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Ghoraba O, Bourauel C, Aldesoki M, Singer L, Ismail AM, Elattar H, Alhotan A, Elshazly TM. Effect of the Height of a 3D-Printed Model on the Force Transmission and Thickness of Thermoformed Orthodontic Aligners. MATERIALS (BASEL, SWITZERLAND) 2024; 17:3019. [PMID: 38930391 PMCID: PMC11205337 DOI: 10.3390/ma17123019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2024] [Revised: 06/12/2024] [Accepted: 06/18/2024] [Indexed: 06/28/2024]
Abstract
This research aims to investigate the influence of model height employed in the deep drawing of orthodontic aligner sheets on force transmission and aligner thickness. Forty aligner sheets (Zendura FLX) were thermoformed over four models of varying heights (15, 20, 25, and 30 mm). Normal contact force generated on the facial surface of the upper right central incisor (Tooth 11) was measured using pressure-sensitive films. Aligner thickness around Tooth 11 was measured at five points. A digital caliper and a micro-computed tomography (µ-CT) were employed for thickness measurements. The normal contact force exhibited an uneven distribution across the facial surface of Tooth 11. Model 15 displayed the highest force (88.9 ± 23.2 N), while Model 30 exhibited the lowest (45.7 ± 15.8 N). The force distribution was more favorable for bodily movement with Model 15. Thickness measurements revealed substantial thinning of the aligner after thermoforming. This thinning was most pronounced at the incisal edge (50% of the original thickness) and least at the gingivo-facial part (85%). Additionally, there was a progressive reduction in aligner thickness with increasing model height, which was most significant on the facial tooth surfaces. We conclude that the thermoplastic aligner sheets undergo substantial thinning during the thermoforming process, which becomes more pronounced as the height of the model increases. As a result, there is a decrease in both overall and localized force transmission, which could lead to increased tipping by the aligner and a diminished ability to achieve bodily movement.
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Affiliation(s)
- Omar Ghoraba
- Oral Technology, Dental School, University Hospital Bonn, 53111 Bonn, Germany
| | - Christoph Bourauel
- Oral Technology, Dental School, University Hospital Bonn, 53111 Bonn, Germany
| | - Mostafa Aldesoki
- Oral Technology, Dental School, University Hospital Bonn, 53111 Bonn, Germany
| | - Lamia Singer
- Oral Technology, Dental School, University Hospital Bonn, 53111 Bonn, Germany
- Orthodontic Department, Dental School, University Hospital Bonn, 53111 Bonn, Germany
| | - Ahmed M. Ismail
- Oral Technology, Dental School, University Hospital Bonn, 53111 Bonn, Germany
- Biomaterials Department, Faculty of Dentistry, Ain Shams University, Cairo 11566, Egypt
| | - Hanaa Elattar
- Orthodontic Department, Faculty of Dentistry, Suez Canal University, Ismailia 8366004, Egypt
| | - Abdulaziz Alhotan
- Department of Dental Health, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, Riyadh 12372, Saudi Arabia
| | - Tarek M. Elshazly
- Oral Technology, Dental School, University Hospital Bonn, 53111 Bonn, Germany
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Bandić R, Vodanović K, Vuković Kekez I, Medvedec Mikić I, Galić I, Kalibović Govorko D. Thickness Variations of Thermoformed and 3D-Printed Clear Aligners. Acta Stomatol Croat 2024; 58:145-155. [PMID: 39036327 PMCID: PMC11256873 DOI: 10.15644/asc58/2/4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Accepted: 04/30/2024] [Indexed: 07/23/2024] Open
Abstract
Objective To assess thickness variations of thermoformed and 3D-printed clear aligners. Materials and Methods Six different thermoplastic materials with different initial thicknesses were used for aligner thermoforming using Biostar® device (Biostar®, SCHEU-DENTAL GmbH, Iserlohn, Germany). Also, two different dental resins were used to create the printed aligners in three digitally designed thicknesses using IZZI Direct printer (3Dtech, Zagreb, Croatia). The aligners were measured using an electronic micrometer (ELECTRONIC UNIVERSAL MICROMETER, Schut Geometrical Metrology, Groningen, The Netherlands, accuracy: 0.001 mm) on a total of 20 points per aligner. Statistical analysis was performed using the JASP program (JASP, University of Amsterdam, Amsterdam, The Netherlands). Results The difference between the thermoformed and printed groups was statistically significant. Significant differences between different thermoformed materials and between 3D-printed materials were found. The thickness of thermoformed aligners deviated more in the upper jaw, whereas the thickness of printed aligners deviated more in the lower jaw. Both differences were statistically significant. The greatest average deviation from the initial thickness was found in Duran 0.75; Erkodur 0.6; Erkoloc-Pro 1.0; IZZI 0.5; NextDent 0.6 and NextDent A 0.6. NextDent group had the lowest deviations for all teeth of both jaws, except for upper and lower first molar where NextDent A group was more accurate. Conclusions Thermoformed aligners showed decreased values, while printed ones showed mostly increased values compared to the original material thickness. The highest mean deviation belonged to IZZI group, and the NextDent group had the lowest mean deviation. The thickness of both aligners was thinner at the edges compared to the thickness at cusps and fissures.
