Eslami S. Effects of intraoral aging on mechanical properties of directly printed aligners vs. thermoformed aligners: an in vivo prospective investigation. Eur J Orthod 2024; 46:cjad063. [PMID: 37936263 DOI: 10.1093/ejo/cjad063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
OBJECTIVE The objective of this study was to examine the impact of intraoral aging on the mechanical properties of directly printed aligners (DPA) compared to thermoformed aligners (TA). MATERIALS AND METHODS This prospective in vivo experiment included three types of aligners: DPAs (group DP) fabricated from Tera Harz TC-85 DAC resin (Graphy, Korea), TA (group INV) made from a polyurethane-based polymer (Align Technology, Inc., CA, USA), and TA (group DUR) made from polyethylene glycol terephthalate based polymer (Scheu-Dental, Germany). Each group was categorized into retrieved (Clin) and unused aligners (Ctr). Thirty patients (10 per group) wore the aligners for 7 days, thereby generating the retrieved samples. Thirty unused aligners were employed as control samples. The following mechanical properties were determined: Martens Hardness (HM), indentation modulus (EIT), elastic index (ηIT), and indentation relaxation (RIT). Intergroup comparisons were conducted using ANOVA/Kruskal-Wallis test. Comparisons between retrieved and control samples were done using Wilcoxon-Mann-Whitney-U/Student's t-test/Welch's test. RESULTS Statistically significant differences between the groups were found for both control and used samples (P < .001). Pairwise comparisons also revealed significant differences between the samples. The mechanical properties did not differ significantly between unused and retrieved INV- and DUR-aligners, whereas for DP-aligners significant differences for ηIT and RIT were found following intraoral service (P-values .012 and .002, respectively). CONCLUSIONS Group DUR showed generally more favorable mechanical properties compared to DP and INV. The much higher RIT and EIT in DP aligners suggest their higher rigidity and force decay, which could compromise their clinical efficacy.
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Affiliation(s)
- Babak Sayahpour
- Department of Orthodontics, Johann-Wolfgang Goethe University, Theodor-Stern-Kai 7, 60596 Frankfurt am Main, Germany
| | - Spiros Zinelis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, 11527 Athens, Greece
| | - Georgios Polychronis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, 11527 Athens, Greece
| | - Theodore Eliades
- Clinic of Orthodontics and Pediatric Dentistry Center of Dental Medicine, University of Zurich, Zurich 8032, Switzerland
| | - Malcolm Goteni
- Private Orthodontic Practice, Grafenberger Alle 57, 40237 Duesseldorf, Germany
| | - Stefan Kopp
- Department of Orthodontics, Johann-Wolfgang Goethe University, Theodor-Stern-Kai 7, 60596 Frankfurt am Main, Germany
| | - Sara Eslami
- Department of Orthodontics, Johann-Wolfgang Goethe University, Theodor-Stern-Kai 7, 60596 Frankfurt am Main, Germany
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Mu C, Sun B, Gong Z, Wei Y, Chen L, Zhang W, Wu H, Zhao B. The tooth movement efficiency of different orthodontic thermoplastics for clear aligners: study protocol for a randomized controlled clinical trial. Trials 2023; 24:684. [PMID: 37872599 PMCID: PMC10594683 DOI: 10.1186/s13063-023-07736-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 10/16/2023] [Indexed: 10/25/2023] Open
Abstract
INTRODUCTION With regard to the esthetics and comfort of orthodontic treatment, the requirement for removable clear aligners (CAs) is increasing. Unlike conventional fixed orthodontic appliances, CAs were made of thermoplastic film by thermoforming on the personalized dental models. The construction of orthodontic thermoplastic is a critical factor for orthodontic tooth movement (OTM). Polyethylene terephthalate glycol-modified (PETG) and thermoplastic polyurethane (TPU) are the most commonly orthodontic thermoplastics; however, the evidence of the differences between different orthodontic thermoplastic are limited to vitro environment and the evidence in vivo environment is not available. Therefore, this trial aims to provide reliable evidence for orthodontists' personalized treatment plans whether the two most commonly used orthodontic thermoplastics of PETG and TPU have differences in the efficiency of OTM. METHODS AND ANALYSIS This randomized controlled clinical study will recruit 44 orthodontic patients for orthodontic treatment. All the subjects will be randomized into two groups (PETG and TPU, n = 22 for each group). In the first stage (M0 to M1), clear aligners will be made of two orthodontic thermoplastics and move the maxillary first or second premolars 2 mm. In the second stage, patients will take the standard orthodontic treatments. The primary outcome will be the efficiency of clear aligners made of different materials on the digital models. The secondary outcome will be the efficiency of clear aligners made of different materials on the cone-beam computed tomography (CBCT). The efficiency will be calculated through the superimposition of the digital models and CBCT. DISCUSSION The results from this trial will serve as evidence for orthodontists and manufacturers and clarify whether the difference in orthodontic thermoplastics significantly impacts the efficiency of OTM. TRIAL REGISTRATION NUMBER ChiCTR2300070980. Registered on 27 April 2023. https://www.chictr.org.cn/showproj.html?proj=186253.
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Affiliation(s)
- Chuangchuang Mu
- Department of Orthodontics, Shanghai Stomatological Hospital, Fudan University, No.356 Beijing East Road, Shanghai, China
| | - Bingjing Sun
- Department of Orthodontics, Shanghai Stomatological Hospital, Fudan University, No.356 Beijing East Road, Shanghai, China
| | - Zhicheng Gong
- Department of Dental Technology, Shanghai Stomatological Hospital, Fudan University, Shanghai, China
| | - Yuanyuan Wei
- Department of Orthodontics, Shanghai Stomatological Hospital, Fudan University, No.356 Beijing East Road, Shanghai, China
| | - Li Chen
- Department of Orthodontics, Shanghai Stomatological Hospital, Fudan University, No.356 Beijing East Road, Shanghai, China
| | - Wei Zhang
- Department of Orthodontics, Shanghai Stomatological Hospital, Fudan University, No.356 Beijing East Road, Shanghai, China
- Department of Biostatistics, School of Public Health, Fudan University, Shanghai, China
| | - Haimiao Wu
- Department of Orthodontics, Shanghai Stomatological Hospital, Fudan University, No.356 Beijing East Road, Shanghai, China
| | - Bingjiao Zhao
- Department of Orthodontics, Shanghai Stomatological Hospital, Fudan University, No.356 Beijing East Road, Shanghai, China.
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Taher BB, Rasheed TA. The Impact of Adding Chitosan Nanoparticles on Biofilm Formation, Cytotoxicity, and Certain Physical and Mechanical Aspects of Directly Printed Orthodontic Clear Aligners. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2649. [PMID: 37836290 PMCID: PMC10574519 DOI: 10.3390/nano13192649] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 09/23/2023] [Accepted: 09/25/2023] [Indexed: 10/15/2023]
Abstract
Aligner treatment is associated with bacterial colonization, leading to enamel demineralization. Chitosan nanoparticles have been demonstrated to have antibacterial properties. This in vitro study aims to determine the effect of adding chitosan nanoparticles to directly 3D-printed clear aligner resin with regard to antibiofilm activity, cytotoxicity, degree of conversion, accuracy, deflection force, and tensile strength. Different concentrations (2%, 3%, and 5% w/w) of chitosan nanoparticles were mixed with the clear resin, and the samples were then 3D printed. Additionally, the thermoforming technique for aligner manufacturing was utilized. The obtained specimens were evaluated for antibiofilm activity against Streptococcus mutans bacteria and cytotoxicity against L929 and 3T3 cell lines. Additionally, Fourier transform infrared spectroscopy via attenuated total reflection analysis was used to assess the degree of conversion. Geomagic Control X software was utilized to analyze the accuracy. In addition, the deflection force and tensile strength were evaluated. The results indicated a notable reduction in bacterial colonies when the resin was incorporated with 3 and 5% chitosan nanoparticles. No significant changes in the cytotoxicity or accuracy were detected. In conclusion, integrating biocompatible chitosan nanoparticles into the resin can add an antibiofilm element to an aligner without compromising the material's certain biological, mechanical, and physical qualities at specific concentrations.
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Affiliation(s)
- Botan Barzan Taher
- Department of Pedodontics, Orthodontics and Preventive Dentistry, College of Dentistry, University of Sulaimani, Sulaymaniyah 46001, Iraq;
| | - Tara Ali Rasheed
- Department of Pedodontics, Orthodontics and Preventive Dentistry, College of Dentistry, University of Sulaimani, Sulaymaniyah 46001, Iraq;
- College of Dentistry, American University of Iraq-Sulaimani, Sulaymaniyah 46001, Iraq
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15
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Mao B, Tian Y, Li J, Zhou Y. Expansion rebound deformation of clear aligners and its biomechanical influence: a three-dimensional morphologic analysis and finite element analysis study. Angle Orthod 2023; 93:572-579. [PMID: 37068033 PMCID: PMC10575640 DOI: 10.2319/102622-734.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 03/01/2023] [Indexed: 04/18/2023] Open
Abstract
OBJECTIVES To determine the expansion rebound deformation (ERD) of clear aligners (CAs) and its biomechanical influence. MATERIALS AND METHODS A four-premolar extraction treatment plan was carried out for a patient with 2 CA companies. Thirty-six digitally scanned clear aligners with the corresponding 36 virtually constructed "ideal" aligners were constructed. The arch width and length between pairs of reference landmarks of the scanned CAs and corresponding dentition models were measured. Cone-beam computed tomography data and digital dental models were used for three-dimensional (3D) finite element analysis (FEA) modeling. Thirty-six scanned CA models with the corresponding 36 ideal CA models were constructed. One-way analysis of variance was used to determine the differences among deviation values at tooth level, and paired t-test was used to compare the displacements of teeth between the two group of CAs. RESULTS All CAs were wider and shorter than the digital model from which they were constructed. In the scanned CA model group, significant stress was observed in the buccolingual area of the periodontal ligament on posterior teeth, and the corresponding displacements of teeth were also noted. Significantly larger coronal displacements were noted for the lateral incisor, the canine, the second premolar, and the first molar in the scanned CA group (P < .05). CONCLUSIONS The general trend of ERD of thermoformed CAs was shown. This deformation may cause unforeseen tooth movements and negatively affect treatment outcomes.
