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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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He X, Huang Z, Yang Y, Yuan X, Wen S, Li Y, Hu G, Lai W, Long H. A Bibliometric Analysis of Clear Aligner Treatment (CAT) From 2003 to 2023. Cureus 2024; 16:e63348. [PMID: 39077282 PMCID: PMC11283927 DOI: 10.7759/cureus.63348] [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] [Accepted: 06/19/2024] [Indexed: 07/31/2024] Open
Abstract
Clear aligner treatment (CAT) has been evolving over the past two decades. This study aims to conduct a comprehensive and up-to-date bibliometric analysis of publications related to CAT, presenting the research trends, landscapes, and hot spots in this field. All publications were retrieved from the Web of Science Core Collection from 2003 to 2023. In addition to a general analysis of research landscapes, the following items were analyzed, i.e., countries, institutions, authors, journals, publications, and keywords. A total of 1031 relevant publications were included in this study. From 2003 to the present, the number of publications and citations in this field showed an increasing trend. Italy led in terms of publication counts, and Sichuan University in China had the highest publication counts among institutions. In total, 33 scholars had published a minimum of 10 articles, and the collaborations among them were mostly within each country. The American Journal of Orthodontics and Dentofacial Orthopedics published the most relevant publications. "Predictability of tooth movements," "influencing factors for clinical efficacy," "biomechanics," and "patients' perception and periodontal health" stood out as the core research focus on CAT. Our study identified the most influential countries, institutions and authors, and their cooperative relationships, and detected hot research topics on CAT, calling for more high-quality international collaborative research in the future.
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Affiliation(s)
- Xian He
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, CHN
| | - Zeyu Huang
- West China School of Stomatology, Sichuan University, Chengdu, CHN
| | - Yi Yang
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, CHN
| | - Xuechun Yuan
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, CHN
| | - Shangyou Wen
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, CHN
| | - Yuetian Li
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, CHN
| | - Guannan Hu
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, CHN
| | - Wenli Lai
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, CHN
| | - Hu Long
- State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, CHN
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Kiong M, Ashari A, Zamani NSM, How RAWM, Wahab RMA, Mohamed AMFS, Lee HJ, Mokhtar MHH. Effect of attachment flash on clear aligner force delivery: an in vitro study. BMC Oral Health 2024; 24:538. [PMID: 38715004 PMCID: PMC11075209 DOI: 10.1186/s12903-024-04284-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 04/22/2024] [Indexed: 05/12/2024] Open
Abstract
BACKGROUND The introduction of auxiliaries such as composite attachment has improved the force delivery of clear aligner (CA) therapy. However, the placement of the attachment may give rise to a flash, defined as excess resin around the attachment which may affect CA force delivery. This in vitro study aims to determine the differences in the force generated by the attachment in the presence or absence of flash in CA. MATERIALS AND METHODS Tristar Trubalance aligner sheets were used to fabricate the CAs. Thirty-four resin models were 3D printed and 17 each, were bonded with ellipsoidal or rectangular attachments on maxillary right central incisors. Fuji Prescale pressure film was used to measure the force generated by the attachment of CA. The images of colour density produced on the films were processed using a calibrated pressure mapping system utilising image processing techniques and topographical force mapping to quantify the force. The force measurement process was repeated after the flash was removed from the attachment using tungsten-carbide bur on a slow-speed handpiece. RESULTS The intraclass correlation coefficient showed excellent reliability (ICC = 0.96, 95% CI = 0.92-0.98). The average mean force exerted by ellipsoidal attachments with flash was 8.05 ± 0.16 N, while 8.11 ± 0.18 N was without flash. As for rectangular attachments, the average mean force with flash was 8.48 ± 0.27 N, while 8.53 ± 0.13 N was without flash. Paired t-test revealed no statistically significant difference in the mean force exerted by CA in the presence or absence of flash for both ellipsoidal (p = 0.07) and rectangular attachments (p = 0.41). Rectangular attachments generated statistically significantly (p < 0.001) higher mean force than ellipsoidal attachments for flash and without flash. CONCLUSION Although rectangular attachment generated a significantly higher force than ellipsoidal attachment, the force generated by both attachments in the presence or absence of flash is similar (p > 0.05).
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Affiliation(s)
- Marisa Kiong
- Department of Family Oral Health, Faculty of Dentistry, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300, Kuala Lumpur, Malaysia
| | - Asma Ashari
- Department of Family Oral Health, Faculty of Dentistry, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300, Kuala Lumpur, Malaysia.
| | - Nurul Syahira Mohamad Zamani
- Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia
| | - Reuben Axel Wee Ming How
- Tristar Aligner Materials, 7-32 Berjaya Times Square, 1 Jalan Imbi, 55100, Kuala Lumpur, Malaysia
| | - Rohaya Megat Abdul Wahab
- Department of Family Oral Health, Faculty of Dentistry, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300, Kuala Lumpur, Malaysia
| | - Alizae Marny Fadzlin Syed Mohamed
- Department of Family Oral Health, Faculty of Dentistry, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300, Kuala Lumpur, Malaysia
| | - HeeJeong Jasmine Lee
- College of Information and Communication Engineering, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Mohd Hadri Hafiz Mokhtar
- Department of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia.
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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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Elshazly TM, Bourauel C, Chavanne P, Elattar H, Keilig L. Numerical biomechanical finite element analysis of different trimming line designs of orthodontic aligners: An in silico study. J World Fed Orthod 2024; 13:65-71. [PMID: 38395726 DOI: 10.1016/j.ejwf.2024.01.001] [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: 12/04/2023] [Revised: 12/23/2023] [Accepted: 01/03/2024] [Indexed: 02/25/2024]
Abstract
BACKGROUND A finite element model was used to investigate the effect of different designs and thicknesses of orthodontic aligner margins on their biomechanical behavior. METHODS A three-dimensional data set of an upper jaw was imported into the 3-matic software. The upper right central incisor tooth (Tooth 11) was separated from the remaining model, and its periodontal ligament and surrounding bone were designed. Aligners were designed with four different trimming lines (scalloped, straight, scalloped extended, straight extended), each with four different thicknesses (0.3, 0.4, 0.5, and 0.6 mm). The models were imported into a finite element package (Marc/Mentat). A linear elastic constitutive material model was applied. A facial 0.2 mm bodily malalignment of tooth 11 was simulated. RESULTS The maximum resultant force was in the range of 1.0 N to 2.2 N. The straight trimming designs deliver higher resultant forces compared with scalloped trimming designs. Increasing the aligner thickness and/or extending the aligner edge beyond the gingival line leads to an increase in the resultant force. All designs showed an uneven distribution of the normal contact forces over the tooth surface with a predominant concentration toward the cervical third and distal third, particularly with the extended trimming designs. All designs showed uncontrolled tipping of the tooth. CONCLUSIONS Based on the current model outcomes, the use of a straight extended trimming line design for aligners is favored because of its positive impact on force distribution and, consequently, the control of tooth movement. CLINICAL RELEVANCE These findings provide aligner companies and orthodontists a valuable biomechanical evidence and guidance to enhance control over tooth movement and therefore optimize treatment outcomes. This can be achieved by trimming the edges of aligners with a straight extended design and selecting the appropriate aligner thickness.
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Affiliation(s)
- Tarek M Elshazly
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany.
| | | | | | - Hanaa Elattar
- Orthodontic Department, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt
| | - Ludger Keilig
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany; Department of Dental Prosthetics, Propaedeutics and Materials Science, Dental School, University Hospital Bonn, Bonn, Germany
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Ardila CM, Arrubla-Escobar DE, Vivares-Builes AM. Efficacy of microchips and 3D sensors for orthodontic force measurement: A systematic review of in vitro studies. Orthod Craniofac Res 2024. [PMID: 38372469 DOI: 10.1111/ocr.12768] [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: 11/10/2023] [Revised: 01/28/2024] [Accepted: 02/03/2024] [Indexed: 02/20/2024]
Abstract
OBJECTIVE To evaluate the efficacy of microchips and 3D microsensors in the measurement of orthodontic forces. METHODS Through September 2023, comprehensive searches were conducted on PubMed/MEDLINE, SCOPUS and SCIELO without restrictions. RESULTS After removing duplicate entries and applying the eligibility criteria, 23 studies were included for analysis. All the studies were conducted in vitro, and slightly more than half of them were centred on evaluating orthodontic forces exerted by aligners. Eight utilized microchips as measurement tools, while the remaining studies made use of 3D microsensors for their assessments. In the context of fixed appliances, key findings included a high level of agreement in 3-dimensional orthodontic force detection between simulation results and actual applied forces. Incorporating critical force-moment combinations during smart bracket calibration reduced measurement errors for most components. Translational tooth movement revealed a moment-to-force ratio, aligning with the bracket's centre of resistance. The primary findings in relation to aligners revealed several significant factors affecting the forces exerted by them. Notably, the foil thickness and staging were found to have a considerable impact on these forces, with optimal force transmission occurring at a layer height of 150 μm. Furthermore, the type of material used in 3D-printing aligners influenced the force levels, with attachments proving effective in generating extrusive forces. Deliberate adjustments in aligner thickness were observed to alter the forces and moments generated. CONCLUSIONS Microchips and 3D sensors provide precise and quantitative measurements of orthodontic forces in in vitro studies, enabling accurate monitoring and control of tooth movement.
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Affiliation(s)
- Carlos M Ardila
- School of Dentistry, University of Antioquia, Medellín, Colombia
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Khursheed Alam M, Hajeer MY, Shqaidef A, Alswairki HJ, Alfawzan AA, Shrivastava D, Chandan Srivastava K, Cicciù M, Minervini G. Impact of various aligner auxiliaries on orthodontic activity: A systematic review and network meta-analysis. Saudi Dent J 2024; 36:199-207. [PMID: 38419986 PMCID: PMC10897539 DOI: 10.1016/j.sdentj.2023.10.013] [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: 07/10/2023] [Revised: 10/18/2023] [Accepted: 10/24/2023] [Indexed: 03/02/2024] Open
Abstract
Background It is imperative to analyze the forces and moments produced by various auxiliaries in order to select the optimal attachments and, eventually, to maximize the efficacy and efficiency of orthodontic therapy. Through this investigation, we aimed to highlight the impact of various aligner auxiliaries on orthodontic activity in patients undergoing orthodontic treatment on a pre/post treatment protocol basis. Methods After a thorough search of the online journals, a total of 482 documents were found using keywords such as "Orthodontic Treatment", "Aligner Auxiliaries", "Elastic Ligatures" and "Tooth Movement." The database research, elimination of duplicate studies, data extraction and risk of bias were performed by the authors independently. This systematic review and network meta-analysis included prospective studies and clinical trials to evaluate research that had looked at the impact of various aligner auxiliaries on orthodontic activity in patients undergoing orthodontic treatment. Results Eight investigations of varying designs were selected for this review. The majority of investigations revealed that aligner auxiliaries significantly improve anterior root torque, rotation, and mesio-distal (M-D) movement, as well as posterior anchoring. They also significantly improved anterior root rotation. However, few studies have presented inconsistent or non-statistically significant findings. Conclusion Auxiliaries for aligners also appear to improve extrusion and other orthodontic movements, but there is insufficient evidence to support these claims. No research has examined posterior bucco-lingual expansion or tilting. Clarification of the effect of attachments and their related variables requires additional clinical investigations.
