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Chen PY, Huang HL, Yu JH, Hsu JT. Optimal positions of clear aligner attachments to achieve lower canine tipping and bodily movement using finite element analysis. J Dent Sci 2024; 19:2007-2017. [PMID: 39347038 PMCID: PMC11437256 DOI: 10.1016/j.jds.2024.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2024] [Revised: 07/05/2024] [Indexed: 10/01/2024] Open
Abstract
Background/purpose Clear aligners are popular orthodontic tools because of their relatively aesthetic appearance and convenience of use. Nevertheless, bodily tooth movements still present challenges. This study evaluated various configurations of attachments placed on the mandibular canine in terms of the efficiency of canine bodily movement and correction of tipping. Materials and methods A finite element model of the mandible was constructed to investigate the effects of various attachment configurations on the overall bodily movement and undesirable tipping of a mandibular canine. Canine movements were categorized into four types, namely tipping and bodily movements in the mesial and distal directions. The size and shape of the attachments were fixed, but their placement and orientation were varied. Five and seven attachment configurations were evaluated for their influence on tipping and bodily movements, respectively. Results Attachment configuration significantly influenced mandibular canine tipping. The mesial occlusal-distal cervical and mesial occlusal-mesial cervical configurations had notable effects on mesial tipping, and the mesial occlusal-mesial cervical configuration excelled in distal tipping by increasing strain by 33.1%. The mesial occlusal-mesial cervical attachment configuration consistently had superior efficiency in facilitating both mesial and distal bodily movements of the canine. Conclusion The mesial occlusal-mesial cervical attachment configuration excelled in all four types of canine movement. Irrespective of the attachment configuration, canines tend to move overall with slight tipping due to skeletal resistance and their center of rotation. The attachment configuration is crucial to the success of clear aligner treatment and must be carefully considered in clinical practice.
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Affiliation(s)
- Pin-Yu Chen
- School of Dentistry, China Medical University, Taichung, Taiwan
| | - Heng-Li Huang
- School of Dentistry, China Medical University, Taichung, Taiwan
- Department of Biomedical Engineering, China Medical University, Taichung, Taiwan
- Department of Bioinformatics and Medical Engineering, Asia University, Taichung, Taiwan
| | - Jian-Hong Yu
- School of Dentistry, China Medical University, Taichung, Taiwan
- Department of Dentistry, China Medical University Hospital, Taichung, Taiwan
| | - Jui-Ting Hsu
- School of Dentistry, China Medical University, Taichung, Taiwan
- Department of Biomedical Engineering, China Medical University, Taichung, Taiwan
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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, 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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Elshazly TM, Bourauel C, Aldesoki M, Salvatori D, Alhotan A, Keilig L, Ghoneima A. Effect of attachment configuration and trim line design on the force system of orthodontic aligners: A finite element study on the upper central incisor. Orthod Craniofac Res 2024. [PMID: 38459802 DOI: 10.1111/ocr.12779] [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: 03/01/2024] [Indexed: 03/10/2024]
Abstract
OBJECTIVES To use the finite element method (FEM) to investigate the effect of various attachment configurations and trimming line designs of orthodontic aligners on their biomechanical performance. METHOD A 3D upper jaw model was imported into 3D design software. The upper right central incisor tooth (Tooth 11) was made mobile, and its periodontal ligament (PDL) and bone structures were designed. Aligners were modelled with three distinct attachment configurations: No attachment, rectangular horizontal, rectangular vertical, and two trimming line designs; scalloped and straight extended, with a homogeneous thickness of 0.6 mm. These models were then imported into an FE software. Simulations were conducted for three different movements, including facial translation, distalization, and extrusion. RESULTS Forces were recorded at 1.3-2.6 N during facial translation, 1.4-5.9 N in distalization, and 0.0-2.0 N in extrusion. The straight extended trimming line consistently generated higher forces than the scalloped design. Attachments had no significant impact on force components during facial translation but were more effective in distalization and extrusion. The combination of a straight extended trimming line with horizontal attachments exhibited the least stresses at the apical third during distalization, and the highest stresses during extrusion, suggesting superior retention. CONCLUSIONS Rectangular attachments offer limited benefits in facial translation, but horizontal rectangular attachments can intensify load in distalization and are crucial for force generation in extrusion. Horizontal attachments are preferred over vertical options. Additionally, the straight extended trim line enhances control of tooth movement and can replace attachments in certain cases. CLINICAL RELEVANCE These findings provide biomechanical evidence and an optimal protocol to guide clinical practice in planning diverse teeth movements. The emphasis is on the influence of attachment utilization and the specific design of aligner trimming lines to enhance control over tooth movement.
