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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: 14] [Impact Index Per Article: 3.5] [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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Fang D, Li F, Zhang Y, Bai Y, Wu BM. Changes in mechanical properties, surface morphology, structure, and composition of Invisalign material in the oral environment. Am J Orthod Dentofacial Orthop 2020; 157:745-753. [PMID: 32487304 DOI: 10.1016/j.ajodo.2019.05.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 05/01/2019] [Accepted: 05/01/2019] [Indexed: 11/15/2022]
Abstract
INTRODUCTION The mechanical properties of Invisalign material have rarely been explored because of the inaccessibility of the patent-protected raw material. The purpose of this study was to systematically evaluate the Invisalign thermoformed aligner material before and after clinical application, including mechanical properties, surface morphology, internal structure, and chemical composition changes. METHODS Twenty sets of "as-received" (0-week) and retrieved (2-week; worn for 2 weeks, 20 ± 2 hours per day) Invisalign aligners were randomly collected from 4 different patients. Tensile tests, stress relaxation, and creep tests were carried out with a dynamic mechanical analyzer to characterize the changes in the mechanical properties of this material, Fourier transform infrared spectroscopy was used to capture the molecular changes on the surface of these aligners, scanning electron microscopy and transmission electron microscopy were used to observe the changes in surface morphology and internal structure, and scanning transmission electron microscopy-energy dispersive x-ray analysis was used to detect any changes in the chemical composition of this material before and after clinical application. RESULTS The elastic modulus of 0-week and 2-week samples were 842 ± 63 MPa and 806 ± 19 MPa, respectively, with no significant difference. In addition, the relative stress after stress relaxation of 2 hours was 19.89 ± 2.25% and 15.91 ± 6.04% for 0-week and 2-week groups, respectively, with no significant difference. Scanning electron microscopy observations showed voids and signs of delamination on the surface of the 2-week samples, and scanning transmission electron microscopy-energy dispersive x-ray analysis indicated the possible release of trace elements during clinical use, such as aluminum. Results of Fourier transform infrared spectroscopy analysis, and transmission electron microscopy observations were quite stable, indicating that the molecular structure on the surface and the internal structure of this material were relatively stable under the oral environment. CONCLUSIONS The surface morphology showed some defects after the clinical use of 2 weeks; however, there was no significant difference in mechanical properties. Trace elements may release out during clinical use and may pose a specific danger to allergic patients.
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Affiliation(s)
- Dongyu Fang
- Department of Orthodontics, Beijing Stomatological Hospital, School of Stomatology, Capital Medical University, Beijing, China; Department of Bioengineering, University of California, Los Angeles, Calif
| | - Fangming Li
- Department of Bioengineering, University of California, Los Angeles, Calif
| | - Yulong Zhang
- Department of Bioengineering, University of California, Los Angeles, Calif
| | - Yuxing Bai
- Department of Orthodontics, Beijing Stomatological Hospital, School of Stomatology, Capital Medical University, Beijing, China.
| | - Benjamin M Wu
- Department of Bioengineering, University of California, Los Angeles, Calif.
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Daniele V, Macera L, Taglieri G, Di Giambattista A, Spagnoli G, Massaria A, Messori M, Quagliarini E, Chiappini G, Campanella V, Mummolo S, Marchetti E, Marzo G, Quinzi V. Thermoplastic Disks Used for Commercial Orthodontic Aligners: Complete Physicochemical and Mechanical Characterization. MATERIALS 2020; 13:ma13102386. [PMID: 32455913 PMCID: PMC7287673 DOI: 10.3390/ma13102386] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Revised: 05/14/2020] [Accepted: 05/18/2020] [Indexed: 12/13/2022]
Abstract
Invisible orthodontic aligners (IOAs) have been introduced in the orthodontic field as an innovative alternative for fixed brackets, in relation to their ability to be easily inserted/removed from the oral cavity without affecting the chewing ability and the aesthetic of the patients. The paper provides a complete physicochemical and mechanical characterization of thermoplastic materials in the form of disks used for commercial IOAs. A wide palette of specific techniques is considered, from tensile tests and dynamic-mechanical analysis, to X-Ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transformation infrared spectroscopy (FTIR-ATR) analyses and water absorption tests. The disks are investigated before and after immersion into staining beverages (red wine, coffee, nicotine and artificial saliva), in terms of colour variations, transparency, and microscopic surface modifications by means of colorimetry, UV-VIS absorbance and scanning electron microscopy (SEM). Among all the samples, polyurethane (PU) exhibited the highest crystallinity and the highest values of mechanical and thermal resistance, while the poly(ethylene terephthalate)-glycol (PETG) samples presented better transparency and less ability to absorb water. Moreover, red wine and coffee give noticeable colour variations after 14 days of immersion, together with a slight reduction of transparency.
