Search Results (29)

The aim of this study was to compare the forces and moments exerted by thermoformed aligners (TFMs) and direct printed aligners (DPAs) on the maxillary left central incisor (21) and adjacent teeth (11, 22) during lingual bodily movement of tooth 21. Methods: An in vitro setup was used to quantify forces and moments on three incisors, which were segmented and fixed onto multi-axis force/moment transducers. TFM were fabricated using 0.76 mm-thick single-layer PET-G foils (ATMOS; American Orthodontics, Sheboygan, WI, USA) and multi-layer TPU foils (Zendura FLX; Bay Materials LLC, Fremont, CA, USA). DPAs were fabricated using TC-85 photopolymer resin (Graphy Inc., Seoul, Republic of Korea). Tooth 21 was planned for bodily displacement by 0.25 mm and 0.50 mm, and six force and moment components were measured on it and the adjacent teeth. Results: TC-85 generated lower forces and moments with fewer unintended forces and moments on the three teeth. TC-85 exerted 0.99 N and 1.53 N of mean lingual force on tooth 21 for 0.25 mm and 0.50 mm activations, respectively; ATMOS produced 3.82 N and 7.70 N, and Zendura FLX produced 3.00 N and 8.23 N of mean lingual force for the same activations, respectively. Bodily movement could not be achieved. Conclusions: The force systems generated by clear aligners are complex and unpredictable. DPA using TC-85 produced lower, more physiological force levels with fewer side effects, which may increase the predictability of tooth movement and enhance treatment outcome. The force levels generated by TFM were considered excessive and not physiologically compatible. Full article

Background: Clear aligner therapy (CAT) has become increasingly popular for treating mild to moderate malocclusions. However, discrepancies between predicted and achieved tooth movement remain a concern, partly due to the limited understanding of aligner material behavior under clinical conditions. Since these materials must deliver controlled and sustained forces, their flexural properties are critical for treatment efficacy. Objective: To identify and analyze in vitro studies investigating the flexural properties of thermoplastic clear aligner materials, summarize their testing methodologies, and examine the factors that may influence their clinical performance. Methods: A scoping review was conducted following the PRISMA-ScR guidelines. Three electronic databases (PubMed, Scopus, and Web of Science) were systematically searched. Studies were screened based on predefined eligibility criteria, and data extraction included testing methods, materials, and clinically relevant variables. Risk of bias was assessed using the QUIN tool. Results: Seventeen studies published between 2008 and 2024 were included. All studies used three-point bending to assess mechanical properties. Common influencing factors included thermoforming, liquid absorption, temperature changes, loading conditions, and material thickness. Most studies reported that these factors negatively affected force delivery. The most frequently tested material was Duran (PET-G). Polyurethane-based materials, such as Zendura, showed comparatively better stress relaxation properties. Conclusions: Thermoforming, intraoral temperature changes, liquid exposure, and prolonged or repeated loading can compromise the mechanical properties and force delivery capacity of aligner materials. Standardized testing methods and further investigation of newer materials are essential to enhance the predictability and performance of clear aligner therapy. Full article

Background/Objectives: The capability of printing aligners directly, eliminating the need for a dental model or thermoforming, represents a significant advancement in aligner therapy. This review aimed to assess the cytotoxicity of 3D-printed aligners to clarify their safety profile, given their growing clinical use. Methods: An electronic literature search was independently conducted by two reviewers up to February 2025 across PubMed, Scopus, and Web of Science. After a thorough selection process, five in vitro studies were included. The quality and risk of bias were evaluated using the QUIN tool. Results: Five studies were included in the systematic review, four of which used TC-85 resin and one TA-28. Two reported no cytotoxic effects. Mild cytotoxicity was observed in one study using UV and heat post-curing, while another reported increased cytotoxicity with extended UV/nitrogen curing. However, notable heterogeneity was present among the studies in terms of the experimental protocols, the cell lines used, and the outcome measures. Conclusions: The cytotoxicity of printed aligners appears to be influenced by post-curing duration and system type, highlighting the importance of strict adherence to manufacturers’ protocols. Nevertheless, due to the limited number of studies and methodological variability, definitive conclusions cannot yet be drawn. Further clinical and standardised in vitro studies are needed to better assess the biocompatibility of 3D-printed aligners. Full article

