Effect of clear aligner attachment design on extrusion of maxillary lateral incisors: A multicenter, single-blind randomized clinical trial

In Vitro Biomechanics of Attachment Use and Their Placement for Extrusive Tooth Movement by Aligner Mechanotherapy

The objective of the presented study was to evaluate the biomechanics of aligners utilising attachments and the effect of their placement for extrusion. An in vitro Orthodontic SIMulator (OSIM) was used to measure forces and moments produced through aligners incorporating attachments. The maxillary teeth on OSIM were digitally scanned to generate an STL model that was modified by placing a rectangular shaped attachment. Four models were designed with variation in attachment placement: Model NA-no attachment; model BA-buccal attachment; model LA-lingual attachment; model BL-both buccal and lingual attachments. Aligners (n = 30/model) were fabricated using a 0.75 mm thick polyethylene terephthalate material using a Biostar machine following the manufacturer's recommendations. A one-way MANOVA, followed by one-way ANOVA was used to test the effect of models on occlusogingival force (Fz) and mesiodistal moment (Mx) at 0.20 mm of gingival displacement of the left lateral incisor. The BL model exerted maximum Fz (1.22 ± 0.20 N), followed by models BA (1.18 ± 0.25 N) and LA (1.07 ± 0.19 N). The model NA exerted a negligible Fz (0.14 ± 0.08 N) that was statistically different from all other models. The models BA and LA generated Mx that has the tendency to tip the crown of tooth lingually (10.00 ± 3.12 Nmm) and buccally (-1.29 ± 2.26 Nmm), respectively. The models show statistically significant differences between models BL, BA and LA. There was no statistically significant difference between models BL and NA. The experimental evidence suggest that attachments on the lateral incisor could improve the predictability of extrusion forces applied with aligners. The models BL and LA provided favourable biomechanics by generating clinically significant extrusion forces without significant tipping of the lateral incisor tooth.

Predictability of mesiodistal tip of maxillary central incisors in clear aligner therapy

INTRODUCTION

Correct positioning of the maxillary central incisors (MxCIs) is a vital component of smile esthetics and the success of orthodontic treatment. This study investigated the efficacy of Invisalign SmartTrack aligners in achieving the mesiodistal tip of MxCIs, with an objective comparison to the ClinCheck (Align Technology, San Jose, Calif) prediction.

METHODS

A total of 174 MxCI teeth from 87 adult patients were selected from the Australasian Aligner Research Database. All patients exhibited pretreatment overlapping MxCI crowns and were treated with Invisalign SmartTrack aligners. The pretreatment tooth position, the planned mesiodistal tip movement using the ClinCheck software, and the achieved posttreatment tooth position were analyzed.

RESULTS

In the planned mesial root tip MxCI group, the mean planned and achieved mesial tips were 2.53° (standard error [SE], 0.29°) and 2.22° (SE, 0.42°), respectively, indicating an undercorrection of 0.31° (SE, 0.38°) (P >0.05). For the planned distal root tip MxCI group, the mean planned and achieved distal tips were 2.09° (SE, 0.22) and 0.39° (SE, 0.36°), respectively, indicating a mean undercorrection of 1.70° (SE, 0.39°) (P <0.001). There was no statistically significant association between the presence of attachments and the efficacy of the mesiodistal tip for MxCIs (P >0.05). No significant relationship was found (P >0.05) between the 1- or 2-week wear schedule and the efficacy of achieving the mesiodistal tip for MxCIs.

CONCLUSIONS

The overall percentage accuracy of mesiodistal tip movements for MxCIs when using Invisalign SmartTrack aligners was 53.3%. The presence of attachments and the influence of a 1- vs 2-week wear schedule were not found to have any significant influence on the efficacy of achieving planned mesiodistal tip movements for MxCIs.

In Vitro Comparison of the Effectiveness of Different Attachment Shapes and Locations on Extrusion of the Upper Left Lateral Incisor Using Thermoplastic Aligners

OBJECTIVES

The aim of this study was to compare the effectiveness of different attachment shapes and locations on the extrusion of the upper left lateral incisor (UL2) using thermoplastic aligners.

MATERIALS AND METHODS

Seven typodonts were digitally printed with hemi-ellipsoid or rectangular attachments in the incisal, middle or cervical third of the UL2. Five clear aligners were fabricated for each typodont; each was tested twice. Forces and moments were measured with an orthodontic force tester during 0.2 mm simulated extrusion of the UL2. Analysis of variance (ANOVA) was used to determine the effects of group, tooth, and the group-by-tooth interaction on the outcomes. A two-sided 5% significance level was used for all tests.