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Affiliation(s)
- Valeria Daniele
- Department of Industrial and Information Engineering and Economics, University of L’Aquila, Piazzale Pontieri 1, Monteluco di Roio, 67100 L’Aquila, Italy; (V.D.); (G.T.); (A.D.G.); (G.S.)
| | - Ludovico Macera
- Department of Industrial and Information Engineering and Economics, University of L’Aquila, Piazzale Pontieri 1, Monteluco di Roio, 67100 L’Aquila, Italy; (V.D.); (G.T.); (A.D.G.); (G.S.)
- Correspondence:
| | - Giuliana Taglieri
- Department of Industrial and Information Engineering and Economics, University of L’Aquila, Piazzale Pontieri 1, Monteluco di Roio, 67100 L’Aquila, Italy; (V.D.); (G.T.); (A.D.G.); (G.S.)
| | - Alessandra Di Giambattista
- Department of Industrial and Information Engineering and Economics, University of L’Aquila, Piazzale Pontieri 1, Monteluco di Roio, 67100 L’Aquila, Italy; (V.D.); (G.T.); (A.D.G.); (G.S.)
| | - Giuseppe Spagnoli
- Department of Industrial and Information Engineering and Economics, University of L’Aquila, Piazzale Pontieri 1, Monteluco di Roio, 67100 L’Aquila, Italy; (V.D.); (G.T.); (A.D.G.); (G.S.)
| | - Alessandra Massaria
- Department of Life, Health & Environmental Sciences, Postgraduate School of Orthodontics, University of L’Aquila, P.le Salvatore Tommasi 1, Ed. Delta 6, 67100 L’Aquila, Italy; (A.M.); (S.M.); (E.M.); (G.M.); (V.Q.)
| | - Massimo Messori
- Department of Engineering ‘Enzo Ferrari’, University of Modena and Reggio Emilia, Via P. Vivarelli 10, 41125 Modena, Italy;
| | - Enrico Quagliarini
- Department of Construction, Civil Engineering and Architecture, Polytechnic University of Marche, 60121 Ancona, Italy;
| | - Gianluca Chiappini
- Department of Industrial Engineering and Mathematical Sciences, Polytechnic University of Marche, via Brecce Bianche snc, 60131 Ancona, Italy;
| | - Vincenzo Campanella
- Department of Clinical Science and Translational Medicine, University of Rome “Tor Vergata”, Via Montpellier 1, 00133 Roma, Italy;
| | - Stefano Mummolo
- Department of Life, Health & Environmental Sciences, Postgraduate School of Orthodontics, University of L’Aquila, P.le Salvatore Tommasi 1, Ed. Delta 6, 67100 L’Aquila, Italy; (A.M.); (S.M.); (E.M.); (G.M.); (V.Q.)
| | - Enrico Marchetti
- Department of Life, Health & Environmental Sciences, Postgraduate School of Orthodontics, University of L’Aquila, P.le Salvatore Tommasi 1, Ed. Delta 6, 67100 L’Aquila, Italy; (A.M.); (S.M.); (E.M.); (G.M.); (V.Q.)
| | - Giuseppe Marzo
- Department of Life, Health & Environmental Sciences, Postgraduate School of Orthodontics, University of L’Aquila, P.le Salvatore Tommasi 1, Ed. Delta 6, 67100 L’Aquila, Italy; (A.M.); (S.M.); (E.M.); (G.M.); (V.Q.)
| | - Vincenzo Quinzi
- Department of Life, Health & Environmental Sciences, Postgraduate School of Orthodontics, University of L’Aquila, P.le Salvatore Tommasi 1, Ed. Delta 6, 67100 L’Aquila, Italy; (A.M.); (S.M.); (E.M.); (G.M.); (V.Q.)