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Affiliation(s)
- Mohammad Khursheed Alam
- Orthodontic Division, Preventive Dentistry Department, College of Dentistry, Jouf University, Sakaka 72345, Saudi Arabia
- Department of Dental Research Cell, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Chennai, India
- Department of Public Health, Faculty of Allied Health Sciences, Daffodil International University, Dhaka, Bangladesh
| | - Mohammad Younis Hajeer
- Department of Orthodontics, University of Damascus Faculty of Dentistry, Damascus, Syria
| | - Abedalrahman Shqaidef
- Department of Clinical Sciences, Center of Medical and Bio-Allied Health Sciences Research, College of Dentistry, Ajman University, Ajman, United Arab Emirates
| | | | - Ahmed Ali Alfawzan
- Department of Preventive Dentistry, College of Dentistry in Ar Rass, Qassim University, Ar Rass 52571, Saudi Arabia
| | - Deepti Shrivastava
- Periodontics Division, Preventive Dentistry Department, College of Dentistry, Jouf University, Sakaka 72345, Saudi Arabia
| | - Kumar Chandan Srivastava
- Department of Oral & Maxillofacial Surgery & Diagnostic Sciences, College of Dentistry, Jouf University, Sakaka 72345, Saudi Arabia
- Department of Oral Medicine and Radiology, Saveetha Dental College, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai 602105, India
| | - Marco Cicciù
- Department of Biomedical and Surgical and Biomedical Sciences, Catania University, 95123 Catania, Italy
| | - Giuseppe Minervini
- Saveetha Dental College & Hospitals, Saveetha Institute of Medical & Technical Sciences, Saveetha University, Chennai 600 077, India
- Multidisciplinary Department of Medical-Surgical and Dental Specialties, University of Campania, Luigi Vanvitelli, 80138 Naples, Italy
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Cintora-López P, Arrieta-Blanco P, Martin-Vacas A, Paz-Cortés MM, Gil J, Aragoneses JM. In vitro analysis of the influence of the thermocycling and the applied force on orthodontic clear aligners. Front Bioeng Biotechnol 2023; 11:1321495. [PMID: 38173871 PMCID: PMC10761475 DOI: 10.3389/fbioe.2023.1321495] [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: 10/14/2023] [Accepted: 12/11/2023] [Indexed: 01/05/2024] Open
Abstract
The mechanical properties of polyurethane dental aligners have been studied in an oral environment at 37°C and subjected to thermal cycling between 5°C and 55°C for long periods of time at different mechanical stresses. The aim is to determine the efficacy of the orthodontic aligner at different stress levels, the effect of thermal cycling with therapy time on tooth position correction. Sixty aligners with the same design were studied applying tensions of 0, 3 and 30 N and determining the deformation at different times from 1 to 760 h. Half of these aligners were subjected to stresses submerged in artificial saliva at 37°C and the other half were subjected to thermal cycles between 2°C and 55°C in salivary medium. Deformation was determined using a high-resolution stereo magnifier and ImageJ image analysis software. Water adsorption by the polyurethane was determined at the different test times. The results showed that in the unloaded aligners there is no appreciable deformation, but with thermal cycling there is a light shrinkage of the aligner due to the semi-crystallization process (ordering of polymeric chains) of the polyurethane. When applying loads of 3 and 30 N, creep curves with constant deformation transition zones can be seen. The transition zones decrease as the applied mechanical load increases. In addition, the significant effect of thermal cycling on the reduction of the transition zone of the aligners has been demonstrated. The transition zones are optimal for dental correction as constant stresses are exerted for tooth movement. The effect of thermal cycling shortens the constant deformation zone and reduces tooth alignment time. It was observed that the absorption of water in the aligner is constant after 1 h of immersion and does not exceed 0.4% by weight of absorbed water.
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Affiliation(s)
| | | | - Andrea Martin-Vacas
- Faculty of Dentistry, Alfonso X El Sabio University, Villanueva de la Cañada, Spain
| | | | - Javier Gil
- Faculty of Medicine and Health Sciences, Bionegineering Institute of Technology, International University of Catalunya, Barcelona, Spain
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Elkholy F, Weber S, Repky S, Jäger R, Schmidt F, Lapatki BG. Are aligners capable of inducing palatal bodily translation or palatal root torque of upper central incisors? A biomechanical in vitro study. Clin Oral Investig 2023; 27:4289-4300. [PMID: 37243819 PMCID: PMC10415518 DOI: 10.1007/s00784-023-05046-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 04/26/2023] [Indexed: 05/29/2023]
Abstract
OBJECTIVES Previous studies have shown that aligners have limited ability to control root movements. The purpose of this study was to investigate which modification geometry and foil thickness are optimal for generating the force-moment (F/M) systems required for palatal root torque of maxillary central incisors. MATERIALS AND METHODS Tooth 11 was separated from a maxillary acrylic model and connected to a movement unit via a 3D F/M sensor. Different modification geometries (crescent, capsular, double-spherical) with different depths were digitally implemented in the labio-cervical region of tooth 11 to induce an increased contact force. We evaluated the F/M systems exerted by aligners with thicknesses of 0.4-1.0 mm. F/M measurements were taken with tooth 11 in the neutral position and during palatal displacement of tooth 11 (simulating its initial clinical movement). RESULTS The mechanical requirements of palatal root torque are a palatally directed force (- Fy) and a palatal root torquing moment (- Mx). These requirements were reliably achieved with modification depths > 0.5 mm. The modification depth and foil thickness had a significant influence on - Fy magnitudes (linear mixed-effect models, p < 0.01). With the 0.75-mm aligners combined with 1.5-mm deep modifications, the palatal root torque range (palTR) started after an initial palatal crown displacement of 0.09, 0.12, and 0.12 mm for the capsular, crescent, and double-spherical modification geometries, respectively. CONCLUSIONS A relatively early start of the palatal torque range (after a 0.1-mm palatal crown displacement) and appropriate - Fy magnitudes were achieved with 0.75-mm-thick aligners containing 1.5-mm deep capsular or crescent pressure regions. Subsequent clinical trials are required to confirm the clinical effects of these modifications. CLINICAL RELEVANCE In vitro testing indicated that modified aligners are capable of generating the F/M components required for palatal root torque of upper central incisors.
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Affiliation(s)
- Fayez Elkholy
- Department of Orthodontics, Universitätsklinikum Ulm/University Hospital Ulm, Ulm, Germany
| | - Sophia Weber
- Department of Orthodontics, Universitätsklinikum Ulm/University Hospital Ulm, Ulm, Germany
| | - Stefan Repky
- Institute of Statistics, Ulm University, Helmholtzstr. 20, 89081, Ulm, Germany
| | - Rudolf Jäger
- Department of Orthodontics, Universitätsklinikum Ulm/University Hospital Ulm, Ulm, Germany
| | - Falko Schmidt
- Department of Orthodontics, Universitätsklinikum Ulm/University Hospital Ulm, Ulm, Germany
| | - Bernd G Lapatki
- Department of Orthodontics, Universitätsklinikum Ulm/University Hospital Ulm, Ulm, Germany.
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Yao S, Jiang W, Wang C, He Y, Wang C, Huang L. Improvements of tooth movement efficiency and torque control in expanding the arch with clear aligners: a finite element analysis. Front Bioeng Biotechnol 2023; 11:1120535. [PMID: 37324442 PMCID: PMC10267454 DOI: 10.3389/fbioe.2023.1120535] [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: 12/10/2022] [Accepted: 05/25/2023] [Indexed: 06/17/2023] Open
Abstract
Objectives: The purpose of this study was to analyze the effect of different movement strategies, embossment structures, and torque compensation of the aligner on tooth movement during arch expansion using clear aligners by finite element analysis. Methods: Models comprising the maxilla, dentition, periodontal ligament, and aligners were created and imported into a finite element analysis software. The tests were performed using the following: three orders of tooth movement (including alternating movement with the first premolar and first molar, whole movement with second premolar and first molar or premolars and first molar), four different shapes of embossment structures (ball, double ball, cuboid, cylinder, with 0.05, 0.1, 0.15-mm interference) and torque compensation (0°, 1°, 2°, 3°, 4°, and 5°). Results: The expansion of clear aligners caused the target tooth to move obliquely. Alternating movement resulted in higher movement efficiency with lower anchorage loss as compared with whole movement. Embossment increased the efficiency of crown movement but did not contribute positively to torque control. As the angle of compensation increased, the tendency of oblique tooth movement was gradually controlled; however, the movement efficiency decreased concurrently, and stress distribution on the periodontal ligament became more even. For each 1° increase in compensation, the torque per millimeter of the first premolar would decrease by 0.26°/mm, and the crown movement efficiency eliminate decreased by 4.32%. Conclusion: Alternating movement increases the efficiency of the arch expansion by the aligner and reduces anchorage loss. Torque compensation should be designed to enhance torque control in arch expansion using an aligner.
