Efficiency, effectiveness and treatment stability of clear aligners: A systematic review and meta-analysis

Efficacy of clear aligner wear protocols in orthodontic tooth movement-a systematic review

BACKGROUND AND OBJECTIVES

Different expedited aligner wear protocols are currently in practice. This review was undertaken to systematically appraise the available evidence on the comparative efficacy of orthodontic tooth movement (OTM) across the different wear protocols.

SEARCH METHODS

Two assessors conducted comprehensive searches of electronic databases, including MEDLINE (via PubMed), Scopus, Embase, Web of Science, Google Scholar, Directory of Open Access Journals, Cochrane Library, OpenGrey, and Clinical Trial Registry, till 18 February 2024. Titles and abstracts were independently screened.

SELECTION CRITERIA

Prospective or retrospective studies comparing expedited wear protocols with the conventional 14-day protocol were included.

DATA COLLECTION AND ANALYSIS

A pre-piloted data extraction form was used. Risk of bias (RoB) assessment employed the Cochrane RoB 2.0 tool for randomized-controlled trials (RCTs) and the Newcastle-Ottawa scale for non-RCTs. The quality of evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluation Pro tool.

RESULTS

Six studies, including 3 RCTs and 3 non-RCTs, were selected from 9076 records. Four studies (two RCTs and two retrospective cohort) found no statistically significant difference (P > 0.05) in the OTM efficacy between expedited and conventional protocols. Two studies (one RCT and one prospective cohort) found greater efficacy (P < 0.05) with the 14-day protocol, with the RCT reporting greater efficacy for certain movements, such as maxillary posterior intrusion, maxillary posterior distal tipping and buccal torquing, and mandibular posterior intrusion and extrusion. One RCT reported statistically insignificant difference (P > 0.05) in pain perception between the 10-day and 14-day protocols. Two studies demonstrated low RoB, two moderate, and two high RoB. The evidence level was very-low for OTM efficacy and high for pain perception. Meta-analysis was precluded due to significant heterogeneity among the studies.

CONCLUSIONS

Within the limitations of the study, the 7-day, 10-day, and 14-day protocols did not show any significant difference in OTM efficacy, except for certain movements that exhibited superior outcomes with the 14-day wear. Hence, a 'hybrid aligner-wear protocol', based on clinical judgement, might serve a better alternative in complex situations.

REGISTRATION

PROSPERO CRD42021288179.

Clear aligner therapy informed consent forms: A quality and readability evaluation

OBJECTIVE

The aim of the present study was to evaluate the quality and readability of content contained within clear aligner therapy (CAT) informed consent forms.

METHODS

CAT informed consent forms were identified via an online search. The presence of details related to CAT-related processes, risks, benefits and alternatives in each form was recorded. A 4-point Likert type scale was used to determine the quality of content (QOC). The readability of content was evaluated with the Simple Measure of Gobbledegook (SMOG) and Flesch Reading Ease Score (FRES).

RESULTS

A total of 42 forms satisfied selection criteria. Nineteen (45.2%) were authored by companies who provided aligners to patients via clinicians. The QOC regarding CAT-related treatment processes [median 2.0; IQR 0, 2] and benefits [median 2.0; IQR 1, 2] was adequate. The QOC scores regarding treatment alternatives, consequences of no treatment and relapse were poor. There was no difference (P=0.59) in the median (IQR) QOC of the informed consent forms provided by direct-to-consumer (DTC) aligner providers [10 (8.25, 16.25)] and non-DTC aligner providers [12 (10, 14)]. The median (IQR) SMOG score was 12.1 (10.9, 12.7) and FRES was 39.0 (36.0, 44.25).

CONCLUSIONS

The QOC of the evaluated forms was incomplete and poor. The content was difficult to read and failed to reach recommended readability standards. Consent is unlikely to be valid if it is based solely on the content of the forms. Clinicians need to be aware of the limitations of informed consent forms for CAT particularly in relation to alternatives, prognosis, risks, and the need for long-term maintenance of results.

Minimally invasive prosthodontics using the concept of prosthetically guided orthodontics

OBJECTIVE

This case report aims to present how digital technology can be employed to plan the orthodontic movement of teeth into their final positions for prosthodontic rehabilitation. An interdisciplinary approach to treatment planning and the result of prosthodontic treatment involves the cooperation of an orthodontist and a prosthodontist. When planned to achieve optimal results for a minimally invasive and functional prosthodontic treatment, orthodontic pretreatment provides superior esthetic results and favorable long-term success.

CLINICAL CONSIDERATIONS

The orthodontic movements of the teeth were planned so that the prosthodontist could reconstruct an optimally functional and esthetic occlusion while preserving the hard dental tissues. The orthodontic pretreatment minimized the need to prepare the teeth, avoiding any mucogingival surgery to improve the gingival architecture.

CONCLUSIONS

In complex clinical cases, it is essential to evaluate the advantages of an orthodontic pretreatment before starting a prosthodontic treatment. This pretreatment can help preserve dental tissues, reduce or eliminate the need for surgical intervention, and achieve long-term stability and esthetic results.

CLINICAL SIGNIFICANCE

This case clearly shows the benefits of orthodontic pretreatment for prosthodontic outcomes. With modern digital tools, such an orthodontic pretreatment should become standard clinical practice when planning a complex clinical case.

Duration of orthodontic treatment with clear aligners versus fixed appliances in crowding cases: a systematic review

OBJECTIVE

To critically appraise and assess the currently observed evidence about the difference in orthodontic treatment duration between clear aligners and fixed appliances in crowding cases.

MATERIALS AND METHODS

An electronic search without limitations was conducted from inception to June 2023 covering nine databases: The Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Scopus, Web of Science, Google Scholar, Trip, CINAHL via EBSCO, EMBASE via OVID and ProQuest. Randomized controlled trials (RCTs) and matched non-randomized studies were included in this systematic review. Risk of Bias was assessed via Cochrane's tool (RoB 2) for RCTs and ROBINS-I tool for non-randomized studies. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework was employed to evaluate the overall quality of evidence.

RESULTS

Out of the 3537 articles initially identified, ten eligible studies were included in this systematic review; six were RCTs. Only one study offered extraction-based treatment, while the other nine adopted non-extraction treatments. According to the GRADE, there is low evidence that treatment duration in mild to moderate crowding cases with clear aligners is similar to that in fixed orthodontic appliances. Meta-analysis was not administered due to high inconsistency.

CONCLUSIONS

Based on currently available information, there was no significant difference in the treatment duration between the CA and FA groups in mild to moderate crowding cases. Further well-performed RCTs, especially in severe cases, are required.

CLINICAL RELEVANCE

Time efficiency is an essential outcome measure for clinical orthodontic practice. While the type of appliance used is a critical determinant of treatment duration, orthodontists should be aware of other factors that can significantly impact treatment time, such as patient and treatment-related factors.

Color and Chemical Stability of 3D-Printed and Thermoformed Polyurethane-Based Aligners

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.

Percentage of patients shifting to another treatment modality: An experience-guided decision

OBJECTIVE

This study aimed to assess the frequency with which orthodontic patients decided to shift to another type of orthodontic appliance, among conventional metal brackets, ceramic brackets, lingual brackets and clear aligner, based on their personal experiences of pain, ulcers, bad breath, hygiene issues and social difficulties.

MATERIAL AND METHODS

This study comprises of patients seeking orthodontic treatment. The sample (n = 500; age group = 19-25 years) was divided equally into four groups based on the treatment modality: conventional metal brackets, ceramic brackets, lingual brackets and clear aligner. Patients rated the questionnaire using a visual analogue scale, to assess variables (such as pain, ulcer etc) that impact various treatment modalities. Subsequently, patients from all groups provided feedback regarding their treatment experiences, and expressed their preference for an alternative modality. Intergroup comparison among the four groups was done using one-way analysis of variance with Tukey's HSD post-hoc test (p ≤ 0.05).

RESULTS

Patients who received lingual brackets reported higher levels of pain and ulceration, as compared to those who received clear aligners. All four groups showed statistically significant differences for ulcers during treatment (p ≤ 0.05). Of the 125 patients who received conventional metal brackets, 28% expressed a preference for clear aligner therapy, while 20% preferred ceramic brackets. In the lingual group, 56% of 125 patients preferred clear aligner therapy, and 8% preferred ceramic brackets to complete their treatment. In the ceramic group, 83% did not want to switch, whereas 17% desired to switch to clear aligner, while in aligner group no patient desired to switch.