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Affiliation(s)
- Tarek M Elshazly
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany
- Department of Orthodontics and Pediatric Dentistry, Hamdan Bin Mohammed College of Dental Medicine (HBMCDM), Mohammed Bin Rashid University of Medicine and Health Sciences (MBRU), Dubai, United Arab Emirates
| | | | - Mostafa Aldesoki
- Oral Technology, Dental School, University Hospital Bonn, Bonn, Germany
| | | | - Abdulaziz Alhotan
- Department of Dental Health, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - 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
| | - Ahmed Ghoneima
- Department of Orthodontics and Pediatric Dentistry, Hamdan Bin Mohammed College of Dental Medicine (HBMCDM), Mohammed Bin Rashid University of Medicine and Health Sciences (MBRU), Dubai, United Arab Emirates
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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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Chen SM, Ho CT, Huang TH, Kao CT. An in vitro evaluation of aligner force decay in artificial saliva. J Dent Sci 2023; 18:1347-1353. [PMID: 37404637 PMCID: PMC10316483 DOI: 10.1016/j.jds.2023.04.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 04/18/2023] [Indexed: 07/06/2023] Open
Abstract
Background/purpose The present study aimed to compare the force decay of invisible aligners for maxillary anterior teeth with 0.1 mm (D1), 0.2 mm (D2), and 0.3 mm (D3) labial movement within a simulated oral environment over 7 days. Materials and methods The prepared invisible aligners were immersed in saliva (S) and subjected to applied force (F) for 7 days. The aligners were set and placed on the maxillary right central incisor with 0.1 mm (D1), 0.2 mm (D2), and 0.3 mm (D3) labial movement. Thin-film pressure sensors were used to measure the aligner force changes. The data were collected and analyzed by statistical methods. Results Significant differences were observed in the initial and first-day force between the D2 and D3 groups under simulated oral environment force (SF) (P < 0.05). There was a significant difference in force decay between Day 1 and Day 7 for all groups (P < 0.05). The SFD1 group showed a significant decrease in force on Day 5 (P < 0.05), while the SFD2 and SFD3 groups showed significant force decay on Day 4 (P < 0.05). The force decay ratio on Day 7 was higher in the SFD3 group than in the SFD1 and SFD2 groups, but no significant difference was observed. Conclusion Larger labial movement of the aligners resulted in higher force decay under artificial saliva environments, and the force decay of invisible aligners was increased by immersion time in artificial saliva.
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Affiliation(s)
- Shou-Min Chen
- School of Dentistry, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan
- Orthodontic Department, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Chun-Te Ho
- School of Dentistry, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan
- Orthodontic Department, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Tsui-Hsein Huang
- School of Dentistry, College of Oral Medicine, Chung Shan Medical University, Taichung, Taiwan
- Dental Department, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Chia-Tze Kao
- Orthodontic Department, Chung Shan Medical University Hospital, Taichung, Taiwan
- Dental Department, Chung Shan Medical University Hospital, Taichung, Taiwan
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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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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: 7] [Impact Index Per Article: 7.0] [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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Zhang Y, Gao J, Wang X, Wang J, Zhang X, Fang S, Wang W, Ma Y, Jin Z. Biomechanical factors in the open gingival embrasure region during the intrusion of mandibular incisors: A new model through finite element analysis. Front Bioeng Biotechnol 2023; 11:1149472. [PMID: 37064220 PMCID: PMC10090539 DOI: 10.3389/fbioe.2023.1149472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 03/21/2023] [Indexed: 03/31/2023] Open
Abstract
