Arch expansion with the Invisalign system: Efficacy and predictability

Effectiveness of dental arch expansion in the orthodontic treatment with clear aligners: a scoping review

BACKGROUND

The clinical protocol and effectiveness of dental expansion with Clear Aligner Therapy (CAT), especially among adults is still unclear. There is a need to map and explore knowledge gaps of dental expansion with CAT among children and adults.

OBJECTIVE

This scoping review explores the extent and depth of the available literature regarding the effectiveness and predictability of CAT in performing orthodontic expansion in both children and adults.

METHODS

The following databases were consulted as sources of information: PubMed, MEDLINE, Embase, Web of Science, Scopus, LILACS, COCHRANE Library, and ProQuest Dissertations & Thesis, in which the search was limited to studies on children or adults requiring transverse arch expansion and using clear orthodontic aligners. Two independent reviewers assessed the citations and extracted data, which was then synthesized in a narrative format.

RESULTS

Over all, 698 citations were retrieved, and 33 were included. Among these, 3 were systematic reviews, 4 were cohort studies, 2 were case-control studies, and 24 were case series. Eighty-five percent of the included studies were published in the last 5 years. Despite different protocols and measurement methods, aligners were effective for arch expansion in adults and children, and the expansion predictability was greater for the lower arch than for the upper arch. The evidence suggests that arch width increment is more predictable in the premolar region and less predictable in the canine and second molar areas, with high variability across studies.

CONCLUSIONS

Orthodontic aligners have demonstrated effectiveness in expanding arches in both adults and children. However, the literature suggests a decrease in arch width toward the posterior region, and there is no evidence of skeletal gains. To provide more conclusive evidence, randomized controlled clinical studies are warranted.

REGISTRATION

This review was registered in the Open Science Framework database (DOI: https://doi.org/10.17605/OSF.IO/6EG8F).

Artificial Intelligence in Aesthetic Dentistry: Is Treatment with Aligners Clinically Realistic?

Smile aesthetics are increasingly prioritized in dental practice, with accurate orthodontic assessment and treatment planning being crucial for optimal outcomes. This study evaluates Invisalign® SmileView™ (SV), an AI-based tool that simulates post-treatment smiles, focusing on its ability to present potential orthodontic outcomes to patients. Background/Objectives: This research aims to study whether SV can simulate predictable orthodontic results and if it makes anatomical modifications to the teeth. Additionally, it will evaluate whether SV displays smiles that conform to the orthodontic criteria described in the literature. Finally, the study will analyze whether the software can align the dental with the facial midline. Methods: A total of 51 subjects were recruited in Madrid, Spain. The operator took a frontal photograph of the subjects with a social smile (T0), following the application's instructions. Subsequently, the subjects followed the steps to modify their smile (T1), resulting in a new image of the subject with a different smile. The following variables were collected, analyzed, and compared with the standards defined in the literature: smile width, vertical exposure of the maxillary central incisor, width of the maxillary central and lateral incisors, proportion of the maxillary lateral incisor width to the central incisor, anterior gingival exposure level, position of the upper and lower dental midlines relative to the facial midline. Results: 58% of the sample showed dental expansion, with an excessive expansion (>5 mm) observed in 8%. In the maxillary arch, 5.9% of incisors exceeded predictable aligner movement (>1.5 mm), with 3.9% showing excessive extrusion and 2% excessive intrusion. For the lateral incisors, the mesiodistal size was reduced less than 0.5 mm in 31.4% of cases, with excessive interproximal reduction (>0.5 mm) in 5.9%. Additionally, 62.7% of cases would require multidisciplinary treatment due to an increase in size. SV centered the upper midline in 77.9% of these cases. Among the sample, the upper midline was initially centered in 74.5% of subjects, and SV maintained it centered in 84.2% of these subjects. Conclusions: SV tends to generate simulations of broader smiles, which are mostly achievable through aligner treatments, from an orthodontic perspective, and showed high predictability regarding the vertical movements of the incisors that can be achieved with aligners. Moreover, it adjusted the mesiodistal size of the upper incisors in its simulations and demonstrated the ability to identify and correct deviations of the dental midlines relative to the facial midline.

In Vitro Comparison of Direct Attachment Shape and Size on the Orthodontic Forces and Moments Generated by Thermoplastic Aligners During Expansion

OBJECTIVE

To evaluate the effects of varying direct attachment shape and size on the forces and moments generated by thermoplastic aligners during simulated expansion.

MATERIALS AND METHODS

An in vitro orthodontic force tester (OFT) was used to measure the forces and moments from a typodont where the buccal teeth were translated lingually 0.2 mm to simulate expansion. Hemi-ellipsoid and rectangular attachments with either 0.5 or 1.0 mm thickness were added on upper right first premolar (UR4), second premolar (UR5) and first molar (UR6). Analysis of variance (ANOVA) was used to determine two-way interactions among the factors on the outcomes.

RESULTS

The interactions between group and tooth were significant for all outcomes (p < 0.001). The greatest buccal forces (Fy) were observed with 1 mm rectangular attachment on the UR4 (0.78 ± 0.29 N), with 1 mm hemi-ellipsoid attachment on UR5 (0.28 ± 0.21 N) and with 0.5 mm rectangular attachment on UR6 (1.71 ± 0.18 N). The greatest buccolingual moments (Mx) were obtained with 1 mm rectangular attachment on UR4 (5.61 ± 1.43 Nmm), without any attachments on UR5 (3.33 ± 1.73 Nmm) and with 1 mm hemi-ellipsoid attachment on UR6 (4.18 ± 4.31).