CONCLUSIONS

A higher percentage of patients from lingual brackets group chose to shift to clear aligners, followed by conventional metal brackets group and by ceramic brackets group, in this descending order. The clear aligner group demonstrated fewer issues than the other treatment modalities.

Can a Self-etching Primer be Effective in Bonding Aligner Attachments to Different Types of Ceramics?

Objective

This in vitro study aimed to evaluate the effectiveness of pretreatment with a self-etching primer for bonding aligner attachments to lithium disilicate (LD) and monolithic zirconia (MZ) ceramics.

Methods

Forty ceramics, including LD (n=20) and MZ (n=20), were divided into four study groups according to the surface pretreatments: LD specimens pretreated with universal primer (Monobond Plus, MP) after hydrofluoric acid etching (Group 1); MZ ceramics pretreated with MP after sandblasting (Group 2); LD ceramics pretreated with self-etching ceramic primer (Monobond etch & prime, MEP) (Group 3); and MZ ceramics pretreated with MEP after sandblasting (Group 4). The aligner composite (GC Aligner Connect) and universal adhesive (GPremio Bond) were used to prepare the resin attachments. The bond strength was evaluated by micro-shear bond strength (SBS) testing (0.1 mm/min) after thermocycling, and the remnant adhesive was scored according to the resin attachment remnant index (RARI). The SBS data were analyzed using ANOVA and Tukey tests, and the RARI scores were analyzed using the chi-square test.

Results

Group 1 had the lowest SBS, and group 2 had the highest SBS. There were significant differences between the groups in terms of bond strength (p<0.05). The RARI scores showed no significant differences, regardless of the pretreatment and ceramic type.

Conclusion

The use of a self-etching primer increased the bond strength of resin attachments on LD ceramics. For zirconia ceramics, both ceramic primers are recommended for aligner attachment bonding.

Impact of clear aligner therapy on masticatory musculature and stomatognathic system: a systematic review conducted according to PRISMA guidelines and the Cochrane handbook for systematic reviews of interventions

BACKGROUND

Clear aligner therapy has gained popularity as a minimally invasive orthodontic treatment option. However, its impact on the masticatory musculature and the stomatognathic system is an area of growing interest, as it involves the adjustment of occlusion and tooth movement. This systematic review aims to comprehensively assess and synthesise existing evidence regarding the influence of clear aligner therapy on the masticatory musculature and the stomatognathic system.

METHODS

An exhaustive search was performed on electronic databases that adhered to PRISMA guidelines. Clinical studies that evaluated the impact of patients receiving aligner orthodontic treatment on the muscles of the mastication and stomatognathic systems were included. A standardised data extraction form was devised for relevant variables. Two reviewers extracted the data variables. ROB-2 was used for bias evaluation in the selected studies.

RESULTS

A total of six studies met the inclusion criteria. The wearing of clear aligners significantly impacted the muscles of mastication. Muscle activity and discomfort showed a significant alteration in the initial days of appliance placement. but this observation was temporary, with no significant changes thereafter in subsequent follow-up. Bite force reduction was also noted. All the studies evaluated showed good methodological quality.

CONCLUSION

The review found that aligned orthodontic treatment may have a variable impact on muscles of mastication, with a potential for initial exacerbation of symptoms followed by possible improvement. However, due to the limited number of studies and their heterogeneous nature, further robust research is recommended to fully understand the relationship between aligned orthodontic treatment and masticatory muscles.

Does aligner refinement have the same efficiency in deep bite correction?: A retrospective study

BACKGROUND

Refinements are very common in clear aligner treatments. The aim of this study is to assess whether the predictability of deep overbite correction is similar over several refinements using clear aligners (Invisalign, Align Technology, San Jose, Calif) and examine the accuracy of vertical movement and inclination change of individual teeth.

METHODS

This retrospective study included 20 deep bite patients (7M and 13F; 32.63 ± 11.88 years old; an initial overbite of 5.09 ± 0.98 mm), consecutively treated from September 2016 and March 2023, who completed at least two sets of aligners, including refinements. The initial, predicted, and achieved models were exported from ClinCheck or OrthoCAD (Cadent Inc, Carlstadt, NJ) and superimposed via best-fit surface-based registration using SlicerCMF (version 4.9.0; cmf.slicer.org). We also examined 15 out of 20 patients who completed treatments. The overbite correction and changes in vertical movement and inclination for individual teeth were measured. Descriptive statistics and a paired t-test or Wilcoxon signed-rank test were performed. P < 0.05 was considered statistically significant.

RESULTS

The mean accuracy of overbite correction was 37.63% after 1st set, followed by 11.19%, 6.32%, and 13.80% (2nd-4th sets), respectively. There were statistically significant differences between the predicted and achieved vertical movements and inclination changes for all teeth for the 1st and 2nd sets. For the completed cases, the mean overbite correction was 38.54% compared to the initially planned overbite correction, which is similar to one of the 1st set. Still, the vertical movements and inclination changes of all teeth present statistically significant differences between the initially planned and finally achieved movements except for maxillary lateral incisor torque.

CONCLUSIONS

The most overbite correction occurs during the 1st set of aligners, and refinement treatment does not significantly improve the deep bite correction.

Effect of attachment configuration and trim line design on the force system of orthodontic aligners: A finite element study on the upper central incisor

OBJECTIVES

To use the finite element method (FEM) to investigate the effect of various attachment configurations and trimming line designs of orthodontic aligners on their biomechanical performance.

METHOD

A 3D upper jaw model was imported into 3D design software. The upper right central incisor tooth (Tooth 11) was made mobile, and its periodontal ligament (PDL) and bone structures were designed. Aligners were modelled with three distinct attachment configurations: No attachment, rectangular horizontal, rectangular vertical, and two trimming line designs; scalloped and straight extended, with a homogeneous thickness of 0.6 mm. These models were then imported into an FE software. Simulations were conducted for three different movements, including facial translation, distalization, and extrusion.

RESULTS

Forces were recorded at 1.3-2.6 N during facial translation, 1.4-5.9 N in distalization, and 0.0-2.0 N in extrusion. The straight extended trimming line consistently generated higher forces than the scalloped design. Attachments had no significant impact on force components during facial translation but were more effective in distalization and extrusion. The combination of a straight extended trimming line with horizontal attachments exhibited the least stresses at the apical third during distalization, and the highest stresses during extrusion, suggesting superior retention.

CONCLUSIONS

Rectangular attachments offer limited benefits in facial translation, but horizontal rectangular attachments can intensify load in distalization and are crucial for force generation in extrusion. Horizontal attachments are preferred over vertical options. Additionally, the straight extended trim line enhances control of tooth movement and can replace attachments in certain cases.

CLINICAL RELEVANCE

These findings provide biomechanical evidence and an optimal protocol to guide clinical practice in planning diverse teeth movements. The emphasis is on the influence of attachment utilization and the specific design of aligner trimming lines to enhance control over tooth movement.

An In Vitro Study of the Abrasive Potential of Various Toothbrushes on the Surface of Aligner Attachments

Background Attachments play a vital role in aligner-led orthodontic therapy, first passively through retention of the appliance and secondly, through bringing about tooth movement, by virtue of its active surfaces, to achieve treatment goals. Additionally, irregularities on the surface of attachments attract plaque adhesion. Thus the effect of brushing with different toothbrushes on the surface of attachments is an important factor to study. This would allow clinicians to better advise patients who are undergoing aligner therapy. Four types of brushes are available commercially, namely hard, medium, soft, and ultra-soft. This study analyses the interaction between the kind of toothbrush used and the wear of the surface of the aligner attachment, to understand the impact of a toothbrush on the attachment. Aim To observe the surface wear and change in the shape of the aligner attachment on brushing with four varying hardness of toothbrush bristle (ultra-soft, soft, medium, and hard) over six months to three years. Material and methods One attachment was bonded to the buccal surface of extracted premolars. One tooth with attachment was subjected to SEM analysis and the rest were divided into four groups of five teeth each, based on the type of toothbrush to be used. Brushing with hard, medium, soft, and ultra-soft toothbrushes was carried out in a brushing simulator in two cycles simulating six months, one year, 18 months, and three years of brushing. A contact profilometer was used to evaluate surface roughness before and after brushing and pre- and post-surface roughness values were compared to quantitate changes after which SEM analysis was carried out for qualitative assessment of the surface of the samples. The Shapiro-Wilks test was applied to evaluate the normality of the data, followed by the one-way ANOVA, and statistical significance was applied at p<0.05. Results At six months, the samples brushed with the medium toothbrush showed the least surface roughness (0.2±0.192) and those brushed with the ultra-soft toothbrushes showed the highest surface roughness (1.9±0.159). At one year, the samples brushed with the soft toothbrush showed the least surface roughness (0.46 ±0.31) and those brushed with the ultra-soft toothbrushes showed the highest surface roughness (2.12 ±0.12). At the 1.5-year point, the surface roughness of the samples was lowest in the ultra-soft toothbrush group (0.43±0.39) and the highest in the soft toothbrush group (1.6± 0.41). At the three-year point, the surface roughness of the samples was lowest in the ultra-soft toothbrush group (0.28 ± 0.17) and the highest in the medium toothbrush group (1.6 ± 0.31). Conclusion Ultra-soft toothbrushes have a high abrasive potential, as seen by higher surface roughness values over six months and one year. Morphometric changes were the most noticeable for attachments brushed by hard-bristled toothbrushes and medium-bristled brushes.