Introduction: Open gingival embrasure (OGE) is a common complication in adults following clear aligner therapy and the influence of gingival or alveolar bone biotype on OGE is of great concern. Unfortunately, due to the limited number of patients with clearaligner therapy and the clinical methods to distinguish the gingival biotype of patients being invasive, it is difficult to carry out clinical studies on the gingival or alveolar bone biotype of the OGE. In the meanwhile, the detailed biomechanics of the occurrence of OGE remains unknown. The goal of this study was to establish a new model to simulate the virtual space region, namely, the OGE region, to investigate the relationship between alveolar bone biotype and the occurrence of OGE, and explore potential biomechanical factors related to OGE.Methods: The OGE region in the interproximal space was established using a filler with a very low modulus of elasticity (1 × 10−6 MPa). To illustrate the biomechanics of OGE more exhaustively, a line was created at the top of the alveolar crest along the proximal tooth root. FEA was then used to analyze the biomechanics of the surrounding tissues, the OGE region and the line at the top of the alveolar crest along the proximal tooth root of the central incisor under two different labial bone thicknesses (thick and thin) with an axial inclination of 80°, 90° and 100°.Results: During intrusion of the incisors in clear aligner therapy, as inclination increased or bone tissue became thinner, the stress in the surrounding tissues [tooth root, alveolar crest, and periodontal ligament (PDL)] was greater. In the OGE region and interproximal alveolar crest, the strain increased with increasing inclination and labial bone thinning. The results from the line at the top of the alveolar crest along the proximal tooth root showed more detailed biomechanics: In all groups, stress and strain were focused on the mesial-labial alveolar crest. Interestingly, our results also demonstrated that when OGE occurs, other complications may arise, including root resorption and bone dehiscence.
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Affiliation(s)
- Yubohan Zhang
- 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, 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, China
| | - Xu Wang
- Xijing Hospital of Digestive Diseases, Air Force Medical University, Xi’an, China
| | - Jihong Wang
- The First People’s Hospital of Xianyang, Xianyang, Shaanxi Province, China
| | - Xu Zhang
- 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, China
| | - Shishu Fang
- General Hospital of Southern Theater Command of the Chinese People’s Liberation Army, Guangzhou, China
| | - Wei Wang
- Urumql DW Innovation InfoTech Co., Ltd., Xinjiang, China
| | - Yanning Ma
- Stomatological Hospital, Shanxi Medical University, Taiyuan, Shanxi Province, China
- *Correspondence: Yanning Ma, ; Zuolin Jin,
| | - 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, China
- *Correspondence: Yanning Ma, ; Zuolin Jin,
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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: 13] [Impact Index Per Article: 13.0] [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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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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12
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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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13
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Zou YR, Gan ZQ, Zhao LX. Clear aligner treatment for a four-year-old patient with anterior cross-bite and facial asymmetry: A case report. World J Clin Cases 2022; 10:5088-5096. [PMID: 35801017 PMCID: PMC9198868 DOI: 10.12998/wjcc.v10.i15.5088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 02/09/2022] [Accepted: 03/26/2022] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Clear aligners have been widely used to treat malocclusions from crowding, extraction cases to orthodontic-orthognathic cases, and practitioners are exploring the border of it. For the first time, clear aligners were used to early intervene anterior cross-bite and facial asymmetry.
CASE SUMMARY This case report described a four-year-old child presented with anterior cross-bite and facial asymmetry associated with functional mandibular shift, who had undergone a failed treatment with conventional appliances. The total treatment time was 18 weeks, and a stable outcome was obtained.
CONCLUSION The increasing need in early treatment highlights the need for clinicians to thoroughly investigate for the patient regarding clinical manifestation as well as patient compliance. We hope that our case will be contemplated by clinicians when seeking for treatment alternatives.