RESULTS

Altering attachment shape and location had a statistically significant effect on the forces and moments generated in each trial (p < 0.01), except for rectangular incisal and hemi-ellipsoid cervical (p > 0.05). The rectangular middle attachment generated the highest extrusive force (Fz = 7.498 N), followed by hemi-ellipsoid cervical (Fz = 6.338 N) and rectangular incisal (Fz = 5.948 N).

CONCLUSIONS

Varying direct attachment shape and location on the UL2 during extrusion has a significant effect on the forces and moments generated by thermoplastic aligners. The rectangular attachment located in the middle third generated the most effective extrusive force and least unwanted moment. For anchorage teeth, hemi-ellipsoid attachments located in the cervical third were found to be the most effective in minimising the reciprocal intrusive forces and unwanted moments.

Expert consensus on the clinical strategies for orthodontic treatment with clear aligners

Clear aligner treatment is a novel technique in current orthodontic practice. Distinct from traditional fixed orthodontic appliances, clear aligners have different material features and biomechanical characteristics and treatment efficiencies, presenting new clinical challenges. Therefore, a comprehensive and systematic description of the key clinical aspects of clear aligner treatment is essential to enhance treatment efficacy and facilitate the advancement and wide adoption of this new technique. This expert consensus discusses case selection and grading of treatment difficulty, principle of clear aligner therapy, clinical procedures and potential complications, which are crucial to the clinical success of clear aligner treatment.

Impacts of surface wear of attachments on maxillary canine distalization with clear aligners: a three-dimensional finite element study

Objectives

This study established three-dimensional finite element models to explore the impacts of surface wear of attachments on maxillary canine distalization with clear aligners, thereby guiding the clinical application of attachments and enhancing the efficiency of clear aligner therapy.

Materials and methods

Finite element models of maxillary canine distalization, including the maxilla, dentition, periodontal ligament, attachments (in both initial and worn states), and clear aligners, were established. Two groups of attachments (vertical rectangular attachment and optimized root control attachment) and five working conditions representing different degrees of attachment wear (M0, M2, M4, M6, and M8) were designed for canine distalization. Tooth displacement and equivalent stress in the roots and periodontal ligaments were analyzed.

Results

The canines in both groups exhibited a tipping movement pattern under all working conditions. By M8, the distal displacement of the canine crown, the equivalent stress values in the roots, and the equivalent stress values in the periodontal ligaments in the rectangular attachment group decreased by 12.04%, 30.80%, and 16.48%, respectively, compared to M0. In the optimized root control attachment group, these values decreased by 24.98%, 34.69%, and 19.15%, respectively. However, under all working conditions, the canines in the rectangular attachment group presented greater displacement and stress. The greatest reduction in canine crown distal displacement and stress values was observed between M6 and M8 in the rectangular attachment group, but the efficiency of canine distalization was still 64.30% at M8, with minimal change. In the optimized root control attachment group, the greatest reduction was observed in M4-M6, and the efficiency of canine distalization decreased to less than 60% in response to M6.

Conclusion

The canines tended to tip when maxillary canine distalization was performed with clear aligners. Attachment wear led to a reduction in the efficiency of canine distalization. Compared with optimized root control attachments, the impact was less significant for rectangular attachments. Once optimized root control attachments have been in place for more than 4 months and maxillary canine distalization is still required, orthodontists should closely monitor the wear of these attachments. If necessary, timely restoration or rebonding of the attachments is recommended.

Innovative Orthodontic-Restorative Treatment With Customized CAD/CAM Smartwires

BACKGROUND

The demand for discreet and low-compliance appliances has driven innovation in orthodontics, particularly with technological advances in artificial intelligence, robotics, and CAD/CAM technology. The evolution of Programmed Non-Sliding Mechanics for precise, automated tooth movement is the latest innovation.

AIM

In this article, we aimed to demonstrate the application of a novel orthodontic lingual appliance, The Gen 2 InBrace system (InBrace, Irvine, CA), in the orthodontic-restorative treatment of an adult patient with anterior tooth-size discrepancies, anterior openbite, and incisor proclination. The Gen 2 InBrace system uses a new generation of CAD/CAM Smartwires, including pre-programmed customized multiloop nickel-titanium lingual archwires, which enable light, continuous, and frictionless tooth movements.