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Affiliation(s)
| | | | - Jing Li
- Corresponding author: Dr Jing Li, Department of Orthodontics, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health, No.22 Zhongguancun South Avenue, Haidian District, Beijing 100081, People’s Republic of China. (e-mail: )
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Lira LF, Otero Amaral Vargas E, Moreira da Silva E, Nunes da Silva Meirelles Dória Maia J, Elzubair A, Siqueira de Morais L, Alvaro de Souza Camargo S, Serra G, Gomes de Souza MM. Effect of oral exposure on chemical, physical, mechanical, and morphologic properties of clear orthodontic aligners. Am J Orthod Dentofacial Orthop 2023; 164:e51-e63. [PMID: 37330727 DOI: 10.1016/j.ajodo.2023.05.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 05/01/2023] [Accepted: 05/01/2023] [Indexed: 06/19/2023]
Abstract
INTRODUCTION The dental industry is heavily committed to developing more esthetic solutions for orthodontic treatments. Invisalign is a system of transparent orthodontic aligners introduced as an alternative to conventional orthodontic fittings with brackets and metal wires. This study aimed to assess the chemical, physical, mechanical and morphologic changes in these polymeric aligners after exposure to the oral environment. METHODS Twenty-four Invisalign orthodontic aligners were equally divided into 2 groups: an in vivo aged group in which patients used aligners for 14 days and the reference group, unexposed to the oral environment. Different experimental techniques were used to study the chemical structure, the color changes and translucency, the density and subsequent volume of the aligners, mechanical properties, surface roughness, morphology and elemental composition. The data were subjected to several statistical analyses. RESULTS Clear orthodontic aligners exhibit chemical stability but undergo a statistically significant optical change in color and translucency. There was a gradual increase in the water absorption rate and the dimensional variation of the polymer, indicating a strong correlation among these factors. The mechanical properties of the polymer showed a statistically significant decrease in its elastic modulus and hardness. There was a slight tendency toward increased surface roughness of the material, but no statistical differences were found between reference and aged groups. The surface morphology of the used aligners demonstrates microcracks, distortions and biofilm formation. CONCLUSION Intraoral aging adversely affected the physical, mechanical, and morphologic properties of the Invisalign appliance.
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Affiliation(s)
- Larine Ferreira Lira
- Department of Pediatric Dentistry and Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Eduardo Otero Amaral Vargas
- Department of Pediatric Dentistry and Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Eduardo Moreira da Silva
- Analytical Laboratory of Restorative Biomaterials-LABiom-R, School of Dentistry, Federal Fluminense University, Niterói, Brazil
| | | | - Amal Elzubair
- Metallurgical and Materials Engineering Program, Alberto Luiz Coimbra Institute for Graduate Studies and Research in Engineering (COPPE), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Liliane Siqueira de Morais
- Department of Pediatric Dentistry and Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Sérgio Alvaro de Souza Camargo
- Metallurgical and Materials Engineering Program, Alberto Luiz Coimbra Institute for Graduate Studies and Research in Engineering (COPPE), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Nanotechnology Engineering Program, COPPE, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Glaucio Serra
- Department of Specific Formation, Federal Fluminense University, Nova Friburgo, Brazil
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Chen SM, Ho CT, Huang TH, Kao CT. An in vitro evaluation of aligner force decay in artificial saliva. J Dent Sci 2023; 18:1347-1353. [PMID: 37404637 PMCID: PMC10316483 DOI: 10.1016/j.jds.2023.04.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 04/18/2023] [Indexed: 07/06/2023] Open
Abstract
Background/purpose The present study aimed to compare the force decay of invisible aligners for maxillary anterior teeth with 0.1 mm (D1), 0.2 mm (D2), and 0.3 mm (D3) labial movement within a simulated oral environment over 7 days. Materials and methods The prepared invisible aligners were immersed in saliva (S) and subjected to applied force (F) for 7 days. The aligners were set and placed on the maxillary right central incisor with 0.1 mm (D1), 0.2 mm (D2), and 0.3 mm (D3) labial movement. Thin-film pressure sensors were used to measure the aligner force changes. The data were collected and analyzed by statistical methods. Results Significant differences were observed in the initial and first-day force between the D2 and D3 groups under simulated oral environment force (SF) (P < 0.05). There was a significant difference in force decay between Day 1 and Day 7 for all groups (P < 0.05). The SFD1 group showed a significant decrease in force on Day 5 (P < 0.05), while the SFD2 and SFD3 groups showed significant force decay on Day 4 (P < 0.05). The force decay ratio on Day 7 was higher in the SFD3 group than in the SFD1 and SFD2 groups, but no significant difference was observed. Conclusion Larger labial movement of the aligners resulted in higher force decay under artificial saliva environments, and the force decay of invisible aligners was increased by immersion time in artificial saliva.
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Affiliation(s)
- Shou-Min Chen
- School of Dentistry, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan
- Orthodontic Department, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Chun-Te Ho
- School of Dentistry, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan
- Orthodontic Department, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Tsui-Hsein Huang
- School of Dentistry, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan
- Dental Department, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Chia-Tze Kao
- Orthodontic Department, Chung Shan Medical University Hospital, Taichung, Taiwan
- Dental Department, Chung Shan Medical University Hospital, Taichung, Taiwan
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18
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Elshazly TM, Nang D, Golkhani B, Elattar H, Keilig L, Bourauel C. Effect of thermomechanical aging of orthodontic aligners on force and torque generation: An in vitro study. J Mech Behav Biomed Mater 2023; 143:105911. [PMID: 37207526 DOI: 10.1016/j.jmbbm.2023.105911] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 05/10/2023] [Accepted: 05/14/2023] [Indexed: 05/21/2023]
Abstract
The aim of the study is to investigate the effects of artificial aging by thermocycling and mechanical loading on force/torque delivery by thermoplastic orthodontic aligners. Ten thermoformed aligners, made of Zendura™ thermoplastic polyurethane sheets, were aged over two weeks in deionized water by thermocycling alone (n = 5) and by both thermocycling and mechanical loading (n = 5). The force/torque generated on upper second premolar (Tooth 25) of a plastic model was measured before aging (as control), and after 2, 4, 6, 10, and 14 days of aging, using a biomechanical set-up. Before aging, the extrusion-intrusion forces were in the range of 2.4-3.0 N, the oro-vestibular forces were 1.8-2.0 N, and the torques on mesio-distal rotation were 13.6-40.0 Nmm. Pure thermocycling had no significant effect on the force decay of the aligners. However, there was a significant decrease in force/torque after 2 days of aging for both thermocycling and mechanical loading aging group, which is no longer significant over 14 days of aging. In conclusion, artificial aging of aligners in deionized water with both thermocycling and mechanical loading results in a significant decrease in force/torque generation. However, mechanical loading of aligners has a greater impact than pure thermocycling.
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Affiliation(s)
- Tarek M Elshazly
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany.
| | - Diva Nang
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany
| | - Bijan Golkhani
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany
| | - Hanaa Elattar
- Orthodontic Department, Faculty of Dentistry, Umm Al-Qura University, Makkah, Saudi Arabia; Orthodontic Department, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt
| | - Ludger Keilig
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany; Department of Dental Prosthetics, Propaedeutics and Materials Science, Dental School, University Hospital Bonn, Bonn, Germany
| | - Christoph Bourauel
- Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany
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Šimunović L, Blagec T, Meštrović S. Resistance of PETG Materials on Thermocycling and Brushing. Dent J (Basel) 2023; 11:dj11050135. [PMID: 37232786 DOI: 10.3390/dj11050135] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 05/11/2023] [Accepted: 05/12/2023] [Indexed: 05/27/2023] Open
Abstract
The aim was to assess the impact of thermocycling and brushing on the surface roughness and mass of PETG material-the most commonly used for orthodontic retainers. A total of 96 specimens were exposed to thermocycling and brushing with three different kinds of toothbrushes depending on the number and thickness of the bristles. Surface roughness and mass were evaluated three times: initially, after thermocycling, and after brushing. In all four brands, both thermocycling and brushing increased surface roughness significantly (p < 0.001), with Biolon having the lowest and Track A having the highest. In terms of brushing, only Biolon samples showed statistically significant increased roughness after brushing with all three types of brushes, in comparison to Erkodur A1, where differences were not statistically significant. Thermocycling increased the mass of all samples, but a statistically significant difference was found only in Biolon (p = 0.0203), while after brushing, decreased mass was found in all specimens, statistically significant only in Essix C+ (CS 1560: p = 0.016). PETG material showed instability when exposed to external influences- thermocycling produced an increase in roughness and mass, and brushing mostly caused an increase in roughness and decrease in mass. Erkodur A1 demonstrated the greatest stability, whereas Biolon demonstrated the lowest.
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Affiliation(s)
- Luka Šimunović
- Department of Orthodontics, School of Dental Medicine Zagreb, University of Zagreb, 10000 Zagreb, Croatia
| | - Tadeja Blagec
- Department of Orthodontics, School of Dental Medicine Zagreb, University of Zagreb, 10000 Zagreb, Croatia
| | - Senka Meštrović
- Department of Orthodontics, School of Dental Medicine Zagreb, University of Zagreb, 10000 Zagreb, Croatia
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Bangalore D, Alshehri AM, Alsadon O, Alaqeel SM, Alageel O, Alsarani MM, Almansour H, AlShahrani O. Coffee Staining and Simulated Brushing Induced Color Changes and Surface Roughness of 3D-Printed Orthodontic Retainer Material. Polymers (Basel) 2023; 15:polym15092164. [PMID: 37177310 PMCID: PMC10180946 DOI: 10.3390/polym15092164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 04/30/2023] [Accepted: 04/30/2023] [Indexed: 05/15/2023] Open
Abstract
This in vitro study evaluated the influence of combined coffee staining and simulated brushing-induced color changes and surface roughness on 3D-printed orthodontic retainers. Specimens measuring 10 × 10 × 0.75 mm3 were obtained either by conventional vacuum forming or 3D printing at four print angulations (0°, 15°, 30°, and 45°) (n = 10). The prepared specimens were immersed in a coffee beverage and then mechanically brushed using a simulating device. The specimen's color difference (ΔE) and surface roughness (Ra) were quantified using a spectrophotometer and a non-contact profilometer, respectively. The highest and lowest mean ΔE values were recorded for the 3D-printed-45° (4.68 ± 2.07) and conventional (2.18 ± 0.87) groups, respectively. The overall mean comparison of ΔE between the conventional and 3D-printed groups was statistically significant (p < 0.01). After simulated brushing, all groups showed a statistically significant increase in the Ra values (p < 0.01). The highest Ra was in the 3D-printed-45° (1.009 ± 0.13 µm) and conventional (0.743 ± 0.12 µm) groups, respectively. The overall ΔE of 3D-printed orthodontic retainers was not comparable to conventional VFRs. Among the different angulations used to print the retainers, 15° angulations were the most efficient in terms of color changes and surface roughness and were comparable to conventional VFRs.