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Affiliation(s)
- Yi-Ran Zou
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, Sichuan Province, China
| | - Zi-Qi Gan
- Department of Orthodontics, Hospital of Stomatology, Guanghua School of Stomatology, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Stomatology, Guangzhou 510055, Guangdong Province, China
| | - Li-Xing Zhao
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, Sichuan Province, China
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14
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Biomechanical Efficacy and Effectiveness of Orthodontic Treatment with Transparent Aligners in Mild Crowding Dentition-A Finite Element Analysis. MATERIALS 2022; 15:ma15093118. [PMID: 35591454 PMCID: PMC9104142 DOI: 10.3390/ma15093118] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 04/24/2022] [Accepted: 04/24/2022] [Indexed: 11/16/2022]
Abstract
Orthodontic treatment increasingly involves transparent aligners; however, biomechanical analysis of their treatment effects under clinical conditions is lacking. We compared the biomechanical efficacy and effectiveness of orthodontic treatment with transparent aligners and of fixed appliances in simulated clinical orthodontic treatment conditions using orthodontic finite element (FE) models. In the FE analysis, we used Model Activation/De-Activation analysis to validate our method. Fixed appliances and 0.75-mm and 0.5-mm thick transparent aligners were applied to a tooth-alveolar bone FE model with lingually-inclined and axially-rotated central incisors. Compared to the fixed appliance, the 0.75-mm and 0.5-mm transparent aligners induced 5%, 38%, and 28% and 21%, 62%, and 34% less movement of the central incisors and principal stress of the periodontal ligament and of the alveolar bone, respectively, for lingual inclination correction. For axial-rotation correction, these aligners induced 22%, 37%, and 40% and 28%, 67%, and 48% less tooth movement and principal stress of the periodontal ligament and of the alveolar bone, respectively. In conclusion, transparent aligners induced less tooth movement, it is sufficient for orthodontic treatment, but 0.5-mm aligners should be used for only mild corrections. Additionally, the Model Activation/De-Activation analysis method is suitable for FE analysis of orthodontic treatment reflecting clinical treatment conditions.
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15
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The force effects of two types of polyethylene terephthalate glyc-olmodified clear aligners immersed in artificial saliva. Sci Rep 2021; 11:10052. [PMID: 33980889 PMCID: PMC8115163 DOI: 10.1038/s41598-021-89425-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 04/20/2021] [Indexed: 11/08/2022] Open
Abstract
Numerous factors can influence the force exerted by clear aligners on teeth. This study aimed to investigate the stability of the force delivered by two different material appliances. 90 clear aligners with 2 materials and three different activations were designed and fabricated. Then, a device was employed to measure the force generated by the two types of PET-G material appliances immersed in artificial saliva for 0, 3, 7, 10, 14 days. Scanning electron microscopy was applied to observe the morphologic alterations on the aligner surfaces, respectively. The forces generated by different activation appliance exhibited differently, 0.0 mm < 0.1 mm < 0.2 mm. In addition, increasing the immersion times and the orthodontic force also decreased, but the forces decreased differently. Compared with the forces of conventional PETG appliances with 0.20 mm activation, the modified PETG appliances with the same activation exhibited significantly higher mean force. When comparing the mean force for modified PETG appliances after 10 and 14 days with conventional PETG appliances, the delivery forces exhibited significant differences (P < 0.05). The force delivered by both materials decreased obviously following artificial saliva immersion, and the force generated by modified aligners exhibited better stability than conventional aligners.
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16
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Ma Y, Li S. The optimal orthodontic displacement of clear aligner for mild, moderate and severe periodontal conditions: an in vitro study in a periodontally compromised individual using the finite element model. BMC Oral Health 2021; 21:109. [PMID: 33691673 PMCID: PMC7945334 DOI: 10.1186/s12903-021-01474-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Accepted: 02/28/2021] [Indexed: 12/02/2022] Open
Abstract
Background Pathologic tooth migration (PTM) is a common complication of mild to severe periodontitis and proper orthodontic treatment is helpful to alleviate periodontal diseases. The goal of this study is to explore an optimal orthodontic displacement of clear aligner using a three-dimensional (3D) finite element model (FEM). Methods The cone beam computed tomography (CBCT) data of a patient received invisible orthodontics without diabetes and other systemic diseases were collected. Based on the new classification scheme for periodontal diseases in 2017 (stage I: mild periodontitis, [M1]; stage II: moderate periodontitis, [M2]; stage III: severe periodontitis, [M3]), 3D-FEMs of mandible were established using MIMICS 10.0 and ABAQUS 6.5 softwares. The 3D stress distribution diagrams and stress value of the teeth (left lower incisor, left lower central incisor, right lower lateral incisor, and right lower central incisor) under three different periodontal conditions (M1, M2, and M3) with axial inclination 90° and 100° were obtained by ABAQUS 6.5. Results The stress of anterior teeth was concentrated in the teeth neck, and became greater when the periodontal condition was worse. The stress value of anterior teeth and the strain at the top of the alveolar crest are greater as the displacement increasing. The stress value of anterior teeth and the strain at the top of the alveolar crest in axial inclination 100° are relatively great compared to those of axial inclination 90°. For patients with excessively inclined anterior teeth (such as 100°), the optimal orthodontic displacement is 0.18 mm. In order to ensure that alveolar ridge crest is not deformed, the displacement is less than 0.18 mm (strain for 0.165 mm), 0.15 mm (strain for 0.167 mm) and 0.10 mm (strain for 0.117 mm) respectively when alveolar bone is normal, resorption 1/3 or 1/3–1/2. Conclusions The optimal orthodontic displacement for patients (M1, M2, and M3) with excessively inclined anterior teeth (axial inclination 100°) is 0.18 mm. To avoid the strain at the top of the alveolar crest, the optimal displacements for M1, M2 and M3 periodontal disease patients are less than 0.18 mm, 0.15 mm and 0.10 mm, respectively.