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Affiliation(s)
- Song Yao
- Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China
| | - Wei Jiang
- Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China
| | - Chunjuan Wang
- Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China
| | - Yao He
- Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China
| | - Chao Wang
- Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Key Laboratory of Biomechanics and Mechanobiology, Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, School of Engineering Medicine, Beihang University, Beijing, China
| | - Lan Huang
- Stomatological Hospital of Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China
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11
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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: 2] [Impact Index Per Article: 2.0] [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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12
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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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13
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Elshazly TM, Salvatori D, Elattar H, Bourauel C, Keilig L. Effect of trimming line design and edge extension of orthodontic aligners on force transmission: A 3D finite element study. J Mech Behav Biomed Mater 2023; 140:105741. [PMID: 36857974 DOI: 10.1016/j.jmbbm.2023.105741] [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: 01/20/2023] [Revised: 02/20/2023] [Accepted: 02/21/2023] [Indexed: 02/27/2023]
Abstract
OBJECTIVES To investigate in a numerical study the effect of the geometry and the extension of orthodontic aligner edges and the aligner thickness on force transmission to upper right central incisor tooth (Tooth 11). METHODS A three-dimensional (3D) digital model, obtained from a 3D data set of a complete dentulous maxilla, was imported into 3-matic software. Aligners with four different trimming line designs (scalloped, straight, scalloped extended, straight extended) were designed, each with four different thicknesses (0.3, 0.4, 0.5, and 0.6 mm). The models were exported to a finite element (FE) software (Marc/Mentat). A facial 0.2 mm bodily malposition of tooth 11 was simulated. RESULTS The maximum resultant force was in the range of (7.5 - 55.2) N. The straight trimming designs had higher resultant force than the scalloped designs. The resultant force increases with increasing the edge extension of the aligner. The normal contact forces were unevenly distributed over the entire surface and were concentrated in six areas: Incisal, Mesio-Incisal, Disto-Incisal, Middle, Mesio-Cervical, and Disto-Cervical. The resultant force increases super linearly with increasing thickness. CONCLUSIONS The design of the trimming line, the edge extension, and the thickness of the aligner affect significantly the magnitude of the resultant force and the distribution of normal contact force. The straight extended trimming design exhibited better force distribution that may favor a bodily tooth movement. CLINICAL RELEVANCE A straight extended trimming design of an orthodontic aligner may improve the clinical outcomes. In addition, the manufacturing procedures of the straight design are much simpler compared to the scalloped design.
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Affiliation(s)
- Tarek M Elshazly
- Oral Technology, 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, Dental School, University Hospital Bonn, Bonn, Germany; Department of Dental Prosthetics, Propaedeutics and Materials Science, Dental School, University Hospital Bonn, Bonn, Germany
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14
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Tepedino M, Colasante P, Staderini E, Masedu F, Ciavarella D. Short-term effect of orthodontic clear aligners on muscular activity and occlusal contacts: A cohort study. Am J Orthod Dentofacial Orthop 2023:S0889-5406(23)00033-1. [PMID: 36870918 DOI: 10.1016/j.ajodo.2022.10.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Revised: 10/01/2022] [Accepted: 10/01/2022] [Indexed: 03/06/2023]
Abstract
INTRODUCTION The simultaneous presence of maxillary and mandibular clear aligners alters the vertical dimension and the quantity and quality of occlusal contacts. Few data in the literature explain how this occurs and the effects on neuromuscular coordination. This study aimed to evaluate occlusal contacts and muscular balance during treatment with clear aligners over a short follow-up time. METHODS Twenty-six female adult patients were enrolled in this study. The center of occlusal force (COF) was evaluated using a T-Scan II device, whereas muscular symmetry and balance were determined through surface electromyography using a standardized protocol that reduces anthropometric and electrode variations. Both evaluations were performed in centric occlusion and with aligners worn before treatment, after 3 months, and after 6 months. RESULTS A statistically significant variation in COF position was reported in the sagittal plane but not in the transverse plane. The shift in the COF position was followed by a change in muscular balance evaluated through surface electromyography. CONCLUSIONS Treatment with clear aligners resulted in an anterior shift of the COF when biting in centric occlusion and a posterior shift when the aligners were worn in healthy female patients after 6 months of observation. This change in occlusal contact was followed by an improvement in muscular function symmetry in the short term when aligners were worn, compared with the centric occlusion during treatment.
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Affiliation(s)
- Michele Tepedino
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
| | - Pietro Colasante
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
| | - Edoardo Staderini
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Roma-Università Cattolica del Sacro Cuore. Istituto di Clinica Odontoiatrica e Chirurgia Maxillo-facciale, Rome, Italy.
| | - Francesco Masedu
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy; Academy of Sciences of Abruzzo Region, L'Aquila, Italy; Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, L'Aquila, Italy
| | - Domenico Ciavarella
- Department of Clinical and Experimental Medicine, University of Foggia, Foggia, Italy
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15
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Kaur H, Khurelbaatar T, Mah J, Heo G, Major PW, Romanyk DL. Investigating the role of aligner material and tooth position on orthodontic aligner biomechanics. J Biomed Mater Res B Appl Biomater 2023; 111:194-202. [PMID: 36318602 DOI: 10.1002/jbm.b.35145] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 07/18/2022] [Accepted: 07/25/2022] [Indexed: 11/11/2022]
Abstract
The primary objective of this work was to investigate the effect of material selection and tooth position on orthodontic aligner biomechanics. Additionally, material property changes with thermoforming were studied to elucidate its role in material performance in-vitro. An orthodontic simulator (OSIM) was used to evaluate forces and moments at 0.20 mm of lingual displacement for central incisor, canine and second premolar using Polyethylene terephthalate (PET), Polyurethane (PU) and Glycol-modified polyethylene terephthalate (PET-G) materials. The OSIM was scanned to generate a model used to fabricate aligners using manufacturer-specified thermoforming procedures. Repeated measures of MANOVA was used to analyze the effect of teeth and material on forces/moments. The role of thermoforming was evaluated by flexural modulus estimated by 3-point bend tests. Pre-thermoformed and post-thermoformed samples were prepared using as-received sheets and those thermoformed over a simplified arch using rectangular geometry, respectively. Groups were compared using Two-way ANOVA. The PET, PU, and PET-G materials exerted maximum buccal force and corresponding moments on the canine. PU exerted more buccal force than PET-G on the canine and second premolar, and more than PET on the second premolar. The impact of thermoforming varied according to the specific polymer: PET-G remained stable, there was a slight change for PET, and a significant increase was noted for PU from pre-thermoformed to post-thermoforming. The results of this study elucidate the influence of material and arch position on the exerted forces and moments. Further, the mechanical properties of thermoplastic materials should be evaluated after thermoforming to characterize their properties for clinical application.
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Affiliation(s)
- Harsimrat Kaur
- Department of Dentistry, University of Alberta, Edmonton, Alberta, USA
| | | | - James Mah
- School of Dental Medicine, University of Nevada, Las Vegas, Nevada, USA
| | - Giseon Heo
- Department of Dentistry, University of Alberta, Edmonton, Alberta, USA.,Department of Dentistry and Dental Hygiene, University of Alberta, Edmonton, Alberta, USA
| | - Paul W Major
- Department of Dentistry, University of Alberta, Edmonton, Alberta, USA.,Department of Dentistry & Dental Hygiene, Division of Orthodontics, University of Alberta, Edmonton, Alberta, USA
| | - Dan L Romanyk
- Department of Dentistry, University of Alberta, Edmonton, Alberta, USA.,Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, USA.,Department of Mechanical Engineering and School of Dentistry, University of Alberta, Edmonton, Alberta, USA
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16
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Elshazly TM, Bourauel C, Aldesoki M, Ghoneima A, Abuzayda M, Talaat W, Talaat S, Keilig L. Computer-aided finite element model for biomechanical analysis of orthodontic aligners. Clin Oral Investig 2023; 27:115-124. [PMID: 35989373 DOI: 10.1007/s00784-022-04692-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 08/15/2022] [Indexed: 02/01/2023]
Abstract
OBJECTIVES To design a finite element (FE) model that might facilitate understanding of the complex mechanical behavior of orthodontic aligners. The designed model was validated by comparing the generated forces - during 0.2-mm facio-lingual translation of upper left central incisor (Tooth 21) - with the values reported by experimental studies in literature. MATERIALS AND METHODS A 3D digital model, obtained from scanning of a typodont of upper jaw, was imported into 3-matic software for designing of aligners with different thicknesses: 0.4, 0.5, 0.6, 0.7 mm. The model was exported to Marc/Mentat FE software. Suitable parameters for FE simulation were selected after a series of sensitivity analyses. Different element classes of the model and different rigidity values of the aligner were also investigated. RESULTS The resultant maximum forces generated on facio-lingual translation of Tooth 21 were within the range of 1.3-18.3 N. The force was direction-dependent, where lingual translation transmitted higher forces than facial translation. The force increases with increasing the thickness of the aligner, but not linearly. We found that the generated forces were almost directly proportional to the rigidity of the aligner. The contact normal stress map showed an uneven but almost repeatable distribution of stresses all over the facial surface and concentration of stresses at specific points. CONCLUSIONS A validated FE model could reveal a lot about mechanical behavior of orthodontic aligners. CLINICAL RELEVANCE Understanding the force systems of clear aligner by means of FE will facilitate better treatment planning and getting optimal outcomes.
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Affiliation(s)
- Tarek M Elshazly
- Oral Technology Department, Dental School, University Hospital Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.
| | - Christoph Bourauel
- Oral Technology Department, Dental School, University Hospital Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany
| | - Mostafa Aldesoki
- Oral Technology Department, Dental School, University Hospital Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany
| | - Ahmed Ghoneima
- Department of Orthodontics, College of Dental Medicine, MBRU, Dubai, United Arab Emirates
| | - Moosa Abuzayda
- Department of Prosthodontics, College of Dental Medicine, MBRU, Dubai, United Arab Emirates
| | - Wael Talaat
- Department of Oral and Craniofacial Health Sciences, College of Dental Medicine, University of Sharjah, Sharjah, United Arab Emirates.,Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt
| | - Sameh Talaat
- Oral Technology Department, Dental School, University Hospital Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.,Department of Orthodontics, Future University in Egypt, Cairo, Egypt
| | - Ludger Keilig
- Oral Technology Department, Dental School, University Hospital Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.,Department of Dental Prosthetics, Propaedeutics and Materials Science, Dental School, University Hospital Bonn, Bonn, Germany
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17
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Cheng Y, Liu X, Chen X, Li X, Fang S, Wang W, Ma Y, Jin Z. The three-dimensional displacement tendency of teeth depending on incisor torque compensation with clear aligners of different thicknesses in cases of extraction: a finite element study. BMC Oral Health 2022; 22:499. [DOI: 10.1186/s12903-022-02521-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 10/13/2022] [Indexed: 11/17/2022] Open
Abstract
Abstract
Background
Despite the popularity of clear aligner treatment, the effect of the thickness of these aligners has not been fully investigated. The objective of this study was to assess the effects of incisor torque compensation with different thicknesses of clear aligner on the three-dimensional displacement tendency of teeth in cases of extraction.