CONCLUSION

Direct attachment shape and size had a significant effect on the orthodontic forces and moments generated by thermoplastic aligners during simulated expansion. Although loads varied significantly by tooth morphology and its location in the arch, best forces and moments for expansion were obtained with 1 mm rectangular attachments on UR4s, 1 mm hemi-ellipsoid attachments on UR5s and 0.5 mm rectangular attachments on UR6s.

Efficacy of clear aligners vs rapid palatal expanders on palatal volume and surface area in mixed dentition patients: A randomized controlled trial

INTRODUCTION

This study aimed to evaluate the efficacy of Invisalign First Phase I treatment compared with tooth-borne rapid maxillary expansion (RME) in mixed dentition patients by examining changes in palatal volume, palatal surface area, and maxillary interdental transverse measurements.

METHODS

In this open-label, 2-arm, parallel, randomized controlled trial, patients with a posterior transverse discrepancy ≤6 mm were allocated into the clear aligner therapy (CAT) group (Invisalign First Phase I treatment) and RME group (tooth-borne RME) according to a computer-generated randomization list immediately before the start of treatment. Digital models were obtained before the beginning of the treatment (T0) and at the end of the retention period/treatment (T1) using an intraoral scanner. Palatal volume was measured as the primary outcome, and palatal surface area and intermolar and intercanine transverse widths at the cusps and gingival level were measured as secondary outcomes. Patients and interventionists were not blinded because of the nature of the intervention.

RESULTS

Out of 50 patients, 41 (19 males and 22 females; mean age, 8.12 ± 1.53 years) were enrolled and divided into 2 groups: 20 in the CAT group and 21 in the RME group. Two participants did not receive the allocated intervention for different reasons (1 patient discontinued the intervention in the CAT group, and another patient was lost to follow-up in the RME group). Thus, 19 patients (5 males and 14 females; mean age, 8.48 ± 1.42 years) were analyzed from the CAT group, and 20 patients (12 males and 8 females; mean age, 7.83 ± 1.19 years) from the RME group. Regarding intragroup comparisons, all outcome measures significantly increased from T0 to T1 in both groups. In terms of intergroup comparisons, there were no significant differences in the variation (Δ) of outcome measures between the 2 groups from T0 to T1, except for the intermolar width at the gingival level (P <0.005). The change in palatal volume was 532.01 ±540.52 mm³ for the RME group and 243.95 ± 473.24 mm³ for the CAT group (P = 0.084), with a moderate effect size (d = 0.57).

CONCLUSIONS

RME showed trends favoring better outcomes compared with Invisalign First Phase I treatment across all assessed measures. The only parameter that showed statistically significant differences between the 2 groups was variation in intermolar width at the gingival level, suggesting the occurrence of buccal tipping in patients undergoing Invisalign First Phase I treatment.

TRIAL REGISTRATION

The trial was registered at ClinicalTrial.gov (no. NCT04760535).

Evaluation of maxillary dimensional changes in the mixed dentition: clear aligners vs acrylic expanders

OBJECTIVES

To compare changes in upper arch dimension and molar inclination between Invisalign First (IF) and removable acrylic expander (RE) treatments during the mixed dentition period.

MATERIALS AND METHODS

Seventeen patients meeting inclusion criteria underwent IF treatment and were age matched with a group that received treatment with a removable acrylic expander (RE). Intercanine width (ICW), intermolar width, arch depth, buccolingual inclination of the first molars (MI), surface area (SA) and volume (VAP) of the anterior palate, and expansion were compared before and after treatment. The predictability of expansion was calculated for the IF group. Analysis of variance and Kruskal-Wallis tests were used to assess differences.

RESULTS

The ICW increased significantly by 2.14 mm in the IF group and 3.49 mm in the RE group, with no significant intergroup difference. Both groups exhibited significant increases in intermolar width (P < .05), except for intermolar distopalatal width in the IF group (P = .246). Mesiobuccal rotation of the first molar was observed with IF treatment. Although SA and VAP increased in both groups, the changes were not significant for the IF group (P > .05). The RE group exhibited significantly higher increases (P < .05), with an SA increase of 34.32 mm2 and VAP increase of 119.15 mm3. MI changes were in the opposite directions. The prediction accuracy of expansion was 70.28% for canines and 34.12% for first molars.

CONCLUSIONS

Both appliances effectively expanded the intercanine region in growing patients. Expansion predictability was lower in first molars than in canines for the IF group. Removable acrylic expanders could be a choice of preference for expansion targeted to the molar region.

Accuracy of arch expansion with two thermoplastic materials in Invisalign® patients: EX30® and SmartTrack®

OBJECTIVE

The purpose of this retrospective study was to compare accuracy of arch expansion using two different thermoplastic materials in Invisalign aligners: EX30® (Polyethylene Terephthalate Glycol, or PETG) and SmartTrack® (polyurethane).

METHODS

The study sample comprised 65 adult patients consecutively treated with Invisalign from two private practices: group 1 - treated with EX30® (358 teeth) and group 2 - treated with SmartTrack® (888 teeth). Six hundred and twenty-three measurements were assessed in three digital models throughout treatment: model 1 - initial, model 2 - predicted tooth position, and model 3 - achieved position. Sixteen reference points per arch were marked and, after best alignment, 2 points per tooth were copied from one digital model to another. Linear values of both arches were measured for canines, premolars, and first molars: on lingual gingival margins and cusp tips of every tooth. Comparisons were performed by Wilcoxon and Mann-Whitney test.

RESULTS

Both termoplastic materials presented significant differences between predicted and achieved values for all measurements, except for the lower molar cusp tip in the SmartTrack® group. There is no statistical difference in the accuracy of transverse expansion between these two materials. Overall accuracy for EX30® aligners in maxilla and mandible were found to be 37 and 38%, respectively; and Smarttrack® presented an overall accuracy of 56.62% in the maxilla and 68.72% in the mandible.