CONCLUSION

The Gen 2 InBrace system can enhance esthetic and occlusal outcomes in patients requiring combined orthodontic-restorative treatment via automatic space management with maximum esthetic and minimal compliance.

CLINICAL SIGNIFICANCE

Precision dentistry and orthodontics using esthetic custom appliances have become a reality. The Gen 2 InBrace system, a new generation custom lingual appliance, offers effective treatment solutions for adults who have previously avoided preprosthetic orthodontics due to the esthetic concerns of wearing traditional labial braces or the compliance challenges associated with clear aligners.

Seeking orderness out of the orderless movements: an up-to-date review of the biomechanics in clear aligners

INTRODUCTION

Although with increasing popularity due to aesthetic appeal and comfort, clear aligners (CAs) are facing challenges in efficacy and predictability. Advancement in the underlying biomechanical field is crucial to addressing these challenges. This paper endeavors to provide a comprehensive framework for understanding the biomechanics of CA and enlightening biomechanics-based improvements on treatment strategies.

METHODS

A thorough review of the English-language literature accessible through PubMed and Google Scholar, without any publication year restrictions, was undertaken to unravel the biomechanical aspects of CA.

RESULTS

This review presented an up-to-date understanding of aligner biomechanics arranged by the framework of the material-dependent mechanical characteristics of CA, the geometric characteristics-dependent force transmission of the CA system, methods for studying the biomechanics of CA, and the biomechanical analyses for different types of tooth movement.

CONCLUSIONS

Biomechanics should be the fundamental concern for concepts, methods and adjuncts attempting to enhance the accuracy and predictability of tooth movement induced by CA. Improvement on material properties and alteration of geometric design of CA are two main approaches to develop biomechanically optimized force system. Exploration of real-world force sensing and monitoring system would make substantial progresses in aligner biomechanics.

Evaluation of the effect of different attachment configurations on molar teeth in maxillary expansion with clear aligners - a finite element analysis

OBJECTIVE

To evaluate the effects of different attachment configurations with and without buccal root torque on expansion movements achieved with aligners through finite element analysis (FEA).

METHODS

FEA modelling was done with 0.25 mm buccal expansion force application to the maxillary molars with different attachment configurations: Eight models were tested (1) no attachment (NA), (2) horizontal attachment (HA), (3) gingivally beveled horizontal attachment (GHA), and (4) occlusally beveled horizontal attachment (OHA), as well as models with 6obuccal root torque, (5) no attachment (TNA), (6) horizontal attachment (THA), (7) gingivally beveled horizontal attachment (TGHA), and (8) occlusally beveled horizontal attachment (TOHA).

RESULTS

The first and second molars exhibited buccal tipping in all models. The highest amount of buccal tipping for the molars was observed in the NA (6CMB, 0.232 mm; 6CMP, 0.246 mm; 7CMB, 0.281 mm; 7CMP, 0.312 mm) and GHA (6CMB, 0.230; 6CMP, 0.245; 7CMB, 0.279 mm; 7CMP, 0.311 mm) models, respectively, while the least tipping was observed in the TOHA model (6CMB, 0.155 mm; 6CMP, 0.168 mm; 7CMB, 0.216 mm; 7CMP, 0.240 mm). In all groups, the buccal tipping of the second molars was higher than that of the first molars.

CONCLUSION

This FEA study showed that expansion with aligners tip maxillary molars buccally and the use of occlusally beveled attachments and addition of buccal root torque reduces uncontrolled buccal tipping.

Aligner biomechanics: Where we are now and where we are heading for

Aligner orthodontics has gained significant popularity as an alternative to traditional braces because of its aesthetic appeal and comfort. The biomechanical principles that underlie aligner orthodontics play a crucial role in achieving successful outcomes. The biomechanics of aligner orthodontics revolve around controlled force application, tooth movement, and tissue response. Efficient biomechanics in aligner orthodontics involves consideration of attachment design and optimized force systems. Attachments are tooth-colored shapes bonded to teeth, aiding in torque, rotation, and extrusion movements. Optimized force systems ensure that forces are directed along the desired movement path, reducing unnecessary strain on surrounding tissues. Understanding and manipulating the biomechanics of aligner orthodontics is essential for orthodontists to achieve optimal treatment outcomes. This approach requires careful treatment planning, considering the mechanics required for each patient's specific malocclusion. As aligner orthodontics continues to evolve, advances in material science and treatment planning software contribute to refining biomechanical strategies, enhancing treatment efficiency, and expanding the scope of cases that can be successfully treated with aligners.