Methods
Three-dimensional finite element models of the maxillary dentition with extracted first premolars, maxilla, periodontal ligaments, attachments, and aligners were constructed and subject to Finite Element Analysis (FEA). Two groups of models were created: (1) with 0.75 mm-thick aligners and (2) with 0.5 mm-thick aligners. A loading method was developed to simulate the action of clear aligners for the en masse retraction of the incisors. Power ridges of different heights were applied to both groups to mimic torque control, and the power ridges favoring the translation of the central incisors were selected. Then, we used ANSYS software to analyze the initial displacement of teeth and the principle stress on the PDL.
Results
Distal tipping, lingual tipping and extrusion of the incisors, distal tipping and extrusion of the canines, and mesial tipping and intrusion of the posterior teeth were all generated by clear aligner therapy. With the 0.5 mm-thick aligner, a power ridge of 0.7 mm could cause bodily retraction of the central incisors. With the 0.75 mm-thick aligner, a power ridge of 0.25 mm could cause translation of the central incisors. Aligner torque compensation created by the power ridges generated palatal root torque and intrusion of the incisors, intrusion of the canines, mesial tipping and the intrusion of the second premolar; these effects were more significant with a 0.75 mm-thick aligner. After torque compensation, the stress placed on the periodontal ligament of the incisors was distributed more evenly with the 0.75 mm-thick aligner.
Conclusions
The torque compensation caused by power ridges can achieve incisor intrusion and palatal root torque. Appropriate torque compensation with thicker aligners should be designed to ensure bodily retraction of anterior teeth and minimize root resorption, although more attention should be paid to the anchorage control of posterior teeth in cases of extraction.
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18
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Elshazly TM, Keilig L, Salvatori D, Chavanne P, Aldesoki M, Bourauel C. Effect of Trimming Line Design and Edge Extension of Orthodontic Aligners on Force Transmission: An in vitro Study. J Dent 2022; 125:104276. [PMID: 36055460 DOI: 10.1016/j.jdent.2022.104276] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 08/26/2022] [Accepted: 08/29/2022] [Indexed: 11/29/2022] Open
Abstract
OBJECTIVES To investigate how the stress distribution and forces transmitted from orthodontic aligners to the tooth surface are affected by the geometry and extension of the trimming line. MATERIALS AND METHODS Thirty-six aligners were thermoformed from Zendura FLX sheets (0.75 mm thick) and divided into four groups based on the design of the trimming line: Scalloped, Scalloped extended, Straight and Straight extended. Fuji pressure-sensitive films were used for pressure measurement. The pressurized films were scanned and evaluated. Pressures and forces were measured over the entire facial surface of an upper right central incisor (Tooth 11) and at 7 different locations [cervical, middle, incisal, mesio-incisal, mesio-cervical, disto-cervical, and disto-cervical]. In addition, the thickness of the aligners at these 7 sites was measured with a digital caliper. RESULTS The active force ranged from (2.2 - 6.9) N, and the average pressure was (1.6 - 2.7) MPa. The highest values were recorded for the (straight extended) design, while the lowest values were recorded for the scalloped design. The forces and stresses were not uniformly distributed over the surface. When the values in each area were compared separately, significant differences were found between the different designs in the cervical area, with the scalloped design transmitting the lowest cervical forces. Aligner thickness was drastically reduced (60-75% thinning) over the entire tooth surface after thermoforming. CONCLUSIONS The straight extended design of aligner's trimming line exhibited more uniform force transfer and stress distribution across the surface than the other designs. CLINICAL RELEVANCE The trimming line design could have a significant impact on the clinical outcome of orthodontic aligner treatment.
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Affiliation(s)
- Tarek M Elshazly
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany.
| | - Ludger Keilig
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany; Department of Dental Prosthetics, Propaedeutics and Materials Science, Dental School, University Hospital Bonn, Bonn, Germany
| | | | | | - Mostafa Aldesoki
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany
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Cheng Y, Gao J, Fang S, Wang W, Ma Y, Jin Z. Torque movement of the upper anterior teeth using a clear aligner in cases of extraction: a finite element study. Prog Orthod 2022; 23:26. [PMID: 35909188 PMCID: PMC9339452 DOI: 10.1186/s40510-022-00421-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 05/30/2022] [Indexed: 11/10/2022] Open
Abstract
Background Clear aligner treatment has become popular over recent years. It is necessary to identify methods by which we could avoid the bowing effect in extractions with clear aligner. The present study was to identify the appropriate method to design torque movement involving the upper anterior teeth of extraction cases, in order to maintain or improve the axis and torque of the upper anterior teeth with a clear aligner during movement and closure of the extraction space. Results As the height of the power ridge increased, the rotation angle of the upper central incisor in the sagittal direction decreased gradually and the location of the rotation center changed significantly; the rotation center moved in the apical direction and then changed to the crown side. The highest von-Mises stress of the upper central incisor root, periodontal ligaments, and alveolar bone, showed little change as the power ridge height increased. When the axial inclination of the upper central incisor was normal (U1-SN = 105°), the tendency of movement for the upper central incisor approached translation with a power ridge height of 0.7 mm (corresponding distorted angle: 5.8415). When the axial inclination of the upper central incisor was oversized (U1-SN = 110°), the axial inclination of the upper central incisor reduced to normal following completion of the anterior segment retraction with a power ridge of 0.4 mm (corresponding distorted angle: 3.4265). Conclusion Analysis indicates that pure palatal tipping movement of the upper anterior teeth is generated without torque control, thus resulting in the bowing effect. The required torque control of the upper anterior teeth with oversize axial inclination is weaker than that of the upper anterior teeth with normal axial inclination because limited torque loss is expected for oversize axial inclination teeth. Variation sensitivity of the rotation center should be considered carefully due to biological problems when designing translation of the upper anterior teeth with normal axial inclination.
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Affiliation(s)
- Yuxun Cheng
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Clinical Research Center for Oral Diseases, Department of Orthodontics, School of Stomatology, Air Force Medical University, Xi'an, 710032, China
| | - Jie Gao
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Clinical Research Center for Oral Diseases, Department of Orthodontics, School of Stomatology, Air Force Medical University, Xi'an, 710032, China
| | - Shishu Fang
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Clinical Research Center for Oral Diseases, Department of Orthodontics, School of Stomatology, Air Force Medical University, Xi'an, 710032, China
| | - Wei Wang
- Urumql DW Innovation InfoTech Co., Ltd, Xinjiang, 830000, China
| | - Yanning Ma
- Shanxi Medical University School and Hospital of Stomatology, Taiyuan, 030001, China.
| | - Zuolin Jin
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Clinical Research Center for Oral Diseases, Department of Orthodontics, School of Stomatology, Air Force Medical University, Xi'an, 710032, China.
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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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Nucera R, Dolci C, Bellocchio AM, Costa S, Barbera S, Rustico L, Farronato M, Militi A, Portelli M. Effects of Composite Attachments on Orthodontic Clear Aligners Therapy: A Systematic Review. MATERIALS 2022; 15:ma15020533. [PMID: 35057250 PMCID: PMC8778413 DOI: 10.3390/ma15020533] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 12/20/2021] [Accepted: 01/04/2022] [Indexed: 12/26/2022]
Abstract
This systematic review aims to highlight the differences between different clear aligner therapies that differ in the presence of attachments or in attachment configuration. Eight electronic databases were searched up to March 2020. Two authors independently proceeded to study selection, data extraction, and risk of bias assessment. The analysis of the results was carried out examining six groups of movements (mesio-distal tipping/bodily movement; anterior bucco-lingual tipping/root torque; posterior bucco-lingual tipping/expansion; intrusion; extrusion; rotation). Five clinical trials were selected and all of them showed a medium risk of bias. Literature showed that attachments mostly increase the effectiveness of orthodontic treatment with clear aligners, improving anterior root torque, rotation, and mesio-distal (M-D) movement; they are also important to increase posterior anchorage. However, some articles showed contradictory or not statistically significant results. Attachments also seem to improve intrusion, but the evidence about this movement, as well as extrusion, is lacking. No studies evaluated posterior bucco-lingual tipping/expansion. Further clinical trials are strongly suggested to clarify the influence of attachments and their number, size, shape, and position on each orthodontic movement.
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Affiliation(s)
- Riccardo Nucera
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, Section of Orthodontics, University of Messina, 98125 Messina, Italy; (R.N.); (A.M.B.); (S.C.); (S.B.); (L.R.); (A.M.)
| | - Carolina Dolci
- Department of Biomedical, Surgical and Dental Sciences, Fondazione IRCCS Cà Granda—Ospedale Maggiore Policlinico, University of Milan, 20122 Milan, Italy; (C.D.); (M.F.)
| | - Angela Mirea Bellocchio
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, Section of Orthodontics, University of Messina, 98125 Messina, Italy; (R.N.); (A.M.B.); (S.C.); (S.B.); (L.R.); (A.M.)
| | - Stefania Costa
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, Section of Orthodontics, University of Messina, 98125 Messina, Italy; (R.N.); (A.M.B.); (S.C.); (S.B.); (L.R.); (A.M.)
| | - Serena Barbera
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, Section of Orthodontics, University of Messina, 98125 Messina, Italy; (R.N.); (A.M.B.); (S.C.); (S.B.); (L.R.); (A.M.)
| | - Lorenzo Rustico
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, Section of Orthodontics, University of Messina, 98125 Messina, Italy; (R.N.); (A.M.B.); (S.C.); (S.B.); (L.R.); (A.M.)
| | - Marco Farronato
- Department of Biomedical, Surgical and Dental Sciences, Fondazione IRCCS Cà Granda—Ospedale Maggiore Policlinico, University of Milan, 20122 Milan, Italy; (C.D.); (M.F.)
| | - Angela Militi
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, Section of Orthodontics, University of Messina, 98125 Messina, Italy; (R.N.); (A.M.B.); (S.C.); (S.B.); (L.R.); (A.M.)
| | - Marco Portelli
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, Section of Orthodontics, University of Messina, 98125 Messina, Italy; (R.N.); (A.M.B.); (S.C.); (S.B.); (L.R.); (A.M.)