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Affiliation(s)
- Durgesh Bangalore
- Dental Health Department, College of Applied Medical Sciences, King Saud University, Riyadh 7268, Saudi Arabia
| | - Abdullah M Alshehri
- Dental Health Department, College of Applied Medical Sciences, King Saud University, Riyadh 7268, Saudi Arabia
| | - Omar Alsadon
- Dental Health Department, College of Applied Medical Sciences, King Saud University, Riyadh 7268, Saudi Arabia
| | - Samer M Alaqeel
- Dental Health Department, College of Applied Medical Sciences, King Saud University, Riyadh 7268, Saudi Arabia
| | - Omar Alageel
- Dental Health Department, College of Applied Medical Sciences, King Saud University, Riyadh 7268, Saudi Arabia
| | - Majed M Alsarani
- Dental Health Department, College of Applied Medical Sciences, King Saud University, Riyadh 7268, Saudi Arabia
| | - Haitham Almansour
- Dental Health Department, College of Applied Medical Sciences, King Saud University, Riyadh 7268, Saudi Arabia
| | - Obaid AlShahrani
- Dental Health Department, College of Applied Medical Sciences, King Saud University, Riyadh 7268, Saudi Arabia
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Spanier C, Schwahn C, Krey KF, Ratzmann A. Fused filament fabrication (FFF): influence of layer height on forces and moments delivered by aligners-an in vitro study. Clin Oral Investig 2023; 27:2163-2173. [PMID: 36790628 PMCID: PMC10159977 DOI: 10.1007/s00784-023-04912-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 02/03/2023] [Indexed: 02/16/2023]
Abstract
OBJECTIVES To investigate the effect of layer height of FFF-printed models on aligner force transmission to a second maxillary premolar during buccal torquing, distalization, extrusion, and rotation using differing foil thicknesses. MATERIALS AND METHODS Utilizing OnyxCeph3™ Lab (Image Instruments GmbH, Chemnitz, Germany, Release Version 3.2.185), the following movements were programmed for the second premolar: buccal torque (0.1-0.5 mm), distalization (0.1-0.4 mm), extrusion (0.1-0.4 mm), rotation (0.1-0.5 mm), and staging 0.1 mm. Via FFF, 91 maxillary models were printed for each staging at different layer heights (100 µm, 150 µm, 200 µm, 250 µm, 300 µm). Hence, 182 aligners, made of polyethylene terephthalate glycol (PET-G) with two thicknesses (0.5 mm and 0.75 mm), were prepared. The test setup comprised an acrylic maxillary model with the second premolar separated and mounted on a sensor, measuring initial forces and moments exerted by the aligners. A generalized linear model for the gamma distribution was applied, evaluating the significance of the factors layer height, type of movement, aligner thickness, and staging on aligner force transmission. RESULTS Foil thickness and staging were found to have a significant influence on forces delivered by aligners, whereas no significance was determined for layer height and type of movement. Nevertheless, at a layer height of 150 µm, the most appropriate force transmission was observed. CONCLUSIONS Printing aligner models at particularly low layer heights leads to uneconomically high print time without perceptible better force delivery properties, whereas higher layer heights provoke higher unpredictability of forces due to scattering. A z-resolution of 150 µm appears ideal for in-office aligner production combining advantages of economic print time and optimal force transmission.
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Affiliation(s)
- Claudia Spanier
- Department of Orthodontics and Craniofacial Orthopedics, University Medicine Greifswald, 17475, Greifswald, Germany
| | - Christian Schwahn
- Department for Prosthodontics, Gerostomatology and Biomaterials, University Medicine Greifswald, Greifswald, Germany
| | - Karl-Friedrich Krey
- Department of Orthodontics and Craniofacial Orthopedics, University Medicine Greifswald, 17475, Greifswald, Germany.
| | - Anja Ratzmann
- Department of Orthodontics and Craniofacial Orthopedics, University Medicine Greifswald, 17475, Greifswald, Germany
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22
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Elkholy F, Schmidt S, Schmidt F, Amirkhani M, Lapatki BG. Force decay of polyethylene terephthalate glycol aligner materials during simulation of typical clinical loading/unloading scenarios. J Orofac Orthop 2023; 84:189-201. [PMID: 34882259 PMCID: PMC10119250 DOI: 10.1007/s00056-021-00364-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 10/28/2021] [Indexed: 11/24/2022]
Abstract
BACKGROUND This in vitro study investigated the effect of three distinct daily loading/unloading cycles on force delivery during orthodontic aligner therapy. The cycles were applied for 7 days and were designed to reflect typical clinical aligner application scenarios. MATERIALS AND METHODS Flat polyethylene terephthalate glycol (PET-G) specimens (Duran®, Scheu Dental, Iserlohn, Germany) with thicknesses ranging between 0.4 and 0.75 mm were tested in a three-point-bending testing machine. Measurements comprised loading/unloading intervals of 12 h/12 h, 18 h/6 h, and 23 h/1 h, and specimens were exposed to bidistilled water during loading to simulate intraoral conditions. RESULTS A very large decay in force for the PET‑G specimens could already be observed after the first loading period, with significantly different residual force values of 24, 20, and 21% recorded for the 12 h/12 h, 18 h/6 h, and 23 h/1 h loading/unloading modes, respectively (Mann-Whitney U test, p < 0.01). In addition, further decays in force from the first to the last loading period at day 7 of 13.5% (12 h/12 h), 9.7% (18 h/6 h), and 8.4% (23 h/1 h) differed significantly among the three distinct loading modes (Mann-Whitney U test, p < 0.01). CONCLUSION Although the initial material stiffness of PET‑G is relatively high, the transmission of excessive forces is attenuated by the high material-related force decay already within a few hours after intraoral insertion.
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Affiliation(s)
- Fayez Elkholy
- Department of Orthodontics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Silva Schmidt
- Department of Orthodontics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Falko Schmidt
- Department of Orthodontics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Masoud Amirkhani
- Institute of Experimental Physics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Bernd G. Lapatki
- Department of Orthodontics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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Shirey N, Mendonca G, Groth C, Kim-Berman H. Comparison of mechanical properties of 3-dimensional printed and thermoformed orthodontic aligners. Am J Orthod Dentofacial Orthop 2023; 163:720-728. [PMID: 37142355 DOI: 10.1016/j.ajodo.2022.12.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 12/01/2022] [Accepted: 12/01/2022] [Indexed: 05/06/2023]
Abstract
INTRODUCTION Orthodontic treatment using clear aligners has experienced exponential growth since its introduction in the late 1990s. Three-dimensional (3D) printing has also grown in popularity among orthodontists, and companies have begun to produce resins to directly print clear aligners. This study aimed to examine the mechanical properties of commercially available thermoformed aligners and direct 3D-printed aligners under laboratory conditions and a simulated oral environment. METHODS Samples were prepared (approximately 2.5 × 20 mm) from 2 thermoformed materials, EX30 and LD30 (Align Technology Inc, San Jose, Calif), as well as 2 direct 3D-printing resins, Material X (Envisiontec, Inc; Dearborn, Mich) and OD-Clear TF (3DResyns, Barcelona, Spain). Wet samples were subjected to phosphate-buffered saline at 37°C for 7 days, whereas dry samples were stored at 25°C. Tensile and stress relaxation tests were carried out on an RSA3 Dynamic Mechanical Analyzer (Texas Instruments, Dallas, Tex) and Instron Universal Testing System (Instron, Norwood, Mass) to calculate elastic modulus, ultimate tensile strength, and stress relaxation. RESULTS The elastic modulus of dry and wet samples was 103.2 ± 17.3 MPa and 114.4 ± 17.9 MPa (EX30), 61.3 ± 9.18 MPa and 103.5 ± 11.4 MPa (LD30), 431.2 ± 16.0 MPa and 139.9 ± 34.6 MPa (Material X), and 38.4 ± 14.7 MPa and 38.3 ± 8.4 MPa (OD-Clear TF), respectively. The ultimate tensile strength of dry and wet samples was 64.41 ± 7.25 MPa and 61.43 ± 7.41MPa (EX30), 40.04 ± 5.00 MPa and 30.09 ± 1.50 MPa (LD30), 28.11 ± 3.75 MPa and 27.57 ± 4.09 MPa (Material X), and 9.34 ± 1.96 MPa and 8.27 ± 0.93 MPa (OD-Clear TF), respectively. Residual stress of wet samples at 2% strain for 2 hours was 59.99 ± 3.02% (EX30), 52.57 ± 12.28% (LD30), 6.98 ± 2.64% (Material X), and 4.39 ± 0.84% (OD-Clear TF). CONCLUSIONS There was a significant difference in elastic modulus, ultimate tensile strength, and stress relaxation among the samples tested. Moisture, specifically a simulated oral environment, appears to have a greater effect on the mechanical properties of direct 3D-printed aligners when compared with thermoformed aligners. This is likely to impact the ability of 3D-printed aligners to generate and maintain adequate force levels for tooth movement.
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Affiliation(s)
- Nic Shirey
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, Mich.
| | - Gustavo Mendonca
- Department of General Practice, School of Dentistry, Virginia Commonwealth University, Richmond, Va
| | - Christian Groth
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, Mich
| | - Hera Kim-Berman
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, Mich
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Lyu X, Cao X, Chen L, Liu Y, Li H, Hu C, Tan J. Accumulated biomechanical effects of mandibular molar mesialization using clear aligners with auxiliary devices: an iterative finite element analysis. Prog Orthod 2023; 24:13. [PMID: 37032410 PMCID: PMC10083150 DOI: 10.1186/s40510-023-00462-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 03/07/2023] [Indexed: 04/11/2023] Open
Abstract
BACKGROUND The biomechanics generated by the clear aligner (CA) material changes continuously during orthodontic tooth movement, but this factor remains unknown during the computer-aid design process and the predictability of molars movement is not as expected. Therefore, the purpose of this study was to propose an iterative finite element method to simulate the long-term biomechanical effects of mandibular molar mesialization (MM) in CA therapy under dual-mechanical systems. METHODS Three groups including CA alone, CA with a button, and CA with a modified lever arm (MLA) were created. Material properties of CA were obtained by in vitro mechanical experiments. MM was conducted by the rebound force exerted by CA material and the mesial elastic force (2N, 30° to the occlusal plane) applied to the auxiliary devices. Stress intensity and distribution on periodontal ligament (PDL), attachment, button and MLA, and displacement of the second molar (M2) during the iterations were recorded. RESULTS There was a significant difference between the initial and cumulative long-term displacement. Specifically, compared to the beginning, the maximum stress of PDL decreased by 90% on average in the intermediate and final steps. The aligner was the main mechanical system at first, and then, the additional system exerted by the button and MLA dominated gradually. The stress of attachments and auxiliary devices is mainly concentrated on their interfaces with the tooth. Additionally, MLA provided a distal tipping and extrusive moment, which was the only group that manifested a total mesial displacement of the root. CONCLUSIONS The innovatively designed MLA was more effective in reducing undesigned mesial tipping and rotation of M2 than the traditional button and CA alone, which provided a therapeutic method for MM. The proposed iterative method simulated tooth movement by considering the mechanical characteristic of CA and its long-term mechanical force changes, which will facilitate better movement prediction and minimize the failure rate.
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Affiliation(s)
- Xinwei Lyu
- Department of Orthodontics, Hospital of Stomatology, Sun Yat-Sen University, Guangzhou, 510055, China
- Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, 510080, China
- Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, 510080, China
| | - Xing Cao
- Department of Orthodontics, Hospital of Stomatology, Sun Yat-Sen University, Guangzhou, 510055, China
- Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, 510080, China
- Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, 510080, China
| | - Luxian Chen
- Department of Orthodontics, Hospital of Stomatology, Sun Yat-Sen University, Guangzhou, 510055, China
- Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, 510080, China
- Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, 510080, China
| | - Yuyao Liu
- Department of Orthodontics, Hospital of Stomatology, Sun Yat-Sen University, Guangzhou, 510055, China
- Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, 510080, China
- Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, 510080, China
| | - Huilin Li
- Department of Orthodontics, Hospital of Stomatology, Sun Yat-Sen University, Guangzhou, 510055, China
- Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, 510080, China
- Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, 510080, China
| | - Cheng Hu
- Department of Orthodontics, Hospital of Stomatology, Sun Yat-Sen University, Guangzhou, 510055, China
- Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, 510080, China
- Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, 510080, China
| | - Jiali Tan
- Department of Orthodontics, Hospital of Stomatology, Sun Yat-Sen University, Guangzhou, 510055, China.
- Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, 510080, China.
- Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou, 510080, China.