CONCLUSIONS

It is not possible to affirm one material expands better than the other. Further controlled clinical studies should be conducted comparing SmartTrack® and EX30® under similar conditions.

[Fixed orthodontic appliances and clear aligner system: a comparative review]

One of the biggest controversies in current orthodontics is determining the appliance to use, since today patients seek better results in shorter times, in addition to putting aesthetics first.

OBJECTIVE

compare the benefits and disadvantages that arise when using fixed orthodontic appliances and transparent aligners.

MATERIALS AND METHODS

An investigation and compilation of specialized bibliographic information on the topic was carried out in scientific search engines such as PubMed, SciElo and Web of Science between the years 1991 to 2023, focused on research work related to the effects of the use of orthodontic appliances. fixed compared to clear aligners.

RESULTS

The review was carried out based on 53 articles found that met the selection criteria.

CONCLUSION

Fixed orthodontic appliances are better in complex cases, they are more precise and less likely to relapse; Transparent aligners are more aesthetic, hygiene is more affective and the bone density of the mandibular condyle decreases.

Clear Aligners in the Growing Patient: A Systematic Review

Mixed dentition represents a critical phase in the oral development of pediatric patients, characterized by the simultaneous presence of primary and permanent teeth. This article proposes a comprehensive systematic review of the application of aligners as an innovative methodology in managing mixed dentition. The primary objective is to explore the efficacy, safety, and acceptability of this emerging orthodontic technology in the evolving age group. This systematic review focuses on randomized controlled trials, cohorts, and observational studies investigating the use of aligners in patients with mixed dentition. Clinical, radiographic, and psychosocial parameters will be considered to assess the overall impact of aligner therapy in this critical phase of dental development. An in-depth analysis of such data aims to provide a comprehensive overview of the potential of this technology in pediatric orthodontics. Expected outcomes may contribute to outlining practical guidelines and targeted therapeutic strategies for orthodontists involved in managing mixed dentition. Furthermore, this article aims to identify gaps in the current research and suggest future directions for studies exploring the use of transparent aligners in patients with mixed dentition, thereby contributing to the ongoing evolution of evidence-based orthodontic practices.

Treatment Efficiency of Maxillary and Mandibular Orovestibular Tooth Expansion and Compression Movements with the Invisalign® System in Adolescents and Adults

OBJECTIVES

Aligners are an effective and esthetic orthodontic treatment option for permanent and mixed dentition. There are only a few studies dealing with the effectiveness of orovestibular tooth movement using aligners and applying adequate examination methods. In the present retrospective study, the aligner efficiency of orovestibular movements for the entire dentition was systematically evaluated using 3D superimposition, taking into account the influence of jaw, tooth type and Invisalign® system.

METHODS

Group 1 (n = 18 adults, Invisalign®) and Group 2 (n = 17 adolescents, Invisalign® Teen) were treated with Invisalign® Ex30 aligner material and Invisalign® specific auxiliary means. In this non-interventional retrospective study, pre- and post-treatment maxillary and mandibular plaster cast models were scanned and superimposed with ClinChecks® via Surface-Surface Matching Algorithm on unmoved teeth providing stable references. Effectivity of planned versus clinically realized movements was evaluated for each tooth. Statistics were performed with a t-test and Bonferroni-Holm correction (α = 0.05).

RESULTS

Orovestibular movement efficiency was excellent without statistical significance regarding jaw, tooth type or Invisalign® system. Mandibular translational tooth movements were highly effective, and outstanding for premolars (91-98%). Maxillary translational tooth movements were successful for incisors and premolars, but less effective for canines and molars. Almost all teeth were moderately or very effectively corrected by crown tipping, performing better for mandibular (70-92%) than maxillary (22-31%) canines as much as for adolescent upper front teeth (81-85%) and lower canines (92%).

CONCLUSIONS

Aligners are able to effectively implement translational orovestibular movements, supported by tilting the crowns for even more efficient implementation of the movements. This phenomenon was observed in our studies for all teeth in both jaws, regardless of the Invisalign® system used. Treatment planning should nevertheless take into account the individual patient parameters with regard to the movements to be performed in order to make the aligner therapy as successful as possible in terms of realizing the desired therapeutic goal.

An evaluation of the Invisalign® Aligner Technique and consideration of the force system: a systematic review

OBJECTIVE

Since its introduction 25 years ago, the Invisalign® system has undergone multiple digital and biomechanical evolutions and its effectiveness is often compared to traditional systems without considering the many differences which characterize them. The main aim of this systematic review is to look at the literature dealing with studies on teeth movements using the Invisalign® system and the management of these movements through digital planning and artificial intelligence.

MATERIALS AND METHODS

The following electronic databases were searched: MEDLINE, Embase, the Cochrane Oral Health Group's Trials Register, and CENTRAL. Unpublished studies were searched on ClinicalTrials.gov, the National Research Register, and Pro-Quest Dissertation Abstracts and Thesis database.

RESULTS

Twenty-four studies (15 retrospective, 5 prospective, 2 pilot, and 2 case-control) were included. The results of the analysis carried out on the available literature show that the Invisalign® system is recognized to be a valid alternative to conventional orthodontic treatment in no-extraction cases. The results are influenced by the methods for assessing the effectiveness of this technique and by the comparison bias of the traditional system with the innovative digital system.