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Affiliation(s)
- Yanning Ma
- Department of Orthodontics, School of Stomatology, Capital Medical University, No. 4, Tian Tan Xi Li, Beijing, 100050, China
| | - Song Li
- Department of Orthodontics, School of Stomatology, Capital Medical University, No. 4, Tian Tan Xi Li, Beijing, 100050, China.
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17
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Zhu Y, Hu W, Li S. Force changes associated with differential activation of en-masse retraction and/or intrusion with clear aligners. Korean J Orthod 2021; 51:32-42. [PMID: 33446619 PMCID: PMC7837798 DOI: 10.4041/kjod.2021.51.1.32] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 09/11/2020] [Accepted: 10/01/2020] [Indexed: 11/10/2022] Open
Abstract
Objective To investigate the three-dimensional forces created by clear aligners on mandibular teeth during differential activation with en-masse retraction and/or intrusion in vitro. Methods Six sets of clear aligners were designed for differential en-masse retraction and/or intrusion procedures in a first premolar extraction model. Group A0 was a control group with no activation. Groups A1-5 underwent different degrees of retractions and/or intrusions. Each group consisted of 10 aligners. Aligner forces were measured on a multi-axis force/ torque transducer measurement system in real-time. Results In the en-masse retraction groups (A1 and A2), lingual and extrusive forces were observed on the incisors; the canines mainly received distal forces; intrusive forces were seen on the second premolars; and the molars received mesial forces. In the enmasse retraction and intrusion groups (A3, A4, and A5), incisors also received lingual and extrusive forces; canines received distal and intrusive forces; mesial and extrusive forces were seen on the second premolars; and the second molars received distal and intrusive forces. The vertical forces on the incisors did not differ significantly among groups A1, A3, and A5. However, the vertical forces on the second premolars reversed from intrusion in group A1 to extrusion in groups A3 and A5. Conclusions With clear aligners, the "bowing effect" is seen during en-masse anterior teeth retraction and can be partially relieved by performing en-masse retraction accompanied by anterior teeth intrusion. Vertical control of incisors remained unsolved during en-masse retraction, even when intrusive activation was added to the anterior teeth.
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Affiliation(s)
- Ye Zhu
- Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, China
| | - Wei Hu
- Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, China
| | - Shuo Li
- Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, China
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18
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Staderini E, Patini R, Meuli S, Camodeca A, Guglielmi F, Gallenzi P. Indication of clear aligners in the early treatment of anterior crossbite: a case series. Dental Press J Orthod 2020; 25:33-43. [PMID: 32965385 PMCID: PMC7510494 DOI: 10.1590/2177-6709.25.4.033-043.oar] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 08/11/2019] [Indexed: 12/16/2022] Open
Abstract
Introduction: Anterior crossbite (AC) is defined as a reverse sagittal relationship
between maxillary and mandibular incisors. According to an evidence-based
orthodontic triage, the treatment need of AC is indicated if any occlusal
interference is forcing the mandible towards a Class III growth pattern.