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Porojan L, Toma FR, Bîrdeanu MI, Vasiliu RD, Matichescu A. Topographical and Optical Characteristics of Thermoplastic Dental Appliances Materials Related to Water Sorption. J Funct Biomater 2023; 14:jfb14040190. [PMID: 37103280 PMCID: PMC10146702 DOI: 10.3390/jfb14040190] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 03/22/2023] [Accepted: 03/27/2023] [Indexed: 03/31/2023] Open
Abstract
Clear thermoplastic materials have increased in popularity in the dental field due to their various applications, combination of excellent aesthetics, and good biomechanical behavior, but they may be influenced by different environmental conditions. The purpose of the present study was to assess the topographical and optical characteristics of thermoplastic dental appliances materials relative to water sorption. PET-G polyester thermoplastic materials were evaluated in this study. Related to water uptake and desiccation stages, surface roughness was analyzed, and three-dimensional AFM profiles were generated for nano-roughness measurements. Optical CIE L*a*b* coordinates were recorded and parameters like translucency (TP), contrast ratio for the opacity (CR), and opalescence (OP) were derived. Levels of color changes were achieved. Statistical analyses were performed. Water uptake significantly increases the specific weight of the materials, and after desiccation, the mass decreases. Roughness increased after water immersion as well. Regression coefficients indicated a positive correlation between TP and a* and between OP and b*. Studied PET-G materials have a different behavior to water exposure, but for all their specific weight, they increased significantly within the first 12 h. It is accompanied by an increase in the roughness values, even if they continue to be kept below the critical mean surface roughness. On nano-level, 3D images show an increase in inhomogeneity in the network structure of particles. Slight color changes were registered.
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Affiliation(s)
- Liliana Porojan
- Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, Victor Babes University of Medicine and Pharmacy Timisoara, Eftimie Murgu Square No. 2, 300041 Timisoara, Romania
- Correspondence:
| | - Flavia Roxana Toma
- Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, Victor Babes University of Medicine and Pharmacy Timisoara, Eftimie Murgu Square No. 2, 300041 Timisoara, Romania
| | - Mihaela Ionela Bîrdeanu
- National Institute for Research and Development in Electrochemistry and Condensed Matter, A. Păunescu Podeanu Str. No. 144, 300569 Timisoara, Romania
| | - Roxana Diana Vasiliu
- Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, Victor Babes University of Medicine and Pharmacy Timisoara, Eftimie Murgu Square No. 2, 300041 Timisoara, Romania
| | - Anamaria Matichescu
- Department of Preventive, Community Dentistry and Oral Health, Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, Victor Babes University of Medicine and Pharmacy Timisoara, Eftimie Murgu Square No. 2, 300041 Timisoara, Romania
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Liu JQ, Zhu GY, Wang YG, Zhang B, Yao K, Zhao ZH. Different biomechanical effects of clear aligners in closing maxillary and mandibular extraction spaces: Finite element analysis. Am J Orthod Dentofacial Orthop 2023; 163:811-824.e2. [PMID: 36964108 DOI: 10.1016/j.ajodo.2022.07.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 07/01/2022] [Accepted: 07/01/2022] [Indexed: 03/26/2023]
Abstract
INTRODUCTION Compared with fixed treatments, clear aligners (CAs) have the advantages of comfort, esthetics, and hygiene, and are popular among patients and orthodontists. However, CAs exhibit control deficiencies in extraction patients because of insufficient root control and retention effects. These deficiencies can magnify biomechanical differences in bimaxillary dentition, further causing different orthodontic requirements between maxillary and mandibular dentition. This study aimed to elaborate on the biomechanical characteristics of bimaxillary dentition in extraction space closure and provided feasible biomechanical compensation strategies for use in clinical practice. METHODS We constructed a 3-dimensional (3D) bimaxillary model based on patient data. Several 3D modeling-related software was used to generate a standard first premolar extraction model, CAs, and attachments. Subsequently, finite element analysis was performed to demonstrate the biomechanical effects. RESULTS The maxillary and mandibular dentition showed a roller coaster effect during space closure. Compared with the maxillary dentition, the mandibular posterior teeth exhibited stronger relative anchorage causing greater anterior teeth retraction. The tipping and vertical movements of the anterior teeth were related to tooth length. The longer the anterior tooth, the less tipping and greater vertical displacement occurred. Generally, when having the same retraction distance, the mandibular dentition exhibited greater retroclination and fewer extrusions. Both mechanical and retention compensations should be considered to prevent these unwanted tipping movements. Adding specific attachments to bimaxillary dentitions compensated for the retention and root control deficiencies of CAs. CONCLUSIONS When applying CAs to extraction patients, different biomechanical effects can present in the bimaxillary dentition because of specific dentition morphologies. To effectively treat these patients, mechanical compensation through overcorrection of the target position should be designed on the basis of bimaxillary control deficiencies, and retention compensation by adding specific attachments should also be considered according to the overcorrections.
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Affiliation(s)
- Jun-Qi Liu
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Guan-Yin Zhu
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yi-Gan Wang
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Bo Zhang
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Ke Yao
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Zhi-He Zhao
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
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Zhu GY, Zhang B, Yao K, Lu WX, Peng JJ, Shen Y, Zhao ZH. Finite element analysis of the biomechanical effect of clear aligners in extraction space closure under different anchorage controls. Am J Orthod Dentofacial Orthop 2023; 163:628-644.e11. [PMID: 36801091 DOI: 10.1016/j.ajodo.2022.02.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 02/01/2022] [Accepted: 02/01/2022] [Indexed: 02/17/2023]
Abstract
INTRODUCTION Clear aligners (CAs) have attracted increasing attention from patients and orthodontists because of their excellent esthetics and comfort. However, treating tooth extraction patients with CAs is difficult because their biomechanical effects are more complicated than those of traditional appliances. This study aimed to analyze the biomechanical effect of CAs in extraction space closure under different anchorage controls, including moderate, direct strong, and indirect strong anchorage. It could provide several new cognitions for anchorage control with CAs through finite element analysis, further directing clinical practice. METHODS A 3-dimensional maxillary model was generated by combining cone-beam computed tomography and intraoral scan data. Three-dimensional modeling software was used to construct a standard first premolar extraction model, temporary anchorage devices, and CAs. Subsequently, finite element analysis was performed to simulate space closure under different anchorage controls. RESULTS Direct strong anchorage was beneficial for reducing the clockwise occlusal plane rotation, whereas indirect anchorage was conducive for anterior teeth inclination control. In the direct strong anchorage group, an increase in the retraction force would require more specific anterior teeth overcorrection to resist the tipping movement, mainly including lingual root control of the central incisor, followed by distal root control of the canine, lingual root control of the lateral incisor, distal root control of the lateral incisor, and distal root control of the central incisor. However, the retraction force could not eliminate the mesial movement of the posterior teeth, possibly causing a reciprocating motion during treatment. In indirect strong groups, when the button was close to the center of the crown, the second premolar presented less mesial and buccal tipping but more intrusion. CONCLUSIONS The 3 anchorage groups showed significantly different biomechanical effects in both the anterior and posterior teeth. Specific overcorrection or compensation forces should be considered when using different anchorage types. The moderate and indirect strong anchorages have a more stable and single-force system and could be reliable models in investigating the precise control of future tooth extraction patients.
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Affiliation(s)
- Guan-Yin Zhu
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Bo Zhang
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Ke Yao
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Wen-Xin Lu
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jia-Jia Peng
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yu Shen
- School of Basic Medical Sciences, Chengdu University, Chengdu, China
| | - Zhi-He Zhao
- State Key Laboratory of Oral Diseases and National Clinical Research Center for Oral Diseases, and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
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Iliadi A, Enzler V, Polychronis G, Peltomaki T, Zinelis S, Eliades T. Εffect of cleansers on the composition and mechanical properties of orthodontic aligners in vitro. Prog Orthod 2022; 23:54. [PMID: 36517652 PMCID: PMC9751251 DOI: 10.1186/s40510-022-00449-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 11/09/2022] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND The aim of the study was to investigate the effect of three aligner cleaners on the composition and mechanical properties of two types of orthodontic aligners. MATERIALS AND METHODS The cleaners tested were two alkaline peroxide solutions (Retainer Brite-RB; Retainer Cleaner-RC) and one peroxide-free (Steraligner-ST) and the aligners Clear Aligner (C, polyester) and Invisalign (I, polyester-urethane). The aligners were immersed in the cleaner solutions as instructed every day (15 min for RB, RC; 5 min for ST) for a two-week period. The acidity of the solutions was tested with a pH meter. The changes in the chemical composition of the aligners were studied by attenuated total-reflection Fourier transform infrared spectrometry (ATR-FTIR), while Instrumented Indentation Testing (IIT) was used for assessment of changes in Martens Hardness (HM), modulus (EIT), elastic index (nIT) and relaxation (RIT). RESULTS RB and RC were weakly acidic (pH = 6.3), whereas ST was mildly acidic (pH = 4.8). The ATR-FTIR analysis demonstrated evidence of acidic hydrolysis of C in ST and I in RB. The IIT-derived properties of I were not affected by the cleaners. However, for C a significant change was found in HM (all cleaners), nIT (all cleaners) and RIT (RB, ST). Although the chemical changes support a hydrolytic material deterioration, the results of mechanical properties may interfere with the material residual stresses during fabrication. CONCLUSIONS Caution should be exerted in the selection of aligner cleaners. The mild acidic cleanser was more aggressive to the polyester, whereas an alkaline peroxide to the polyester-urethane aligner.
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Affiliation(s)
- Anna Iliadi
- grid.5216.00000 0001 2155 0800Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Vera Enzler
- grid.7400.30000 0004 1937 0650Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Plattenstrasse 11, 8032 Zurich, Switzerland
| | - Georgios Polychronis
- grid.5216.00000 0001 2155 0800Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Timo Peltomaki
- grid.502801.e0000 0001 2314 6254Department of Oral and Maxillofacial Diseases, Tampere University Hospital, Tampere, Finland Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland ,grid.410705.70000 0004 0628 207XDepartment of Oral and Maxillofacial Diseases, Kuopio University Hospital, Kuopio, Finland ,grid.9668.10000 0001 0726 2490Faculty of Health Sciences, Institute of Dentistry, University of Eastern Finland, Kuopio, Finland
| | - Spiros Zinelis
- grid.5216.00000 0001 2155 0800Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Theodore Eliades
- grid.7400.30000 0004 1937 0650Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Plattenstrasse 11, 8032 Zurich, Switzerland
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Advances in orthodontic clear aligner materials. Bioact Mater 2022; 22:384-403. [PMID: 36311049 PMCID: PMC9588987 DOI: 10.1016/j.bioactmat.2022.10.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/05/2022] [Accepted: 10/06/2022] [Indexed: 11/24/2022] Open
Abstract
Rapid technological improvements in biomaterials, computer-aided design (CAD) and manufacturing (CAM) have endorsed clear aligner therapy (CAT) as a mainstay of orthodontic treatment, and the materials employed for aligner fabrication play an all-important role in determining the clinical performance of clear aligners. This narrative review has attempted to comprehensively encompass the entire gamut of materials currently used for the fabrication of clear aligners and elucidate their characteristics that are crucial in determining their performance in an oral environment. Historical developments and current protocols in aligner fabrication, features of contemporary bioactive materials, and emerging trends related to CAT are discussed. Advances in aligner material chemistry and engineering possess the potential to bring about radical transformations in the therapeutic applications of CAT; in the absence of which, clear aligners would continue to underperform clinically, due to their inherent biomechanical constraints. Finally, while innovations in aligner materials such as shape memory polymers, direct three-dimensional (3D) printed clear aligners and bioactive materials combined with clear aligner materials are essential to further advance the applications of CAT; increased awareness of environmental responsibilities among aligner manufacturers, aligner prescribing clinicians and aligner users is essential for better alignment of our climate change goals towards a sustainable planet.