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Affiliation(s)
- Ružica Bandić
- Department of Orthodontics, University of Split School of Medicine
| | | | | | - Ivana Medvedec Mikić
- Department of Endodontics and Restorative Dental Medicine, University of Split School of Medicine
- Department of Oral Surgery, University of Split School of Medicine
| | - Ivan Galić
- Department of Oral Surgery, University of Split School of Medicine
- Department of Maxillofacial Surgery, University Hospital of Split
| | - Danijela Kalibović Govorko
- Department of Orthodontics, University of Split School of Medicine
- Department of Maxillofacial Surgery, University Hospital of Split
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Spangler T, Ammoun R, Carrico CK, Bencharit S, Tüfekçi E. The effect of crowding on the accuracy of 3-dimensional printing. Am J Orthod Dentofacial Orthop 2023; 164:879-888. [PMID: 37656070 DOI: 10.1016/j.ajodo.2023.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 08/01/2023] [Accepted: 08/01/2023] [Indexed: 09/02/2023]
Abstract
INTRODUCTION The purpose of this study was to evaluate the accuracy of 3-dimensional (3D) printed aligners compared to conventional vacuum-formed thermoplastic aligners with varying levels of dental crowding. METHODS Digital intraoral scans of 10 cases were assigned to their respective groups (n = 10, each, 30 total) as follows: no crowding (control), moderate crowding, and severe crowding. Digital images of these models were created in standard tessellation language (STL) file format using 3Shape software and randomly 3D printed. The STL files of each case were also sent to a dental laboratory to fabricate vacuum-formed samples, the current technology used for manufacturing aligners. The intaglio surfaces of fabricated aligners in both groups were scanned using cone beam computed tomography to create STL files, which were then compared to the original STL files of the cases using Geomagic Control X software. Absolute deviations from the original file and root mean square values were recorded. A Kruskal-Wallis test was conducted to analyze the difference in average deviation, and a t-test was repeated for the RMS measure. The significance level was set at 0.05. RESULTS The crowding did not affect the trueness of aligners manufactured using 3D printing or conventional vacuum-forming techniques (P = 0.79). 3D-printed aligners showed less deviation than the vacuum-formed samples (0.1125 mm vs 0.1312 mm; P <0.01). Aligners manufactured with the vacuum-forming technique had significantly higher variation than those with the 3D printing process (P = 0.04). CONCLUSIONS 3D aligners printed directly from an STL file exhibited better precision and trueness than those fabricated using the conventional vacuum-forming technique. Since accuracy is defined as a combination of precision and trueness, it is concluded that direct printing from an STL file can be used to manufacture aligners.
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Affiliation(s)
- Tonya Spangler
- Department of Orthodontics, School of Dentistry, Virginia Commonwealth University, Richmond, Va
| | - Rami Ammoun
- Department of General Practice, School of Dentistry, Virginia Commonwealth University, Richmond, Va
| | - Caroline K Carrico
- Department of Dental Public Health and Policy, School of Dentistry, Virginia Commonwealth University, Richmond, Va
| | - Sompop Bencharit
- Office of Oral Health Innovation, Department of Oral Rehabilitation, James B. Edwards College of Dental Medicine, Medical University of South Carolina, Charleston, SC
| | - Eser Tüfekçi
- Department of Orthodontics, School of Dentistry, Virginia Commonwealth University, Richmond, Va.
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Mao B, Tian Y, Li J, Zhou Y. Expansion rebound deformation of clear aligners and its biomechanical influence: a three-dimensional morphologic analysis and finite element analysis study. Angle Orthod 2023; 93:572-579. [PMID: 37068033 PMCID: PMC10575640 DOI: 10.2319/102622-734.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 03/01/2023] [Indexed: 04/18/2023] Open
Abstract
OBJECTIVES To determine the expansion rebound deformation (ERD) of clear aligners (CAs) and its biomechanical influence. MATERIALS AND METHODS A four-premolar extraction treatment plan was carried out for a patient with 2 CA companies. Thirty-six digitally scanned clear aligners with the corresponding 36 virtually constructed "ideal" aligners were constructed. The arch width and length between pairs of reference landmarks of the scanned CAs and corresponding dentition models were measured. Cone-beam computed tomography data and digital dental models were used for three-dimensional (3D) finite element analysis (FEA) modeling. Thirty-six scanned CA models with the corresponding 36 ideal CA models were constructed. One-way analysis of variance was used to determine the differences among deviation values at tooth level, and paired t-test was used to compare the displacements of teeth between the two group of CAs. RESULTS All CAs were wider and shorter than the digital model from which they were constructed. In the scanned CA model group, significant stress was observed in the buccolingual area of the periodontal ligament on posterior teeth, and the corresponding displacements of teeth were also noted. Significantly larger coronal displacements were noted for the lateral incisor, the canine, the second premolar, and the first molar in the scanned CA group (P < .05). CONCLUSIONS The general trend of ERD of thermoformed CAs was shown. This deformation may cause unforeseen tooth movements and negatively affect treatment outcomes.