Impact of molar teeth distalization by clear aligners on maxillary alveolar bone thickness and root resorption: a three‑dimensional study

OBJECTIVE

This study aimed to evaluate the impact of molar teeth distalization movement by clear aligners on changes in the alveolar bone thickness and orthodontically induced inflammatory root resorption (OIIRR) in maxillary molars using conebeam computed tomography (CBCT).

MATERIALS AND METHODS

Three-dimensional CBCT scans of 35 adult patients (one hundred forty maxillary molars) with pre-designed selection criteria and a mean age of 24.4 ± 7.1 years were included. The measured parameters, including alveolar bone thickness for maxillary molars and root resorption (OIIRR), were analyzed using pre-and post-treatment CBCT (T0 and T1, respectively) with Invivo 6.0 software.

RESULT

Post-treatment, relevant statistically significant changes included deposition of bone in the average palatal surface of the 1st molars. The reduction of bone was seen in the average buccal surface of the first molars and both surfaces of the second molars. Regarding root length after treatment, the average maxillary 1st molar roots showed significant OIIRR (p < 0.001).

CONCLUSION

Clear aligner treatment could effectively reduce the incidence of alveolar bone thickness reduction and OIIRR in treating Class II malocclusions compared to conventional braces, as shown in previous studies. This research will aid in fully grasping the benefits of clear aligners.

Effectiveness of the Attachment Design and Thickness of Clear Aligners during Orthodontic Anterior Retraction: Finite Element Analysis

OBJECTIVE

Clear aligner treatment (CAT) provides orthodontic patients with a comfortable treatment alternative; however, this device has limited capacity to facilitate tooth movements. Although composite attachment has been proposed to facilitate tooth displacement, some of its aspects, such as aligner thickness, can influence CAT's precision. This work aimed to compare the stress distribution patterns produced by clear aligners with different thicknesses and composite attachment shapes during anterior retraction.

MATERIALS AND METHODS

Maxillary models consisting of clear aligners, maxillary teeth, and various attachments to the upper central incisor's labial surface were generated. Three models were built to mimic the retraction of the upper central incisors. Each had a distinct attachment design (rectangular attachment, ellipsoid attachment, and pyramidal attachment) and various aligner thicknesses (0.75, 0.85, 0.95, 1.05, and 1.15 mm). Upper central incisor retraction was accomplished using clear aligners. Finite element analysis was used to examine the built models. Stress distribution pattern was examined.

RESULTS

The greater the thickness of the aligner, the higher the stress experienced by the teeth. The 0.75 mm-thick aligner induces the lightest stress with a minimum of 0.0037623 MPa and a maximum of 0.32859 MPa. Meanwhile, the 1.5 mm-thick aligner has the highest stress with a minimum of 0.004679 MPa and a maximum of 0.43858 MPa. The force distribution on rectangular attachments appears evenly distributed. The maximum pressure force on rectangular attachments has a minimum of 0.38828 MPa, which is smaller than the maximum on ellipsoid and pyramidal attachments at 0.40933 and 0.45099 MPa, respectively.

CONCLUSION

The best aligner thickness is 0.75 to 0.85 mm for anterior retraction. An aligner with 0.95 mm thickness can still be used when a remarkable amount of tooth movement force is needed; however, this exception is only applicable to a limited number of clear aligner trays. The ellipsoid attachment is the best type of attachment because the resulting force is substantial and evenly distributed.

Effects of Orthodontic Mechanics on Root Resorption: A Comparative Study

Background

Orthodontic treatment is a common dental procedure aimed at correcting malocclusions and improving dental aesthetics. However, one of the potential side effects of orthodontic treatment is root resorption, which can lead to permanent damage to the tooth's root structure.

Materials and Methods

In this comparative study, 60 orthodontic patients were divided into three groups, each receiving a different orthodontic treatment approach: Group A-conventional fixed orthodontic appliances, Group B-self-ligating orthodontic appliances, and Group C-clear aligners. Digital radiographs were taken before and after treatment to assess root resorption. The extent of root resorption was quantified using a standardized measurement scale.

Results

The results indicated that Group A exhibited an average root resorption of 0.2 mm, Group B showed an average root resorption of 0.1 mm, and Group C had the lowest average root resorption of 0.05 mm. These findings suggest that clear aligners resulted in significantly less root resorption compared to conventional fixed orthodontic appliances and self-ligating orthodontic appliances (P < 0.05).

Conclusion

This comparative study highlights the differential effects of various orthodontic mechanics on root resorption. Clear aligners demonstrated the least amount of root resorption when compared to conventional fixed orthodontic appliances and self-ligating orthodontic appliances.

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.

Comparison of Mechanical Behavior of Clear Aligner and Rapid Palatal Expander on Transverse Plane: An In Vitro Study

(1) Background: This study aims to investigate, within a controlled laboratory environment, the magnitude of the transversal load and the force decay over time produced by clear aligners in comparison to a Rapid Palatal Expander (RPE). (2) Methods: Resin models of a dental maxillary arch, additively manufactured from an intraoral scan, were inserted in a testing machine with uniaxial load cells to measure the force trend over time expressed by RPE and clear aligners. The mechanical load was recorded during a certain timeframe for both appliances. (3) Results: The force expressed by the RPE ranged from 30 to 50 N for each activation, decreasing with a nonlinear pattern over time. The force expressed by the clear aligner ranged from 3 to 5 N, decreasing with a linear pattern over time. In contrast, the force generated by the clear aligner fell within the range of 3 to 5 N, showing a linear reduction in force magnitude over the observed period of time. (4) Conclusions: The RPE exerted a force magnitude approximately ten times greater than that generated by clear aligners. Nevertheless, it is essential to acknowledge that the oral environment can significantly influence these results. These limitations underscore the need for caution when applying these findings to clinical settings.

Orthodontic aligners: between passion and science

INTRODUCTION

The benefits and safety of using orthodontic aligners have been reported more by clinical experience and expert opinion than by scientific evidence. Another important aspect is that aligners are constantly evolving. It is important to obtain evidence that allows for new updates in manufacturing technology, in the development of new movement planning protocols, in the incorporation and design of attachments, and in the aid of skeletal anchorage.

METHODS

Evidence retrieved from six electronic databases (CINAHL, MEDLINE, EMBASE, Psych Info, the Cochrane Library and the Joanna Briggs Library) is presented by means of questions and answers.

CONCLUSIONS

There is evidence that the aligners presented different levels of difficulty in performing each type of movement, with rotational and vertical movements being the most difficult to perform. Regarding perception of pain due to tooth movement, it seems to have less impact at the beginning of treatment; but dealing with more phonoarticulatory changes seems to require more treatment time in more complex cases. Aligners do not prevent the occurrence of root resorption, although the incidence and severity of resorption may be reduced, making oral hygiene easier and accepting the risk of white spots, caries and periodontal disease. Given the conflicting evidence, the release of bisphenol-A from the aligner cannot be denied. Solutions must be found to reduce the environmental impact of aligners disposal. There is an urgent need for well-designed randomized controlled trials.

Treatment of Class II malocclusion with 2-maxillary premolar extractions: Monthly vs biweekly appointments, which is more efficient?