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Mechanical Properties of Thermoplastic Polymers for Aligner Manufacturing: In Vitro Study. Dent J (Basel) 2020; 8:dj8020047. [PMID: 32397575 PMCID: PMC7345642 DOI: 10.3390/dj8020047] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 05/06/2020] [Accepted: 05/07/2020] [Indexed: 12/24/2022] Open
Abstract
The use of metal-free thermoplastic materials plays a key role in the orthodontic digital workflow due to the increasing demand for clear aligner treatments. Three thermoplastic polymers commonly used to fabricate clear aligners, namely Duran®, Biolon® and Zendura®, were investigated to evaluate the effect of thermoforming (T.), storage in artificial saliva (S.A.S.) and their combination on their mechanical properties. Elastic modulus and yield stress of the specimens were characterized. Each material was characterized for each condition through tensile tests (ISO527-1). The results showed that thermoforming does not lead to a significant decrease in yield stress, except for Zendura® that showed about a 30% decrease. An increase of the elastic modulus of Duran® and Zendura®, instead, was observed after thermoforming. The same increase was noticed for the yield stress of Duran®. For S.A.S. specimens, the elastic modulus generally decreases compared to supplier condition (A.S.) and simply thermoformed material. A decrease of yield stress, instead, is significant for Zendura®. The results demonstrated that the impact of the operating conditions on the mechanical properties can vary according to the specific polymer. To design reliable and effective orthodontic treatments, the materials should be selected after their mechanical properties are characterized in the simulated intraoral environment.
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ATR-FTIR Analysis and One-Week Stress Relaxation of Four Orthodontic Aligner Materials. MATERIALS 2020; 13:ma13081868. [PMID: 32316154 PMCID: PMC7215293 DOI: 10.3390/ma13081868] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 04/14/2020] [Accepted: 04/15/2020] [Indexed: 02/06/2023]
Abstract
The aim of this study was to estimate possible differences in the chemical composition and relaxation of orthodontic aligner materials. Four commercially available thermoplastic materials CAM (Scheu-Dental, Iserlohn, Germany), COP (Essix, Dentsply Raintree Essix Sarasota,FL, USA), DUR (Great Lakes Dental Technologies, Tonawanda, NY) and ERK (Erkodent Erich Kopp, Pfalzgrafenweiler Germany) were included in this study. Rectangular strips from each material were prepared according to the manufacturer's instructions and subjected to attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and stress relaxation characterization. The reduction in applied stress (RAS) after one week was estimated and statistically analyzed by one-way ANOVA at the 0.05 level of significance. All specimens were subjected to optical microscopy before and after stress relaxation testing under transmittance polarized illumination. ATR-FTIR microscopy revealed that all materials are made of polyethylene terephthalate glycol (PETG) while no significant differences were identified in RAS values among materials tested, which ranged from 6%-10% (p ≥ 0.05). All samples illustrated the developments of shear bands during relaxation testing according to optical microscopy findings. The tested materials illustrated similar chemical composition and relaxation behavior and thus no differences in their clinical efficacy are anticipated.
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Effect of different attachment geometries on the mechanical load exerted by PET‑G aligners during derotation of mandibular canines : An in vitro study. J Orofac Orthop 2019; 80:315-326. [PMID: 31595320 DOI: 10.1007/s00056-019-00193-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 07/30/2019] [Indexed: 10/25/2022]
Abstract
AIM Derotation of rounded teeth has proved difficult for aligners to achieve. In this study, we investigated the effect of aligner attachment geometry on the three-dimensional (3D) force and moment (F/M) values exerted during derotation of a mandibular canine. MATERIALS AND METHODS The experiment setup comprised an acrylic mandibular arch model with a separated right canine (tooth 43) mounted on a hexapod via a 3D F/M sensor. Polyethylene terephthalate glycol (PET‑G) aligners with thicknesses of 0.5, 0.625, and 0.75 mm were tested in combination with quarter-sphere, vertical-ellipsoid, and pyramidal attachments bonded to tooth 43. The experimentally measured movement consisted of mesio- and distorotation of tooth 43 in 1° steps up to ±15° in each direction. RESULTS Compared with no attachment, vertical-ellipsoid and quarter-sphere attachments increased the rotational moment by a median factor of 1.5-12.3. Moment increases for pyramidal attachments were significantly smaller (Mann-Whitney U‑test, p < 0.05). Quarter-sphere attachments inhibited the intrusive forces up to 6.07° distorotation, whereas the intrusion prevention range for most aligner attachment combinations was significantly smaller (2.95° for vertical-ellipsoid and 2.88° for pyramidal attachments; Mann-Whitney U‑test, p < 0.05). None of the attachment geometries could completely prevent intrusive forces during mesiorotation. CONCLUSION The quarter-sphere geometry had the best overall mechanical properties because it induced relatively high rotational moment increases and counteracted unwanted intrusive forces most effectively of all three geometries. The determined maximum attachment dislodgement and intrusion prevention angles of approximately 6° provide a guide to determining setup increments for mandibular canine derotation.