CONCLUSIONS

Since the introduction of SmartForce and SmartTrack material, the efficacy of the treatment has improved. There is still a shortage of high-quality evidence concerning the treatment modality. In order to make the treatment with the aligners more efficient, a correct management of the ClinCheck® software and a proper use of the biomechanics are necessary. The aligned force-driven system should be taken into account when developing the digital planning.

Effects of upper arch expansion using clear aligners on different stride and torque: a three-dimensional finite element analysis

BACKGROUND

During maxillary arch expansion with a clear aligner (CA), buccal tipping of the posterior teeth often occurs, resulting in an unsatisfactory arch expansion effect. The aim of this study was to analyze the appropriate maxillary arch expansion stride length and torque compensation angle for maxillary dentition to achieve an ideal moving state when a CA was used for upper arch expansion.

METHODS

This study established a three-dimensional (3D) finite element model including a CA, maxilla, periodontal ligament (PDL), and maxillary dentition. The stress distribution, stress situation, expansion efficiency, and movement trends of the maxillary dentition during upper arch expansion of different stride (0.1 mm, 0.2 mm, and 0.3 mm) and torque compensation (0°, 0.5°, 1°, and 1.5°) were measured.

RESULTS

Maxillary arch expansion lead to buccal tilt of the posterior teeth, lingual tilt of the anterior teeth, and extrusion of the incisors. As the angle of compensation increased, the degree of buccal tilt on the posterior teeth decreased, with this reducing the efficiency of upper arch expansion. When the stride length was 0.1 mm, the torque compensation was 1.2°, and when stride length was 0.2 mm and the torque compensation was approximately 2°, there was a tendency for the posterior teeth to move bodily. However, when the stride length was 0.3 mm, the increase in torque compensation could not significantly improve the buccal tilt phenomenon. In addition, the equivalent von-Mises stress values of the maxillary root, PDL, and alveolar bone were in the same order of magnitude.

CONCLUSIONS

This study indicated that the posterior teeth cause a degree of buccal tilt when maxillary arch expansion is ensured. The specific torque compensation angle should be determined based on the patient's situation and the desired effect.

Efficiency and Predictability of Coronal Maxillary Expansion Repercussion with the Aligners System: A Retrospective Study

The Invisalign® system (SmartForce® G8) aims to guarantee aesthetics and provide good orthodontic treatment results. Dentoalveolar expansion is possible with clear aligners and can be used to correct dentoalveolar crossbite, resolve crowding or modify the arch shape. Despite the treatment's effectiveness, there is still disagreement among professionals concerning its true clinical potential. This study aimed to analyze the effectiveness and predictability of coronal tooth expansion movement in permanent dentition in patients who had completed the first phase of treatment with Invisalign® orthodontic aligners.

MATERIALS AND METHODS

The tooth movement tables of 75 previously selected cases were analyzed in terms of dental-arch width and expansion efficiency, through the Invisalign® platform, considering the pre-treatment (T0), planned treatment (TP) and post-treatment models (T1) using ClinCheck Pro® 6.0 software. All patients were treated by an orthodontic specialist and Invisalign® Diamond Provider in a private practice (T.P.).

RESULTS

Difference between T1 and T0: for each maxillary and mandibular measurement, there was a statistically significant difference between pre- and post-aligner treatment values. The greatest amount of expansion occurred in both the upper and the lower premolars. Difference between TP and T1: for each maxillary measurement, statistically significant differences were verified for the molar and canine. At the mandibular level, statistically significant differences were only verified in the first molar.

CONCLUSIONS

The Invisalign® clear aligners are effective for simultaneous intra-arch expansion in both jaws.

The tooth movement efficiency of different orthodontic thermoplastics for clear aligners: study protocol for a randomized controlled clinical trial

INTRODUCTION

With regard to the esthetics and comfort of orthodontic treatment, the requirement for removable clear aligners (CAs) is increasing. Unlike conventional fixed orthodontic appliances, CAs were made of thermoplastic film by thermoforming on the personalized dental models. The construction of orthodontic thermoplastic is a critical factor for orthodontic tooth movement (OTM). Polyethylene terephthalate glycol-modified (PETG) and thermoplastic polyurethane (TPU) are the most commonly orthodontic thermoplastics; however, the evidence of the differences between different orthodontic thermoplastic are limited to vitro environment and the evidence in vivo environment is not available. Therefore, this trial aims to provide reliable evidence for orthodontists' personalized treatment plans whether the two most commonly used orthodontic thermoplastics of PETG and TPU have differences in the efficiency of OTM.

METHODS AND ANALYSIS

This randomized controlled clinical study will recruit 44 orthodontic patients for orthodontic treatment. All the subjects will be randomized into two groups (PETG and TPU, n = 22 for each group). In the first stage (M0 to M1), clear aligners will be made of two orthodontic thermoplastics and move the maxillary first or second premolars 2 mm. In the second stage, patients will take the standard orthodontic treatments. The primary outcome will be the efficiency of clear aligners made of different materials on the digital models. The secondary outcome will be the efficiency of clear aligners made of different materials on the cone-beam computed tomography (CBCT). The efficiency will be calculated through the superimposition of the digital models and CBCT.

DISCUSSION

The results from this trial will serve as evidence for orthodontists and manufacturers and clarify whether the difference in orthodontic thermoplastics significantly impacts the efficiency of OTM.

TRIAL REGISTRATION NUMBER

ChiCTR2300070980. Registered on 27 April 2023. https://www.chictr.org.cn/showproj.html?proj=186253.

A new way of analyzing tooth movement using universal coordinate system geometry single point superposition in a 3D model

INTRODUCTION

Superposing 3D models is an imminent need. However, current methods rely on marking multiple points on the maxilla and mandible, which could increase point marking and overlapping errors.