- Correspondence: ; Tel.: +39-0902216905
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Behyar M, Ratzmann A, Shojaei Khatouni S, Quasthoff M, Pink C, Ladisch J, Krey KF. Modular 3D printable orthodontic measuring apparatus for force and torque measurements of thermoplastic/removable appliances. BIOMED ENG-BIOMED TE 2021; 66:593-601. [PMID: 34695307 DOI: 10.1515/bmt-2020-0294] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 10/01/2021] [Indexed: 12/28/2022]
Abstract
The magnitude of forces and moments applied on teeth during orthodontic treatment is crucial to achieve the desired tooth movement. The aim of this study is to introduce a modular 3D printable orthodontic measurement apparatus (M3DOMA), which can be used for measurements of forces and moments acting on teeth during treatment with aligners. The measurement device was characterized regarding signal to noise ratio (SNR) of the sensors, repeatability of measurements, influence of thermoforming, as well as reliability. Forces and moments were evaluated for an activation range of 0.1-0.4 mm, comparing them among different activation patterns with two aligner thicknesses. The sensors exhibited a SNR from 13-33 dB. Repeatability with repeated measurements showed standard deviations ≤0.015 N and 0.769 Nmm. The influence of thermoforming represented by standard deviation of forces ranges from 0.019-0.147 N. The device showed a range of intra class correlation (ICC) for repeated measurements for all sensors from 0.932 to 0.999. Hence the reliability of the device has been proven to be excellent.
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Affiliation(s)
- Masoud Behyar
- Departments of Orthodontics and Dentofacial Orthopedics, University Medicine Greifswald, Center for Oral Health, Greifswald, Germany
| | - Anja Ratzmann
- Departments of Orthodontics and Dentofacial Orthopedics, University Medicine Greifswald, Center for Oral Health, Greifswald, Germany
| | | | - Maximilian Quasthoff
- Faculty of Mechanical Engineering, University of Applied Sciences, Stralsund, Germany
| | - Christiane Pink
- Departments of Orthodontics and Dentofacial Orthopedics, University Medicine Greifswald, Center for Oral Health, Greifswald, Germany
| | - Jens Ladisch
- Faculty of Mechanical Engineering, University of Applied Sciences, Stralsund, Germany
| | - Karl-Friedrich Krey
- Departments of Orthodontics and Dentofacial Orthopedics, University Medicine Greifswald, Center for Oral Health, Greifswald, Germany
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Li R, She W, Luo Y, Wang J, Peng Y, Ye Q. The optimal activation of plastic aligner for canine distal movement: a three-dimensional finite element analysis. Odontology 2021; 110:305-312. [PMID: 34626315 DOI: 10.1007/s10266-021-00663-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 09/29/2021] [Indexed: 10/20/2022]
Abstract
This study aimed to investigate the optimal activation of plastic aligner for the canine distal movement by combining the stress and strain of periodontal ligament. Computer-aided design models of the upper canine, periodontal ligament, alveolar bone, and plastic aligner were constructed. The stresses and strains of periodontal ligament were acquired by fitting plastic aligner on the canine, which will cause the canine distal-direction movement. The activation of plastic aligner was set into 12 groups, including 0.050, 0.100, 0.125, 0.150, 0.175, 0.200, 0.225, 0.250, 0.275, 0.300, 0.350, and 0.400 mm. Assuming the volume-averaged hydrostatic stress (VAHS) ranging from 4.7 to 16 kPa to be the optimal stress, and an average strain no less than 0.3 to be the optimal strain. The optimal activation of plastic aligner was acquired based on the optimal stress and average strain. As the activation increased, the stress and strain of periodontal ligament increased visibly. The degree of activation of plastic aligner was nonlinearly and positively related to VAHS and average strain. According to the fitted curves, the activation corresponding to the optimal stress was 0.07-0.24 mm and the activation was not less than 0.21 mm based on the optimal strain. The optimal activation of plastic aligner for the canine distal movement was 0.21-0.24 mm in this study. The degree of activation affects the force system of orthodontic tooth movement, and it should be taken into consideration to obtain healthy and efficient tooth movement. The activation with 0.21-0.24 mm seems optimal for orthodontic tooth movement in the plastic aligner system in this study.
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Affiliation(s)
- Ruohan Li
- Renmin Hospital of Wuhan University, Wuhan, Hubei, China
| | - Wenting She
- Renmin Hospital of Wuhan University, Wuhan, Hubei, China
| | - Yu Luo
- Renmin Hospital of Wuhan University, Wuhan, Hubei, China
| | - Juan Wang
- Renmin Hospital of Wuhan University, Wuhan, Hubei, China
| | - Youjian Peng
- Renmin Hospital of Wuhan University, Wuhan, Hubei, China.
| | - Qingsong Ye
- Renmin Hospital of Wuhan University, Wuhan, Hubei, China.
- Massachusetts General Hospital, Harvard School of Dental Medicine, Boston, MA, USA.
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An in vitro evaluation of orthodontic aligner biomechanics around the maxillary arch. Am J Orthod Dentofacial Orthop 2021; 160:401-409. [PMID: 34456005 DOI: 10.1016/j.ajodo.2021.04.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 02/01/2021] [Accepted: 04/01/2021] [Indexed: 11/24/2022]
Abstract
INTRODUCTION The objective of this study was to evaluate the forces and moments exerted by orthodontic aligners on 3 different displaced maxillary teeth and their adjacent supporting teeth. METHODS An in vitro orthodontic simulator was used to measure the forces and moments of a 0.75-mm thick glycol-modified polyethylene terephthalate material for 3 maxillary teeth: central incisor, canine, and second premolar. Forces and moments were recorded for tested teeth displaced lingually one by one for 0.20 mm. Repeated measures of multivariate analysis of variance was used to assess the outcome. RESULTS The mean buccolingual force applied on a displaced canine (2.25 ± 0.38 N) was significantly (P <0.001) more than the central incisor (1.49 ± 0.18 N) and second premolar (1.50 ± 0.16 N). The mean moment (that tends to tip the teeth buccally) exerted on a canine (-20.11 ± 5.27 Nmm) was significantly more (P <0.001) than the central incisor (-8.42 ± 1.67 Nmm) and second premolar (-11.45 ± 1.29 Nmm). The forces and moments acting on teeth adjacent to the displaced tooth were clinically significant and acted in opposing directions to those on the displaced tooth. CONCLUSIONS The results of this study highlighted that for the same amount of displacement on a given tooth, the forces and moments imposed by the orthodontic aligner depend on location around the arch. These findings highlight the need to further study aligner mechanics around the dental arch and optimize aligner design to impose desired mechanical loads to avoid detrimental effects during orthodontic tooth movement.
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Ayidağa C, Kamiloğlu B. Effects of Variable Composite Attachment Shapes in Controlling Upper Molar Distalization with Aligners: A Nonlinear Finite Element Study. JOURNAL OF HEALTHCARE ENGINEERING 2021; 2021:5557483. [PMID: 34457219 PMCID: PMC8397573 DOI: 10.1155/2021/5557483] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 06/20/2021] [Accepted: 08/07/2021] [Indexed: 11/17/2022]
Abstract
The objective of the present study is to describe the stress and displacement patterns created by clear aligners and composite attachments bonded with the acid-etch technique on the labial surface of the maxillary first upper molar during its distalization. Maxillary molar distalization is a clinical orthodontics procedure used to move the first maxillary molar distally. The procedure is useful in patients with some Class II malocclusion allowing the first molar to move into a Class I relationship and the correction of associated malocclusion features. Three finite element models were designed to simulate the alveolar bone, molar tooth, periodontal ligament, aligner, and composite attachments. The first model had no composite attachment, the second model had a vertical rectangular attachment, and the third model had a newly designed attachment. A loading method was developed that mimicked the aligner's molar distal movement. PDL was set as a viscoelastic material with a nonlinear mechanical response. von Mises and maximum principal stresses and tooth displacement patterns were analyzed using dedicated software. All the configurations showed some form of clockwise rotation in addition to the distal movement. The crown portion of the tooth showed maximum displacement in all three models; however, in the absence of attachment, the root apex moved in the opposite direction which was compatible with uncontrolled tipping movement. Simulations with attachments exhibited the best performance regarding the movement patterns. The third group, with the newly designed attachment, exhibited the best performance concerning stress distribution (principal stress and von Mises stresses) and higher stresses in the periodontal ligament and tooth. Incorporating a vertical rectangular attachment in a clear aligner resulted in the reduction of mesiodistal tipping tendency during molar distalization. The third model was the most efficient considering both displacement pattern and stress distribution. The level of stress generated by the third model needs to be further investigated in future studies.
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Affiliation(s)
- Cengiz Ayidağa
- Department of Orthodontics, Faculty of Dentistry, Near East University, Near East Boulevard, Nicosia-Northern Cyprus, Mersin 10, Turkey
| | - Beste Kamiloğlu
- Department of Orthodontics, Faculty of Dentistry, Near East University, Near East Boulevard, Nicosia-Northern Cyprus, Mersin 10, Turkey
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Golkhani B, Weber A, Keilig L, Reimann S, Bourauel C. Variation of the modulus of elasticity of aligner foil sheet materials due to thermoforming. J Orofac Orthop 2021; 83:233-243. [PMID: 34414481 PMCID: PMC9225978 DOI: 10.1007/s00056-021-00327-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 05/25/2021] [Indexed: 11/24/2022]
Abstract
Objective Investigate and compare the mechanical properties of different aligner materials before and after deep drawing and determine differences in the mechanical properties after thermoforming. Materials and methods Four aligner film sheets from three manufacturers (Duran Plus® [Scheu Dental, Iserlohn, Germany]; Zendura® [ClearCorrect, Bay Materials LLC, Fremont, CA, USA]; Essix ACE® and Essix® PLUS™ [Dentsply Sirona Deutschland, Bensheim, Germany]) were tested in 3‑point bending with support distances of 8, 16, and 24 mm. Dimension of the specimens was 10 × 50 mm2. Two groups each were tested: (1) 10 specimens were investigated in the as-received state (before thermoforming), (2) 10 specimens were deep drawn on a master plate with cuboids of the dimension 10 × 10 × 50 mm3. Then, specimens were cut out of the upper side and lateral walls and were measured in 3‑point bending. Forces and reduction in thickness were measured and corrected theoretical forces of drawn sheets after thickness reduction as well as Young’s modulus were calculated. Results At a support distance of 8 mm and a displacement of 0.25 mm Essix® PLUS™, having the highest thickness in untreated state, showed highest forces of 28.2 N, followed by Duran Plus® (27.3 N), Essix ACE® (21.0 N) and Zendura® (19.7 N). Similar results were registered for the other distances (16, 24 mm). Thermoforming drastically reduced thickness and forces in the bending tests. Forces decreased to around 10% or less for specimens cut from the lateral walls. Young’s modulus decreased significantly for deep drawn foil sheets, especially for Essix® PLUS™. Conclusions Three-point bending is an appropriate method to compare different foil sheet materials. Young’s modulus is significantly affected by thermoforming. Supplementary Information The online version of this article (10.1007/s00056-021-00327-w) contains supplementary information, which is available to authorized users.