Removable and fixed appliances have been suggested to correct AC. Objective: The present report aims at presenting the benefits of an alternative therapy
for the early treatment of anterior crossbite using clear aligners. Methods: Two cases of anterior crossbite corrected using clear aligners in 8-years-old
children are presented. Results: In both cases, AC was successfully corrected within 5 months. At the end of
the treatment, overjet and overbite were corrected. No major discomfort or
speech impairment was noticed by the parents. Conclusions: Due to the perceived shortcomings of alternative approaches, the use of clear
aligners for correcting AC in mixed dentition should be considered as a
comfortable and well tolerated appliance for young patients.
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Affiliation(s)
- Edoardo Staderini
- Università Cattolica del Sacro Cuore, Facoltà di Medicina e Chirurgia, Istituto di Odontoiatria e Chirurgia Maxillo-Facciale (Roma, Italy)
| | - Romeo Patini
- Università Cattolica del Sacro Cuore, Facoltà di Medicina e Chirurgia, Istituto di Odontoiatria e Chirurgia Maxillo-Facciale (Roma, Italy)
| | - Simonetta Meuli
- Università Cattolica del Sacro Cuore, Facoltà di Medicina e Chirurgia, Istituto di Odontoiatria e Chirurgia Maxillo-Facciale (Roma, Italy)
| | - Andrea Camodeca
- Università Cattolica del Sacro Cuore, Facoltà di Medicina e Chirurgia, Istituto di Odontoiatria e Chirurgia Maxillo-Facciale (Roma, Italy)
| | - Federica Guglielmi
- Università Cattolica del Sacro Cuore, Facoltà di Medicina e Chirurgia, Istituto di Odontoiatria e Chirurgia Maxillo-Facciale (Roma, Italy)
| | - Patrizia Gallenzi
- Università Cattolica del Sacro Cuore, Facoltà di Medicina e Chirurgia, Istituto di Odontoiatria e Chirurgia Maxillo-Facciale (Roma, Italy)
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19
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Wu J, Liu Y, Wang D, Huang S, Zhang J, Chen J, Dong X. Dynamic measurement of orthodontic force using a tooth movement simulation system based on a wax model. Technol Health Care 2020; 29:457-466. [PMID: 32925124 DOI: 10.3233/thc-202451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Orthodontic force is often statically measured in general, and only the initial force derived from appliances can be assessed. OBJECTIVE We aimed to investigate a technological method for measuring dynamic force using tooth movement simulation. METHODS Tooth movement was simulated in a softened wax model. A canine tooth was selected for evaluation and divided into the crown and root. A force transducer was plugged in and fixed between the two parts for measuring force. Forces on this tooth were derived by ordinary nickel-titanium (Ni-Ti) wire, hyperelastic Ni-Ti wire, low-hysteresis (LH) Ti-Ni wire and self-made glass fibre-reinforced shape memory polyurethane (GFRSMPU) wire. These forces were measured after the tooth movement. RESULTS The canine tooth moved to the desired location, and only a 0.2 mm deviation remained. The changing trends and magnitudes of forces produced by the wires were consistent with the data reported by other studies. The tooth had a higher moving velocity with ordinary Ni-Ti wires in comparison to the other wires. Force attenuation for the GFRSMPU wire was the lowest (40.17%) at the end of the test, indicating that it provided light but continuous force. CONCLUSIONS Mimicked tooth movements and dynamic force measurements were successfully determined in tooth movement simulation. These findings could help with estimating treatment effects and optimising the treatment plan.