OBJECTIVE

This study aimed at developing a method for superimposing 3D models of the maxillary and mandibular arches with Autodesk Inventor® engineering software, using a single universal coordinate system (UCS) point superposition.

METHODS

A total of 104 STL (stereolithography) models of the maxillary and mandibular arches exported from My iTero® platform were retrospectively selected, in which T0 and T1 were the initial and refinement periods, respectively (n=26 per group). The X, Y, and Z coordinates associated with a single point in each arch were inserted into the models with SlicerCMF® software for model orientation. The arch models with UCS registration were transferred to Autodesk Inventor® for superimposition and to measure tooth movements performed during Invisalign® treatment. Arch expansion, intrusion and rotation were analyzed by two examiners. The statistics were performed using intraclass correlation coefficients (ICC), Dahlberg's formula, and t-test (p<0.05).

RESULTS

A reliable method of superimposing 3D digital models using a single UCS point in the maxilla and mandible was developed. ICC showed excellent intra- and inter-examiner correlation (ICC>0.90). A systematic error was not found concerning linear and angular measurements (<1mm and <1.5°, respectively). Digital dental movements could be analyzed, including arch expansion, dental intrusion, and tooth rotation.

CONCLUSIONS

The developed method was proven reliable and reproducible for superimposing 3D models of the maxillary and mandibular arches by using UCS system.

Dimensional changes in the palate associated with Invisalign First System: a pilot study

OBJECTIVES

To compare palatal dimensions and molar inclinations after Invisalign First System (IFS) to those in patients treated with slow maxillary expansion (SME) and normal controls.

MATERIALS AND METHODS

Twenty-three mixed dentition patients treated with IFS were gender- and dental age-matched to another two groups: Haas-type SME and control group. The intercanine width (ICW), intermolar width (IMW), palatal surface area (SA), volume (V), and first molar buccolingual inclinations (MI) were measured before (T1) and after (T2) treatment. Analysis of variance was used to compare the differences among the three groups.

RESULTS

The ICW increased significantly by 3.10 mm after IFS, 4.77 mm with SME, and 0.54 mm in controls; the difference among the groups was statistically significant (P < .001). The IMW increased by 1.95 mm in IFS, 4.76 mm in SME, and 0.54 mm in controls, with significant intra- and intergroup differences. Palatal SA and volume increased by 43.50 mm2 and 294.85 mm3 in the IFS group, which differed significantly from SME, but was similar to controls. The right and left MI increased 0.24° and 0.08° buccally, respectively, in the IFS group, which was comparable to controls, while significantly increased buccal MI was observed in the SME group.

CONCLUSIONS

IFS expands the upper arch with increased ICW and IMW compared to controls, but the expansion amount is smaller than SME. Unlike SME, IFS has no effects on palatal dimensions and molar inclinations.

Clinical outcomes of arch expansion with Invisalign: a systematic review

OBJECTIVE

This study aims to assess the scientific evidence regarding the clinical outcomes of Invisalign therapy in controlling orthodontic tooth movement.

MATERIALS AND METHODS

An electronic search was conducted on PubMed, Cochrane Library, Web of Science, Embase, and Scopus from November 2015 to November 2022 to identify relevant articles. Methodological shortcomings were highlighted, and an evaluation of the quality of the included studies was completed using the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool.

RESULTS

Fifteen non-randomized controlled trials were included in the analysis. Most non-randomized controlled trials (n=11; 73%) were rated with a moderate risk of bias according to the ROBINS-I tool. There were statistically significant differences between the pretreatment and posttreatment arches. The average expansion was significantly different from that predicted for each type of tooth in both the maxilla and mandible. Furthermore, the efficiency decreased from the anterior area to the posterior area in the upper arch.

CONCLUSION

Despite the fact that arch expansion with Invisalign® is not entirely predictable, clear aligner treatment is a viable option for addressing dentition crowding. The efficacy of expansion is greatest in the premolar area. More research focusing on treatment outcomes with different materials of aligners should be conducted in the future. Overcorrection should be considered when planning arch expansion with Invisalign. In the maxilla, the expansion rate decreases from the anterior to the posterior, and presetting sufficient buccal root torque of posterior teeth may result in improved efficiency of expansion.

Accuracy (trueness and precision) of 3D printed orthodontic models finalized to clear aligners production, testing crowded and spaced dentition

BACKGROUND

The study's objective was to assess the accuracy (trueness and precision) of orthodontic models obtained from crowded and spaced dentition finalized for the production of clear aligners. Four 3D printers featuring different technologies and market segments were used for this purpose.

METHODS

Two digital master models were obtained from two patients featuring respectively crowded dentition (CM group) and diastema/edentulous spaces (DEM group). The 3D printers tested were: Form 3B (SLA technology, medium-professional segment), Vector 3SP (SLA technology, industrial segment), Asiga Pro 4K65 (DLP technology, high-professional segment), and Anycubic Photon M3 (LCD technology, entry-level segment). Each 3D printed model was scanned and superimposed onto the reference master model and digital deviation analysis was performed to assess the trueness and precision calculated as root mean square (RMS). All data were statistically examined to obtain intra-group and inter-groups comparisons(p 0.05).

RESULTS

In both CM and DEM groups, SLA 3D printers (Vector 3SP and Form 3B) showed lower trueness error compared to DLP/LCD technologies (Asiga Pro 4K65, Anycubic Photon M3) (p < 0.001). In general, the entry-level printer (Anycubic Photon M3) showed the greatest trueness error (p < 0.001). Comparing CM and DEM models generated with the same 3D printer, statistically significant differences were found only for Asiga Pro 4k65 and Anycubic Photon M3 printers (p > 0.05). Concerning data of precision, the DLP technology (Asiga Pro 4k65) showed lower error compared to the other 3D printers tested. The trueness and precision errors were within the accepted clinical error for clear aligner manufacturing (< 0.25 mm), with the entry-level 3D printer nearly reaching this value.