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Albertini P, Mazzanti V, Mollica F, Pellitteri F, Palone M, Lombardo L. Stress Relaxation Properties of Five Orthodontic Aligner Materials: A 14-Day In-Vitro Study. Bioengineering (Basel) 2022; 9:bioengineering9080349. [PMID: 36004874 PMCID: PMC9405504 DOI: 10.3390/bioengineering9080349] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 07/25/2022] [Accepted: 07/27/2022] [Indexed: 11/16/2022] Open
Abstract
We aimed to investigate the stress relaxation properties of five different thermoplastic aligner materials subjected to 14 days of constant deflection. Five different thermoplastic aligner materials were selected, whose elastic properties varied: F22 Evoflex, F22 Aligner, Durasoft, Erkoloc-Pro and Duran. The static properties of these materials—in particular, stiffness, stress–strain curve and yield stress—were measured with a three-point bending test. For all the tests that were performed, a minimum of three samples per material were tested. The yield load, yield strength, deformation and particularly the stiffness of each material were found to be similar in the single-layer samples, while the double-layer samples showed far lower stiffness values and were similar one to another. F22 Evoflex and Erkoloc-Pro maintained the highest percentages of stress, 39.2% and 36.9%, respectively, during the 15-day period. Duran and Durasoft obtained the lowest final stress values, 0.5 MPa and 0.4 MPa, respectively, and the lowest percentage of normalized stress, 4.6% and 3.9%, respectively, during the 15-day period. All the materials that we tested showed a rapidity of stress decay during the first few hours of application, before reaching a plateau phase. The F22 Evoflex material showed the greatest level of final stress, with relatively constant stress release during the entire 15-day period. Further research after in vivo aging is necessary in order to study the real aligners’ behavior during orthodontic treatment.
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Affiliation(s)
- Paolo Albertini
- Department of Orthodontics, University of Ferrara, Via Luigi Borsari, 46, 44121 Ferrara, Italy; (F.P.); (M.P.); (L.L.)
- Correspondence: ; Tel.: +39-3486649586
| | - Valentina Mazzanti
- Department of Engineering, University of Ferrara, 44121 Ferrara, Italy; (V.M.); (F.M.)
| | - Francesco Mollica
- Department of Engineering, University of Ferrara, 44121 Ferrara, Italy; (V.M.); (F.M.)
| | - Federica Pellitteri
- Department of Orthodontics, University of Ferrara, Via Luigi Borsari, 46, 44121 Ferrara, Italy; (F.P.); (M.P.); (L.L.)
| | - Mario Palone
- Department of Orthodontics, University of Ferrara, Via Luigi Borsari, 46, 44121 Ferrara, Italy; (F.P.); (M.P.); (L.L.)
| | - Luca Lombardo
- Department of Orthodontics, University of Ferrara, Via Luigi Borsari, 46, 44121 Ferrara, Italy; (F.P.); (M.P.); (L.L.)
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Pratsinis H, Papageorgiou SN, Panayi N, Iliadi A, Eliades T, Kletsas D. Cytotoxicity and estrogenicity of a novel 3-dimensional printed orthodontic aligner. Am J Orthod Dentofacial Orthop 2022; 162:e116-e122. [PMID: 35842359 DOI: 10.1016/j.ajodo.2022.06.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 06/06/2022] [Accepted: 06/06/2022] [Indexed: 11/15/2022]
Abstract
INTRODUCTION Orthodontic aligners printed with in-office 3-dimensional (3D) procedures have been described, but no data on their biocompatibility exist. This study investigates the cytotoxicity and estrogenicity of a 3D-printed orthodontic aligner by assessing its biological and behavioral effects. METHODS Ten sets of 1 type of aligner were immersed in sterile deionized water for 14 days, and the cytotoxicity and estrogenicity of released factors were assessed via MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assays on human gingival fibroblasts and the estrogen-sensitive MCF-7 and the estrogen-insensitive MDA-MB-231 breast cancer cell lines. 17β-Estradiol and bisphenol-A were used as positive controls. The statistical analysis of data was performed with generalized linear models at a 0.05 level of significance. RESULTS No signs of cytotoxicity were seen for the aligner samples for concentrations (v/v) of 20% (P = 0.32), 10% (P = 0.79), or 5% (P = 0.76). The antioxidant activity expressed as the capacity to reduce intracellular levels of reactive oxygen species was not affected in the aligner samples (P = 0.08). No significant estrogenicity was induced by the aligner samples compared with eluents from the negative control for both MCF-7 (P = 0.65) and MDA-MB-231 (P = 0.78). As expected, 17β-Estradiol and bisphenol-A stimulated MCF-7 cell proliferation, whereas no effect was observed on MDA-MB-231 cells. CONCLUSIONS In conclusion, if any factors were released during the 14-day aging of 3D-printed aligners in water, these were not found to be cytotoxic for human gingival fibroblasts and did not affect their intracellular reactive oxygen species levels. Moreover, no estrogenic effects of these putative eluates were observed based on an E-screen assay.
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Affiliation(s)
- Harris Pratsinis
- Laboratory of Cell Proliferation and Ageing, Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos," Athens, Greece
| | - Spyridon N Papageorgiou
- Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland
| | - Nearchos Panayi
- Department of Dentistry, European University Cyprus, Nicosia, Cyprus; Private practice, Limassol, Cyprus
| | - Anna Iliadi
- Department of Dental Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Theodore Eliades
- Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
| | - Dimitris Kletsas
- Laboratory of Cell Proliferation and Ageing, Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos," Athens, Greece
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Levent Paralı, Koç M, Yıldız Z. 2D/3D Direct Writing of Thermoplastics through Electrohydrodynamic Printing. POLYMER SCIENCE SERIES A 2022. [DOI: 10.1134/s0965545x22700183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Casavola C, Pappalettera G, Pappalettere C, Patronelli M, Renna G, Laurenziello M, Ciavarella D. A full-field DIC analysis of the mechanical-deformation behavior of polyethylene terephthalate glycol (PET-G) aligners. J Mech Behav Biomed Mater 2022; 134:105391. [PMID: 35930946 DOI: 10.1016/j.jmbbm.2022.105391] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 07/15/2022] [Accepted: 07/17/2022] [Indexed: 11/16/2022]
Abstract
OBJECTIVES The aim was to investigate the full-field mechanical-deformation behavior of clear aligners made by polyethylene terephthalate glycol (PET-G) subjected to cyclic compression tests. METHODS Digital Image Correlation (DIC) (Chu et al., 1985; Schreier et al., 2009), a contactless full-field measurement technique, and Optical Microscope (OM) analysis were applied to study two PET-G aligners thermoformed from discs of a thickness of 0.75 mm and 0.88 mm. The clear aligners were placed on dental shape resin casts and were subjected to cyclic compression up to 13000 load cycles from 0 to 50 N at room temperature. The chosen number of load cycles simulates the average load history to which an aligner is subjected for one week. Local displacements and strains were measured for each test at 2, 6, 10, 20, 1000, 5000 and 13000 loading cycles. RESULTS Both aligners showed greater displacements in the early stages of loading, more pronounced for the 0.88 mm one. Local displacement and strain maps are derived both along the load direction and to the transverse one (never done from other researchers). Load-displacement cyclic curves allowed to evaluate the evolution of the stored energy and the stiffness during the test. The OM analyses showed significant morphological variations on the aligners' surface, such as wear and tear, high depressions and cracks, especially for the 0.75 mm specimen. SIGNIFICANCE Full-field analysis allowed to understand the mechanical behavior of device with complex geometry and complex load distribution, like invisible aligners. The knowledge of the stiffness and the direction of the total displacement helps the orthodontist to implement the best strategy to improve the patient's comfort and the treatment time.
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Affiliation(s)
- Caterina Casavola
- Politecnico di Bari, Dipartimento di Meccanica Matematica e Management, Via Orabona 4, 70125, Bari, Italy
| | - Giovanni Pappalettera
- Politecnico di Bari, Dipartimento di Meccanica Matematica e Management, Via Orabona 4, 70125, Bari, Italy
| | - Carmine Pappalettere
- Politecnico di Bari, Dipartimento di Meccanica Matematica e Management, Via Orabona 4, 70125, Bari, Italy
| | - Marika Patronelli
- Politecnico di Bari, Dipartimento di Meccanica Matematica e Management, Via Orabona 4, 70125, Bari, Italy.
| | - Gilda Renna
- Politecnico di Bari, Dipartimento di Meccanica Matematica e Management, Via Orabona 4, 70125, Bari, Italy
| | - Michele Laurenziello
- Università di Foggia, Dipartimento di Medicina Sperimentale e Clinica, Via Gramsci 89/91, 71122, Foggia, Italy
| | - Domenico Ciavarella
- Università di Foggia, Dipartimento di Medicina Sperimentale e Clinica, Via Gramsci 89/91, 71122, Foggia, Italy
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Porojan L, Toma FR, Bîrdeanu MI, Vasiliu RD, Uțu ID, Matichescu A. Surface Characteristics and Color Stability of Dental PEEK Related to Water Saturation and Thermal Cycling. Polymers (Basel) 2022; 14:polym14112144. [PMID: 35683817 PMCID: PMC9183185 DOI: 10.3390/polym14112144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/15/2022] [Accepted: 05/23/2022] [Indexed: 12/10/2022] Open
Abstract
(1) Background: The study was undertaken to evaluate the surface characteristics, microhardness, and color stability of PEEK materials related to water saturation and in vitro aging. (2) Methods: Custom specimens of unmodified and modified PEEK CAD/CAM materials were investigated: BioHPP, a ceramic reinforced PEEK, and Finoframe PEEK and Juvora medical PEEK, 100% PEEK materials. Forty-eight plates were sectioned in rectangular slices. The specimens were immersed in distilled water at 37 °C for a period of 28 days, and then subjected to aging by thermal cycling (10,000 cycles). Surface roughness was measured with a contact profilometer; nanosurface topographic characterization was made by Atomic Force Microscopy; Vickers hardness measurements were performed with a micro-hardness tester; color changes were calculated. All registrations were made before immersion in water and then subsequently once a week for 4 weeks, and after thermocycling. (3) Results: The studied reinforced and unfilled PEEK materials reached water saturation after the first week of immersion, without significant differences between them. The most affected from this point of view was the reinforced PEEK material. Thermocycling induces a significant increase inmicroroughness, without significant differences between the studied materials. In relation to the nanosurface topography and roughness, the reinforced PEEK material was the least modified by aging. The color changes after 4 weeks of water immersion and one year of simulated in vitro aging ranged from extremely slight to slight, for all materials. (4) Conclusions: Water absorption was associated with a decrease in microhardness. Surface characteristics are affected by water immersion and thermocycling. Perceivable or marked color changes of the materials were not detected during the study.
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Affiliation(s)
- Liliana Porojan
- Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, Victor Babeș University of Medicine and Pharmacy Timișoara, Eftimie Murgu Square No. 2, 300041 Timișoara, Romania; (F.R.T.); (R.D.V.)