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Affiliation(s)
| | | | - Jing Li
- Corresponding author: Dr Jing Li, Department of Orthodontics, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health, No.22 Zhongguancun South Avenue, Haidian District, Beijing 100081, People’s Republic of China. (e-mail: )
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Grant J, Foley P, Bankhead B, Miranda G, Adel SM, Kim KB. Forces and moments generated by 3D direct printed clear aligners of varying labial and lingual thicknesses during lingual movement of maxillary central incisor: an in vitro study. Prog Orthod 2023; 24:23. [PMID: 37423974 DOI: 10.1186/s40510-023-00475-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 05/15/2023] [Indexed: 07/11/2023] Open
Abstract
OBJECTIVE The objective of this study was to measure the forces and moments exerted by direct printed aligners (DPAs) with varying facial and lingual aligner surface thicknesses, in all three planes of space, during lingual movement of a maxillary central incisor. MATERIALS AND METHODS An in vitro experimental setup was used to quantify forces and moments experienced by a programmed tooth to be moved and by adjacent anchor teeth, during lingual movement of a maxillary central incisor. DPAs were directly 3D-printed with Tera Harz TC-85 (Graphy Inc., Seoul, South Korea) clear photocurable resin in 100-µm layers. Three multi-axis sensors were used to measure the moments and forces generated by 0.50 mm thick DPAs modified with labial and lingual surface thicknesses of 1.00 mm in selective locations. The sensors were connected to three maxillary incisors (the upper left central, the upper right central, and the upper left lateral incisors) during 0.50 mm of programmed lingual bodily movement of the upper left central incisor. Moment-to-force ratios were calculated for all three incisors. Aligners were benchtop tested in a temperature-controlled chamber at intra-oral temperature to simulate intra-oral conditions. RESULTS The results showed that increased facial thickness of DPAs slightly reduced force levels on the upper left central incisor compared to DPAs of uniform thickness of 0.50 mm. Additionally, increasing the lingual thickness of adjacent teeth reduced force and moment side effects on the adjacent teeth. DPAs can produce moment-to-force ratios indicative of controlled tipping. CONCLUSIONS Targeted increases in thickness of direct 3D-printed aligners change the magnitude of forces and moments generated, albeit in complex patterns that are difficult to predict. The ability to vary labiolingual thicknesses of DPAs is promising to optimize the prescribed orthodontic movements while minimizing unwanted tooth movements, thereby increasing the predictability of tooth movements.
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Affiliation(s)
- James Grant
- Department of Orthodontics, Saint Louis University, 3320 Rutger St, St Louis, MO, 63104, USA
| | - Patrick Foley
- Department of Orthodontics, Saint Louis University, 3320 Rutger St, St Louis, MO, 63104, USA
| | - Brent Bankhead
- Department of Orthodontics, Saint Louis University, 3320 Rutger St, St Louis, MO, 63104, USA
| | - Gabriel Miranda
- Department of Orthodontics, Saint Louis University, 3320 Rutger St, St Louis, MO, 63104, USA
| | - Samar M Adel
- Department of Orthodontics, Saint Louis University, 3320 Rutger St, St Louis, MO, 63104, USA
- Department of Orthodontics, Faculty of Dentistry, Alexandria University, Alexandria, Egypt
| | - Ki Beom Kim
- Department of Orthodontics, Saint Louis University, 3320 Rutger St, St Louis, MO, 63104, USA.
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Park SY, Choi SH, Yu HS, Kim SJ, Kim H, Kim KB, Cha JY. Comparison of translucency, thickness, and gap width of thermoformed and 3D-printed clear aligners using micro-CT and spectrophotometer. Sci Rep 2023; 13:10921. [PMID: 37407694 DOI: 10.1038/s41598-023-36851-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 06/11/2023] [Indexed: 07/07/2023] Open
Abstract
The present study compared the thickness and gap width of thermoformed and 3D-printed clear aligners (CAs) using micro-computed tomography (micro-CT) and evaluated their translucency using spectrophotometer. Four groups of CAs were tested: thermoformed with polyethylene terephthalate glycol (TS) or copolyester-elastomer combination (TM), and 3D-printed TC-85 cleaned with alcohol (PA) or with centrifuge (PC). CIELab coordinates were measured (n = 10) to evaluate translucency. CAs (n = 10) were fitted onto respective models and micro-CT was performed to evaluate the thickness and gap width. Thickness and gap width were measured for different tooth type and location in sagittal sections on all sides. The PC group showed significantly higher translucency than the PA group, which was similar to the TS and TM groups (p < 0.01). After the manufacturing process, thickness reduction was observed in the thermoformed groups, whereas thickness increase was observed in the 3D printed-groups. The TM group showed the least gap width amongst the groups (p < 0.01). Thermoformed and 3D-printed CAs had significantly varied thicknesses and regions of best fit depending on the tooth type and location. Differences in the translucency and thickness of the 3D-printed CAs were observed depending on the cleaning methods.