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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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Papadopoulou AK, Cantele A, Polychronis G, Zinelis S, Eliades T. Changes in Roughness and Mechanical Properties of Invisalign ® Appliances after One- and Two-Weeks Use. MATERIALS 2019; 12:ma12152406. [PMID: 31357697 PMCID: PMC6696190 DOI: 10.3390/ma12152406] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 07/23/2019] [Accepted: 07/26/2019] [Indexed: 11/25/2022]
Abstract
The aim of this study was to estimate the possible changes of surface roughness and the mechanical properties of Invisalign® appliances over one- and two-week of service. Forty appliances with attachments were retrieved after the end of orthodontic treatment from different patients. Half of them had been used for one week (1W), and the rest for two weeks (2W). Ten unused Invisalign® appliances were used as the control (CON). An equal number of teeth possessing attachments were cut of aligners deriving from all groups (1W, 2W, and CON), and the Sa, Sq, Sz, Sc, and Sv roughness parameters of the internal surface of the aligner attachment area and the opposite lingual side (which was in contact to enamel) were determined by optical profilometry. Then, ten first molars originating from all groups were embedded in acrylic resin, and were ground and polished. Instrumented indentation testing (IIT) was performed in order to determine the Martens hardness (HM), indentation modulus (EIT), and relaxation index (RIT), according to ISO 14577-2002. The produced data were statistically processed by one- or two-way analysis of variance (ANOVA) and multiple comparison post-hoc tests (a = 0.05). Both the surface roughness and mechanical properties of the retrieved groups (1W and 2W) showed statistically significant differences compared with CON, but without statistically significant differences between each other. The roughness variables of the as-received material were shown to be reduced after intraoral service demonstrating a wear effect. Ageing has a detrimental effect on the surface roughness and mechanical properties of Invisalign® appliances, although this effect is restricted to the first week of clinical usage.
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Affiliation(s)
| | - Aurelie Cantele
- Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, 8032 Zurich, Switzerland
| | - Georgios Polychronis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, 11527 Athens, Greece
| | - Spiros Zinelis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, 11527 Athens, Greece
| | - Theodore Eliades
- Clinic of Orthodontics and Pediatric Dentistry, Center of Dental Medicine, University of Zurich, 8032 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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Skaik A, Wei XL, Abusamak I, Iddi I. Effects of time and clear aligner removal frequency on the force delivered by different polyethylene terephthalate glycol-modified materials determined with thin-film pressure sensors. Am J Orthod Dentofacial Orthop 2019; 155:98-107. [PMID: 30591174 DOI: 10.1016/j.ajodo.2018.03.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 03/01/2018] [Accepted: 03/01/2018] [Indexed: 10/27/2022]
Abstract
INTRODUCTION Many factors influence the force changes of clear aligners. The purpose of this study was to identify the various factors that influence the force changes generated by polyethylene terephthalate glycol-modified (PET-G) materials. Therefore, a force measurement system based on a flexible thin-film pressure sensor was established. METHODS A series of clear aligners with 2 material properties and different activations at the maxillary central incisor, maxillary second premolar, and maxillary permanent first molar was designed and fabricated. The first material was conventional PET-G; the second material was modified PET-G with a higher modulus of elasticity and greater abrasion resistance. Several models, including teeth and aligners, were produced. Then, a force change detection device, including a thin-film pressure sensor, a signal acquisition circuit board, and a computer, was applied to measure changes in the forces delivered by the conventional and modified PET-G materials with increased frequencies of appliance removal. Finally, the forces were repeatedly measured to detect the force changes over 48 hours. RESULTS The forces of both materials decreased similarly over time. These forces also decreased when the aligner removal frequency increased, but the forces decreased differently. The modified PET-G, with a higher modulus of elasticity and greater abrasion resistance, showed a more stable and lower force change than did the conventional PET-G. CONCLUSIONS The forces delivered by both materials were within the orthodontic force range. Force changes were apparent when the appliance removal frequency increased. Compared with the conventional material, the modified PET-G material showed better stability. Therefore, the modified PET-G is a promising and applicable material with advantages for both orthodontists and patients.