This study evaluated the effects of different clear aligner (CA) designs on forces and moments during maxillary second molar distalization. Four designs were tested: attachment only (group 1), neither attachment nor enhanced structure (group 2), a combination of attachment and enhanced structure (group 3), and enhanced structure only (group 4). CAs were fabricated from thermoformed polyethylene terephthalate glycol with 30 CAs per group. Forces and moments were measured using a multi-axis transducer as the molars were distally displaced by 0.25 mm. All groups experienced buccodistal and intrusive forces. Group 3 showed the highest distalizing force (Fy = 2.51 ± 0.37 N) and intrusive force (Fz = −2.04 ± 0.48 N) and also the largest rotational moment (Mz = 3.89 ± 0.71 Nmm). Groups 3 and 4 (with enhanced structures) demonstrated significant intrusive forces (p < 0.05). Most groups exhibited mesiodistal angulation, lingual inclination, and distal rotational moments. Group 2 had the lowest moment-to-force ratio (Mx/Fy = 3.27 ± 0.44 mm), indicating inefficient bodily movement. Group 3 demonstrated significantly greater moments across all axes compared to other groups. The results indicate that designs incorporating enhanced structures with attachments increase CA stiffness and applied forces/moments, enhancing distalization efficiency while minimizing vertical side effects. This suggests that, clinically, reinforced CAs can serve as a simple yet effective modification to existing protocols in Class II orthodontic cases, enabling more efficient molar distalization without requiring complete appliance redesign or additional fabrication and allowing easy adaptation to individual treatment needs. Full article

Purpose: This paper investigates the biomechanical effect of thermoformed aligners equipped with complementary biomechanical attachments (CBAs) on periodontal ligaments (PDLs) during the expansion process of the maxillary arch. The analysis was conducted using advanced simulations based on the finite element method (FEM). Methods: High-resolution 3D CAD models were created for four tooth types: canine, first premolar, second premolar, and first molar. Additional 3D models were developed for aligners, CBAs, and PDLs. These were integrated into a comprehensive FEM model to simulate clinical rehabilitation scenarios. Validation was achieved through comparative analysis with empirical medical data. Results: The FEM simulations revealed the following: for canine, the displacement was 0.134 mm with a maximum stress of 4.822 KPa in the amelocemental junction. For the first premolar, the displacement was 0.132 mm at a maximum stress of 3.273 KPa in the amelocemental junction. The second premolar had a displacement of 0.129 mm and a stress of 1.358 KPa at 1 mm from the amelocemental junction; and first molar had a displacement of 0.124 mm and a maximum stress of 2.440 KPa. Conclusions: The inclusion of CBAs significantly reduced tooth tipping during maxillary arch expansion. Among the models tested, the vestibular CBA demonstrated superior performance, delivering optimal tooth movement when combined with thermoformed aligners. Significance: FEM techniques provide a robust and cost-effective alternative to in vivo experimentation, offering precise and reliable insights into the biomechanical efficacy of CBAs in thermoformed aligners. This approach minimizes experimental variability and accelerates the evaluation of innovative orthodontic configurations. Full article

(1) Background: Clear aligners are favored for their aesthetics in orthodontics, with newer 3D-printed technologies allowing the design of aligners with differential thicknesses and materials, offering advantages in terms of force distribution on the teeth, thereby optimizing treatment biomechanics. This study aimed to compare the initial and final forces of three types of 3D-printed aligners (with different thickness gradients and gingival margins) and traditional thermoformed aligners (with different gingival margins), evaluating stress relaxation and force consistency to determine which material and configuration may be optimal for better force distribution; (2) Methods: Twenty-seven 3D-printed aligners with three design variations and 18 thermoformed aligners were analyzed. Customized models were used to assess force at specific points on the upper incisor (1.1) and molar (2.6). A 3 h stress-relaxation test was conducted at 37 °C, and force data were recorded every second using a motorized compression stand. Statistical analysis was performed using ANOVA, post hoc tests, and Kruskal–Wallis tests for comparisons; (3) Results and Conclusions: Aligners with vertical and horizontal thickness gradients and a gingival margin trimmed 2 mm above the gingival contour exerted the highest forces, particularly at incisal/occlusal points. No significant differences in stress relaxation were observed. The force applied to the molars was consistently higher than the force applied to the incisors. These 3D-printed aligners with both horizontal and vertical gradients may offer a viable alternative to thermoformed aligners. Full article

In this research work, the mechanical performance of a thermoformed clear dental aligner is studied. Its performance is evaluated under the cyclic compression test, which is designed to simulate the occlusal forces applied on the aligner during swallowing operations for its entire usage period. The mechanical results show that the aligner exhibit stable energy absorption and stiffness behaviour throughout its use period and thus can potentially be used for clinical applications. The microplastic released from the aligner due to the fatigue-like damage is analysed using optical microscopy. Most of the microplastics released have larger dimensions, which may be excreted from the gastrointestinal tracts and have less possibility to pass through the epithelium passively. Therefore, the use of aligner may not pose any cytotoxic health risks. Full article