INTRODUCTION

This study compared whether there is a difference in treatment time (TT) and efficiency when appointments are held once a month or at 2-week intervals in patients with Class II malocclusion treated with 2-premolar extractions METHODS: The patients of this retrospective sample were treated with the same orthodontic mechanics and divided into 2 groups according to frequencies of orthodontic appointments. Group 1 consisted of 18 patients (10 males, 8 females), with an initial mean age of 14.38 ± 1.38 years and appointments once a month. Group 2 consisted of 19 patients (9 males, 10 females), with an initial mean age of 14.12 ± 1.38 years and biweekly appointments. Edgewise fixed appliances with a slot size of 0.022 × 0.028 mm were used, and the anterior teeth were retracted en-masse with a rectangular wire and elastic chains. The Peer Assessment Rating and Objective Grading System indexes were measured in the dental models at the beginning and the end of treatment. Efficiency was assessed by dividing the percentage of improvement of each occlusal index concerning the multiplication of TT and the number of appointments.

RESULTS

Both groups presented similar Peer Assessment Rating and Objective Grading System indexes at the end of treatment. Groups 1 and 2 presented different TTs (28.06 and 22.05 months, respectively); however, there were no differences regarding the efficiency of both protocols.

CONCLUSIONS

Patients with Class II malocclusion treated with 2-maxillary premolars had significantly shorter treatment times when seen on biweekly appointments than those with monthly appointments; however, there was no difference in efficiency between protocols.

Three-dimensional finite element analysis of retracting pathological migration of the right upper central incisor with a clear aligner

We aimed to explore the best orthodontic step distance of the right upper central incisor with mild, moderate, and severe pathological displacement achieved via a clear aligner. Three-dimensional models of maxilla-tooth-periodontal ligament clear aligner of the right upper central incisors with five different steps of 0.1, 0.125, 0.15, 0.165, 0.25 mm and three different alveolar bone heights were established via finite element analysis. We analysed the changing trends in initial displacement, the periodontal ligament, the alveolar bone, and apical stress of right upper central incisor. In the process of retraction, the right upper central incisor a movement trend of the crown deviating from the distal root to the mesial, and with the decrease of the height of the alveolar bone and the increase of the displacement, the crown would appear distal labial torsion with a deepening trend of vertical overlay.The maximum stress distribution of the periodontal ligament and alveolar bone showed a positive correlation. The overall stress distribution of the periodontal ligament and apical stress increased with decrease of alveolar bone height and the increase of alveolar bone displacement. In patients with mild, moderate, and severe pathological displacement of the right upper central incisor, the best step distance of anterior tooth retraction is 0.165, 0.15, and 0.125 mm, respectively.

Outcome assessment of orthodontic clear aligner vs fixed appliance treatment in adolescents with moderate to severe malocclusions

OBJECTIVE

To compare the efficacy and efficiency of treatment with clear aligners (CAT) vs fixed appliances (FAT) in adolescents with Class I and II moderate to severe malocclusions.

MATERIALS AND METHODS

One operator's (Garfinkle) cases from 2014 to 2019, started at age 12-18 years, with pre- and posttreatment records were identified and used according to an institutional review board-approved protocol. Records were measured by two calibrated, blinded investigators, aided by software (OrthoCAD [Cadent, Fairview, N.J.], Dolphin Imaging & Management Solutions [Chatsworth, Calif]). Discrepancy index (DI) and cast radiograph evaluation (CRE) scores, treatment duration, number of scheduled and emergency visits, and reported appliance and interarch elastic wear compliance were compared between groups using Wilcoxon rank sum and Fisher's exact tests. Cephalometric superimpositions were completed to evaluate craniofacial growth and dental changes.

RESULTS

Records from 72 cases met the criteria and were included. For the 47 CAT and 25 FAT cases, mean DI (21 ± 5 and 24 ± 8, respectively; P = .20) and CRE (35 ± 10 and 34 ± 9, respectively; P = .90) scores were not significantly different. Other case attributes and reported appliance and interarch elastic wear compliance were also not significantly different. CAT vs FAT cases had significantly smaller treatment durations (24 ± 6 vs 27 ± 5 months; P = .01) and visit numbers (16 ± 5 vs 24 ± 4; P < .01), but emergency visit numbers were not significantly different (2 ± 2 vs 3 ± 2; P = .08).

CONCLUSIONS

In adolescents with Class I and II malocclusions and moderate to severe DI scores, on average, CAT vs FAT cases were completed 3 months faster with eight fewer visits, but treatment efficacy was not significantly different.

Accuracy of lingual straight-wire orthodontic treatment with passive self-ligating brackets and square slot: a retrospective study

OBJECTIVES

To investigate the accuracy of torque, tip and rotation and linear intra-arch movements yielded by passive self-ligating lingual straight-wire appliances with brackets featuring square slots.

MATERIALS AND METHODS

Twenty-five adult Caucasian patients (16 females and 9 males; mean age 26.5 ± 4.3 years) with Class I or mild Class II head-to-head malocclusion were orthodontically treated via passive lingual self-ligating straight-wire appliances (ALIAS, Ormco, Orange, CA) with no extraction. Records were retrospectively analysed, and digital models of pre-treatment (T0), planned (T1) and achieved (T2) phase were acquired for both arches in each patient via an intraoral scanner (Medit I500 (iScan Medit, Seoul, Korea). VAM software (Vectra, Canfield Scientific, Fairfield, NJ, USA) was used to measure both angular values (torque, tip and rotation) and linear intra-arch widths (between canines, first and second premolars and first and second molars). Measurements were obtained for all the movements investigated for each tooth group (incisors, canines, premolars and molars), by arch (maxillary and mandibular) and for both arches at T0, T1 and T2. The accuracy of angular values was compared using Student's t-test against a hypothetical 100%, and among the various tooth groups by post-hoc tests. Transverse linear measurements were investigated by means of the non-parametric Friedman test. The significance threshold was set at 0.05.

RESULTS

The mean accuracy of angular values was 77.25 ± 7.71% for torque, 78.41 ± 6.17% for tip and 77.99 ± 6.58% for rotation. In all cases, however, there was a significant difference between planned and achieved movements, and accuracy was significantly lower than the hypothetical 100% for all tooth groups, individual arches and dentition (p < 0.001). For intra-arch diameters, the greatest accuracy values were found for the anterior sectors (83.54 ± 5.19% for the maxillary inter-canine distance) and the lowest for the posterior sectors (67.28% for the maxillary inter-second molar distance).

CONCLUSION

Straight-wire lingual treatment with passive self-ligating appliances featuring with square slot displayed excellent clinical accuracy, albeit with statistical accuracy decreasing antero-posteriorly.

A cross-sectional study into the reasons behind orthodontic re-treatment

OBJECTIVE

This study aims to identify the motivations behind orthodontic re-treatment in Saudi Arabia.

MATERIALS AND METHODS

This is a cross-sectional study performed through a patient questionnaire. The questionnaire elicited data on the respondents' socio-demographic data, type of previous orthodontic treatment, retention, satisfaction level, and reasons for undergoing orthodontic re-treatment.

RESULTS

Four hundred and nineteen responses were received during the study period from June to July 2022. The result showed a pre-dominant female predilection (83, 29%), with the majority belonging to the 21-25 age group (47.26%). Most participants had had one previous orthodontic treatment (77%), with an active treatment time of approximately 1-3 years (55.85%). There was no significant difference between the satisfaction of outcomes after the initial treatment and at the time of the survey. Most participants received retention appliances (69.45%) and were informed about the importance of appliances. The type of retention was mainly removable retainers (47.5%). Around one-third of the sample (31.98%) were interested in seeking orthodontic re-treatment, with self-motivation as the primary drive and improving the smile as the predominant reason.

CONCLUSION

The study's findings show that a large portion of the population is seeking orthodontic re-treatment, which must be considered. Self-motivation was a driving force rather than external motivation. The most common reason for seeking orthodontic re-treatment was to improve their smile and the increased esthetic demand.

The best method of reconditioning ceramic brackets to get an optimum shear bond strength compared with new ceramic brackets - Systematic review and meta-analysis of in vitro studies

PURPOSE

Bracket debonding is an undesirable problem during fixed orthodontic treatment. As ceramic brackets have no flexibility, there is no change in the slot dimension. So, reconditioning a ceramic bracket can be done without compromising the quality of treatment and could be a cost-effective measure. The objective of this systematic review is to deduce and validate the best method of reconditioning ceramic bracket in order to get optimum clinical shear bond strength.

MATERIAL AND METHODS

Studies such as randomized controlled trials (RCTs); In vitro studies comparing different interventions with control group, cross sectional studies were included. Electronic databases such as Cochrane database, PubMed, Web of Science, Embase were searched up to July 2022. Grey literature search and cross-referencing/snowballing methods were also used. Two reviewers independently selected studies and assessed the risk of bias using amalgamation of five tools for in vitro studies. Then meta-analysis was performed using random effects model.