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Affiliation(s)
- So Yeon Park
- Department of Orthodontics, College of Dentistry, Yonsei University, Seoul, South Korea
| | - Sung-Hwan Choi
- Department of Orthodontics, Institute of Craniofacial Deformity, College of Dentistry, Institute for Innovation in Digital Healthcare, Yonsei University, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, South Korea
| | - Hyung-Seog Yu
- Department of Orthodontics, Institute of Craniofacial Deformity, College of Dentistry, Institute for Innovation in Digital Healthcare, Yonsei University, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, South Korea
| | - Su-Jung Kim
- Department of Orthodontics, Kyung Hee University School of Dentistry, Seoul, South Korea
| | - Hoon Kim
- Laboratory of Adhesion & Bio-Composites, Forestry and Bioresources, Seoul National University, Seoul, South Korea
| | - Ki Beom Kim
- Department of Orthodontics, Saint Louis University, Saint Louis, MO, USA
| | - Jung-Yul Cha
- Department of Orthodontics, Institute of Craniofacial Deformity, College of Dentistry, Institute for Innovation in Digital Healthcare, Yonsei University, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, South Korea.
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Inchingolo AM, Ceci S, Coloccia G, Azzollini D, Malcangi G, Mancini A, Inchingolo F, Trerotoli P, Dipalma G, Patano A. Predictability and Effectiveness of Nuvola ® Aligners in Dentoalveolar Transverse Changes: A Retrospective Study. Biomedicines 2023; 11:biomedicines11051366. [PMID: 37239039 DOI: 10.3390/biomedicines11051366] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 04/28/2023] [Accepted: 05/03/2023] [Indexed: 05/28/2023] Open
Abstract
Nowadays, many people use clear aligners to address their dental issues. The efficacy of transparent dental aligners must be investigated even though they are more aesthetically pleasing, easy to use, and tidy than permanent tools. Thirty-five patients in this study's sample group who used Nuvola® clear aligners for their orthodontic therapy were prospectively observed. Initial, simulated, and final digital scans were analysed with a digital calliper. The actual results were compared with the prescribed ending position to evaluate the efficacy of transversal dentoalveolar expansion. Aligner treatments in Groups A (12) and B (24), particularly in the dental tip measures, demonstrated high adherence to the prescription. On the other hand, the gingival measures exhibited a greater level of bias, and the differences were statistically significant. However, there was no difference in the outcomes between the two groups (12 vs. 24). Within specific parameters, the evaluated aligners were shown to be helpful in predicting movements in the transverse plane, particularly when considering movements linked to the vestibular-palatal inclination of the dental elements. This article compares the expansion effectiveness of Nuvola® aligners compared with other work in the literature using competitor companies.
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Affiliation(s)
| | - Sabino Ceci
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124 Bari, Italy
| | - Giovanni Coloccia
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124 Bari, Italy
| | - Daniela Azzollini
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124 Bari, Italy
| | - Giuseppina Malcangi
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124 Bari, Italy
| | - Antonio Mancini
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124 Bari, Italy
| | - Francesco Inchingolo
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124 Bari, Italy
| | - Paolo Trerotoli
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124 Bari, Italy
| | - Gianna Dipalma
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124 Bari, Italy
| | - Assunta Patano
- Department of Interdisciplinary Medicine, University of Bari "Aldo Moro", 70124 Bari, Italy
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Palone M, Brucculeri L, Cremonini F, Albertini P, Lombardo L. Treatment of severe Class II skeletal malocclusion in a hyperdivergent adult patient via hybrid clear aligner approach: A case report of successful camouflage therapy. J Orthod 2022; 50:205-214. [DOI: 10.1177/14653125221138588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This case report describes the camouflage treatment of an adult patient with hyperdivergent facial pattern presenting with severe Class II skeletal malocclusion, through the use of a hybrid clear aligner approach, that relies on both a partial lingual fixed appliance and the continuous use of Class II elastics throughout therapy. After 11 months of treatment, the goals had been achieved, highlighting that the correct diagnostic framework, proper patient selection and careful digital planning of a compromise treatment can provide satisfactory aesthetic and functional outcomes.
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Affiliation(s)
- Mario Palone
- Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy
| | - L Brucculeri
- Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy
| | - F Cremonini
- Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy
| | - P Albertini
- Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy
| | - L Lombardo
- Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy
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Ammann R, Tanner C, Schulz G, Osmani B, Nalabothu P, Töpper T, Müller B. Three-dimensional analysis of aligner gaps and thickness distributions, using hard x-ray tomography with micrometer resolution. J Med Imaging (Bellingham) 2022; 9:031509. [PMID: 36267352 PMCID: PMC9574087 DOI: 10.1117/1.jmi.9.3.031509] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 05/31/2022] [Indexed: 07/02/2024] Open
Abstract
PURPOSE The morphology of a polymer aligner, designed according to an orthodontic treatment plan, determines clinical outcomes. A fundamental element of orthodontic tooth movement with aligner treatment is the fit of the aligner's surface to the individual teeth. Gaps between the aligner and teeth do occur because current aligner fabrication is not capable of completely reproducing the complex anatomy of the individual denture. Our study aims at a quantitative three-dimensional assessment of the fit between optically transparent aligners placed on a polymeric model of the upper dental arch for two thermofoil thicknesses at preselected thermoforming temperatures. APPROACH Using an intraoral scan of a subject's upper dental arch, eight models were printed using a stereolithographic system. A series of eight NaturAligners® was manufactured with a pressure molding process, using thermofoils with thicknesses of 550 and 750 μ m and preselected process temperatures between 110°C and 210°C. These aligners placed on the corresponding models were imaged by an advanced micro computed tomography system. The aligners and the models were segmented to extract the gaps and aligners' local thicknesses as a function of the processing temperature for the two foil thicknesses. RESULTS The results indicate that the aligners show a better fit when the foils are processed at higher temperatures. Nevertheless, processing temperatures can be kept below 150°C, as the gain becomes negligible. Thermal processing reduces the average thickness of the aligners to 60% with respect to the planar starting foil. These thickness distributions demonstrate that the aligners are generally thicker on the occlusal surfaces of molars and premolars but thinner around the incisors and buccal as well as on oral surfaces. CONCLUSIONS Hard x-ray tomography with micrometer resolution is a powerful technique employed to localize the gaps between aligners and teeth, and it also enables film thickness measurements after thermoforming. The thicker film on the occlusal surfaces is most welcome because of aligner abrasion during wear. The NaturAligner® surfaces consist of a 25 - μ m -thin cellulose layer, and thus the microplastics released via abrasion of less than this thickness are expected to be substantially less critical than for other commercially available, optically transparent aligners.