An inaccurate bonding procedure of the attachments related to clear aligner systems could influence the predictability of tooth movement The aim of this study was to compare the positioning reliability of horizontal and vertical orthodontic clear aligner attachments. Materials and Methods: A total of 70 horizontal and 70 vertical orthodontic clear aligner attachments were bonded to five upper and five lower experimental anatomically based acrylic resin models with 14 clinical crowns each. The experimental anatomically based acrylic resin models were randomly distributed to the following study groups: Group A—horizontal orthodontic clear aligner attachments (n = 70) (HORIZONTAL) and Group B—vertical orthodontic clear aligner attachments (n = 70) (VERTICAL). Afterward, the orthodontic clear aligner attachments were digitally planned using orthodontic planning software, and orthodontic templates were manufactured by thermoforming on 3D-printed models in trilayer glycol-modified polyethylene terephthalate. Both horizontal and vertical orthodontic clear aligner attachments were put through an intra-oral scan to obtain a postoperative digital image, and PAPver, PCPver, PMVver, AUver, Alver, PPMhor, PPDhor, PMVhor, AMhor and ADhor cephalometric parameters were analyzed using a t-test or a non-parametric Mann–Whitney–Wilcoxon test. Results: The results showed that all cephalometric parameters showed statistically significant differences (p < 0.05) between the accuracy of the indirect bonding technique for horizontal and vertical orthodontic clear aligner attachments, except for the PAPver (p = 0.6079) and PMVhor (p = 0.5001) cephalometric parameters. Conclusions: The vertical orthodontic clear aligner attachments are more accurate than the horizontal orthodontic clear aligner attachments through the indirect bonding technique. Full article

Background: Retention is a critical aspect of orthodontic treatment with aligners as it counteracts vertical displacing forces and ensures greater predictability of tooth movement. The aim of this study is to evaluate and compare the retention effectiveness of 3D-printed aligners and thermoformed aligners, analyzing how margin design and thickness gradients affect retention under different occlusal conditions. Methods: Tensile tests were conducted using a Sauter TVO-A01 machine, recording the force required to displace each aligner from the models. Quantitative data on the retention force of each aligner were collected based on malocclusion type and design specifics. Results: Scalloped thermoformed aligners demonstrated significantly lower retention values (p = 0.029) compared to 3D-printed aligners with high margins with horizontal and vertical gradients. Scalloped margin aligners exhibited significantly lower retention values (p = 0.008) compared to straight margin aligners. Additionally, 3D-printed aligners with uniform thickness gradients had significantly lower retention values (p = 0.040) compared to thermoformed aligners. Conclusions: The 3D printing production process enables customizable designs tailored to the unique characteristics of each patient. High-margin 3d-printed aligners with horizontal and vertical gradients provide superior retention, particularly in complex clinical situations such as dental crowding. Full article

This study aimed to optimize space closure efficiency by comparing the forces and moments exerted by different designs of clear aligners (CAs) during the movement of maxillary canines into the premolar extraction space. The forces and moments were measured using a multi-axis force/moment transducer on the maxillary right canine. The CAs were fabricated from thermoformed polyethylene terephthalate glycol. The following four edentulous space designs were tested: the edentulous space was left intact (Group 1); the edentulous space was replaced with a premolar pontic (Group 2); the edentulous space was replaced with a half-sized premolar pontic (Group 3); and the edentulous space was replaced with a rectangular column beam (Group 4). The maxillary right canine was moved 0.25 mm distally. All groups experienced buccodistal and intrusive forces; compared with the other groups, Group 1 showed significantly greater intrusive and smaller distal forces, and Group 4 showed significantly greater distal forces. All groups experienced distal tilting, lingual inclination, and mesial rotational moments. These findings suggest that modifying the thickness and extent of the adjacent teeth in the edentulous area of the CA can improve local stiffness, thereby reducing the tipping of the teeth into the edentulous space. This study emphasizes the importance of the CA design in controlling forces and moments for effective orthodontic treatment. Full article