- Correspondence:
| | - Flavia Roxana Toma
- Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, Victor Babeș University of Medicine and Pharmacy Timișoara, Eftimie Murgu Square No. 2, 300041 Timișoara, Romania; (F.R.T.); (R.D.V.)
| | - Mihaela Ionela Bîrdeanu
- National Institute for Research and Development in Electrochemistry and Condensed Matter, 300569 Timisoara, Romania;
| | - Roxana Diana Vasiliu
- Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, Victor Babeș University of Medicine and Pharmacy Timișoara, Eftimie Murgu Square No. 2, 300041 Timișoara, Romania; (F.R.T.); (R.D.V.)
| | - Ion-Dragoș Uțu
- Department of Materials and Fabrication Engineering, Politehnica University Timişoara, Bulevard MihaiViteazul nr.1, 300222 Timişoara, Romania;
| | - Anamaria Matichescu
- Department of Preventive, Community Dentistry and Oral Health, Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, Victor Babes University of Medicine and Pharmacy Timișoara, Eftimie Murgu Square No. 2, 300041 Timișoara, Romania;
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Optical Behavior and Surface Analysis of Dental Resin Matrix Ceramics Related to Thermocycling and Finishing. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12094346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Color preservation of esthetic dental restorative materials in the oral environment represents, besides longevity, a concern, and there is still limited knowledge related to the effect of aging on the optical behavior of resin matrix ceramics. The study analyzed the finishing and thermocycling of resin matrix ceramic material surfaces, in order to assess their consequences on optical properties. Five resin matrix CAD/CAM ceramics, namely a polymer-infiltrated ceramic and four types of nanoparticle-filled resins, were selected for the study, and finished by polishing and glazing. Thermocycling was chosen as the in vitro aging method. Surface microroughness, optical and hardness evaluations were achieved before and after artificial aging. Statistical analyses were performed with IBM SPSS Statistics software at a significance value of p < 0.05. Micro-roughness values increased after thermocycling, but were kept under the clinically accepted values. The optical characteristics of resin matrix ceramics were not significantly modified by thermocycling. Values of the glazed samples became closer to those of the polished ones, after hydrothermal aging, even if the differences were insignificant. Thermocycling significantly decreased the microhardness, mainly for glazed samples. This could be the consequence of glaze removal during thermocycling, which means that glazes provide a surface protection for a limited time.
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Kwok M, Porto B, Mohebi S, Zhu L, Hans M. Physical and chemical properties of five different clear thermoplastic materials. J Appl Polym Sci 2022. [DOI: 10.1002/app.51957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Man‐Hin Kwok
- Department of Macromolecular Science and Engineering Case Western Reserve University Cleveland Ohio USA
| | - Betina Porto
- Department of Orthodontics, School of Dental Medicine Case Western Reserve University Cleveland Ohio USA
| | - Shadi Mohebi
- Department of Orthodontics, School of Dental Medicine Case Western Reserve University Cleveland Ohio USA
| | - Lei Zhu
- Department of Macromolecular Science and Engineering Case Western Reserve University Cleveland Ohio USA
| | - Mark Hans
- Department of Orthodontics, School of Dental Medicine Case Western Reserve University Cleveland Ohio USA
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Lee SY, Kim H, Kim HJ, Chung CJ, Choi YJ, Kim SJ, Cha JY. Thermo-mechanical properties of 3D printed photocurable shape memory resin for clear aligners. Sci Rep 2022; 12:6246. [PMID: 35428796 PMCID: PMC9012852 DOI: 10.1038/s41598-022-09831-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 03/14/2022] [Indexed: 11/22/2022] Open
Abstract
To overcome the limitations of the conventional vacuum thermoforming manufacturing method, direct 3D printing of clear aligners has been developed. The present study investigated the thermo-mechanical and viscoelastic properties of a photocurable resin TC-85, which is a new material for the direct 3D printed clear aligners, comparing to a conventional thermoplastic material polyethylene terephthalate glycol. Dynamic mechanical analysis was performed to analyse the mechanical behaviours of the two materials at 37 °C and 80 °C, respectively. Furthermore, the shape memory property of the two materials was evaluated using a U-shape bending test, and the shape recovery ratio for 60 min at 37 °C was calculated. The results indicate that TC-85 can constantly apply a light force to the teeth when used for the 3D printed clear aligners, owing to its flexibility and viscoelastic properties. In addition, it is expected that the force decay induced by repeated insertion of the clear aligners will be reduced and a constant orthodontic force will be maintained. Furthermore, its geometric stability at high temperatures and the shape memory properties provide advantages for the clinical application.
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Affiliation(s)
- Se Yeon Lee
- Department of Orthodontics, College of Dentistry, Yonsei University, Seoul, Korea
| | - Hoon Kim
- Research Institute of Agriculture and Life Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea.,Graphy Inc., Graphy R&D Center, Seoul, Korea
| | - Hyun-Joong Kim
- Research Institute of Agriculture and Life Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea.,Laboratory of Adhesion and Bio-Composites, Department of Agriculture, Forestry and Bioresources, Seoul National University, Seoul, Korea
| | - Chooryung J Chung
- Department of Orthodontics, Gangnam Severance Hospital, Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, Seoul, Korea
| | - Yoon Jeong Choi
- Department of Orthodontics, Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea
| | - Su-Jung Kim
- Department of Orthodontics, Kyung Hee University School of Dentistry, Seoul, Korea
| | - Jung-Yul Cha
- Department of Orthodontics, Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea.
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Takara Y, Haga S, Kimura H, Maki K. Mechanical analysis of factors affecting clear aligner removability. Dent Mater J 2022; 41:534-544. [PMID: 35321972 DOI: 10.4012/dmj.2021-176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
It is difficult to control corrective forces in orthodontic treatment with clear aligners. The grip of aligners on teeth is important to ensure accurate corrective forces from aligners. This study aimed to measure the gripping force of aligners under various conditions to clarify factors that influence it. We created aligners with different attachment morphologies and placement sites and different margin lengths. We developed a device to measure the mechanics involved in the removal of these aligners. The gripping force was evaluated at five different aligner removal sites on the teeth. We found that the gripping force of the aligner was the weakest on the lingual side of the first molar and strongest on the labial side of the central incisors and that the attachment morphology and placement sites affected the gripping force of aligners.
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Affiliation(s)
- Yurie Takara
- Department of Orthodontics, School of Dentistry, Showa University
| | - Shugo Haga
- Department of Orthodontics, School of Dentistry, Showa University
| | - Hitoshi Kimura
- Department of Engineering Design, Tamagawa University College of Engineering
| | - Koutaro Maki
- Department of Orthodontics, School of Dentistry, Showa University
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Masking Abilities of Dental Cad/Cam Resin Composite Materials Related to Substrate and Luting Material. Polymers (Basel) 2022; 14:polym14030364. [PMID: 35160353 PMCID: PMC8838689 DOI: 10.3390/polym14030364] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/11/2022] [Accepted: 01/15/2022] [Indexed: 12/05/2022] Open
Abstract
An outstanding treatment challenge related to aesthetic monolithic materials is to mask discolored substrates in aesthetic areas. The purpose of the study is to evaluate the substrate masking ability of different resin composite materials and the influence of their association with luting agents and substrates. Five types of 2M2 HT (high translucency) resin composite materials were selected: Vita Enamic [E] and four types of nanoparticle-filled composites Lava Ultimate [L], Cerasmart [C], Shofu HC [S], and Hyramic [H]. Resin composite Vita VM LC with different shades was used for the substrates: 2M2, 3M2, and CP2. Variolink Esthetic Try-inpastes neutral, light+, and warm+ colors were chosen to simulate the luting agent color. Optical parameters (TP (translucency), CR (contrast ratio), and OP (opalesce)) and color differences ΔE (chromatic difference) were calculated. Statistical analyses were performed to evaluate the comparisons between the groups and establish correlations. TP average values for all materials were in the range of 21.49–24.53. OP average values were in the rage of 6.31–7.85. OP is moderate positive correlated to TP and CR is negative and strong correlated to TP. Related to materials, average color changes decrease as following: E > H > C > L > S. Referring to the tryin material, warm colors induce marked color changes of the restoration. The differences of the color changes determined by all studied substrates are significant. For the final aesthetic aspect of the restoration, it is essential to consider the underlying dental structure, luting agent, and restoration material as a whole unit. The masking ability of the investigated resin matrix ceramic materials materials shows differences, the best behavior demonstrated Shofu HC and Lava Ultimate. Marked color changes are related to high chroma substrates. For substrates with a darker color, the association with warm try-in pastes lead to marked color changes, but with neutral and light try-in pastes at most perceivable.
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Bresolato D, Volpato A, Favero L, Favero R. Effect of Water-Based Disinfectants or Air-Drying on Dimensional Changes in a Thermoplastic Orthodontic Aligner. MATERIALS 2021; 14:ma14247850. [PMID: 34947444 PMCID: PMC8703843 DOI: 10.3390/ma14247850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 12/14/2021] [Accepted: 12/16/2021] [Indexed: 12/03/2022]
Abstract
The polymer structure of thermoplastic materials currently used to make aligners is altered by the oral conditions and this negatively affects their capacity to move teeth. This study aimed to compare different options for storing aligners when not in use by superimposing successive 3D images to identify which storage method least affects material shape and weight. Fifty PET-G aligners, produced using the CA Digital method, were divided into four groups (1A, 1B, 1C, and 2D) and were stored for 18 h a day in artificial saliva at 37 °C. Then, to mimic their storage conditions when not in use, aligners in group 1A were immersed for the remaining 8 hours a day in bicarbonate solution, those in group 1B in chlorhexidine solution, those in group 1C in distilled water, and those in group 2D were stored dry. The samples were scanned at the baseline (before the immersion cycles began) and again two weeks later. The digital scans were superimposed and the median deformation, its variability, and weight differences were recorded for each group. Statistical analysis showed aligner deformation (expansion) in all three groups stored in wet conditions, with a statistically significant difference between groups 1A and 1C. Aligners in group 2D shrank slightly, and to a significantly greater degree with respect to group 1C. Variability in the degree of deformation was similar among the three groups stored in wet conditions, but significantly greater in group 2D. Weight gains were recorded in all four groups, the smallest in group 2D and the largest in group 1A. Storing aligners in dry conditions promoted lower deformation in the material, involving a slight shrinkage, whereas wet storage conditions caused an expansion of the aligner, especially when distilled water is used.