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Affiliation(s)
- Adham Skaik
- Department of Orthodontics, Medical Center of Stomatology, Second Xiangya Hospital, Central South University, Changsha, China
| | - Xiao Li Wei
- Department of Orthodontics, Medical Center of Stomatology, Second Xiangya Hospital, Central South University, Changsha, China.
| | - Islam Abusamak
- Department of Orthodontics, Medical Center of Stomatology, Second Xiangya Hospital, Central South University, Changsha, China
| | - Iddi Iddi
- Department of Orthodontics, Medical Center of Stomatology, Second Xiangya Hospital, Central South University, Changsha, China
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Ryu JH, Kwon JS, Jiang HB, Cha JY, Kim KM. Effects of thermoforming on the physical and mechanical properties of thermoplastic materials for transparent orthodontic aligners. Korean J Orthod 2018; 48:316-325. [PMID: 30206530 PMCID: PMC6123073 DOI: 10.4041/kjod.2018.48.5.316] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 05/14/2018] [Accepted: 05/29/2018] [Indexed: 11/13/2022] Open
Abstract
Objective The aim of this systematic multiscale analysis was to evaluate the effects of thermoforming on the physical and mechanical properties of thermoplastic materials used to fabricate transparent orthodontic aligners (TOAs). Methods Specimens were fabricated using four types of thermoplastic materials with different thicknesses under a thermal vacuum. Transparency, water absorption and solubility, surface hardness, and the results of three-point bending and tensile tests were evaluated before and after thermoforming. Data were analyzed using one-way analysis of variance and Student's t-test. Results After thermoforming, the transparency of Duran and Essix A+ decreased, while the water absorption ability of all materials; the water solubility of Duran, Essix A+, and Essix ACE; and the surface hardness of Duran and Essix A+ increased. The flexure modulus for the 0.5-mm-thick Duran, Essix A+, and eCligner specimens increased, whereas that for the 0.75-/1.0-mm-thick Duran and eClginer specimens decreased. In addition, the elastic modulus increased for the 0.5-mm-thick Essix A+ specimens and decreased for the 0.75-mm-thick Duran and Essix ACE and the 1.0-mm-thick Essix ACE specimens. Conclusions Our findings suggest that the physical and mechanical properties of thermoplastic materials used for the fabrication of TOAs should be evaluated after thermoforming in order to characterize their properties for clinical application.
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Affiliation(s)
- Jeong-Hyun Ryu
- Department and Research Institute for Dental Biomaterials and Bioengineering, Yonsei University College of Dentistry, Seoul, Korea.,BK21 PLUS Project for Interdisciplinary Oral Science Graduate Program, Yonsei University College of Dentistry, Seoul, Korea
| | - Jae-Sung Kwon
- Department and Research Institute for Dental Biomaterials and Bioengineering, Yonsei University College of Dentistry, Seoul, Korea.,BK21 PLUS Project for Interdisciplinary Oral Science Graduate Program, Yonsei University College of Dentistry, Seoul, Korea
| | - Heng Bo Jiang
- School of Stomatology, Taishan Medical University, Tai'an, Shandong, PR China
| | - Jung-Yul Cha
- Department of Orthodontics, The Institute of Craniofacial Deformity, Yonsei University College of Dentistry, Seoul, Korea
| | - Kwang-Mahn Kim
- Department and Research Institute for Dental Biomaterials and Bioengineering, Yonsei University College of Dentistry, Seoul, Korea.,BK21 PLUS Project for Interdisciplinary Oral Science Graduate Program, Yonsei University College of Dentistry, Seoul, Korea
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Lombardo L, Martines E, Mazzanti V, Arreghini A, Mollica F, Siciliani G. Stress relaxation properties of four orthodontic aligner materials: A 24-hour in vitro study. Angle Orthod 2016; 87:11-18. [PMID: 27314603 DOI: 10.2319/113015-813.1] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
OBJECTIVE To investigate the stress release properties of four thermoplastic materials used to make orthodontic aligners when subjected to 24 consecutive hours of deflection. MATERIALS AND METHODS Four types of aligner materials (two single and two double layered) were selected. After initial yield strength testing to characterize the materials, each sample was subjected to a constant load for 24 hours in a moist, temperature-regulated environment, and the stress release over time was measured. The test was performed three times on each type of material. RESULTS All polymers analyzed released a significant amount of stress during the 24-hour period. Stress release was greater during the first 8 hours, reaching a plateau that generally remained constant. The single-layer materials, F22 Aligner polyurethane (Sweden & Martina, Due Carrare, Padova, Italy) and Duran polyethylene terephthalate glycol-modified (SCHEU, Iserlohn, Germany), exhibited the greatest values for both absolute stress and stress decay speed. The double-layer materials, Erkoloc-Pro (Erkodent, Pfalzgrafenweiler, Germany) and Durasoft (SCHEU), exhibited very constant stress release, but at absolute values up to four times lower than the single-layer samples tested. CONCLUSIONS Orthodontic aligner performance is strongly influenced by the material of their construction. Stress release, which may exceed 50% of the initial stress value in the early hours of wear, may cause significant changes in the behavior of the polymers at 24 hours from the application of orthodontic loads, which may influence programmed tooth movement.
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Li X, Ren C, Wang Z, Zhao P, Wang H, Bai Y. Changes in force associated with the amount of aligner activation and lingual bodily movement of the maxillary central incisor. Korean J Orthod 2016; 46:65-72. [PMID: 27019820 PMCID: PMC4807150 DOI: 10.4041/kjod.2016.46.2.65] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 11/03/2015] [Accepted: 11/14/2015] [Indexed: 12/13/2022] Open
Abstract
Objective The purposes of this study were to measure the orthodontic forces generated by thermoplastic aligners and investigate the possible influences of different activations for lingual bodily movements on orthodontic forces, and their attenuation. Methods Thermoplastic material of 1.0-mm in thickness was used to manufacture aligners for 0.2, 0.3, 0.4, 0.5, and 0.6 mm activations for lingual bodily movements of the maxillary central incisor. The orthodontic force in the lingual direction delivered by the thermoplastic aligners was measured using a micro-stress sensor system for the invisible orthodontic technique, and was monitored for 2 weeks. Results Orthodontic force increased with the amount of activation of the aligner in the initial measurements. The attenuation speed in the 0.6 mm group was faster than that of the other groups (p < 0.05). All aligners demonstrated rapid relaxation in the first 8 hours, which then decreased slowly and plateaued on day 4 or 5. Conclusions The amount of activation had a substantial influence on the orthodontic force imparted by the aligners. The results suggest that the activation of lingual bodily movement of the maxillary central incisor should not exceed 0.5 mm. The initial 4 or 5 days is important with respect to orthodontic treatment incorporating an aligner.
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Affiliation(s)
- Xiaowei Li
- Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China
| | - Chaochao Ren
- Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China
| | - Zheyao Wang
- Institute of Microelectronics, Tsinghua University, Beijing, China
| | - Pai Zhao
- Institute of Microelectronics, Tsinghua University, Beijing, China
| | - Hongmei Wang
- Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China
| | - Yuxing Bai
- Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China
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Lombardo L, Arreghini A, Maccarrone R, Bianchi A, Scalia S, Siciliani G. Optical properties of orthodontic aligners--spectrophotometry analysis of three types before and after aging. Prog Orthod 2015; 16:41. [PMID: 26582007 PMCID: PMC4651973 DOI: 10.1186/s40510-015-0111-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 11/09/2015] [Indexed: 11/10/2022] Open
Abstract
Background The aim was to assess and compare absorbance and transmittance values of three types of clear orthodontic aligners before and after two cycles of in vitro aging. Methods Nine samples of orthodontic aligners from three different manufacturers (Invisalign, Align Technology, Santa Clara, CA, USA; All-In, Micerium, Avegno, GE, Italy; F22 Aligner, Sweden & Martina, Due Carrare, PD, Italy) were selected, and each sample was subjected to spectrophotometry analysis of both its transmittance and absorbance a total of 27 times. Samples were subsequently aged in vitro at a constant temperature in artificial saliva supplemented with food colouring for two cycles of 14 days each. The spectrophotometry protocol was then repeated, and the resulting data were analysed and compared by means of ANOVA (p < 0.05). Results All types of aligners tested yielded lower transmittance and higher absorbance values after aging, but the difference was not significant in any case. That being said, the F22 aligners were found to be most transparent, both before and after aging, followed by Invisalign and All-In, and these differences were statistically significant. Conclusions Commercial aligners possess significantly different optical, and therefore aesthetic, properties, both as delivered and following aging.