RESULTS

Eleven studies were included in which ten studies were considered as good quality studies. According the meta-analysis performed, the best performance in terms of shear bond strength was of new brackets. Among the different reconditioning methods, the meta-analysis showed that the method with the closest bond strength to the new brackets was silicatisation with a mean difference of 6.35MPa (95% CI between 2.39 and 10.31) followed by sandblasting+silane application with a mean difference of 3.36MPa (95% CI between 0.3 and 6.96) compared to other methods.

CONCLUSIONS

Due to the lack of in vivo studies, only in vitro studies were evaluated. The data available from the in vitro studies was considered to be of good quality, leading to the conclusion that the best method for reconditioning debonded ceramic brackets is silicatisation followed by sandblasting and silane application.

Maxillary Impacted Canine and Upper Lateral Incisor Agenesis Treatment with "Canine First Technique" and Clear Aligners: A Case Report

The aim of this study was to show a case of an impacted canine in an adult patient with agenesis of the maxillary lateral incisor treated with clear aligners (CA). A 19-year-old male with a persistence of 5.3 and absence of 1.2 came to our department of the School of Orthodontics at the University of Federico II in Naples and asked for an aesthetic treatment. The Canine First approach was used to surgically expose the canine and pull it into the dental arch. In order to ensure long-term aesthetic, periodontal, and occlusal results, a treatment with CAs to close the space through the mesial placement of the canine and the enameloplasty of the tooth crown was performed. At the end of the treatment, the occlusal objectives were achieved.

Perceived esthetics and value of clear aligner therapy systems: A survey among dental school instructors and undergraduate students

OBJECTIVE

To investigate the attractiveness, acceptability, visibility and willingness-to-pay for clear aligner therapy (CAT) systems in first-year and final-year dental students and instructors.

METHODS

A questionnaire designed to collect information regarding esthetic preferences and intentions related to seven CAT systems was handed out to 120 undergraduate students and instructors at the Academic Centre for Dentistry Amsterdam (ACTA). Proportional odds models and population average generalized estimating equation models were used to examine potential association between participant characteristics, esthetic perceptions and CAT systems.

RESULTS

Overall, the examined CAT systems received favorable esthetic ratings. Expertise status was significantly associated with willingness-to-pay additionally for CAT, compared to fixed orthodontic appliances. There was no association between sex, previous orthodontic treatment history, satisfaction with own dental appearance and potential interest in treatment and aligner visibility and willingness-to-pay. CAT system was significantly associated with the perceived aligner visibility, acceptability and attractiveness by students and instructors.

CONCLUSIONS

CAT systems were considered to a great extent attractive and acceptable for future treatment by dental school instructors and students. Willingness-to-pay for CAT systems was significantly associated with expertise status, with instructors appearing more reluctant to pay for CAT.

Three-dimensional spatial analysis of the temporomandibular joint in adult patients with Class II division 2 malocclusion before and after orthodontic treatment: a retrospective study

BACKGROUND

To investigate changes in the three-dimensional (3D) spatial morphology of the temporomandibular joint (TMJ) and condyle position in adult patients with Class II division 2 malocclusion using a 3D spatial measurement method and to investigate the similarities and differences in the effects of fixed appliance and clear aligner treatments on the TMJ.

METHODS

Cone-beam computed tomography (CBCT) data of 47 adult patients with Class II division 2 malocclusion (25, fixed appliance group; 22, clear aligner group) were collected before and after treatment. Mimics 21.0 was used to reconstruct the TMJ 3D model. Fourteen measurement items, such as the anterior, upper, and posterior joint spaces, were measured directly on the 3D model and compared.

RESULTS

Post-orthodontic treatment, the shape and position of the condyle changed in adult patients with Class II division 2 malocclusion. Reduction in the anterior joint space and increase in the posterior joint space after orthodontic treatment were significant in both fixed appliance and clear aligner treatments; the condyle moved forward to the center of the fossa. The superior joint space and depth of the glenoid fossa increased after clear aligner treatment, but there was no significant change after fixed appliance treatment.

CONCLUSIONS

The condylar shape and position in patients with Class II division 2 malocclusion changed significantly post-treatment, indicating that the condyle undergoes adaptive reconstruction during orthodontic treatment in these patients. These results provide a reference for diagnosis, design of treatment plan, and monitoring of treatment in orthodontic clinics.

Dental Restorations

Fulfilling a patient's request for a healthy, functional and esthetic smile represents a daily challenge for dental practitioners [...].

Effect of thermomechanical aging of orthodontic aligners on force and torque generation: An in vitro study

The aim of the study is to investigate the effects of artificial aging by thermocycling and mechanical loading on force/torque delivery by thermoplastic orthodontic aligners. Ten thermoformed aligners, made of Zendura™ thermoplastic polyurethane sheets, were aged over two weeks in deionized water by thermocycling alone (n = 5) and by both thermocycling and mechanical loading (n = 5). The force/torque generated on upper second premolar (Tooth 25) of a plastic model was measured before aging (as control), and after 2, 4, 6, 10, and 14 days of aging, using a biomechanical set-up. Before aging, the extrusion-intrusion forces were in the range of 2.4-3.0 N, the oro-vestibular forces were 1.8-2.0 N, and the torques on mesio-distal rotation were 13.6-40.0 Nmm. Pure thermocycling had no significant effect on the force decay of the aligners. However, there was a significant decrease in force/torque after 2 days of aging for both thermocycling and mechanical loading aging group, which is no longer significant over 14 days of aging. In conclusion, artificial aging of aligners in deionized water with both thermocycling and mechanical loading results in a significant decrease in force/torque generation. However, mechanical loading of aligners has a greater impact than pure thermocycling.

Effects of different designs of orthodontic clear aligners on the maxillary central incisors in the tooth extraction cases: a biomechanical study

BACKGROUND

Controlling the 3D movement of central incisors during tooth extraction cases with clear aligners is important but challenging in invisible orthodontic treatment. This study aimed to explore the biomechanical effects of central incisors in tooth extraction cases with clear aligners under different power ridge design schemes and propose appropriate advice for orthodontic clinic.

METHODS

A series of Finite Element models was constructed to simulate anterior teeth retraction or no retraction with different power ridge designs. These models all consisted of maxillary dentition with extracted first premolars, alveolar bone, periodontal ligaments and clear aligner. And the biomechanical effects were analysed and compared in each model.

RESULTS

For the model of anterior teeth retraction without power ridge and for the model of anterior teeth no retraction with a single power ridge, the central incisors exhibited crown lingual inclination and relative extrusion. For the model of anterior teeth no retraction with double power ridges, the central incisors tended to have crown labial inclination and relative intrusion. For the model of anterior tooth retraction with double power ridges, the central incisors exhibited a similar trend to the first kind of model, but as the depth of the power ridge increased, there was a gradual decrease in crown retraction value and an increase in crown extrusion value. The simulated results showed that von-Mises stress concentration was observed in the cervical and apical regions of the periodontal ligaments of the central incisors. The clear aligner connection areas of adjacent teeth and power ridge areas also exhibited von-Mises stress concentration and the addition of power ridge caused the clear aligner to spread out on the labial and lingual sides.

CONCLUSIONS

The central incisors are prone to losing torque and extruding in tooth extraction cases. Double power ridges have a certain root torque effect when there are no auxiliary designs, but they still cannot rescue tooth inclination during tooth retraction period. For tooth translation, it may be a better clinical procedure to change the one-step aligner design to two-step process: tilting retraction and root control.

Alveolar bone changes following bi-maxillary vertical molars' movements using clear aligners

OBJECTIVE

This study aimed to assess the alveolar bone changes following maxillary and mandibular molars' intrusion and extrusion movements using Clear Aligners using Cone-Beam Computed Tomography (CBCT).

MATERIALS AND METHODS

This is a retrospective clinical study in which 24 adult patients with pre-designed selection criteria and a mean age of 31.1 + 9.9 years were enrolled. The alveolar bone changes around one hundred thirty-three maxillary and mandibular molars intruded or extruded by Clear Aligners therapy were analyzed from CBCT using Invivo 6.0 software. Intra- and inter-examiner reliability analysis was performed using the intra-class correlation coefficient (ICC) and Cronbach's Alpha statistics. The paired t-test was used to analyze significant differences before and after treatment (T0-T1). The significance level was considered at P < 0.05.

