Clear aligners in orthodontic treatment

Comparison of dental movements in digital setups created by orthodontists and "3shape design service®" engineers: A cross-sectional study

INTRODUCTION

The demand for faster and invisible orthodontic treatments has led to the increased use of clear aligners, facilitated by advancements in digital treatment planning. This study aims to evaluate the reliability of digital orthodontic setups performed by orthodontists compared to those by 3Shape Design Service®engineers.

MATERIAL AND METHODS

A monocentric, cross-sectional observational study was conducted at Bretonneau Hospital from October 2022 to May 2023. All patients meeting the inclusion criteria and willing to participate were included in the study. Intraoral scans were used to create treatment setups using the Ortho System® software, performed by both orthodontists and 3Shape® engineers. The primary objective was to compare the dental movements (rotation, intrusion, extrusion, buccolingual inclination, tipping, mesiodistal translation and buccolingual translation) between the two groups. Secondary objectives included the number of teeth displaced, aligners needed, interproximal enamel reduction and number of attachments placed.

RESULTS

Nineteen patients with mild to moderate malocclusion were included. Statistically significant differences were found in tooth displacements between the two groups with engineers executing greater dental movements for derotation (4.9±2.6 vs. 3.7±2.3), tipping (0.79±0.69 vs. 0.26±0.44), bucco-lingual (0.40±0.26 vs. 0.08±0.11) and mesio-distal translations (0.31±0.20 vs. 0.20±0.17). Secondary measures showed no significant differences except for the number of teeth displaced (15.32±5.21 vs. 9.68±4.82), which was higher in the 3Shape group.

DISCUSSION

While digital setups by engineers showed more significant tooth movements, the practical impact on mild malocclusion treatment was minimal. This study highlights the need for precise treatment objectives and consideration of overcorrection practices.

CONCLUSION

For mild malocclusions, outsourcing setups to 3Shape engineers can be an alternative to in-office setups by orthodontists. However, further studies are needed to evaluate setup reliability for more complex malocclusions.

Age-stratified assessment of orthodontic tooth movement outcomes with clear aligners

OBJECTIVE

This study compared the achieved tooth movement to that predicted in the preliminary simulated digital treatment plan between adults and teenagers.

MATERIALS AND METHODS

Records of 60 patients (30 adults; mean age: 36.6 ± 11.36 years, and 30 teenagers; mean age: 16.23 ± 2.25 years) were randomly selected. Initial and predicted models were obtained from the initial simulated treatment plan. The first model of the refinement scan was labeled as achieved. SlicerCMF software (version 3.1; https://www.slicer.org ) was used to superimpose the achieved and predicted digital models over the initial ones with regional superimposition on relatively stable first molars. 600 teeth were measured in each group for horizontal, vertical, angular movements, and transverse dimensions. Accuracy was defined as the achieved amount of movement minus predicted and was calculated for each individual and compared between teens and adults.

RESULTS

The mandibular inter-canine width accuracy was statistically significant between groups (p = 0.050). Significant under-correction in horizontal movements was noted for mandibular first premolars in teenagers compared to adults (p = 0.037). There was considerable over-correction in horizontal movements for mandibular central and lateral incisors between groups (p < 0.05). No significant difference was observed between groups in the vertical plane. Rotations were underachieved for maxillary first premolars, more in adults than teenagers (p = 0.017).

CONCLUSION

The accuracy of achieved versus predicted tooth movement between adults and teenagers was significant for the inter-canine width. Mandibular central and lateral incisors showed significantly greater over-correction in adults in the horizontal plane. The accuracy of rotations and vertical movements was comparable.