CONCLUSIONS

The accuracy of orthodontic models generated for clear aligners can be affected by different 3D printer technologies and anatomical characteristics of dental arches.

Is maxillary arch expansion with Invisalign® efficient and predictable? A systematic review

BACKGROUND

The main objective of this review is to assess the effectiveness and predictability of the transverse expansion movement performed by Invisalign®. The secondary objectives are to determine whether the expansion is of a dentoalveolar or skeletal nature, and to locate the areas of expansion on the dental arch.

METHODS

Two investigators used the PubMed database to search for articles related to the subject. After using a research equation, specific inclusion and exclusion criteria were applied and the final selection of articles was done after being read in full. The ROBINS-I tool for non-randomized studies was applied to assess risk of bias in the results of each included study.

RESULTS

After reading the articles in full, 12 articles were included. Regarding effectiveness, most studies showed an increase in all measured interdental distances, with a maximum expansion at the premolar level. As for predictability, significant differences were found between post-treatment models and Clincheck® models, making it generally weak. Concerning the nature and areas of expansion, increase of arch width was due to buccal tipping of the crowns following a decreasing gradient from anterior to posterior.

CONCLUSIONS

Invisalign® treatment is effective in achieving a maxillary transverse expansion. However, this expansion is mainly dentoalveolar, with a facial crown tipping of the posterior teeth. Clincheck® software tends to overestimate the expansion movement when compared to the clinical outcome, therefore the predictability of movement is low.

Predictability and Effectiveness of Nuvola® Aligners in Dentoalveolar Transverse Changes: A Retrospective Study

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.

Effectiveness and predictability of treatment with clear orthodontic aligners: A scoping review

INTRODUCTION

In an ideal clinical setting, orthodontic therapy with clear aligners (CA) should improve the patients' initial malocclusion and must guarantee equivalence between the results predicted and those obtained clinically to be considered an effective treatment. Therefore, this scoping review aimed to identify the orthodontic literature concerning the effectiveness and predictability of CA treatments.

METHODS

A systematic computerized search was performed in 3 databases: PubMed, Scopus, and Embase. Inclusion criteria selected observational and clinical studies performed in at least 10 adult orthodontic patients, whose results of CA treatment's effectiveness and/or predictability were assessed.

RESULTS

The 3 database computerized searches resulted in 1,553 articles, and 169 full texts were considered potentially relevant. After applying the eligibility criteria, 33 studies were included. Most studies (76%) were designed as cohort studies and have been published in the last 5 years (79%). The majority included only non-extraction treatments (73%), and 79% reported results achieved with the Invisalign® system. The most predictable movement was the buccolingual tipping, while the least predictable movements were rotation, intrusion, and extrusion. Aligner treatment was effective for mild to moderate crowding resolution, and the success of overbite correction still seems to be limited.

CONCLUSIONS

The studies have demonstrated improvement of initial malocclusion through CA treatments. Still, predictability degree is overestimated and does not accurately reflect the occlusion immediately at the end of treatment. In future studies, there should be an effort to broaden the utilization of alternative aligner systems beyond Invisalign® and broadly disseminate their outcomes to strengthen clear aligners evidence base.

Efficacy and Accuracy of Maxillary Arch Expansion with Clear Aligner Treatment

The aim of this work was to evaluate the efficacy and accuracy of maxillary arch transverse expansion using the Invisalign^® clear aligner system without auxiliaries other than Invisalign attachments. Knowing the accuracy of a movement through a clear aligner system allows the clinician to plan the treatment with greater precision and to achieve the expected result faster. The study group included 28 patients with a mean age of 17 ± 3.2 years. The treatment protocol for all the selected patients included the application of the Invisalign^® clear aligner system without auxiliaries, except for the Invisalign^® attachments; in no case were tooth extraction or interproximal enamel reduction (IPR) performed. Linear measurements of the expansion were assessed before treatment (T0), at the end of treatment (T1), and on final virtual models by ClinCheck^® (TC). A paired t-test was used to compare T0-T1 and T1-TC differences. A paired t-test was applied, and one normality was validated with the Shapiro-Wilks test. If normality was not met, the nonparametric test (Mann-Whitney U test) was applied. The level of significance was set at 5%. Statistically significant differences were found for all measurements at T0-T1. The results showed an average accuracy of efficacy of 70.88%. The differences in predictability between the various vestibular measurements (intercanine, inter-premolar, and intermolar) were not statistically significant, while they were for gingival measurements. The overall accuracy of the expansion treatment was 70%, regardless of tooth type.

Maxillary molar distalization with a 2-week clear aligner protocol in patients with Class II malocclusion: A retrospective study

INTRODUCTION

This study aimed to investigate the efficacy of molar distalization with or without anterior teeth retraction.

METHODS

Forty-three patients who received maxillary molar distalization with clear aligners were retrospectively enrolled and further divided into 2 groups: a retraction group (with maxillary incisor retraction ≥2 mm in ClinCheck) and a nonretraction group (without anteroposterior movement or with the labial movement of the maxillary incisor in ClinCheck). Pretreatment and posttreatment models were collected and laser-scanned to obtain the virtual models. Three-dimensional digital assessments of molar movement, anterior retraction and arch width were analyzed in the reverse engineering software Rapidform 2006. To calculate the efficacy of tooth movement, the achieved tooth movement assessed on the virtual model was compared with the predicted tooth movement in ClinCheck.