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Pratto I, Busato MCA, Bittencourt PRS. Thermal and mechanical characterization of thermoplastic orthodontic aligners discs after molding process. J Mech Behav Biomed Mater 2021; 126:104991. [PMID: 34864573 DOI: 10.1016/j.jmbbm.2021.104991] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/17/2021] [Accepted: 11/18/2021] [Indexed: 10/19/2022]
Abstract
Polymeric aesthetic aligners were introduced in orthodontics as an innovative alternative to fixed appliances, however, their compositions and the thermal molding process may influence the biomechanical characteristics of these aligners. In this study four different clear aligner brands were used, ACE 035 Essix, C + Essix, Crystal 0.75 and Crystal 1.0, whose aim was to identify the thermal-processing influence on the mechanical and physicochemical properties of these materials, and to suggest a orthodontic sequence of wear for these appliances to achieve more effective treatment results. For the tensile tests the sample size calculation was based on probability distributions from the F test. The effect size used was 0.3, type 1 error of 0.05. Statistical Yield strength and Young's Modulus results were evaluated using the Shapiro-Wilk test. The groups were compared using the parametric test of analysis of variance, with Tukey post-test. Differences were statistically considered at the p < 0.05. The Infrared spectroscopy analysis showed no changes in the samples' chemical structure after thermal-processing. However, in the polypropylene aligner, differences were verified in the region attributed to the crystalline phase. Differential Scanning Calorimetry analysis for the same sample showed a crystallinity fraction decrease due to relaxation between polymer chains after molding. In the tensile tests evaluated, the tensile strength and 'Young's modulus presented higher values for aligners containing 100% polyethylene terephthalate glycol. Performing an analogy exercise of the properties of orthodontic wires used in conventional fixed appliances and, relating them to orthodontic plastics, aligners composed of different materials and/or thicknesses could be used in increasing sequence in terms of the modulus of elasticity, starting with C+, which has a lower elastic modulus value, using the ACE 035 as an intermediate and finishing with the Crystal 0.75 and 1.0, providing the desired stiffness to the aligners for the final phase.
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Affiliation(s)
- Isabella Pratto
- Universidade Estadual do Oeste do Paraná (UNIOESTE), Departamento de Odontologia, ZIP 85819-110, Cascavel, Paraná, Brazil
| | - Mauro Carlos Agner Busato
- Universidade Estadual do Oeste do Paraná (UNIOESTE), Departamento de Odontologia, ZIP 85819-110, Cascavel, Paraná, Brazil
| | - Paulo Rodrigo Stival Bittencourt
- Universidade Tecnológica Federal do Paraná (UTFPR), Departamento Acadêmico de Química, Bloco I4, ZIP 85884-000, Medianeira, Paraná, Brazil.
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Porojan L, Toma FR, Vasiliu RD, Topală FI, Porojan SD, Matichescu A. Optical Properties and Color Stability of Dental PEEK Related to Artificial Ageing and Staining. Polymers (Basel) 2021; 13:polym13234102. [PMID: 34883606 PMCID: PMC8658820 DOI: 10.3390/polym13234102] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 11/20/2021] [Accepted: 11/21/2021] [Indexed: 12/11/2022] Open
Abstract
Considering that the processes of PEEK discoloration caused by either intrinsic or extrinsic factors require elucidation, the aim of this study was to investigate the long-term effect of the combined action of ageing and immersing solutions on the optical properties and color stability of PEEK material, related to surface processing (polishing or glazing). (2) Methods: This study aims to determine the influence of different ageing and staining protocols on optical properties, color changes, and surface roughness of a reinforced PEEK material (bioHPP, Bredent, Senden, Germany). For ageing, specimens were submitted to 5000 cycles in a 55 °C bath and a 5 °C bath filled with distilled water. For staining, thermal cycling was performed in a hot coffee bath (55 °C) and a bath filled with distilled water (37 °C) and in a cold juice bath (5 °C) and a bath filled with distilled water (37 °C). Translucency (TP) and opalescence (OP) parameters were determined, the total color change value (ΔΕ*) was calculated, specimens’ surface roughness was analyzed, and statistical analyses were performed. (3) Results: The mean TP values of the studied samples were in the interval of 1.25–3.60, which is lower than those reported for natural teeth or other aesthetic restoration materials. The OP values of PEEK were registered in the range of 0.27–0.75, being also lower than those of natural teeth or other aesthetic restoration materials. OP has a very strong positive relationship with TP. The mean registered Ra values for all subgroups were below 0.13 µm. Artificial ageing and staining in hot coffee proved to increase the roughness values. (4) Conclusions: The glazing of PEEK has a favorable effect on surface roughness and opalescence, irrespective of the artificial ageing or staining protocols. Artificial ageing damages the color stability and roughness of PEEK, regardless of surface processing, and decreases the translucency and opalescence of glazed surfaces. Immersion in hot coffee leads to perceivable discolorations.
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Affiliation(s)
- Liliana Porojan
- Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, “Victor Babeș” University of Medicine and Pharmacy Timișoara, Eftimie Murgu Sq. No. 2, 300041 Timișoara, Romania; (L.P.); (F.R.T.)
| | - Flavia Roxana Toma
- Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, “Victor Babeș” University of Medicine and Pharmacy Timișoara, Eftimie Murgu Sq. No. 2, 300041 Timișoara, Romania; (L.P.); (F.R.T.)
| | - Roxana Diana Vasiliu
- Department of Dental Prostheses Technology (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, “Victor Babeș” University of Medicine and Pharmacy Timișoara, Eftimie Murgu Sq. No. 2, 300041 Timișoara, Romania; (L.P.); (F.R.T.)
- Correspondence:
| | - Florin-Ionel Topală
- Department of Prosthodontics, Faculty of Dental Medicine, “Victor Babeș” University of Medicine and Pharmacy Timișoara, Eftimie Murgu Sq. No. 2, 300041 Timișoara, Romania;
| | - Sorin Daniel Porojan
- Department of Oral Rehabilitation (Dental Technology), Center for Advanced Technologies in Dental Prosthodontics, Faculty of Dental Medicine, “Victor Babeș” University of Medicine and Pharmacy Timișoara, Eftimie Murgu Sq. No. 2, 300041 Timișoara, Romania;
| | - Anamaria Matichescu
- Department of Preventive, Community Dentistry and Oral Health, Faculty of Dental Medicine, “Victor Babes” University of Medicine and Pharmacy Timișoara, 14A Tudor Vladimirescu Ave., 300173 Timisoara, Romania;
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Zinelis S, Panayi N, Polychronis G, Papageorgiou SN, Eliades T. Comparative analysis of mechanical properties of orthodontic aligners produced by different contemporary 3D printers. Orthod Craniofac Res 2021; 25:336-341. [PMID: 34569692 PMCID: PMC9544566 DOI: 10.1111/ocr.12537] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 09/22/2021] [Accepted: 09/23/2021] [Indexed: 12/11/2022]
Abstract
OBJECTIVE The aim of this study was to compare the mechanical properties of orthodontic aligners among different commercially available 3D printing devices. MATERIALS AND METHODS Five 3D printers (Ka:rv LP 550, Swinwon; "KAR"), (L120, Dazz 3D; "L12"), (MiiCraft 125, Miicraft Jena; "MIC"), (Slash 2, Uniz; "SLS") and (Pro 95, SprintRay; "PRO") were used to prepare orthodontic aligners with dental resin (Tera Harz TC-85DAW, Graphy). The central incisors of each aligner were cut, prepared and evaluated in terms of Martens-Hardness (HM), indentation-modulus (EIT ) and elastic-index (ηIT ) as per ISO14577-1:2002. Force-indentation curves were recorded and differences among printers were checked with generalized linear regressions (alpha=5%). RESULTS Statistically significant differences were seen for all mechanical properties (P < .05), which were in descending order: HM (N/mm2 ) as median (Interquartile Range [IQR]): SLS 108.5 (106.0-112.0), L12 103.0 (102.0-107.0), KAR 101.5 (97.5-103.0), MIC 100.0 (97.5-101.5) and PRO 94.0 (93.0-96.0); EIT (MPa) as mean (Standard Deviation [SD]): SLS 2696.3 (124.7), L12 2627.8 (73.5), MIC 2566.2 (125.1), KAR 2565.0 (130.2) and PRO 2491.2 (53.3); and ηIT (%) as median (IQR): SLS 32.8 (32.3-33.1), L12 31.6 (30.8-32.3), KAR 31.3 (30.9-31.9), MIC 30.5 (29.9-31.2) and PRO 29.5 (29.1-30.0). Additionally, significant differences existed between liquid crystal display (LCD) and digital light processing (DLP) printers for HM (P < .001), EIT (P = .002) and ηIT (P < .001), with aligners from the former having higher values than aligners from the latter printer. CONCLUSION Under the limitations of this study, it may be concluded that the mechanical properties of 3D-printed orthodontic aligners are dependent on the 3D printer used, and thus, differences in their clinical efficacy are anticipated.
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Affiliation(s)
- Spiros Zinelis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | | | - Georgios Polychronis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Spyridon N Papageorgiou
- Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland
| | - Theodore Eliades
- Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland
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Alexandropoulos A, Al Jabbari YS, Zinelis S, Eliades T. Chemical and mechanical characteristics of contemporary thermoplastic orthodontic materials. AUSTRALASIAN ORTHODONTIC JOURNAL 2021. [DOI: 10.21307/aoj-2020-151] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Abstract
Aim
The aim of the present study was to characterise the chemical and mechanical properties of contemporary thermoplastic orthodontic materials.
Materials and methods
Four thermoplastic materials were tested: Clear Aligner (Scheu-Dental), ACE and A+ (Dentsply), and Invisalign (Align Technology). Eight appliances were fabricated from each material and a small portion from each was analysed by ATR-FTIR spectroscopy. The appliances were cut and, following metallographic grinding and polishing, were subjected to instrumented indentation testing (IIT) employing a Vickers indenter. Martens Hardness (HM), Indentation Modulus (EIT), Elastic to Total Work Ratio (elastic index (ηIT)) and Indentation Creep (CIT) were determined according to ISO 14577-1. The mean values of the mechanical properties were statistically analysed by one way ANOVA and Tukey Kramer multiple comparison test at a = 0.05.
Results
ATR-FTIR analysis identified that Invisalign was a polyurethane-based material, whereas the others were based on polyester, polyethylene glycol terephthalate (PETG). Invisalign showed higher hardness and modulus values, a slightly higher brittleness and lesser creep resistance compared with the PETG-based products.
Conclusions
The materials tested showed significant differences in their chemical structure and mechanical properties and therefore differences in their clinical behaviour are anticipated.
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Affiliation(s)
- Alexandras Alexandropoulos
- * Department of Biomaterials , School of Dentistry , National and Kapodistrian University of Athens , Athens , Greece
| | - Youssef S. Al Jabbari
- * Prosthetic Dental Sciences Department , College of Dentistry , King Saud University , Riyadh , Saudi Arabia
- + Dental Biomaterials Research and Development Chair , King Saud University , Riyadh , Saudi Arabia
| | - Spiros Zinelis
- * Department of Biomaterials , School of Dentistry , National and Kapodistrian University of Athens , Athens , Greece
- + Dental Biomaterials Research and Development Chair , King Saud University , Riyadh , Saudi Arabia
| | - Theodore Eliades
- ± Clinic of Orthodontics and Pediatric Dentistry , Center of Dental Medicine , University of Zurich , Zurich , Switzerland
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The force effects of two types of polyethylene terephthalate glyc-olmodified clear aligners immersed in artificial saliva. Sci Rep 2021; 11:10052. [PMID: 33980889 PMCID: PMC8115163 DOI: 10.1038/s41598-021-89425-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 04/20/2021] [Indexed: 11/08/2022] Open
Abstract
Numerous factors can influence the force exerted by clear aligners on teeth. This study aimed to investigate the stability of the force delivered by two different material appliances. 90 clear aligners with 2 materials and three different activations were designed and fabricated. Then, a device was employed to measure the force generated by the two types of PET-G material appliances immersed in artificial saliva for 0, 3, 7, 10, 14 days. Scanning electron microscopy was applied to observe the morphologic alterations on the aligner surfaces, respectively. The forces generated by different activation appliance exhibited differently, 0.0 mm < 0.1 mm < 0.2 mm. In addition, increasing the immersion times and the orthodontic force also decreased, but the forces decreased differently. Compared with the forces of conventional PETG appliances with 0.20 mm activation, the modified PETG appliances with the same activation exhibited significantly higher mean force. When comparing the mean force for modified PETG appliances after 10 and 14 days with conventional PETG appliances, the delivery forces exhibited significant differences (P < 0.05). The force delivered by both materials decreased obviously following artificial saliva immersion, and the force generated by modified aligners exhibited better stability than conventional aligners.