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Affiliation(s)
- Rémi Ammann
- University of Basel, Biomaterials Science Center, Department of Biomedical Engineering, Allschwil, Switzerland
- University of Basel, Biomaterials Science Center, Department of Clinical Research, Basel, Switzerland
| | - Christine Tanner
- University of Basel, Biomaterials Science Center, Department of Biomedical Engineering, Allschwil, Switzerland
- University of Basel, Biomaterials Science Center, Department of Clinical Research, Basel, Switzerland
| | - Georg Schulz
- University of Basel, Biomaterials Science Center, Department of Biomedical Engineering, Allschwil, Switzerland
- University of Basel, Core Facility Micro- and Nanotomography, Department of Biomedical Engineering, Allschwil, Switzerland
| | - Bekim Osmani
- University of Basel, Biomaterials Science Center, Department of Biomedical Engineering, Allschwil, Switzerland
- University of Basel, Biomaterials Science Center, Department of Clinical Research, Basel, Switzerland
| | - Prasad Nalabothu
- University Hospital Basel, Department of Oral and Craniomaxillofacial Surgery, Basel, Switzerland
- University of Basel, Center for Dental Medicine, Department of Pediatric Oral Health and Orthodontics, Basel, Switzerland
| | - Tino Töpper
- University of Basel, Biomaterials Science Center, Department of Biomedical Engineering, Allschwil, Switzerland
- University of Basel, Biomaterials Science Center, Department of Clinical Research, Basel, Switzerland
| | - Bert Müller
- University of Basel, Biomaterials Science Center, Department of Biomedical Engineering, Allschwil, Switzerland
- University of Basel, Biomaterials Science Center, Department of Clinical Research, Basel, Switzerland
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Koenig N, Choi JY, McCray J, Hayes A, Schneider P, Kim KB. Comparison of dimensional accuracy between direct-printed and thermoformed aligners. Korean J Orthod 2022; 52:249-257. [PMID: 35466087 PMCID: PMC9314211 DOI: 10.4041/kjod21.269] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 11/19/2022] Open
Abstract
Objective The purpose of this study was to evaluate and compare the dimensional accuracy between thermoformed and direct-printed aligners. Methods Three types of aligners were manufactured from the same reference standard tessellation language (STL) file thermoformed aligners were manufactured using Zendura FLXTM (n = 12) and Essix ACETM (n = 12), and direct-printed aligners were printed using Tera HarzTM TC-85DAP 3D Printer UV Resin (n = 12). The teeth were not manipulated with any tooth-moving software in this study. The samples were sprayed with an opaque scanning spray, scanned, imported to Geomagic® Control XTM metrology software, and superimposed on the reference STL file by using the best-fit alignment algorithm. Distances between the aligner meshes and the reference STL file were measured at nine anatomical landmarks. Results Mean absolute discrepancies in the Zendura FLXTM aligners ranged from 0.076 ± 0.057 mm to 0.260 ± 0.089 mm and those in the Essix ACETM aligners ranged from 0.188 ± 0.271 mm to 0.457 ± 0.350 mm, while in the direct-printed aligners, they ranged from 0.079 ± 0.054 mm to 0.224 ± 0.041 mm. Root mean square values, representing the overall trueness, ranged from 0.209 ± 0.094 mm for Essix ACETM, 0.188 ± 0.074 mm for Zendura FLXTM, and 0.140 ± 0.020 mm for the direct-printed aligners. Conclusions This study showed greater trueness and precision of direct-printed aligners than thermoformed aligners.