Effectiveness of palatal anchorage device (PAD) for maxillary anterior retraction with clear aligners using finite element study

The palatal anchorage device (PAD) is commonly used in fixed appliance for anchorage, but the biomechanics of PAD in patients treated with clear aligners(CAs)remains poorly understood, especially in its elastic mode and force magnitude. This study aimed to assess the biomechanical effects of using PAD for retraction during clear aligner treatment (CAT) with the extraction of two maxillary first premolars. Four finite element models were created: (1) Incisors retraction (IR) with active contraction of the clear aligner only; (2) IR with PAD using different forces (50,75,100 g) or not; (3) PAD without IR (forces of 50,75,100 g), and (4) Different elastic directions (D1, D2, D3) from aligner to PAD without IR. IR caused lingual tipping and extrusion of the central incisors, as well as mesial and buccal tipping of the first molar. PAD during IR provided strong anchorage for the first molar, with elastics slightly increasing the lingual tipping and extrusion of the central incisors. Elastics applied to the U-shaped arch led to central incisor intrusion and reduced lingual retraction. The highest stress was observed on the mesial attachment of the canine. PAD effectively reinforced posterior anchorage in CAT, while anterior positioning facilitated anterior teeth intrusion. The biomechanical importance of the canine's mesial attachments in maxillary teeth treatment planning was highlighted.

3D-printed one-piece versus two-piece orthodontic clear aligner attachments bonded with provisional crowns: A proof of concept

OBJECTIVES

This study aimed to introduce a novel technique for fabricating provisional crowns integrated as a single unit with aligner attachments.

METHODS

A total of 60 crowns with attachments were prepared: 20 conventional (Protemp) and 40 3D-printed (20 bonded with attachments; 20 integrated with composite attachments as a single unit) using NextDent resin. Two central incisors were scanned (once without attachments and once with attachments) to create STL files for specimen printing. Half of the specimens (30, n = 10 per group) underwent thermal cycling (5000 cycles). Shear bond strengths (MPa) were evaluated using a universal testing machine. The debonded areas and attachment failures were analyzed to determine the fracture type. Data analyses were performed using ANOVA and post hoc Tukey tests (α = 0.05).

RESULTS

The 3D-printed specimens showed higher strength values than the bonded attachments per group (P < 0.001). The 3D-printed crowns with attachments demonstrated the highest strength (12.39 ± 1.92 MPa). Thermal cycling significantly decreased the bond strength of the attachments (P < 0.001), except in the 3D-printed crowns with composite attachments as a single unit, which showed no significant change after thermal cycling (P = 0.643). In the bonded attachment groups, the adhesive type was the predominant failure mode, while in the 3D-printed groups, attachment fractures were the primary cause of failure.

CONCLUSION

The 3D-printed provisional crowns with attachments have high strength and is clinically appropriate for orthodontic treatment when temporization of teeth is indicated.

CLINICAL SIGNIFICANCE

The developed technique for fabricating 3D-printed provisional restorations with orthodontics attachments as a single unit is a promising approach. The technique may be incorporated into the digital orthodontic treatment workflow when temporization is indicated.

Effect of interproximal enamel reduction on interradicular bone volume in clear aligner therapy: a three-dimensional cone-beam computed tomography study

OBJECTIVES

To assess the effect of inter-proximal enamel reduction (IPR) on interradicular bone volume and incisal inclination in patients undergoing clear aligner therapy (CAT).

MATERIALS AND METHODS

The study sample consisted of 60 cases which underwent orthodontic CAT, in a private clinic in Dammam, KSA. A total of 120 CBCT scans (60 pre-treatment and 60 post- treatment) were measured using the CS 3D Imaging software to examine bone volume (using height, width, and depth of the interproximal area) and incisal inclination. The corresponding ClinCheck models were collected to determine the amount and locations of interproximal reduction performed. Little's Irregularity Index values were measured using OrthoCAD software. Paired sample t-test was used to address the measurements of bone height, width, depth, bone volume, and inclination of upper and lower incisors before and after IPR.

RESULTS

IPR did not affect the upper or lower bone volume except at LR3-2 and UL 2 - 1 where a significant difference between the bone volume with and without IPR was detected (p = 0.02 and p = 0.04 respectively). Upper and lower incisor inclination showed a statistically significant decrease after IPR. There was no correlation between IPR and bone volume difference between upper and lower teeth except at LR3-2 and UL 2 - 1.

CONCLUSIONS

IPR had no significant effect on inter-radicular bone volume except at areas of lower right canine-lateral and at areas of upper left central-lateral. There was a positive correlation between the amount of IPR and incisal inclination.