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Chan E, Panayi N, Polychronis G, Papageorgiou SN, Zinelis S, Eliades G, Eliades T. In-house 3D-printed aligners: effect of in vivo ageing on mechanical properties. Eur J Orthod 2021; 44:51-55. [PMID: 33950232 DOI: 10.1093/ejo/cjab022] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE To investigate alterations in the mechanical properties of in-house three-dimensional (3D) printed orthodontic aligners after intraoral ageing. MATERIALS AND METHODS Sixteen 3D-printed aligners (TC-85DAC resin, Graphy, Seoul, Korea) were used for the purpose of the study, which were divided into 10 control (not used) aligners and 6 materials retrieved from 4 patients after 1-week service (retrieved group). Samples from the control group were analysed by attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) spectroscopy. Samples from control/retrieved groups were embedded resin and subjected to instrumented indentation testing (IIT) to record force-indentation depth curves, calculating the following (as per ISO 14577-1, 2002 standard): Martens hardness (HM), indentation modulus (EIT), and elastic index (ηIT), and the indentation relaxation index (RIT). Differences between control and retrieved 3D-printed aligners were checked with Mann-Whitney/t-tests at an alpha = 5%. RESULTS ATR-FTIR analysis showed that aligners were made of a vinyl ester-urethane material. The results of the IIT testing were: HM (control: median 91.5 N/mm2, interquartile range [IQR] 88.0-93.0/as-retrieved: median 90.5 N/mm2, IQR 89.0-93.0); EIT (control, mean 2616.3 MPa, standard deviation [SD] 107.0 MPa/retrieved, mean 2673.2 MPa, SD 149.4 MPa); ηIT (control: median 28.6%, IQR 28.2-30.9%/as-retrieved: median 29.0%, IQR 28.7-29.2%); and RIT (control: median 45.5%, IQR 43.0-47.0%/as-retrieved: median 45.1%, IQR 45.0-45.3%). No differences between as-retrieved and control aligners were found for any of the mechanical properties tested (P > 0.05 in all instances). CONCLUSION The mechanical properties of the in-house 3D-printed aligners tested were not affected after 1 week in service period.
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Affiliation(s)
- Esad Chan
- Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland
| | | | - Georgios Polychronis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Spyridon N Papageorgiou
- Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland
| | - Spiros Zinelis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - George Eliades
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Theodore Eliades
- Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland
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Li S, Wang T, Hu J, Li Z, Wang B, Wang L, Zhou Z. Surface porous poly-ether-ether-ketone based on three-dimensional printing for load-bearing orthopedic implant. J Mech Behav Biomed Mater 2021; 120:104561. [PMID: 33965810 DOI: 10.1016/j.jmbbm.2021.104561] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 04/16/2021] [Accepted: 04/19/2021] [Indexed: 02/07/2023]
Abstract
Poly-ether-ether-ketone (PEEK) possesses excellent biocompatibility and similar elastic modulus as bones but yet suffers from poor osseointegration. In order to balance PEEK's mechanical and osseointegration properties, a novel surface porous PEEK (SP-PEEK) is successfully fabricated by fused deposition modelling three-dimensional printing (FDM 3DP) and characterized by mechanical and osteogenesis in vitro tests. Moreover, the effects of pore diameter and pore layer number on the mechanical behaviors of SP-PEEK are investigated by theoretical model and numerical simulation. Comparison among experimental, theoretical and simulation results show good agreement. As pore diameter decreases, the equivalent strength and modulus become more sensitive to the decrease of pore layer number. In addition, the SP-PEEK exhibits the mechanical properties within the range of human trabecular bone and cortical bone, and thus can be tailored to mimic human bone by adjusting the pore diameter and pore layer number, which is benefit to mitigate stress shielding. The effects of pore diameter on the cell proliferation and osteogenic differentiation of SP-PEEK are tested by the co-culture of osteoblast precursor cells (MC3T3-E1) and SP-PEEK round discs. Results showcase that porous surface improves the osteogenesis in vitro, and the SP-PEEK group that the pore diameter is 0.6 mm exhibits optimal-performance osteogenesis in vitro.
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Affiliation(s)
- Shuai Li
- National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Harbin Institute of Technology, Harbin, 150080, China
| | - Tianyu Wang
- Department of Orthopedics, First Affiliated Hospital of Harbin Medical University, Harbin, 150001, China
| | - Jiqiang Hu
- National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Harbin Institute of Technology, Harbin, 150080, China
| | - Zhibin Li
- National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Harbin Institute of Technology, Harbin, 150080, China
| | - Bing Wang
- National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Harbin Institute of Technology, Harbin, 150080, China.
| | - Lianchao Wang
- National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Harbin Institute of Technology, Harbin, 150080, China
| | - Zhengong Zhou
- National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Harbin Institute of Technology, Harbin, 150080, China
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Inoue S, Yamaguchi S, Uyama H, Yamashiro T, Imazato S. Orthodontic Aligner Incorporating Eucommia ulmoides Exerts Low Continuous Force: In Vitro Study. MATERIALS 2020; 13:ma13184085. [PMID: 32937965 PMCID: PMC7560245 DOI: 10.3390/ma13184085] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 09/11/2020] [Accepted: 09/11/2020] [Indexed: 01/26/2023]
Abstract
The aim of this study was to investigate the orthodontic force exerted by thermoplastic orthodontic appliances incorporating Eucommiaulmoides in terms of usefulness as the aligner-type orthodontic device. Erkodur, Essix C+®, Eucommia elastomer, and edgewise brackets were used (n = 3, each; thickness = 1.0 mm, each). The orthodontic force on the upper right incisor was measured every 24 h for two weeks using a custom-made measuring device. The force of the Eucommia elastomer (4.25 ± 0.274 N) and multi bracket system (5.32 ± 0.338 N) did not change from the beginning to the end (p > 0.01). The orthodontic force exerted by the Eucommia elastomer was lower than that of the multi-bracket orthodontic appliance from the beginning to the end. The force of Erkodur significantly decreased from the beginning to 24 h (6.47 ± 1.40 N) and 48 h (3.30 ± 0.536 N) (p < 0.01). The force of Essix C+® significantly decreased from the beginning (13.2 ± 0.845 N) to 24 h (8.77 ± 0.231 N) (p < 0.01). The thermoplastic orthodontic appliance made of Eucommia elastomer continuously exerted a constant orthodontic force for two weeks under water immersion conditions. The orthodontic force of Eucommia elastomer was found to be similar to the orthodontic force exerted by the multi-bracket orthodontic appliance with 0.019 × 0.025 in nickel–titanium wire. These results suggest that the Eucommia elastomer has possibly become one of the more useful materials to form thermoplastic orthodontic appliance exerting low continues orthodontic force.
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Affiliation(s)
- Sayuri Inoue
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan; (S.I.); (S.I.)
- Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan;
| | - Satoshi Yamaguchi
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan; (S.I.); (S.I.)
- Correspondence: ; Tel.: +81-6-6879-2917
| | - Hiroshi Uyama
- Division of Applied Chemistry, Osaka University Graduate School of Engineering, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan;
| | - Takashi Yamashiro
- Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan;
| | - Satoshi Imazato
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan; (S.I.); (S.I.)
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Porojan L, Vasiliu RD, Porojan SD, Bîrdeanu MI. Surface Quality Evaluation of Removable Thermoplastic Dental Appliances Related to Staining Beverages and Cleaning Agents. Polymers (Basel) 2020; 12:polym12081736. [PMID: 32756439 PMCID: PMC7464035 DOI: 10.3390/polym12081736] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 07/30/2020] [Accepted: 08/01/2020] [Indexed: 01/04/2023] Open
Abstract
(1) Background: Thermoplastic materials are not inert and subject to changes in the oral environment, which affect their surface quality. Color stability and topographic characteristics of clear thermoplastic appliances are critical considerations. The study aimed to evaluate the optical changes and surface topography of different thermoplastic materials related to staining beverages and cleaning agents. (2) Methods: Thermoplastic polyethylene terephthalate glycol (PET-G) material specimens were selected for the study: S (Duran, Scheu-Dental GmbH, Iserlohn, Germany), D (Biolon, Dreve Dentamid GmbH, Unna, Germany), and B (Crystal, Bio Art Dental Equipment, Sao Carlos, Brazil). Four different media were involved for immersion: coffee (C) and black tea (T) at 55 °C, Coca-Cola (K) at 5 °C, and distilled water (W) at 22 °C. As for cleaning, chemical options and mechanical brushing were selected (P-powder, T-tablets, and X-brushing). Color changes, and mean surface roughness were measured at 24 h, 48 h, and after 7 days. Statistical analysis was performed. After the testing period, atomic force microscopy (AFM) analyses and SEM images were registered in order to characterize the surface topography. (3) Results: Quantitative color change evaluations revealed a slight change in color after 24 h and an extremely marked change after 48 h, respective 7 days. Mean roughness values are kept below the clinically acceptable limit of 0.20 µm for all samples. Related to mean nanoroughness values Sa, and 3D evaluations of the surface quality, Biolon samples have demonstrated the most constant behavior, while Crystal samples are visibly influenced by water immersion. Related to the cleaning method, the topography of Duran samples was influenced by mechanical brushing. (4) Conclusions: Nanoscale investigations provided high accuracy and more realistic surface quality examinations of the examined samples compared to profilometry. Both SEM and AFM should be used for a more detailed description of the surface topography.
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Affiliation(s)
- Liliana Porojan
- Department of Dental Prostheses Technology (Dental Technology), “Victor Babeș” University of Medicine and Pharmacy Timișoara, Romania, Eftimie Murgu Sq. no. 2, 300041 Timișoara, Romania;
| | - Roxana-Diana Vasiliu
- Department of Dental Prostheses Technology (Dental Technology), “Victor Babeș” University of Medicine and Pharmacy Timișoara, Romania, Eftimie Murgu Sq. no. 2, 300041 Timișoara, Romania;
- Correspondence: ; Tel.: +40-745225523
| | - Sorin-Daniel Porojan
- Department of Oral Rehabilitation (Dental Technology), “Victor Babeș” University of Medicine and Pharmacy Timișoara, Romania, Eftimie Murgu Sq. no. 2, 300041 Timișoara, Romania;
| | - Mihaela-Ionela Bîrdeanu
- National Institute for Research and Development in Electrochemistry and Condensed Matter, 300569 Timisoara, Romania;
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The use of attachments in aligner treatment: Analyzing the “innovation” of expanding the use of acid etching–mediated bonding of composites to enamel and its consequences. Am J Orthod Dentofacial Orthop 2020; 158:166-174. [DOI: 10.1016/j.ajodo.2020.04.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 04/22/2020] [Indexed: 11/23/2022]
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