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Affiliation(s)
- Nickolas Koenig
- Department of Orthodontics, Saint Louis University, Saint Louis, MO, USA
| | - Jin-Young Choi
- Department of Orthodontics, Graduate School of Dentistry, Kyung Hee University, Seoul, Korea
| | - Julie McCray
- Department of Orthodontics, Saint Louis University, Saint Louis, MO, USA
| | - Andrew Hayes
- Department of Orthodontics, Saint Louis University, Saint Louis, MO, USA
| | - Patricia Schneider
- Department of Orthodontics, Saint Louis University, Saint Louis, MO, USA
| | - Ki Beom Kim
- Department of Orthodontics, Saint Louis University, Saint Louis, MO, USA
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Lee SY, Kim H, Kim HJ, Chung CJ, Choi YJ, Kim SJ, Cha JY. Thermo-mechanical properties of 3D printed photocurable shape memory resin for clear aligners. Sci Rep 2022; 12:6246. [PMID: 35428796 PMCID: PMC9012852 DOI: 10.1038/s41598-022-09831-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 03/14/2022] [Indexed: 11/22/2022] Open
Abstract
To overcome the limitations of the conventional vacuum thermoforming manufacturing method, direct 3D printing of clear aligners has been developed. The present study investigated the thermo-mechanical and viscoelastic properties of a photocurable resin TC-85, which is a new material for the direct 3D printed clear aligners, comparing to a conventional thermoplastic material polyethylene terephthalate glycol. Dynamic mechanical analysis was performed to analyse the mechanical behaviours of the two materials at 37 °C and 80 °C, respectively. Furthermore, the shape memory property of the two materials was evaluated using a U-shape bending test, and the shape recovery ratio for 60 min at 37 °C was calculated. The results indicate that TC-85 can constantly apply a light force to the teeth when used for the 3D printed clear aligners, owing to its flexibility and viscoelastic properties. In addition, it is expected that the force decay induced by repeated insertion of the clear aligners will be reduced and a constant orthodontic force will be maintained. Furthermore, its geometric stability at high temperatures and the shape memory properties provide advantages for the clinical application.
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Affiliation(s)
- Se Yeon Lee
- Department of Orthodontics, College of Dentistry, Yonsei University, Seoul, Korea
| | - Hoon Kim
- Research Institute of Agriculture and Life Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea.,Graphy Inc., Graphy R&D Center, Seoul, Korea
| | - Hyun-Joong Kim
- Research Institute of Agriculture and Life Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea.,Laboratory of Adhesion and Bio-Composites, Department of Agriculture, Forestry and Bioresources, Seoul National University, Seoul, Korea
| | - Chooryung J Chung
- Department of Orthodontics, Gangnam Severance Hospital, Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, Seoul, Korea
| | - Yoon Jeong Choi
- Department of Orthodontics, Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea
| | - Su-Jung Kim
- Department of Orthodontics, Kyung Hee University School of Dentistry, Seoul, Korea
| | - Jung-Yul Cha
- Department of Orthodontics, Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea.
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SHIOGAMA M, NAKANO H, SAWAMURA M, YAMAGUCHI N, TAKANO N, MAKI K. Measurement of elastic strain recovery in an orthodontic aligner as a driving force for orthodontic treatment. Dent Mater J 2022; 41:688-697. [DOI: 10.4012/dmj.2021-339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Motoya SHIOGAMA
- Department of Orthodontics, School of Dentistry, Showa University
| | - Haruhisa NAKANO
- Department of Orthodontics, School of Dentistry, Showa University
| | - Moeka SAWAMURA
- Department of Orthodontics, School of Dentistry, Showa University
| | | | - Naoki TAKANO
- Department of Mechanical Engineering, Keio University
| | - Koutaro MAKI
- Department of Orthodontics, School of Dentistry, Showa University
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Force delivery modification of removable thermoplastic appliances using Hilliard precision thermopliers for tipping an upper central incisor. Clin Oral Investig 2022; 26:6105-6118. [PMID: 35641836 PMCID: PMC9525432 DOI: 10.1007/s00784-022-04560-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 05/20/2022] [Indexed: 12/24/2022]
Abstract
OBJECTIVES To evaluate the force delivered by removable thermoplastic appliances (RTAs, aligners), altered with Hilliard precision thermopliers, on an upper central incisor to tip it in the palatal and vestibular directions. MATERIALS AND METHODS A total of 10 aligners made from Ideal Clear® (polyethylene terephthalate glycol copolyester, PET-G) with a thickness of 1 mm were used in force analysis. Different-sized spot-thermoformed protuberances (bumps) were generated by activating the thermoplier (thin and thick) up to 30°, 60° and 90° in the centre of the palatal and vestibular surfaces of the aligner in 15° steps. The tipping (Fx) and intrusive (Fz) force components were measured on the isolated upper central incisor as part of a standardized resin model, with or without vertical loading by a weight equivalent. RESULTS Thermoplier activation at 30°, 60° and 90° resulted in different bump heights. The analysis revealed significantly higher Fx and Fz values with increasing bump heights for every activation step in all cases (p < 0.0001, respectively). Overall, the values of the Fx force component were higher than those observed for Fz. Significant differences between the palatal and vestibular tipping procedures were found depending on the resulting force components when the thin thermoplier was used; in contrast, the thick thermoplier resulted in a larger dispersion of the force magnitudes. CONCLUSIONS Aligners modified with Hilliard precision thermopliers showed altered biomechanical parameters. This approach could be an option for treatment modification. CLINICAL RELEVANCE The instrumental examination provided informative results for daily practice, as activation, force dosage and different force values under chewing pressure can be estimated more precisely based on the determined force levels.