RESULT

The patients were divided into two groups: extrusion (48.9%, n = 65 molars' root) and intrusion (51.1%, n = 68 molars' root) group. There was a significant decrease in the alveolar bone changes in the buccal surface of the mandibular right and left 1st molars in the extrusion group (-1.05 ± 0.97, -0.76 ± 1.12 mm, respectively) and the maxillary left 2nd molars in intrusion group (-0.42 ± 0.77 mm), and the lingual surface of intrusion of the mandibular left 1st molar (-0.64 ± 0.76 mm). Comparing the mean maxillary and mandibular changes (T0-T1) of both studied groups showed that the buccal alveolar bone changes for the left 1st and right 2nd molars showed a significant difference in extrusion and intrusion groups, respectively.

CONCLUSIONS

The buccal alveolar bone changes is considered the most affected surface following maxillary and mandibular molars' intrusion and extrusion movements using clear aligners, with mandibular molars being more affected than the maxillary ones.

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.

The effects of aligner anchorage preparation on mandibular first molars during premolar-extraction space closure with clear aligners: A finite element study

INTRODUCTION

This study aimed to determine the effectiveness of different aligner anchorage preparations on mandibular first molars during premolar-extraction space closure with clear aligners and to assess the effects of different modes of Class II elastics on mandibular first molars.

METHODS

Finite element models were constructed on the basis of cone-beam computed tomography data from an orthodontic patient. The models comprised maxilla, mandible, maxillary and mandibular teeth without first premolars, periodontal ligaments, attachments and aligners. Tooth displacement tendencies were calculated using different aligner anchorage preparations and Class II elastics on the models from the same patient. Three group sets were designed on the basis of the positions of aligner cutouts and buttons (mesiobuccal, distobuccal and lingual). Four groups were established in each of the 3 group sets. Four groups were created: (1) no elastic traction + no anchorage preparation, (2) anchorage preparation only, (3) elastic traction only, and (4) elastic traction + anchorage preparation. Different aligner anchorage preparations (0°, 1°, 2°, 3°) were applied on mandibular second premolars and molars. The Class II traction force was set to 100 g.

RESULTS

With clear aligners, mandibular first molars were subject to mesial tipping, lingual tipping and intrusion. In the condition of no elastic traction, aligner anchorage preparation resulted in distal tipping, buccal tipping, and extrusion effect on mandibular first molars. Aligner anchorage preparation was more effective in the distal and lingual cutout groups than in the mesial cutout group. In the condition of Class II elastic traction, the bodily movement of mandibular first molars was achieved with a 3° anchorage preparation for the mesial cutout group and a 1.7° anchorage preparation for distal and lingual cutout groups. Absolute maximal anchorage was achieved with a 2° anchorage preparation for distal and lingual cutout groups.

CONCLUSIONS

Clear aligner therapy caused mesial tipping, lingual tipping and intrusion of mandibular first molars during premolar-extraction space closure. Aligner anchorage preparation effectively prevented mesial and lingual tipping of mandibular molars. Distal and lingual cutout modes were more effective than mesial cutout modes in aligner anchorage preparation. For each aligner stage (0.25 mm), 1.7° aligner anchorage preparation and Class II elastics with distal or lingual cutouts led to the bodily movement of mandibular first molars, whereas 2° anchorage preparation reached absolute maximal anchorage.

Biomechanical factors in the open gingival embrasure region during the intrusion of mandibular incisors: A new model through finite element analysis

Introduction: Open gingival embrasure (OGE) is a common complication in adults following clear aligner therapy and the influence of gingival or alveolar bone biotype on OGE is of great concern. Unfortunately, due to the limited number of patients with clearaligner therapy and the clinical methods to distinguish the gingival biotype of patients being invasive, it is difficult to carry out clinical studies on the gingival or alveolar bone biotype of the OGE. In the meanwhile, the detailed biomechanics of the occurrence of OGE remains unknown. The goal of this study was to establish a new model to simulate the virtual space region, namely, the OGE region, to investigate the relationship between alveolar bone biotype and the occurrence of OGE, and explore potential biomechanical factors related to OGE.

Methods: The OGE region in the interproximal space was established using a filler with a very low modulus of elasticity (1 × 10−6 MPa). To illustrate the biomechanics of OGE more exhaustively, a line was created at the top of the alveolar crest along the proximal tooth root. FEA was then used to analyze the biomechanics of the surrounding tissues, the OGE region and the line at the top of the alveolar crest along the proximal tooth root of the central incisor under two different labial bone thicknesses (thick and thin) with an axial inclination of 80°, 90° and 100°.

Results: During intrusion of the incisors in clear aligner therapy, as inclination increased or bone tissue became thinner, the stress in the surrounding tissues [tooth root, alveolar crest, and periodontal ligament (PDL)] was greater. In the OGE region and interproximal alveolar crest, the strain increased with increasing inclination and labial bone thinning. The results from the line at the top of the alveolar crest along the proximal tooth root showed more detailed biomechanics: In all groups, stress and strain were focused on the mesial-labial alveolar crest. Interestingly, our results also demonstrated that when OGE occurs, other complications may arise, including root resorption and bone dehiscence.

Short-term effect of orthodontic clear aligners on muscular activity and occlusal contacts: A cohort study

INTRODUCTION

The simultaneous presence of maxillary and mandibular clear aligners alters the vertical dimension and the quantity and quality of occlusal contacts. Few data in the literature explain how this occurs and the effects on neuromuscular coordination. This study aimed to evaluate occlusal contacts and muscular balance during treatment with clear aligners over a short follow-up time.

METHODS

Twenty-six female adult patients were enrolled in this study. The center of occlusal force (COF) was evaluated using a T-Scan II device, whereas muscular symmetry and balance were determined through surface electromyography using a standardized protocol that reduces anthropometric and electrode variations. Both evaluations were performed in centric occlusion and with aligners worn before treatment, after 3 months, and after 6 months.

RESULTS

A statistically significant variation in COF position was reported in the sagittal plane but not in the transverse plane. The shift in the COF position was followed by a change in muscular balance evaluated through surface electromyography.

CONCLUSIONS

Treatment with clear aligners resulted in an anterior shift of the COF when biting in centric occlusion and a posterior shift when the aligners were worn in healthy female patients after 6 months of observation. This change in occlusal contact was followed by an improvement in muscular function symmetry in the short term when aligners were worn, compared with the centric occlusion during treatment.

Combined use of F22 aligners and intermaxillary elastics in mild skeletal Class II: Two case reports

INTRODUCTION

The aim of these two case-reports is to illustrate and compare the therapeutic effects of Class II elastics in combination with F22 aligners in an adult and an adolescent patient, respectively.

CASE PRESENTATION

Two patients with a mild skeletal Class II malocclusion, associated with mild-to-moderate crowding, presented for orthodontic treatment. The first patient was 12 years old, while the second was 40 years old. In both cases, the goal was to obtain bilateral molar and canine Class I with ideal overjet and overbite, and Class II skeletal relationship improvement in the young patient as well. Both treatments were approached without extractions and using clear aligners (CAs) in combination with Class II elastics, giving the patient the opportunity to take advantage of a therapy that is both comfortable and aesthetic.

DISCUSSION

Final records of both cases demonstrate how appropriate analysis and diagnosis enable CAs in conjunction with Class II elastics to be used with considerable efficiency and efficacy for Class II treatment. In the first case, the key to success was exploiting residual jaw growth, while in the second case it was careful orthodontic digital planning.

CONCLUSION

In the presence of good patient compliance, CAs associated with Class II elastics provide satisfactory occlusal outcomes if biomechanics and digital set-up are carefully evaluated and executed and if diagnosis is appropriate.

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.

Clear Aligners Treatment of Class III Subdivision with an Extraction of a Lower Bicuspid

The aim of this study was to show a case of a Class III subdivision adult patient treated with clear aligners (CA) and the extraction of a lower bicuspid. A 19-year-old male with a class III canine and molar relationship on the right side and a deviation of lower dental midline to the left asked for an aesthetic treatment. He refused orthognathic surgical procedures, so he was offered a camouflage orthodontic treatment with the extraction of lower right first premolar to achieve a canine Class I relationship and to center the lower midline. The treatment was performed with clear aligners and the use of Class III elastics to maintain distal anchorage on the right side during the canine distalization. At the end of the treatment, the occlusal objectives were achieved.