RESULTS

The achieved efficacy rates of molar distalization for the maxillary first and second molars were 36.48% and 41.94%, respectively. There was a significant difference in molar distalization efficacy between the retraction group (31.50% at the first molar and 35.63% at the second molar) and the nonretraction group (48.14% at the first molar and 52.51% at the second molar). In the retraction group, the efficacy of incisor retraction was 56.10%. The efficacy of dental arch expansion was more than 100% at the first molar levels in the retraction group and at the second premolar and first molar levels in the nonretraction group.

CONCLUSIONS

There is a discrepancy between the outcome and the predicted maxillary molar distalization with clear aligners. The efficacy of molar distalization with clear aligners was significantly affected by anterior teeth retraction, and the arch width significantly increased at the premolar and molar levels.

Assessment of Posterior Dentoalveolar Expansion with Invisalign in Adult Patients

PURPOSE

The primary aim was to evaluate dentoalveolar expansion with Invisalign clear aligners comparing linear measurements in ClinCheck vs. cone beam computed tomography (CBCT). This would enable an assessment of to what extent expansion gained from Invisalign clear aligners was due to buccal tipping and/or bodily translation of the posterior teeth. The study also evaluated the predictive value of Invisalign ClinCheck^® (Align Technology, San Jose, CA, USA) to final outcomes.

METHODS

The orthodontic records of thirty-two (32) subjects comprised the sample to conduct this study. Linear values of the upper arch width were measured for premolars and molars at two different points (occlusal and gingival) utilized for ClinCheck^® measurements and three different points for CBCT measurements before (T₀ and after treatment (T₁). Paired T-tests at a significance level of 0.05 were used for analyses.

RESULTS

Expansion was found to be possible with Invisalign clear aligners. However, more expansion was measured at the cusp tips compared to gingival margins (p < 0.0001), indicating more tipping was occurring than bodily translation. ClinCheck^® also showed a significant overestimation of the amount of expansion capable, with nearly 70% expression in the first premolar area, and the expression decreased as one moved posteriorly with only 35% expressed at the first molar area (p < 0.0001).

CONCLUSIONS

Dentoalveolar expansion with Invisalign is achieved through buccal tipping of posterior teeth and bodily translation; and there is a significant overestimation of the amount of expansion achieved between ClinCheck^® and clinical results.

The Predictability of Transverse Changes in Patients Treated with Clear Aligners

Arch expansion might be used to correct buccal corridors, improve smile aesthetics, resolve dental cross bite, and gain space to resolve crowding. In clear aligner treatment, the predictability of the expansion is still unclear. The purpose of this study was to evaluate the predictability of dentoalveolar expansion and molar inclination with clear aligners. In the study, 30 adult patients (27 ± 6.1 years old) treated with clear aligners were selected (treatment time: 8.8 ± 2.2 months). The upper and lower arch transverse diameters were measured for canines, first and second premolars, and first molars on two different sides (gingival margins and cusp tips); moreover, molar inclination was measured. A paired t-test and Wilcoxon test were used to compare prescription (planned movement) and achieved movement. In all cases, except for molar inclination, a statistically significant difference was found between achieved movement and prescription (p < 0.05). Our findings showed a total accuracy of 64% for the lower arch, 67% at the cusp level, and 59% at the gingival level, with a total accuracy of 67% for the upper arch, 71% at the cusp level, and 60% at the gingival level. The mean accuracy for molar inclination was 40%. Average expansion was greater at cusps of canines than for premolars, and it was lowest for molars. The expansion achieved with aligners is mainly due to the tipping of the crown rather than bodily movement of the tooth. The virtual plan overestimates the expansion of the teeth; thus, it is reasonable to plan an overcorrection when the arches are highly contracted.

Predictability of crowding resolution in clear aligner treatment

BACKGROUND

To assess the predictability of crowding resolution and the efficacy of different strategies to gain space during clear aligners treatment.

METHODS

A total of 10 clinicians were randomly recruited using the Doctor Locator by Align Technology (California). For each clinician, four consecutive patients treated with aligners and manual stripping were selected for a total of 40 subjects. Thus, 80 arches were collected and uploaded on the Orthoanalyzer software for arch measurements. The data were gained on the starting arch form (T0), on the virtual arch developed with digital planning (vT1), and on the arch form achieved at the end of the aligner sequences (T1). The following parameters were scored: Little's Irregularity Index, transversal arch diameters, (intercuspid, interpremolar, and intermolar width), incisor position/arch length, and enamel interproximal reduction (IPR).

RESULTS

For all the measurements, statistically significant differences were found at different stages. The predictability of crowding resolution was very high, ranging from 87% in the upper arch and 81% in the lower one. Among the different strategies to gain space, variations in sagittal incisor position were predictable, with a value of 70% both in the upper and lower arch. Conversely, changes in arch diameters were less reliable varying between 49 and 67% in the lower arch and 59-83% in the upper one. Moreover, IPR was the least accurate procedure, wavering at 49% in the upper arch and 42% in the lower arch.

CONCLUSIONS

The predictability of crowding resolution during treatment with aligners was high. However, the virtual arch forms obtained at the end of digital planning (vT1) did not correspond with the arch forms at the end of the aligner sequences (T1). The IPR was the least predictable strategy to gain space, being, perhaps, an operator-dependent procedure.