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Upadhyay M, Arqub SA. Biomechanics of clear aligners: hidden truths & first principles. J World Fed Orthod 2021; 11:12-21. [PMID: 34965910 DOI: 10.1016/j.ejwf.2021.11.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 11/23/2021] [Indexed: 11/19/2022]
Abstract
Over the past two decades clear aligner-based treatment has received remarkableattention from the orthodontic profession and more so from general practitioners.Different companies have emerged using vigorous advertisement to promote theirproducts mainly to patients and clinicians through social media. A variety of concepts,methods, and adjuncts have been introduced to enhance the efficacy andeffectiveness of clear aligners. However, the accuracy of tooth movement (vspredicted) with aligners still hovers around 50%. Fixed appliances fare much better onaccuracy and predictability of treatment. Why is there a discrepancy betweenexpected and actual outcomes? This paper utilizes 'first principles' and the existingevidence to unravel some of the key drawbacks of aligner-based therapy. Severalshortcomings in the biomechanical properties of aligner material (thermoplastics) thataffect clinical performance are discussed. Based on the first principles of alignerbiomechanics, this paper provides clinical insights for improving predictability and effectiveness of aligner therapy.
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Affiliation(s)
- Madhur Upadhyay
- Division of Orthodontics, University of Connecticut Health, Farmington, Connecticut, USA.
| | - Sarah Abu Arqub
- Division of Orthodontics, University of Connecticut Health, Farmington, Connecticut, USA
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Pratto I, Busato MCA, Bittencourt PRS. Thermal and mechanical characterization of thermoplastic orthodontic aligners discs after molding process. J Mech Behav Biomed Mater 2021; 126:104991. [PMID: 34864573 DOI: 10.1016/j.jmbbm.2021.104991] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/17/2021] [Accepted: 11/18/2021] [Indexed: 10/19/2022]
Abstract
Polymeric aesthetic aligners were introduced in orthodontics as an innovative alternative to fixed appliances, however, their compositions and the thermal molding process may influence the biomechanical characteristics of these aligners. In this study four different clear aligner brands were used, ACE 035 Essix, C + Essix, Crystal 0.75 and Crystal 1.0, whose aim was to identify the thermal-processing influence on the mechanical and physicochemical properties of these materials, and to suggest a orthodontic sequence of wear for these appliances to achieve more effective treatment results. For the tensile tests the sample size calculation was based on probability distributions from the F test. The effect size used was 0.3, type 1 error of 0.05. Statistical Yield strength and Young's Modulus results were evaluated using the Shapiro-Wilk test. The groups were compared using the parametric test of analysis of variance, with Tukey post-test. Differences were statistically considered at the p < 0.05. The Infrared spectroscopy analysis showed no changes in the samples' chemical structure after thermal-processing. However, in the polypropylene aligner, differences were verified in the region attributed to the crystalline phase. Differential Scanning Calorimetry analysis for the same sample showed a crystallinity fraction decrease due to relaxation between polymer chains after molding. In the tensile tests evaluated, the tensile strength and 'Young's modulus presented higher values for aligners containing 100% polyethylene terephthalate glycol. Performing an analogy exercise of the properties of orthodontic wires used in conventional fixed appliances and, relating them to orthodontic plastics, aligners composed of different materials and/or thicknesses could be used in increasing sequence in terms of the modulus of elasticity, starting with C+, which has a lower elastic modulus value, using the ACE 035 as an intermediate and finishing with the Crystal 0.75 and 1.0, providing the desired stiffness to the aligners for the final phase.
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Affiliation(s)
- Isabella Pratto
- Universidade Estadual do Oeste do Paraná (UNIOESTE), Departamento de Odontologia, ZIP 85819-110, Cascavel, Paraná, Brazil
| | - Mauro Carlos Agner Busato
- Universidade Estadual do Oeste do Paraná (UNIOESTE), Departamento de Odontologia, ZIP 85819-110, Cascavel, Paraná, Brazil
| | - Paulo Rodrigo Stival Bittencourt
- Universidade Tecnológica Federal do Paraná (UTFPR), Departamento Acadêmico de Química, Bloco I4, ZIP 85884-000, Medianeira, Paraná, Brazil.
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Impact of Dental Model Height on Thermoformed PET-G Aligner Thickness—An In Vitro Micro-CT Study. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11156674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The aim of the present study was to investigate whether base height of 3D-printed dental models has an impact on local thickness values from polyethylene terephthalate glycol (PET-G) aligners. A total of 20 aligners were thermoformed on dental models from the upper jaw exhibiting either a 5 mm high (H) or narrow (N), i.e., 0 mm, base height. The aligners were digitized using micro-CT, segmented, and local thickness values were computed utilizing a 3D-distance transform. The mean thickness values and standard deviations were assessed for both groups, and local thickness values at pre-defined reference points were also recorded. The statistical analysis was performed using R. Aligners in group H were significantly thinner and more homogenous compared to group N (p < 0.001). Significant differences in thickness values were observed among tooth types between both groups. Whereas thickness values were comparable at cusp tips and occlusal/incisal/cervical measurement locations, facial and palatal surfaces were significantly thicker in group N compared to group H (p < 0.01). Within the limits of the study, the base height of 3D-printed models impacts on local thickness values of thermoformed aligners. The clinician should consider potential implication on exerted forces at the different tooth types, and at facial as well as palatal surfaces.