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Affiliation(s)
- Jianlei Wu
- Sino-German Institute of Intelligent Manufacturing, Ningbo Polytechnic, Ningbo, Zhejiang, China.,Faculty of Mechanical Engineering and Mechanics, Ningbo University, Ningbo, Zhejiang, China.,Seal R&D Department, Jianxin Zhao Group Co., Ltd, Ningbo, Zhejiang, China
| | - Yunfeng Liu
- College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang, China.,Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou, Zhejiang, China
| | - Dongcai Wang
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou, Zhejiang, China
| | - Senda Huang
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou, Zhejiang, China
| | - Jianxing Zhang
- Department of Stomotology, Zhejiang Provincial People's Hospital, Hangzhou, Zhejiang, China
| | - Jie Chen
- Department of Mechanical Engineering, Purdue School of Engineering and Technology, Indiana University-Purdue University Indianapolis, Indianapolis, USA
| | - Xingtao Dong
- College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang, China.,Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou, Zhejiang, China
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20
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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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21
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Kim WH, Hong K, Lim D, Lee JH, Jung YJ, Kim B. Optimal Position of Attachment for Removable Thermoplastic Aligner on the Lower Canine Using Finite Element Analysis. MATERIALS (BASEL, SWITZERLAND) 2020; 13:E3369. [PMID: 32751305 PMCID: PMC7436137 DOI: 10.3390/ma13153369] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 07/21/2020] [Accepted: 07/27/2020] [Indexed: 01/08/2023]
Abstract
Malocclusion is considered as a developmental disorder rather than a disease, and it may be affected by the composition and proportions of masseter muscle fibers. Orthodontics is a specialty of dentistry that deals with diagnosis and care of various irregular bite and/or malocclusion. Recent developments of 3D scanner and 3D printing technology has led to the use of a removable thermoplastic aligner (RTA), which is widely used due to its aesthetic excellence, comfortableness, and time efficiency. However, orthodontics using only an RTA has lower treatment efficacy and accuracy due to the differing movement of teeth from the plan. In order to improve these disadvantages, attachments were used, and biomechanical analyses were performed with and without them. However, there is insufficient research on the movement of teeth and the transfer of load according to the attachment position and shape. Therefore, in our study, we aimed to identify the optimal shape and position of attachments by analyzing various shapes and positions of attachments. Through 3D finite element analysis (FEA), simple tooth shape and mandibular canine shape were extracted in order to construct the orthodontics model which took into account the various shapes and positions of attachments. The optimal shape of a cylinder was derived through the FEA of simple tooth shape and analyzing various positions of attachments on teeth revealed that fixing the attachments at the lingual side of the tooth rather than the buccal side allowed for torque control and an effective movement of the teeth. Therefore, we suggest fixing the attachments at the lingual side rather than the buccal side of the tooth to induce effective movement of teeth in orthodontic treatment with the RTA in case of canine teeth.
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Affiliation(s)
- Won-Hyeon Kim
- Clinical Translational Research Center for Dental Science, Seoul National University Dental Hospital, Seoul 03080, Korea;
- Department of Mechanical Engineering, Sejong University, Seoul 05006, Korea;
| | | | - Dohyung Lim
- Department of Mechanical Engineering, Sejong University, Seoul 05006, Korea;
| | - Jong-Ho Lee
- Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University, Seoul 03080, Korea;
| | - Yu Jin Jung
- Research Center for Advanced Specialty Chemicals, Korea Research Institute of Chemical Technology, Ulsan 44412, Korea
| | - Bongju Kim
- Clinical Translational Research Center for Dental Science, Seoul National University Dental Hospital, Seoul 03080, Korea;
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22
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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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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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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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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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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: 70] [Impact Index Per Article: 11.7] [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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Liu Y, Hu W. Force changes associated with different intrusion strategies for deep-bite correction by clear aligners. Angle Orthod 2018; 88:771-778. [PMID: 30035613 DOI: 10.2319/121717-864.1] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
OBJECTIVES: To investigate the relationships among different intrusion patterns of clear overlay aligners and the corresponding orthodontic forces and to provide guidance for clinical treatment. MATERIALS AND METHODS: Five sets of removable thermoplastic-formed aligners with the same thickness, designed for different intrusion procedures (G0 aligners as a control group, with no activation; G1 aligners for intruding canines; G2 aligners for intruding incisors; G3 aligners for intruding canines and incisors with the same activations; G4 aligners for intruding canines and incisors with different activation), were manufactured, and the corresponding intrusion forces were measured with a multiaxis force/torque transducer measurement system in real time. RESULTS: With the same activation (0.2-mm intrusion) and rectangular attachments placed on the premolars and first molars, the canines experienced the largest intrusive force when intruded alone using G1 aligners. The canines received a larger intrusive force than incisors in G3. The incisors received similar forces in G2 and G3. First premolars endured the largest extrusive forces when all anterior teeth were intruded with G3 aligners. Extrusion forces were exerted on canines and lateral incisors when using G4 aligners. CONCLUSIONS: Aligners with different intrusion patterns exert different forces on incisors, canines, and premolars, and the forces were closely related to the designed activation, shape and position of the attachment and relative movement of the adjacent teeth.
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