CLINICAL RELEVANCE

The current study findings suggest that while IPR has a minimal and localized effect on bone volume in certain areas, it plays a role in adjusting incisal inclination, highlighting its significance in the careful planning of orthodontic treatment using clear aligners.

Towards Sustainable Orthodontics: Environmental Implications and Strategies for Clear Aligner Therapy

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

Deep overbite reduction in adolescent patients treated with Invisalign: A retrospective analysis

INTRODUCTION

Data regarding the efficacy of deep overbite correction with clear aligner therapy in adolescent patients are lacking. This study aimed to investigate the efficacy of deep overbite reduction in adolescent patients treated with Invisalign (Align Technology, San Jose, Calif) aligners.

METHODS

This retrospective study investigated a sample of 102 patients aged 10-17 years from a large database. All patients had completed wear of a prescribed series of Invisalign aligners with planned overbite reduction on a nonextraction basis. The predicted, pretreatment, and posttreatment overbite measurement values were obtained from Align Technology's ClinCheck digital facility. Linear modeling, with Bland-Altman plots, was used to compare the effect of age, the use of bite ramps, and the adoption of the eighth-generational (G8) protocol on the difference between predicted and achieved overbite measurements.

RESULTS

A total of 102 patients with a mean ± standard deviation age of 13.94 ± 1.53 years satisfied the selection criteria. A mean ± standard deviation of 41.38 ± 30.43% of the predicted overbite reduction was achieved. There were no differences in the predictability of overbite reduction between patients who were aged <14 years or those aged 14-17 years (P = 0.73), between patients prescribed and not prescribed bite ramps (P = 0.25), or between patients prescribed the G8 protocol and not prescribed the G8 protocol (P = 0.65).

CONCLUSIONS

The average achieved overbite was less than half of what was planned by the orthodontists via the ClinCheck facility. The age grouping, the provision of bite ramps, and the G8 protocol appear to have little influence on the efficacy of overbite reduction in adolescent patients.

Does Invisalign Outperform Fixed Appliance in Treating Vertical Discrepancies?

Aligners became popular among adult patients for their superior aesthetics and comfort in comparison to conventional fixed appliances. It has undergone numerous enhancements over time, allowing it to address more complex malocclusions. Many researchers argued that managing vertical discrepancies is more challenging than addressing anteroposterior issues. This complexity arose from the mechanical requirements for treatment and the required mechanics to prevent relapse. Studies assessing the treatment outcome of anterior open bite closure using clear aligners have yielded conflicting results regarding the mechanisms of bite closure. Proposed mechanisms included extrusion of upper or lower incisors, lingual tipping of upper or lower incisors, intrusion of upper or lower molars, counterclockwise rotation of the mandible, or various combinations of these mechanisms. The research highlighted the biomechanical challenges associated with using aligners for the treatment of deep bites as mandibular incisor intrusion and leveling the curve of Spee remain among the least predictable movements. Given the widespread use of aligners, it is imperative to rigorously assess the effectiveness of clear aligners in achieving overbite correction to ensure they deliver the desired outcome. This review aimed to assess the performance of Invisalign in the management of vertical discrepancies. It sought to identify the dentoskeletal effects of clear aligners in addressing deep bite and anterior open bite cases, understand the mechanisms behind overbite correction, and provide a comprehensive overview of the existing research on this topic.

The effect of surface treatment and thermal aging on the bonding of clear aligner attachments to provisional resin-based material: shear bond strength analysis

Objectives

The aim of this study is to evaluate the effect of different surface treatments on the shear bond strength (SBS) of clear aligner attachments bonded to Bis-acryl provisional crowns.

Methods

120 cylindrical bisacrylic composite material (ProTemp type) specimens were prepared and divided into six groups (n = 20) based on surface treatment, control: (no treatment); super coarse grit diamond bur, carbide bur, alumina-blasting, non-thermal plasma treatment, and Er:YAG laser treatment. The features of treated surfaces were examined using scanning electron microscopy (SEM). A flowable composite resin (Transbond XT; 3M Unitek) was bonded to the specimens forming the attachment. Half of specimens were subjected to thermal cycling (5,000 cycles). SBS was measured before and after thermal cycling. Each specimen was loaded at the attachment/resin interface at a speed of 0.5 mm/min until failure. The nature of the failure was analyzed using the composite remnants index (CRI). Two-way ANOVA and Tukey HSD were used for data analysis α =  0.5. For CRI scores analysis, Kruskal-Wallis test and Dunn's multiple comparison were used as post-hoc test.