Quality assessment of online information on orthodontic Web sites in the United States

INTRODUCTION

The objective of this study was to assess the quality of online information on orthodontic treatment provided by orthodontic Web sites in the United States and investigate their claims.

METHODS

Three hundred and one American orthodontic Web sites were identified after an advanced Google search. Data collection included: the location of the clinic, treatment options offered, quality-of-information assessment using the DISCERN tool, and finally, claims when promoting 1 treatment option against another, as well as the presence of information on relapse risk and retention needs.

RESULTS

All Web sites belonged to private clinics, with more than half (60.5%) in a single location. Invisalign (Align Technology, Santa Clara, Calif) was the most commonly promoted treatment option (94%), followed by the full fixed appliance (FFA) (92%). The mean DISCERN total score was poor (36.78 out of 80.00), whereas the mean reliability (questions 1-8) and quality-of-information (questions 9-15) scores were 17.06 out of 40.00 and 16.85 out of 35.00, respectively. Almost one-third (28%) of the Web sites compared aligners to FFA, whereas 25% claimed that aligners are less painful than FFA, faster than FFA (14%), or give better results than FFA (1%). Almost half of the Web sites (47%) failed to display information on relapse risk and retention needs after orthodontic treatment (41%). The Web sites that displayed such info had higher DISCERN total scores (P <0.001).

CONCLUSIONS

Invisalign seems to be the treatment modality most commonly mentioned online. According to DISCERN, U.S. orthodontic Web sites display poor or fair quality information. On many Web sites, aligner treatment was compared with FFA, with some stating that aligners cause less pain than FFA or are more efficient/faster than FFA. Moreover, almost half of the American orthodontic Web sites failed to display information on the relapse risk or retention need. Display of such information can be an indicator of better-quality Web sites. There is ample room for improvement in the online information American orthodontists provide to potential patients.

Predictability of the deep overbite correction using clear aligners

INTRODUCTION

The objective of this study was to investigate the predictability of overbite correction in patients with deepbite using the clear aligners (Invisalign, Align Technology, San Jose, Calif) and examine the accuracy of vertical movement and inclination change of individual teeth.

METHODS

This retrospective study included 24 deepbite patients (10 males and 14 females; aged 32.8 ± 11.9 years; an initial overbite of 5.20 ± 0.95 mm; an average treatment period of 11.04 ± 4.14 months) consecutively treated from September 2016 and completed before August 2021. SmartTrack materials were used for all patients. The initial, predicted, and achieved final models were exported from ClinCheck and superimposed via best-fit surface-based registration using Slicer CMF (version 4.9.0; cmf.slicer.org). The overbite correction, changes in vertical movement, and inclination for individual teeth were measured. Descriptive statistics and a paired t test or Wilcoxon signed-rank test were performed. P <0.05 was considered statistically significant.

RESULTS

Mean overbite correction was 33%, with a 1.15 mm improvement after the first set of aligners. All teeth demonstrated statistically significant differences between planned and achieved amounts in vertical movement and inclination change, with the largest difference in maxillary central incisors. Mandibular incisor intrusion and mandibular premolar extrusion had similar accuracies. Regarding inclination change, maxillary central incisors showed the lowest accuracy of 13.3%.

CONCLUSIONS

Clear aligner treatment showed an average of 33% overbite correction. Overcorrection and additional refinement treatments are needed in most patients with a deepbite.

IPR treatment and attachments design in clear aligner therapy and risk of open gingival embrasures in adults

BACKGROUND

The incidence of open gingival embrasures (OGE) in patients after fixed appliance treatment is relatively high, while there are no detailed reports on patients after clear aligner therapy. Also, no clinical studies with large sample size have investigated whether interproximal enamel reduction (IPR) can actually avoid OGE. The purpose of this study was to determine the prevalence of OGE in adults after clear aligner therapy and to investigate the risk of OGE associated with IPR treatment and attachment design, focusing on the amount and distribution in mandibular anterior teeth.

METHODS

Pre-treatment and post-treatment intraoral frontal photographs of 225 non-extraction patients were evaluated retrospectively for the occurrence and severity of OGE. The amount of IPR and the number of attachments in the anterior teeth from subjects after screening were recorded according to the first version of clear aligner software (Clincheck, San Jose, USA) and clinical medical documents. Logistic regression analysis was performed to identify the factors contributing to OGE.

RESULTS

The incidence of OGE in non-extraction patients after clear therapy between maxillary and mandibular central incisors was 25.7% and 40.3%, respectively. IPR was not associated with the occurrence of OGE but was associated with severity (P < 0.05). The number of attachments in the anterior teeth or central incisors was significantly related to the incidence of OGE (P < 0.05) but was not associated with severity.

CONCLUSION

A high rate of OGE occurs after clear aligner therapy. Clinicians should be aware of the application of IPR and the design of attachments during clear aligner therapy.

Analysis of overcorrection to be included for planning clear aligner therapy: a retrospective study

OBJECTIVES

To provide clinical information on overcorrection to be included in the initial digital setup to make clear aligner therapy (CAT) more efficient.

MATERIALS AND METHODS

Prescription data for 150 patients (80 women and 70 men; mean age 33.7 ± 12.7 years) treated successfully with CAT (F22 Aligners, Sweden & Martina, Due Carrare, Italy) and requiring only a single, minimal finishing phase were acquired retrospectively. The inclusion criteria were Class I dental malocclusion with only minimal crowding (≤3 mm), 12-20 aligner steps per arch, no use of auxiliaries or interarch elastics, and rotations ≤25° for round-shaped teeth. The prescribed and corrective movements to be achieved in the main and finishing treatment phases, respectively, were quantified by the dedicated clear aligner setup software. The magnitudes of inclination (buccal-lingual crown tipping), angulation (mesial-distal crown tipping), rotation, intrusion, and extrusion were extracted and analyzed by tooth type, maxilla and mandible, and both arches. Descriptive statistics, that is, mean, standard deviation, and percentage, were calculated for each movement investigated. Classification and regression trees (CART) were generated using the model-based recursive partitioning approach, and the corrective movements were correlated with respect to both the amount of the movements prescribed and the tooth type. Statistical significance was set at 5%.

RESULTS

Inclination and rotation required the greatest correction, whereas angulation, intrusion, and extrusion required only minimal correction. Expressed as a percentage of prescribed movement, mean corrective movements were 20.5% for inclination, 14.5% angulation, 28.4% rotation, 11.7% extrusion, and 22% intrusion. According to CART, all corrective movements except extrusion depended on both tooth type and the magnitude of prescribed movement.

CONCLUSIONS

To achieve more efficient CAT, approximately 20% overcorrection should be added to the initial planning phase when planning challenging movements such as inclination and rotation.

Edge level of aligners and periodontal health: a clinical perspective study in young patients

INTRODUCTION

Although the superiority of clear aligners over multi-bracket appliances in keeping gingiva healthy has been suggested, the possible benefits of one aligner design over another have not yet been investigated, especially with regard to the vestibular edge.

OBJECTIVE

The aim of this study was to measure several periodontal indexes in adolescents undergoing orthodontic treatment with aligners, comparing two different types of rim.

METHODS

The study involved 43 patients aged between 14 and 18 years. The periodontal health was assessed using plaque index (PI), gingival index (GI), and gingival bleeding index (GBI), at the start of the treatment with aligners (T0), with a vestibular rim (VR) reaching up to 3 mm beyond the gingival margin. Three months later (T1), aligners were set to obtain a juxtagingival rim (JR) on the second quadrant and VR on the first quadrant. The periodontal indexes were measured again, both at T1 and then three months later (T2).

RESULTS

Intra-quadrant comparisons revealed a statistically significant worsening of the periodontal indexes only for the second quadrant (p<0.05), at T1 (GI), and especially at T2 (PI, GI, GBI), while no statistically significant changes were found for the first quadrant.

CONCLUSIONS

More severe mechanical irritation, especially during insertion and removal of the aligner, can explain the worsening inflammatory indexes with the JR. In addition, the pressure exerted by the JR on the gingival sulcus seemed to facilitate plaque deposition, whereas the VR had a protective effect, reducing the risk of mechanical trauma.

Upper arch dimensional changes with clear aligners in the early mixed dentition : A prospective study

BACKGROUND

One goal of orthodontic treatment in mixed dentition is to expand the maxillary arch to allow proper tooth alignment and a correction of sagittal and vertical malocclusions. However, for most treatment protocols, expected outcome is not really clear to allow for a standardization of phase I orthodontic treatments. This lack of information makes it difficult for clinicians to predict tooth movements, including transverse expansion efficacy with Invisalign® (Align Technology, Santa Clara, CA, USA) in children. Therefore, the aim of the present study was to evaluate the transverse maxillary arch development with the Invisalign First System® in growing subjects.