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Affiliation(s)
- Bijan Golkhani
- Private Practice, Frechen, Germany.,Oral Technology, University of Bonn, Bonn, Germany
| | - Anna Weber
- Oral Technology, University of Bonn, Bonn, Germany
| | - Ludger Keilig
- Oral Technology and Department of Prosthodontics, Preclinical Education and Dental Materials Science, University of Bonn, Bonn, Germany
| | | | - Christoph Bourauel
- Oral Technology, University of Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.
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Impact of Dental Model Height on Thermoformed PET-G Aligner Thickness—An In Vitro Micro-CT Study. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11156674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The aim of the present study was to investigate whether base height of 3D-printed dental models has an impact on local thickness values from polyethylene terephthalate glycol (PET-G) aligners. A total of 20 aligners were thermoformed on dental models from the upper jaw exhibiting either a 5 mm high (H) or narrow (N), i.e., 0 mm, base height. The aligners were digitized using micro-CT, segmented, and local thickness values were computed utilizing a 3D-distance transform. The mean thickness values and standard deviations were assessed for both groups, and local thickness values at pre-defined reference points were also recorded. The statistical analysis was performed using R. Aligners in group H were significantly thinner and more homogenous compared to group N (p < 0.001). Significant differences in thickness values were observed among tooth types between both groups. Whereas thickness values were comparable at cusp tips and occlusal/incisal/cervical measurement locations, facial and palatal surfaces were significantly thicker in group N compared to group H (p < 0.01). Within the limits of the study, the base height of 3D-printed models impacts on local thickness values of thermoformed aligners. The clinician should consider potential implication on exerted forces at the different tooth types, and at facial as well as palatal surfaces.
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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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Inoue S, Yamaguchi S, Uyama H, Yamashiro T, Imazato S. Influence of constant strain on the elasticity of thermoplastic orthodontic materials. Dent Mater J 2020; 39:415-421. [PMID: 31827059 DOI: 10.4012/dmj.2019-104] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The aim of this study was to identify a physical property suitable for evaluating the orthodontic force by analyzing the physical properties of thermoplastic materials. Four thermoplastic materials were used: Essix A+® Plastic (EA), DURAN® (DU), Erkodur (ER), and Essix C+® Plastic (EC). Finite element analysis (FEA), a water absorption test, constant strain loading test, X-ray diffraction (XRD) and Fourier transformation infrared spectroscopy analysis were conducted. FEA found a significant correlation between the elastic modulus and the orthodontic force. The water absorption of EC was significantly smaller than the other materials. EC showed no elastic modulus change. The XRD pattern indicated that EC was a crystalline polymer. FEA of thermoplastics showed that the elastic modulus is suitable for the evaluation of orthodontic force. The crystalline thermoplastic EC demonstrated a stable elastic modulus even under strain in a wet environment, suggesting the advantage of its use as an orthodontic aligner material.
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Affiliation(s)
- Sayuri Inoue
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry.,Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry
| | - Satoshi Yamaguchi
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry
| | - Hiroshi Uyama
- Division of Applied Chemistry, Osaka University Graduate School of Engineering
| | - Takashi Yamashiro
- Department of Orthodontics and Dentofacial Orthopedics, Osaka University Graduate School of Dentistry
| | - Satoshi Imazato
- Department of Biomaterials Science, Osaka University Graduate School of Dentistry.,Department of Advanced Functional Materials Science, Osaka University Graduate School of Dentistry
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Ihssen BA, Willmann JH, Nimer A, Drescher D. Effect of in vitro aging by water immersion and thermocycling on the mechanical properties of PETG aligner material. J Orofac Orthop 2019; 80:292-303. [PMID: 31578595 DOI: 10.1007/s00056-019-00192-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 06/27/2019] [Indexed: 11/29/2022]
Abstract
PURPOSE The mechanical properties of orthodontic aligners made from thermoplastic polymers decrease over time in the intraoral milieu. However, there is a lack of information on this topic in the literature. Thus, the elastic properties of polyethylene terephthalate glycol (PETG) aligner films were investigated in vitro under extreme temperature changes simulated by thermocycling, environmental temperature and water absorption. MATERIALS AND METHODS A total of 60 specimens made from PETG aligner films (CA Clear Aligner, Scheu Dental, Iserlohn, Germany) were divided into three groups (immersed in distilled water, subjected to accelerated ageing by thermocycling, control). These groups were again divided and tensile testing was performed for all groups at 22 and at 37 °C. Young's modulus (E), 0.2% offset yield strength (Rp02) and ultimate tensile strength (UTS) were evaluated. Water absorption was determined using an analytical scale. RESULTS All treated specimens showed water absorption, whereby specimens that were thermocycled absorbed 48% more water than the immersed ones. Young's modulus and UTS were significantly lower for all three groups at 37 °C compared to the corresponding groups tested at 22 °C. Thermocycled and immersed groups showed a significantly lower Young's modulus compared to the control group tested at the same temperature. The mean Rp02 was statistically different when comparing the control group tested at 22 °C to the one tested at 37 °C. CONCLUSIONS The results of this study add to the understanding of the clinically well-known degradation of orthodontic aligners during wear time. Extreme alternating temperatures along with warming up to intraoral temperature and water absorption can reduce the material's Young's modulus and may therefore promote a decrease of resulting orthodontic forces.
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Affiliation(s)
- Benjamin A Ihssen
- Department of Orthodontics, University of Duesseldorf, Moorenstraße 5, 40225, Duesseldorf, Germany
| | - Jan H Willmann
- Department of Orthodontics, University of Duesseldorf, Moorenstraße 5, 40225, Duesseldorf, Germany.
| | - Amr Nimer
- Division of Surgery, Imperial College London, South Kensington, SW7 2AZ, London, UK
| | - Dieter Drescher
- Department of Orthodontics, University of Duesseldorf, Moorenstraße 5, 40225, Duesseldorf, Germany
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Bucci R, Rongo R, Levatè C, Michelotti A, Barone S, Razionale AV, D'Antò V. Thickness of orthodontic clear aligners after thermoforming and after 10 days of intraoral exposure: a prospective clinical study. Prog Orthod 2019; 20:36. [PMID: 31495908 PMCID: PMC6732265 DOI: 10.1186/s40510-019-0289-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 08/06/2019] [Indexed: 12/18/2022] Open
Abstract
Background Clear aligners (CA) are among the most chosen orthodontic therapies for patients who require an invisible treatment. Previous studies showed that the thermoforming process and the complexity of the intraoral environment might alter the properties of these devices. The aim of the current prospective clinical study was to assess the thickness changes of the CA after 10 days of intraoral use. The secondary aim was to assess the reproducibility of the thermoforming process, in terms of aligner thickness. Materials and methods CA from 18 consecutive patients (13 women, 5 men, mean age 28.8 ± 9.6 years) were investigated. Before intraoral exposure (T0), the thickness of the unused CA was measured at different occlusal points on a 3D model with a dedicated software (Geomagic Qualify 2013; 3D Systems, Rock Hill, SC, USA). Two CA configurations were studied: passive maxillary aligner (P—no tooth movement; no shape for attachments) and active maxillary aligner (A—tooth movement; shape for attachments and divot). The used aligners were returned after 10 days (T1) and the thickness measurements were repeated. A Student’s t test for paired data (T1 vs. T0) was applied to compare the thicknesses of used and unused devices (significance level after Bonferroni correction for multiple comparison was set at p < 0.0014). Furthermore, to study the reproducibility of the thermoforming process, P and A aligners were thermoformed twice, and the thicknesses of the two unused thermoformed devices were compared by means of Student’s t test for paired data (significance level after Bonferroni correction for multiple comparison was set at p < 0.0014) and Dahlberg’s error. Results The thermoforming process showed good reproducibility for both aligner configurations, with a maximum Dahlberg’s error of 0.13 mm. After intraoral use, the thickness of P showed some statistically significant, but not clinically relevant, thickness changes as compared to the unused aligners, while A did not show any significant changes. Conclusion Considering the thickness changes, the thermoforming process is reliable both with active and passive aligner configurations. Also, the CA examined show good thickness stability after physiological intraoral ageing in a population of healthy adults.
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Affiliation(s)
- Rosaria Bucci
- Department of Neurosciences, Reproductive Sciences and Oral Sciences, University of Naples Federico II, via Pansini 5, 80131, Naples, Italy
| | - Roberto Rongo
- Department of Neurosciences, Reproductive Sciences and Oral Sciences, University of Naples Federico II, via Pansini 5, 80131, Naples, Italy
| | - Carmine Levatè
- Department of Neurosciences, Reproductive Sciences and Oral Sciences, University of Naples Federico II, via Pansini 5, 80131, Naples, Italy
| | - Ambrosina Michelotti
- Department of Neurosciences, Reproductive Sciences and Oral Sciences, University of Naples Federico II, via Pansini 5, 80131, Naples, Italy
| | - Sandro Barone
- Department of Civil and Industrial Engineering, University of Pisa, Largo Lucio Lazzarino 1, 56122, Pisa, Italy
| | - Armando Viviano Razionale
- Department of Civil and Industrial Engineering, University of Pisa, Largo Lucio Lazzarino 1, 56122, Pisa, Italy
| | - Vincenzo D'Antò
- Department of Neurosciences, Reproductive Sciences and Oral Sciences, University of Naples Federico II, via Pansini 5, 80131, Naples, Italy.