Analysis of Maxillary First Molar Derotation with Invisalign Clear Aligners in Permanent Dentition

The objective of this study was to examine the distal rotation of mesial rotated maxillary first permanent molars in a sample of Class II dental malocclusion adult patients treated with Invisalign Clear Aligners (CA). Forty patients (20 males, 20 females, 22.4 ± 3.9 years) were included in the study sample (Department of Orthodontics of University of Rome “Tor Vergata”). Inclusion criteria were: Caucasian ancestry, complete permanent dentition with fully erupted upper second molars, Class II molar relationship, absence of tooth or craniofacial anomalies or caries and periodontal diseases. Pre-treatment (T1), post-treatment (T2) digital casts, and final ClinCheck simulation models (T2CC) were analysed. To measure the rotation of maxillary first molars, Henry’s angle (H°) was evaluated. Maxillary first molars with an H° > 11° were considered mesio-rotated (in total 59 teeth). The treatment CA protocol included disto-rotation without distalization movements. At T1, T2 and T2CC five measurements on the collected dental casts were analysed: Henry’s angle (H°); mesial buccal expansion (ME); distal buccal expansion (DE); mesial buccal sagittal (MS); and distal buccal sagittal (DS). A comparison between the results of T2-T1 and T2CC-T2 was performed using a paired t-test. The differences between T2-T1 highlighted a significant distal rotation of the maxillary first molars (−7.4°) and an expansion movement of 2.20 mm for ME and 1.50 mm for DE. In the post-treatment, the mesial buccal cusps shifted of 1.0 mm, while the distal buccal cusps showed a distal movement of 0.9 mm. Analysing the H° comparison between T2CC-T2, the difference was −1.1°. The T2CC-T2 comparison in the sagittal plane showed a difference of 0.9 mm for the MS and 0.7 mm for the DS. The accuracy was 82% for molar derotation movement. In conclusion, CA provides the upper arch expansion associated with the upper first molars’ distal rotation. These movements provide 2 mm of improvement in arch perimeter and molar intercuspation.

The Efficacy and Predictability of Maxillary First Molar Derotation with Invisalign: A Prospective Clinical Study in Growing Subjects

To analyze the derotation of maxillary mesio-rotated first permanent molars in subjects with Class II edge-to-edge dental malocclusion in mixed dentition treated with Invisalign Clear Aligners (CA). In total, 36 patients (16 males, 20 females, 9.9 ± 1.9 years) treated with CA are enrolled from the Department of Orthodontics. Inclusion criteria are the following: Caucasian ancestry, mixed dentition, molar Class II edge-to-edge, no tooth/craniofacial anomalies, no caries/periodontal diseases. Pre-treatment (T1) and post-treatment (T2) digital casts, and final ClinCheck representations (T2ClinCheck) are acquired. The Henry’s angle (HA) is used to assess maxillary first molars rotation. The molars with an HA > 11° are taken (53 teeth). Five measurements are performed at T1, T2, and T2ClinCheck: Henry’s angle (HA), mesiobuccal-expansion (MBE), distobuccal-expansion (DBE), mesiobuccal-sagittal (MBS), and distobuccal-sagittal (DBS). A paired t-test was used to compare T2-T1 and T2ClinCheck-T2. The T2-T1 shows a distal-rotation (difference −6.3°) with an expansion of 2.2 mm for MBE and 1.5 mm for DBE. At T2, the mesiobuccal cusps show a distal movement of 1.0 mm and the distobuccal cusps of 0.9 mm. The HA’s T2ClinCheck-T2 difference is −4.2°. In the sagittal plane, the difference is 0.9 mm for the MBS and 0.7 mm for the DBS. The expansion showed the highest predictability (60% HA, 52.6% MBS, and 56.25% DBS). The CA effectively produces an arch expansion and upper molars’ distal rotation. Upper molar derotation provides a 1 mm of gain in arch perimeter and occlusal improvement.

Efficacy and predictability of maxillary and mandibular expansion with the Invisalign® system

Background

The purpose of this study is to evaluate the efficacy and predictability of upper and lower orthodontic expansion with the Invisalign® system.

Material and Methods

From a sample of 167 patients; 64 upper and 51 lower arches were randomly selected from patients who had been treated with plastic orthodontics (Invisalign® aligners, SmartTrack® material). Digital models were extracted at the beginning (ModT1) and at the end of treatment (ModT2) as well as the final ClinCheck® (CkT2). The canine, premolar and molar width was measured at the gingival and cuspid level of both arches, as well as the inclination of the upper first molar. Likewise, both arches were divided regarding the planned expansion at the level of the first molar into mild, moderate and severe.

Results

The efficacy of expansion in the upper and lower arches showed a statistically significant difference (p<0.00005). During the measurements of predictability, around 98-100% was achieved at the coronal level and between 85-90% at the gingival level. Analyzing predictability regarding to the magnitude of expansion, superior and inferior moderate expansion, both gingival and cuspid, presented higher values.

Conclusions

The Invisalign® system aligners (SmartTrack® material), proved to be a positive alternative for expansion movement offering high degree of predictability, both in the upper and lower arches. As a result, the most predictable level of expansion was moderate, having being the lower arch more foreseeable at the gingival level than the upper arch.

Key words:Predictability, Efficacy, Expansion, Aligner, Invisalign®.

Clear aligner orthodontic treatment: Angle Society of Europe consensus viewpoint

Orthodontics has witnessed not only an exponential rise in demand from adult patients but accompanying this, the emergence of alternate aesthetic treatment options to the more traditional fixed labial appliance. The concept of using clear aligners as a means of achieving tooth movement has increased in popularity among both patients and clinicians alike. However, the question over best research evidence as to their clinical effectiveness to treat a range of malocclusion traits remains elusive and controversial among the profession.In an attempt to offer the profession some clear guidance, The Angle Society of Europe reviewed and discussed the current published evidence (2005-2018) on their clinical use, during the annual meeting in January 2020, to help formulate a consensus viewpoint on the clinical applications.