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Mantovani E, Parrini S, Coda E, Cugliari G, Scotti N, Pasqualini D, Deregibus A, Castroflorio T. Micro computed tomography evaluation of Invisalign aligner thickness homogeneity. Angle Orthod 2021; 91:343-348. [PMID: 33476365 DOI: 10.2319/040820-265.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 10/01/2020] [Indexed: 01/07/2023] Open
Abstract
OBJECTIVES To measure the thickness homogeneity of Invisalign (Align Technology Inc, San José, Calif) aligners with micro-computed tomography (micro-CT) scans. MATERIALS AND METHODS Starting from micro-CT scanning of 20 different aligners, multiplanar reconstructions were obtained. An orthodontist blinded about the study measured aligner thickness in different regions (molar, canine, incisor) and in different sites (gingival-buccal, buccal, occlusal, lingual, and gingival-lingual). To assess various thicknesses in different aligner sites and regions, the sample was stratified into subgroups and linear regression analysis was performed. RESULTS Descriptive analysis showed that mean thickness of aligners in the incisor region ranged from 0.582 mm to 0.639 mm, in the canine region from 0.569 mm to 0.644 mm, and in the molar region from 0.566 mm to 0.634 mm. Student's t-tests showed no significant differences in the aligner thickness of different regions when data were stratified by different sites. Student's t-tests showed significant differences in thickness homogeneity for the molar region when the data were stratified by tooth (mean difference = 0.068 mm; 95% confidence interval, 0.009-0.126 mm; P = .024). CONCLUSIONS Invisalign aligner thickness is characterized by small differences. The only significant difference was revealed in the molar region where thickness of the gingival-lingual edge is significantly thinner than that measured at the occlusal aspect. From a clinical perspective, the results of the present study could be considered to explain the reduced predictability of several orthodontic tooth movements in the molar region.
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Palone M, Longo M, Arveda N, Nacucchi M, Pascalis FD, Spedicato GA, Siciliani G, Lombardo L. Micro-computed tomography evaluation of general trends in aligner thickness and gap width after thermoforming procedures involving six commercial clear aligners: An in vitro study. Korean J Orthod 2021; 51:135-141. [PMID: 33678629 PMCID: PMC7940810 DOI: 10.4041/kjod.2021.51.2.135] [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: 05/13/2020] [Revised: 11/28/2020] [Accepted: 12/09/2020] [Indexed: 11/10/2022] Open
Abstract
Objective To assess the effects of thermoforming on aligner thickness and gap width in six aligner systems with the same nominal thickness. Methods Six passive upper aligners of different brands were adapted to a single printed cast. Each sample was evaluated with high-resolution micro-computed tomography. To investigate aligner thickness and gap width, two-dimensional (2D) analysis was conducted assessing the effects of the following variables tooth type (central incisor, canine, and first molar), 2D reference points, and aligner type. Data were analyzed and compared using analysis of variance and Tukey’s post-hoc tests (p < 0.05). Results Tooth type, dental region, and aligner type affected both the gap width and aligner thickness. The aligner thickness remained moderately stable across the arch only in the F22. Conclusions All thermoformed samples displayed smaller aligner thickness and gap width at anterior teeth and both gingival and coronal centers than at posterior teeth and occlusal surfaces.
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Affiliation(s)
- Mario Palone
- Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy
| | - Mattia Longo
- Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy
| | - Niki Arveda
- Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy
| | - Michele Nacucchi
- Division for Sustainable Materials, Research Centre of Brindisi, Brindisi, Italy
| | - Fabio De Pascalis
- Division for Sustainable Materials, Research Centre of Brindisi, Brindisi, Italy
| | | | - Giuseppe Siciliani
- Department of Translational Medicine and for Romagna, School of Dentistry, University of Ferrara, Ferrara, Italy
| | - Luca Lombardo
- Postgraduate School of Orthodontics, University of Ferrara, Ferrara, Italy
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Putrino A, Barbato E, Galluccio G. Clear Aligners: Between Evolution and Efficiency-A Scoping Review. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18062870. [PMID: 33799682 PMCID: PMC7998651 DOI: 10.3390/ijerph18062870] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/18/2021] [Accepted: 03/02/2021] [Indexed: 12/21/2022]
Abstract
In recent years, clear aligners have diversified and evolved in their primary characteristics (material, gingival margin design, attachments, divots, auxiliaries), increasing their indications and efficiency. We overviewed the brands of aligners used in Italy and reviewed the literature on the evolution of clear aligners based on their characteristics mentioned above by consulting the main scientific databases (PubMed, Scopus, Lilacs, Google Scholar, Cochrane Library). Inclusion and exclusion criteria were established. The data were collected on a purpose-made data collection form and analyzed descriptively. From the initial 580 records, 527 were excluded because they were not related to the subject of the review or because they did not meet the eligibility criteria. The remaining 31 studies were deemed comprehensive for the purpose of the review, although the “gingival margin design” feature and “auxiliaries” tool are not well represented in the more recent literature. Current knowledge on invisible aligners allows us to have a much clearer idea of the basic characteristics of aligner systems. There remains a need to deepen the use of systems other than Invisalign™ to give greater evidence to aligners that are very different based on the characteristics analyzed here and that are very widespread on the market.
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