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Affiliation(s)
- Luca Lombardo
- Postgraduate School of Orthodontics, University of Ferrara, Via Montebello 31, 44100, Ferrara, Italy.
| | - Angela Arreghini
- Postgraduate School of Orthodontics, University of Ferrara, Via Montebello 31, 44100, Ferrara, Italy.
| | - Roberta Maccarrone
- Postgraduate School of Orthodontics, University of Ferrara, Via Montebello 31, 44100, Ferrara, Italy.
| | - Anna Bianchi
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 17/19, 44121, Ferrara, Italy.
| | - Santo Scalia
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Fossato di Mortara 17/19, 44121, Ferrara, Italy.
| | - Giuseppe Siciliani
- Postgraduate School of Orthodontics, University of Ferrara, Via Montebello 31, 44100, Ferrara, Italy.
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Iijima M, Kohda N, Kawaguchi K, Muguruma T, Ohta M, Naganishi A, Murakami T, Mizoguchi I. Effects of temperature changes and stress loading on the mechanical and shape memory properties of thermoplastic materials with different glass transition behaviours and crystal structures. Eur J Orthod 2015; 37:665-70. [PMID: 25788333 DOI: 10.1093/ejo/cjv013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND/OBJECTIVE To investigate the effects of temperature changes and stress loading on the mechanical and shape memory properties of thermoplastic materials with different glass transition behaviours and crystal structures. MATERIALS/METHODS Five thermoplastic materials, polyethylene terephthalate glycol (Duran®, Scheu Dental), polypropylene (Hardcast®, Scheu Dental), and polyurethane (SMP MM®, SMP Technologies) with three different glass transition temperatures (T g) were selected. The T g and crystal structure were assessed using differential scanning calorimetry and X-ray diffraction. The deterioration of mechanical properties by thermal cycling and the orthodontic forces during stepwise temperature changes were investigated using nanoindentation testing and custom-made force-measuring system. The mechanical properties were also evaluated by three-point bending tests; shape recovery with heating was then investigated. RESULTS The mechanical properties for each material were decreased significantly by 2500 cycles and great decrease was observed for Hardcast (crystal plastic) with higher T g (155.5°C) and PU 1 (crystalline or semi-crystalline plastic) with lower T g (29.6°C). The Duran, PU 2, and PU 3 with intermediate T g (75.3°C for Duran, 56.5°C for PU 2, and 80.7°C for PU 3) showed relatively stable mechanical properties with thermal cycling. The polyurethane polymers showed perfect shape memory effect within the range of intraoral temperature changes. The orthodontic force produced by thermoplastic appliances decreased with the stepwise temperature change for all materials. CONCLUSIONS/IMPLICATIONS Orthodontic forces delivered by thermoplastic appliances may influence by the T g of the materials, but not the crystal structure. Polyurethane is attractive thermoplastic materials due to their unique shape memory phenomenon, but stress relaxation with temperature changes is expected.
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Affiliation(s)
- Masahiro Iijima
- *Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu,
| | - Naohisa Kohda
- *Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu
| | - Kyotaro Kawaguchi
- *Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu
| | - Takeshi Muguruma
- *Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu
| | - Mitsuru Ohta
- Analytical Applications Department, Kyoto Application Development Center, Shimadzu Corporation, Kyoto, Japan
| | - Atsuko Naganishi
- Analytical Applications Department, Kyoto Application Development Center, Shimadzu Corporation, Kyoto, Japan
| | - Takashi Murakami
- Analytical Applications Department, Kyoto Application Development Center, Shimadzu Corporation, Kyoto, Japan
| | - Itaru Mizoguchi
- *Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu
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