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Experimental Study of the Pressures and Points of Application of the Forces Exerted between Aligner and Tooth. NANOMATERIALS 2019; 9:nano9071010. [PMID: 31336979 PMCID: PMC6669747 DOI: 10.3390/nano9071010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 07/08/2019] [Accepted: 07/10/2019] [Indexed: 12/28/2022]
Abstract
The analysis of forces, moments and pressure points has long been of great interest in orthodontics. Hence, we set out to define a method for measuring the pressure exerted by aligners on the teeth, and specifically to identify the precise points of pressure exertion. Intraoral scans were performed on a patient with optimal alignment and levelling before and after 2º vestibularisation of the upper central incisor. Pressure sensor film was placed in a dedicated housing between the aligner and teeth in order to record the pressure exerted after 15 s of aligner application. The images captured by the film were scanned, digitised, and subsequently analysed. Areas and amounts of pressure generated by the aligners were evaluated, and the net force of each was calculated, adjusted to take into consideration passive values. The method revealed the areas of contact by which the aligner transmits force on the teeth, and the pressures at which it does so. The pressure exerted by an aligner is not evenly distributed across the entire surface of the tooth during lingual tipping of an upper incisor. The areas of force concentration were not identical, as these are influenced by factors resulting from the manufacturing and casting processes.
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Iliadi A, Koletsi D, Eliades T. Forces and moments generated by aligner-type appliances for orthodontic tooth movement: A systematic review and meta-analysis. Orthod Craniofac Res 2019; 22:248-258. [PMID: 31237410 DOI: 10.1111/ocr.12333] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 06/19/2019] [Accepted: 06/20/2019] [Indexed: 12/27/2022]
Abstract
The aim of this review was to systematically appraise the evidence on aligner mechanics and forces and moments generated across difference types of aligners. In vitro- laboratory studies for model simulated tooth movement with aligners. Database searches within Medline via Pubmed, Cochrane Central Register of Controlled Trials (CENTRAL), LILACS via BIREME Virtual Health Library. Unpublished literature was also searched in Open Grey, ClinicalTrials.gov (www.clinicaltrials.gov), the National Research Register (www.controlled-trials.com) and Center for Open Science (Open Science Framework), using the terms "aligner" AND "orthodontic". Risk of bias assessment was based on the Cochrane Risk of Bias tool. Random effects meta-analyses were conducted. A total of 447 studies were identified through electronic search and after careful consideration of pre- defined eligibility criteria, 13 deemed eligible for inclusion, while 2 were included in the quantitative synthesis. When palatal tipping of the upper central incisor through PET-G aligners was considered, aligner thickness of 0.5, 0.625 or 0.75 mm was not associated with a significantly different moment to force (M/F) ratio, given a common gingival edge width of 3-4 mm. Aligner thickness does not appear to possess a significant role in forces and moments generated by clear aligners under specific settings, while the most commonly examined tooth movements are tipping and rotation. The findings of this review may be applicable to certain conditions in laboratory settings.
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Affiliation(s)
- Anna Iliadi
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
| | - Despina Koletsi
- Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.,Clinic of Orthodontics and Paediatric Dentistry, School of Dental Medicine, University of Zurich, Zurich, Switzerland
| | - Theodore Eliades
- Clinic of Orthodontics and Paediatric Dentistry, School of Dental Medicine, University of Zurich, Zurich, Switzerland
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Mechanical Characterization of Thermoplastic Aligner Materials: Recommendations for Test Parameter Standardization. JOURNAL OF HEALTHCARE ENGINEERING 2019; 2019:8074827. [PMID: 31275537 PMCID: PMC6560334 DOI: 10.1155/2019/8074827] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 04/16/2019] [Accepted: 05/13/2019] [Indexed: 01/06/2023]
Abstract
Background Understanding of the different mechanical properties of thermoplastic materials is essential for a successful aligner treatment and further developments. However, data of previous material testing studies are scarcely comparable. Aim of the current study was to evaluate the different test parameters to lay the foundations for guidelines for future, more standardized three-point-bending aligner material tests. Materials and Methods Several parameters concerning the specimen preparation and experimental three-point-bending setup were varied. The specimens were collected from polyethylene terephthalate glycol (PET-G) Duran® foils with different thicknesses. Both raw foils and foils thermoformed using different geometrical forms were investigated. The three-point-bending tests were performed using span lengths of 8 and 16 mm and variable deflection ranges between 0.1 and 0.2 mm. The influence of water storage on the bending forces was studied using unloaded and loaded specimens. Experimental results were validated using a beam cantilever mathematical model. Results Local macroscopic cracks after long-term loading could be avoided by keeping the deflections within a thickness-dependent individual range. The mathematical calculations confirmed that these individual deflection ranges lead to local stresses between 14 and 18 MPa. Constantly loaded specimens immersed for 24 hours in water showed a decrease of the bending force by 50%. This reduction was much smaller for the unloaded specimens (14%). Conclusion During clinical aligner therapy, very small bending deflections are combined with small distances between the tooth surface regions supporting the aligner. In vitro aligner material testing by three-point bending should consider these geometrical aspects, while keeping the material stresses in a range between 14 and 18 MPa to avoid local microcracks. Considering these aspects, thickness-dependent deflections were established for three-point bending of the PET-G specimen for a span length of 8 mm. We recommend the application of these test parameters in future aligner material studies to achieve valid and comparable test results.
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Elkholy F, Mikhaiel B, Schmidt F, Lapatki BG. Mechanical load exerted by PET-G aligners during mesial and distal derotation of a mandibular canine : An in vitro study. J Orofac Orthop 2019; 78:361-370. [PMID: 28357471 DOI: 10.1007/s00056-017-0090-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION The six force-moment (F/M) components exerted by aligners of different thickness during simulated mesiorotation and distorotation of a mandibular canine were studied. MATERIALS AND METHODS An acrylic mandibular model with a separated right canine mounted on a hexapod via a 3D F/M sensor was used. Duran+® aligners (Scheu Dental, Germany) of thickness 0.5, 0.625, and 0.75 mm were fabricated on plaster models with the measurement tooth in its neutral position. The F/M values were recorded during progressive mesiorotation or distorotation of tooth 43 in 1° steps up to ±15°, corresponding to 0.5 mm displacements of the tooth's interdental contacts. Each rotation step included renewed seating of the aligner on the acrylic model. Three aligners were tested three times each for each thickness and direction of rotation. RESULTS The median rotational moments for the 0.5 mm aligner and 15° distorotation of tooth 43 was 27.49 Nmm (interquartile range, IQR 1.45 Nmm). The corresponding values for the 0.625 and 0.75 mm aligners were 41.04 Nmm (IQR 5.62 Nmm) and 42.48 Nmm (IQR 2.17 Nmm), respectively. The average rotational moments for distorotation were 15% higher than for mesiorotation (p = 0.01). Relatively high collateral F/M components, specifically an intrusive force and labiolingual and mesiodistal tipping moments, were observed. CONCLUSION To avoid overloading of periodontal structures, derotation of lower canines should be limited to 10° per setup step, leading to rotational moments of about 15 Nmm. The mechanical behavior of the 0.625 and 0.75 mm aligners were similar; thus, it may be omitted from the aligner sequence. Further studies are required to investigate specific aligner modifications or attachments for minimizing collateral F/M components or unwanted movements, respectively, during canine derotation.
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Affiliation(s)
- F Elkholy
- Department of Orthodontics, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
| | - B Mikhaiel
- Department of Prosthodontics, University of Ulm, Ulm, Germany
| | - F Schmidt
- Department of Orthodontics, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - B G Lapatki
- Department of Orthodontics, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
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Tepedino M, Paoloni V, Cozza P, Chimenti C. Movement of anterior teeth using clear aligners: a three-dimensional, retrospective evaluation. Prog Orthod 2018; 19:9. [PMID: 29607469 PMCID: PMC5879033 DOI: 10.1186/s40510-018-0207-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 03/08/2018] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Clear aligner treatment offers several advantages, but the available literature shows that some kind of tooth movements are unpredictable. In addition, the majority of the studies are focused on one clear aligner system, while different characteristics of various systems can provide different treatment outcomes. The aim of the present retrospective cohort study was to evaluate the predictability of Nuvola® aligner system in achieving torque movements of anterior teeth. METHODS Thirty-nine adult patients, who were consecutively treated with clear aligners, were retrospectively selected, and digital models pre-treatment (T0), post-treatment (T1) and the digital setup models (TS) were collected. Only the first phase of treatment made of 12 aligners was considered for the present study. Torque of anterior teeth was measured as labiolingual inclination on digital models at T0, T1, and TS using VAM software. Any difference between the predicted and achieved torque movements was evaluated using Wilcoxon signed-rank test or paired sample t test. First-type error was set as p < 0.008. RESULTS No statistically significant difference was found for all the anterior teeth between predicted and achieved torque movements. CONCLUSIONS The studied clear aligner system was able to produce clinical outcomes comparable to the planning of the digital setup relative to torque movements of the anterior teeth.
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Affiliation(s)
- Michele Tepedino
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, Viale S.Salvatore, Edificio Delta 6, 67100, L'Aquila, Italy.
| | - Valeria Paoloni
- Department of Clinical Sciences and Translational Medicine, University of Rome Tor Vergata, Viale Oxford 81, 00133, Rome, Italy
| | - Paola Cozza
- Department of Clinical Sciences and Translational Medicine, University of Rome Tor Vergata, Viale Oxford 81, 00133, Rome, Italy
| | - Claudio Chimenti
- Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, Viale S.Salvatore, Edificio Delta 6, 67100, L'Aquila, Italy
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Elkholy F, Schmidt F, Jäger R, Lapatki BG. Forces and moments applied during derotation of a maxillary central incisor with thinner aligners: An in-vitro study. Am J Orthod Dentofacial Orthop 2017; 151:407-415. [PMID: 28153171 DOI: 10.1016/j.ajodo.2016.08.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Revised: 08/01/2016] [Accepted: 08/01/2016] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Recent studies have shown that therapeutic loads applied to individual teeth by aligners may substantially exceed recommended values. The primary purpose of this study was to quantify force and moment components during derotation of a maxillary central incisor when 0.3-mm-thick or 0.4-mm-thick polyethylene terephthalate glycol aligners were used instead of conventional polyethylene terephthalate glycol aligners with a minimum thickness of 0.5 mm. METHODS The test setup consisted of an acrylic model of a maxilla with a separated right central incisor mounted on a 3-dimensional force and moment sensor. The force and moment components were recorded for aligners with thicknesses ranging from 0.3 to 0.75 mm during ±10° rotation and derotation of the separated incisor. RESULTS Moments exerted by the thinnest aligner currently available, 0.5 mm, were 73.57 Nmm for the 10° mesiorotation. In comparison, the corresponding moments with the 0.4-mm and 0.3-mm aligners were 41.08 and 17.84 Nmm, respectively. Moment values for derotation of the maxillary right central incisor into neutral position showed nonlinear return curves indicating viscoelastic material behavior. CONCLUSIONS A significant load reduction can be achieved with the new thinner aligners. Because of the form instability of the 0.3-mm aligner during handling, we suggest the novel sequence 0.4, 0.5, and 0.75 mm for aligner systems based on sequentially increased material thickness. This sequence combines sufficiently low initial aligner stiffness and steady load increases in single setup steps. The viscoelastic behavior of polyethylene terephthalate glycol aligners observed during incisor derotation should lead to a reduction of the high initial load exerted directly after intraoral aligner insertion.