Results

SEM analysis showed that all surface treatments altered surface properties and increase surface bonding area. The specimens treated with plasma, Er:YAG laser, and alumina-blasting had higher SBS values before and after thermal cycling. In comparison to control plasma, Er:YAG laser, and alumina-blasting showed a significant increase in SBS (P < 0.001) while carbide and diamond bur groups showed no significant differences (P > 0.05). Thermal cycling significantly decreased the SBS of control, carbide bur, diamond bur, and Er:YAG laser while no significant effect of alumina-blasting and plasma group. Er:YAG laser and plasma groups significantly exhibited more dominance for scores 2 and score 3 and the absence of score 0.

Conclusion

Alumina-blasting, Er:YAG laser, or non-thermal plasma surface treatments increased the shear bond strength between clear aligner attachments and resin-based restorations.

Assessment of Food Masticatory Capability with Clear Aligners

Nowadays, aligners represent a possible therapeutical approach that combines both esthetic and function in order to address dental malocclusion. However, they require a significant level of compliance from the patient. According to the manufacturer, at least 22 h of wearing a day is demanded to reach the optimal therapeutical level; hence, aligners can only be removed during meals. Patients' compliance might increase and the duration of the treatment might decrease if they were allowed to eat with aligners on. The idea of patients keeping the aligners on during meals has been contemplated, not only to favor patients' compliance but also treatment effectiveness. This study aims to assess the degree of chewing difficulty that aligners cause when eating certain kinds of food and the quantity of residue left.

MATERIAL AND METHODS

A questionnaire titled "Questionnaire for the Assessment of Masticatory Function with Aligners" was administered using Google Forms to 240 patients in treatment with clear aligners. The survey was validated through the reliability test using the test-retest method. This method had a higher correlation coefficient of 0.9 across all items (with a cutoff of 0.8) with statistical significance, and an excellent internal correlation coefficient (α > 0.9). The statistical analysis performed consisted of descriptive analysis, frequencies, percentages, Pearson's correlation test and Friedman's test.

RESULTS

Pearson's test showed a statistically significant correlation between all items except between meat or clams and yogurt or ice cream and with mozzarella or soft cheese regarding food chewing difficulties. Pearson's test showed a statistically significant correlation between all items regarding food residues. A total of 69.2% of the cohort reported some movements of aligners during mastication. In total, 88.3% of them affirmed not to have perceived deformations or breakage of aligners during chewing. Furthermore, 79.2% of them declared that they would continue to eat if eating with aligners was proven to speed up treatment.

CONCLUSIONS

Wearing clear aligners while chewing foods such as yogurt, ice cream, soft cheese, bread, rice, etc., can be possible and can help shorten the duration of orthodontic treatment, benefiting both the patient and the orthodontist. However, further research using qualitative methods is needed to understand the barriers and facilitators to chewing food with aligners.

Clear aligner therapy practices among orthodontists practicing in Canada

BACKGROUND

The acceptability and preference for clear aligner therapy (CAT) has been increasing among orthodontists, but there is still a lack of consensus regarding CAT best practices. Consequently, this study aimed to investigate CAT practices among orthodontists practicing in Canada.

METHODS

The survey was conducted among orthodontists practicing in Canada using a modified previously published survey. Sixty orthodontists participated (6.1% response rate). It consisted of 11 sections with open and closed questions related to demographic information and particularities about using or not using CAT. The survey responses were exported from REDCap to a Microsoft Excel (Microsoft, Redmond, Wash) spreadsheet, then statistically analyzed using SPSS software (SPSS for Windows, version 21.0; IBM Inc., Armonk, NY, USA). The comments were categorized under themes and subthemes. Data were organized in descriptive statistics, expressing frequencies and percentages.