The increasing concern over environmental sustainability has prompted various industries to reassess their practices and explore greener alternatives. Dentistry, as a significant contributor to waste generation, is actively seeking methods to minimize its environmental footprint. This paper examines the environmental implications of clear aligner therapy (CAT) in orthodontics and explores strategies to prioritize sustainability in aligner manufacturing and usage. CAT has gained popularity as a viable alternative to traditional fixed appliances due to advancements in biomaterials and computer-aided design (CAD) and manufacturing (CAM) technologies. The global market for clear aligners is expanding rapidly, with significant growth projected in the coming years. To address these challenges, this paper proposes adopting the principles of reduce, reuse, recycle, and rethink (4Rs) in orthodontic practices. Strategies such as minimizing resource consumption, incorporating recycled materials, and promoting proper aligner disposal and recycling can significantly reduce environmental harm. This paper explores emerging technologies and materials to mitigate the environmental impacts of CAT. Additionally, initiatives promoting aligner recycling and repurposing offer promising avenues for reducing plastic waste and fostering a circular economy. In conclusion, while CAT offers numerous benefits in orthodontic treatment, its environmental impact cannot be overlooked. By implementing sustainable practices and embracing innovative solutions, the orthodontic community can contribute to a more environmentally conscious future while continuing to provide quality care to patients. Full article

Introduction: Transparent orthodontic aligners have revolutionized dentistry and orthodontics since the 1990s, offering advantages over traditional fixed appliances in terms of hygiene, comfort, and aesthetics. With the increasing demand for invisible orthodontic treatments, clear aligners have gained popularity, prompting research into materials to enhance their efficacy and performance. Materials and Methods: A scoping review was conducted using electronic databases (Pubmed, Medline, Cochrane Library, Embase, and Scopus) to identify studies on clear aligner materials published in the last decade. Selection criteria focused on studies specific to dental materials, excluding those unrelated to materials or clear aligners. Results: The review included 11 relevant studies evaluating 17 different clear aligner materials. Materials such as polyvinyl chloride derivatives, thermoplastic polyurethanes (TPU), and polyethylene terephthalate glycol (PETG) were commonly used. The studies assessed mechanical, physical, chemical, and optical properties, as well as thermoforming effects, stress decay, and surface characteristics. Discussion and Conclusions: Various materials exhibited distinct properties, with PETG materials offering transparency and flexibility, while TPU-based materials like Smart Track providing durability and elasticity. Thermoforming affected mechanical properties, with both PETG and TPU materials showing decreased efficacy post-thermoforming. Polymer blending improved mechanical properties, but variations existed among different brands and materials. Clear aligner materials exhibit diverse characteristics, influencing their suitability for orthodontic use. PETG-based materials offer transparency and flexibility, while TPU-based materials provide durability and elasticity. However, both materials undergo mechanical changes post-thermoforming, emphasizing the need for further research to optimize material performance for clinical use. Full article

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. Full article

The significant rise in the use of clear aligners for orthodontic treatment is attributed to their aesthetic appeal, enhancing patient appearance and self-confidence. The aim of this study is to evaluate the aligners’ response to common staining agents (coffee, black tea, Coca-Cola, and Red Bull) in color and chemical stability. Polyurethane-based thermoformed and 3D-printed aligners from four brands were exposed to common beverages to assess color change using a VITA Easyshade compact colorimeter after 24 h, 48 h, 72 h, and 7 days, as well as chemical stability using ATR-FTIR spectroscopy. The brand, beverage, and manufacturing method significantly influence color stability. ATR-FTIR analysis revealed compositional differences, with variations in response to beverage exposure affecting the integrity of polymer bonds. Color change analysis showed coffee as the most potent staining agent, particularly affecting Tera Harz TC85 aligners, while ClearCorrect aligners exhibited the least susceptibility. 3D-printed aligners showed a greater color change compared to thermoformed ones. Aligners with a PETG outer layer are more resistant to stains and chemical alterations than those made of polyurethane. Additionally, 3D-printed polyurethane aligners stain more than thermoformed ones. Therefore, PETG-layered aligners are a more reliable choice for maintaining the aesthetic integrity of aligners. Full article

The effectiveness of clear aligners in correcting malocclusions is closely linked to the properties of the materials used to make them. The polymers used in the manufacture of clear aligners have well-established properties. However, the process of manufacturing clear aligners, known as thermoforming, involves thermal and mechanical shocks that may alter these properties. The objective of this study was to evaluate the effects of thermoforming on the mechanical, optical, chemical, and morphological properties of sixty PET-G specimens. The study compared the thickness, weight, absorbance, chemical structure, surface roughness, elastic modulus, yield strength, and breaking load of thirty thermoformed specimens with thirty non-thermoformed specimens. The study introduces a new approach by using standardized samples to analyze both chemical and physical properties. The results showed statistically significant differences in thickness (−15%), weight (−11%), and surface roughness (+1233% in roughness average; +1129% in RMS roughness) of the material. Additionally, a correlation was found between reduction in thickness and increase in opalescence. There was no significant change in the functionality of the aligners after thermoforming, as no significant mechanical changes were found. However, the increase in surface roughness may lead to plaque and fluid accumulation and worsen the fit of the aligners. Full article