METHODS

The study group included 23 subjects (9 females, 14 males, mean age 9.4 ± 1.2 years). Patients were treated nonextraction with Invisalign First System® clear aligners with no auxiliaries other than Invisalign® attachments. Transverse interdental widths were measured only in the upper arch on each model at the start (T1) and at the end (T2) of treatment. A paired t‑test was chosen to compare T2-T1 changes. The level of significance was set at 5%.

RESULTS

The greatest increase of maxillary width was detected at the level of the upper first deciduous molars (+3.7 ± 1.4 mm; P < 0.001), followed by the level of the second deciduous molars (+3.4 ± 1.6 mm; P < 0.001) and by the deciduous canine (+2.6 ± 2.0 mm; P < 0.001). Upper first molars showed a greater expansion in the intermolar mesial width (+3.2 ± 1.2 mm; P < 0.001) than in the intermolar distal (+1.7 ± 1.2 mm; P < 0.001) and transpalatal width (+1.2 ± 1.2 mm; P < 0.01).

CONCLUSIONS

The Invisalign First System® can be considered effective in growing patients who require maxillary arch development. The greatest net increase was detected at the level of upper first deciduous molars, whereas the upper first molars showed a greater expansion in the intermolar mesial width due to a rotation that occurs around its palatal root.

Treatment of severe Class II skeletal malocclusion in a hyperdivergent adult patient via hybrid clear aligner approach: A case report of successful camouflage therapy

This case report describes the camouflage treatment of an adult patient with hyperdivergent facial pattern presenting with severe Class II skeletal malocclusion, through the use of a hybrid clear aligner approach, that relies on both a partial lingual fixed appliance and the continuous use of Class II elastics throughout therapy. After 11 months of treatment, the goals had been achieved, highlighting that the correct diagnostic framework, proper patient selection and careful digital planning of a compromise treatment can provide satisfactory aesthetic and functional outcomes.

Comparison of the Compression and Tensile Modulus of Two Chosen Resins Used in Dentistry for 3D Printing

(1) The CAD/CAM technique exploiting 3D printing is becoming more and more popular in dentistry. The resins are used in all the dental specialties, including conservative dentistry, prosthodontics, surgery, and orthodontics. The interest in investigating the different properties of dental materials has been an aim of researchers. The purpose of the presented study was to compare the properties of two 3D-printable dental resins (both rigid, used for medical purposes). (2) Methods: Ten blocks of two-type shapes were printed on a printer designed for medical use. The tensile modulus and compression were investigated and compared. The axial compression test was performed according to the PN-EN ISO 604:2003 norm, while the tensile test was performed according to the PN-En ISO 527-1-2019 (E) norm. In the first test, the sample size of the perpendicular shape was 10 ± 0.2 mm × 10 ± 0.2 mm × 4 ± 0.2 mm and in the second it was 75 mm, the end width 10 mm, and the thickness 2 mm. (3) Results: The statistical analysis based on ANOVA tests showed that all the obtained results were statistically significant. Both of the examined materials had similar properties and were resistant and stable in shape. The tensile modulus and compression tests performed on them gave similar results. They also showed high durability to compression and tensility. (4) Conclusions: Both of the examined materials were durable and rigid materials. BioMed Amber was more resistant to compression, while Dental LT clear was more resistant in the tensility test. Although both resins had similar physical properties, it is still disputable whether the chosen materials could be used interchangeably.

Orthodontics on autopilot through digital customization and Programmed Non-Sliding Mechanics

Orthodontic tooth movement occurs in six degrees of freedom, which includes opening and closing spaces. Traditionally, opening and closing spaces are achieved with auxiliaries such as power chains or springs because all traditional bracket systems cannot achieve this tooth movement by themselves. The InBrace system has the capability to program tooth movement in all six degrees of freedom, including opening and closing spaces, through digital customization and its use of Programmed Non-Sliding Mechanics.

Advances in orthodontic clear aligner materials

Rapid technological improvements in biomaterials, computer-aided design (CAD) and manufacturing (CAM) have endorsed clear aligner therapy (CAT) as a mainstay of orthodontic treatment, and the materials employed for aligner fabrication play an all-important role in determining the clinical performance of clear aligners. This narrative review has attempted to comprehensively encompass the entire gamut of materials currently used for the fabrication of clear aligners and elucidate their characteristics that are crucial in determining their performance in an oral environment. Historical developments and current protocols in aligner fabrication, features of contemporary bioactive materials, and emerging trends related to CAT are discussed. Advances in aligner material chemistry and engineering possess the potential to bring about radical transformations in the therapeutic applications of CAT; in the absence of which, clear aligners would continue to underperform clinically, due to their inherent biomechanical constraints. Finally, while innovations in aligner materials such as shape memory polymers, direct three-dimensional (3D) printed clear aligners and bioactive materials combined with clear aligner materials are essential to further advance the applications of CAT; increased awareness of environmental responsibilities among aligner manufacturers, aligner prescribing clinicians and aligner users is essential for better alignment of our climate change goals towards a sustainable planet.

Dynamics of Social Media Popularity of “Do It Yourself” Orthodontic Aligners: A YouTube Case Study

Objective

To have an understanding of the fact how the popularity of “do it yourself” (DIY) videos available on YouTube correlate with authorship, content, quality, reliability, and how they appeal to and influence the customers.

Materials and Methods

A new YouTube account was created, this was followed by a determination of the most commonly used keywords regarding DIY aligners by using “Google Trends.” The keywords were used to search the YouTube website. A total of 112 videos were assessed for various parameters, such as completeness of the content, reliability using a modified version of the DISCERN tool, and quality using a Global Quality Score (GQS). Out of 112 videos, 26 were rejected based on their relevance, duplication, videos without audio, and video language. Pearson’s correlation coefficient was used to study the relationship between the variables, authorship, popularity, and recommendations.

Results

The majority of the videos were uploaded by the laypeople (43%), followed by DIY aligner companies (38%), and dentists and orthodontists (16%). The content for most of the videos was poor (82%), with DISCERN reliability score of zero (65%), and GQS of 1 and 2 (poor to generally poor quality). The view of uploaded videos, view rate, and likes was in proportion to the quality of the videos, their popularity, and reliability. Further authors with a financial interest and poor quality, content, and less reliability of the videos usually recommended the DIY aligners. The reduced cost was one of the important factors for the customers to consider DIY aligner treatment.

Conclusion

YouTube videos on DIY aligners should not be considered a reliable source for the public in general who are looking for orthodontic treatment for correction of their dentofacial irregularities. The dental professional bodies and orthodontists should use social media platforms (YouTube) to increase awareness about the DIY aligners among the public.

Public perception of Invisalign® clear aligner treatment: A cross-sectional survey-based study

Objectives:

The demand for clear aligner treatment has increased in recent years. Thus, this study investigated public knowledge regarding Invisalign clear aligner treatment.

Material and Methods:

A web-based survey was administered through different social media platforms covering different aspects of Invisalign treatment, namely: Treatment efficiency, patient discomfort, appliance esthetic attractiveness, oral hygiene maintenance, and treatment aesthetic results. Participants were also asked to outline their perception of Invisalign treatment cost. A Likert-type scale was used to rank the participant responses. Data were analyzed with the Chi-square test and Bonferroni correction for multiple comparisons.

Results:

Out of 934 eligible adult participants, 19.6% were aware of Invisalign. Most of the Invisalign-familiar respondents were unaware of its cost (27.9%) but agree it is generally better (49.7%), requires fewer visits (38.2%), results in shorter treatment duration (39.4%) and reduced teeth discomfort (35%), more esthetically attractive (64%), yields easier oral hygiene maintenance (55.2%), and produces superior esthetic results (43.7%) than traditional braces. In addition, males and average-income participants were more likely to believe that Invisalign treatment produces superior esthetic results than traditional braces (P = 0.0002 and P = 0.002, respectively). Average-income participants also believed that Invisalign treatment was generally better (P < 0.0001). While participants in the age-range 55–64 years strongly believe, it is cheaper (P < 0.0001) than traditional braces.

Conclusion:

This study highlighted the lack of public knowledge about Invisalign treatment. The results also indicated the importance of ensuring public access to reliable information backed up by high-quality evidence.