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Affiliation(s)
- Fayez Elkholy
- Department of Orthodontics, University of Ulm, Ulm, Germany.
| | - Falko Schmidt
- Department of Orthodontics, University of Ulm, Ulm, Germany
| | - Rudolf Jäger
- Department of Orthodontics, University of Ulm, Ulm, Germany
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Brockmeyer P, Kramer K, Böhrnsen F, Gruber RM, Batschkus S, Rödig T, Hahn W. Removable thermoplastic appliances modified by incisal cuts show altered biomechanical properties during tipping of a maxillary central incisor. Prog Orthod 2017; 18:28. [PMID: 28845511 PMCID: PMC5572558 DOI: 10.1186/s40510-017-0183-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 08/02/2017] [Indexed: 11/10/2022] Open
Abstract
Background The present study aimed to evaluate the force delivery of removable thermoplastic appliances (RTAs), modified by different sized incisal cuts, during tipping of a maxillary central incisor in palatal and vestibular direction. Methods Forty-five RTAs from three different materials (Biolon®, Erkodur®, Ideal Clear®) of the same thickness (1 mm) were used. Analysis was performed on a separated maxillary central incisor which was part of a resin model with a complete dentition. In 15 RTAs, of different material, a cut was inserted at the incisal edge of tooth 11. In 15 other appliances, the cut was extended to teeth 12 and 21. Fifteen aligners remained uncut. The experimental tooth was tipped starting from the zero position in 0.05° steps to a maximal deflection of ± 0.42° of the incisal edge in vestibular and palatal direction, after positioning the RTA onto the model. Results The horizontal (Fx) and the vertical (Fz) force components were decreased by approximately half with increasing cut size. Fz values changed during palatal tipping from a weak intrusive force, for aligners without cut, to an extrusive force with increasing cut size. Compared to both other materials used (Erkodur® and Ideal Clear®), the Biolon® aligners showed significantly higher Fx and Fz values (p < 0.0001, respectively). Conclusions RTAs modified by different sized incisal cuts show altered biomechanical properties and an inversion of the vertical force component, during tipping of a maxillary central incisor.
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Affiliation(s)
- Phillipp Brockmeyer
- Department of Oral and Maxillofacial Surgery, University Medical Centre Goettingen, Robert-Koch-Str. 40, 37075, Goettingen, Germany.
| | - Katharina Kramer
- Department of Medical Statistics, University Medical Centre Goettingen, Humboldtallee 32, 37073, Goettingen, Germany
| | - Florian Böhrnsen
- Department of Oral and Maxillofacial Surgery, University Medical Centre Goettingen, Robert-Koch-Str. 40, 37075, Goettingen, Germany
| | - Rudolf Matthias Gruber
- Department of Oral and Maxillofacial Surgery, University Medical Centre Goettingen, Robert-Koch-Str. 40, 37075, Goettingen, Germany
| | - Sarah Batschkus
- Department of Orthodontics, University Medical Centre Goettingen, Robert-Koch-Str. 40, 37075, Goettingen, Germany
| | - Tina Rödig
- Department of Preventive Dentistry, Periodontology and Cariology, University Medical Centre Goettingen, Robert-Koch-Str. 40, 37075, Goettingen, Germany
| | - Wolfram Hahn
- Department of Orthodontics, University Medical Centre Goettingen, Robert-Koch-Str. 40, 37075, Goettingen, Germany.,Private practice, Goettingen, Germany
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Barone S, Paoli A, Razionale AV, Savignano R. Computational design and engineering of polymeric orthodontic aligners. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2017; 33:e2839. [PMID: 27704706 DOI: 10.1002/cnm.2839] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 09/27/2016] [Accepted: 09/30/2016] [Indexed: 06/06/2023]
Abstract
Transparent and removable aligners represent an effective solution to correct various orthodontic malocclusions through minimally invasive procedures. An aligner-based treatment requires patients to sequentially wear dentition-mating shells obtained by thermoforming polymeric disks on reference dental models. An aligner is shaped introducing a geometrical mismatch with respect to the actual tooth positions to induce a loading system, which moves the target teeth toward the correct positions. The common practice is based on selecting the aligner features (material, thickness, and auxiliary elements) by only considering clinician's subjective assessments. In this article, a computational design and engineering methodology has been developed to reconstruct anatomical tissues, to model parametric aligner shapes, to simulate orthodontic movements, and to enhance the aligner design. The proposed approach integrates computer-aided technologies, from tomographic imaging to optical scanning, from parametric modeling to finite element analyses, within a 3-dimensional digital framework. The anatomical modeling provides anatomies, including teeth (roots and crowns), jaw bones, and periodontal ligaments, which are the references for the down streaming parametric aligner shaping. The biomechanical interactions between anatomical models and aligner geometries are virtually reproduced using a finite element analysis software. The methodology allows numerical simulations of patient-specific conditions and the comparative analyses of different aligner configurations. In this article, the digital framework has been used to study the influence of various auxiliary elements on the loading system delivered to a maxillary and a mandibular central incisor during an orthodontic tipping movement. Numerical simulations have shown a high dependency of the orthodontic tooth movement on the auxiliary element configuration, which should then be accurately selected to maximize the aligner's effectiveness.
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Affiliation(s)
- S Barone
- Department of Civil and Industrial Engineering, University of Pisa, Pisa, Italy
| | - A Paoli
- Department of Civil and Industrial Engineering, University of Pisa, Pisa, Italy
| | - A V Razionale
- Department of Civil and Industrial Engineering, University of Pisa, Pisa, Italy
| | - R Savignano
- Department of Civil and Industrial Engineering, University of Pisa, Pisa, Italy
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Liu CL, Sun WT, Liao W, Lu WX, Li QW, Jeong Y, Liu J, Zhao ZH. Colour stabilities of three types of orthodontic clear aligners exposed to staining agents. Int J Oral Sci 2016; 8:246-253. [PMID: 27660048 PMCID: PMC5168413 DOI: 10.1038/ijos.2016.25] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/03/2016] [Indexed: 02/05/2023] Open
Abstract
The aim of this study was to evaluate and compare the colour stabilities of three types of orthodontic clear aligners exposed to staining agents in vitro. Sixty clear orthodontic aligners produced by three manufacturers (Invisalign, Angelalign, and Smartee) were immersed in three staining solutions (coffee, black tea, and red wine) and one control solution (distilled water). After 12-h and 7-day immersions, the aligners were washed in an ultrasonic cleaner and measured with a colourimeter. The colour changes (ΔE*) were calculated on the basis of the Commission Internationale de I'Eclairage L*a*b* colour system (CIE L*a*b*), and the results were then converted into National Bureau of Standards (NBS) units. Fourier transformation infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were conducted to observe the molecular and morphologic alterations to the aligner surfaces, respectively. The three types of aligners exhibited slight colour changes after 12 h of staining, with the exception of the Invisalign aligners stained with coffee. The Invisalign aligners exhibited significantly higher ΔE* values (ranging from 0.30 to 27.81) than those of the Angelalign and Smartee aligners (ΔE* values ranging from 0.33 to 1.89 and 0.32 to 1.61, respectively, P<0.05). FT-IR analysis confirmed that the polymer-based structure of aligners did not exhibit significant chemical differences before and after the immersions. The SEM results revealed different surface alterations to the three types of aligner materials after the 7-day staining. The three types of aesthetic orthodontic appliances exhibited colour stability after the 12-h immersion, with the exception of the Invisalign aligners stained by coffee. The Invisalign aligners were more prone than the Angelalign and Smartee aligners to pigmentation. Aligner materials may be improved by considering aesthetic colour stability properties.
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Affiliation(s)
- Chen-Lu Liu
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Wen-Tian Sun
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Wen Liao
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Wen-Xin Lu
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Qi-Wen Li
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yunho Jeong
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jun Liu
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Zhi-He Zhao
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
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Elkholy F, Schmidt F, Jäger R, Lapatki BG. Forces and moments delivered by novel, thinner PET-G aligners during labiopalatal bodily movement of a maxillary central incisor: An in vitro study. Angle Orthod 2016; 86:883-890. [DOI: 10.2319/011316-37r.1] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
ABSTRACT
Objective: To evaluate whether overloading of teeth can be avoided by utilizing aligners with reduced thicknesses of 0.4 mm or 0.3 mm.
Materials and Methods: The experimental setup included an acrylic maxillary jaw model with tooth 11 separated and fixed via a 3-D force-moment transducer to a hexapod for experimental movement. Aligners tested were fabricated on duplicate stone models using commercially available polyethylene terephthalate glycol (PET-G) foils with thicknesses between 0.5 and 0.75 mm, and novel 0.4-mm- and 0.3-mm-thick foils. With the test aligner seated, 11 was bodily displaced in a labiopalatal direction in the range of ±0.25 mm while all six force-and-moment components exerted on this tooth were registered.
Results: With the thinnest commercially available 0.5-mm aligner, median forces of −7.89 N and 8.37 N were measured for the maximum 0.25-mm movement of 11 in a labial and palatal direction, respectively. In comparison, force values were 35% and 71% lower for the novel aligners with a thickness of 0.4 mm and 0.3 mm, respectively.
Conclusions: Novel “leveling” aligners with reduced thickness may reduce overloading of individual teeth during aligner therapy. Due to form instability of 0.3-mm aligners, we suggest a novel sequence of 0.4–0.5–0.75 mm for aligner systems using several foil thicknesses for load graduation within single setup steps. This would combine low stiffness of the initial aligner and relatively constant load increases throughout the treatment.
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Affiliation(s)
- Fayez Elkholy
- Orthodontist and Staff Member, Department of Orthodontics, University of Ulm, Ulm, Germany
| | - Falko Schmidt
- Researcher, Department of Orthodontics, University of Ulm, Ulm, Germany
| | - Rudolf Jäger
- Researcher, Department of Orthodontics, University of Ulm, Ulm, Germany
| | - Bernd G. Lapatki
- Professor and Department Chair, Department of Orthodontics, University of Ulm, Ulm, Germany
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