RESULTS

Almost 30% of the orthodontist's annual caseload was treated with CAT, most frequently prescribed to adult patients. Case complexity and patient cooperation were the factors that most influenced the decision to prescribe CAT. Almost half of orthodontists reported sometimes combining CAT with adjunctive fixed appliances.

CONCLUSIONS

Most orthodontists prescribe CAT, and its use is based on the malocclusion's complexity. Orthodontists who do not prescribe CAT believe that fixed appliance therapy has superior treatment outcomes.

Evaluation of the effects of temperature and centrifugation time on elimination of uncured resin from 3D-printed dental aligners

The study investigated the effects of temperature and centrifugation time on the efficacy of removing uncured resin from 3D-printed clear aligners. Using a photo-polymerizable polyurethane resin (Tera Harz TC-85, Graphy Inc., Seoul, Korea), aligners were printed and subjected to cleaning processes using isopropyl alcohol (IPA) or centrifugation (g-force 27.95g) at room temperature (RT, 23 °C) and high temperature (HT, 55 °C) for 2, 4, and 6 min. The control group received no treatment (NT). Cleaning efficiency was assessed through rheological analysis, weight measurement, transparency evaluation, SEM imaging, 3D geometry evaluation, stress relaxation, and cell viability tests. Results showed increased temperature and longer centrifugation times significantly reduced aligner viscosity, weight (P < 0.05), and transmittance. IPA-cleaned aligners exhibited significantly lower transparency and rougher surfaces in SEM images. All groups met ISO biocompatibility standards in cytotoxicity tests. The NT group had higher root mean square (RMS) values, indicating greater deviation from the original design. Stress relaxation tests revealed over 95% recovery in all groups after 60 min. The findings suggest that a 2-min HT centrifugation process effectively removes uncured resin without significantly impacting the aligners' physical and optical properties, making it a clinically viable option.

Assessment of the Effect of Thermoforming Process and Simulated Aging on the Mechanical Properties of Clear Aligner Material

Background Choosing the optimal aligner material on the market is crucial to ensure constant forces for tooth displacement. Processes like manufacturing and intraoral usage can result in the degradation of certain properties, which can affect the overall efficacy of treatment. Objective The objective of the study is to compare the surface roughness and flexural modulus of two aligner materials following the processes of thermoforming and aging. Materials and methods Two groups of 12 samples each were tested: Group 1 consisted of polyethylene terephthalate glycol (PET-G) and Group 2 of zendura-polyurethane (PU). The groups were tested at three time points: T0 - pre-thermoformed; T1 - after thermoforming; T2 - after thermoforming and aging. The surface roughness and the flexural modulus were evaluated. One-way ANOVA followed by a Bonferroni post hoc test was conducted to compare the changes within each group across the three times. An independent t-test was done to compare the values between the two groups at each time point. The statistical tests were performed using SPSS software version 26 (IBM Corp., Armonk, NY, USA). P-values >0.05 were considered statistically significant. Results There was a significant change in the surface roughness post-aging in Group 2 (p=0.03) and flexural strength within Group 1 (p=0.031) and Group 2 (p=0.06) across the three time points. Comparing the changes within the three time points in Group 1, significant changes were observed between T0-T1 (p=0.045) and T0-T2 (p=0.07). In Group 2, significant changes were observed between T0-T2 (p=0.012). Comparing the flexural strength between the two groups, significant differences were observed at T0 (p=0.012) and T1 (p=0.001). Conclusion The aging process affected the surface roughness in Zendura (PU). The thermoforming and aging process resulted in reduced flexural strength in both Zendura (PU) and Duran groups (PET-G).

Research on path planning for clear aligner flexible manufacturing

In recent years, clear aligner can enhance individual appearance with dental defects, so it used more and more widely. However, in manufacturing process, there are still some problems, such as low degree of automation and high equipment cost. The problem of coordinate system mismatch between gingival curve point cloud and dental CAD model is faced to. The PCA-ICP registration algorithm is proposed, which includes coarse match algorithm and improve-ICP registration algorithm. The principal component analysis (PCA) based method can roughly find the posture relationship between the two point clouds. Using z-level dynamic hierarchical, the ICP registration can accurately find the posture between these two clouds. The final registration maximum distance error is 0.03 mm, which is smaller than robot machining error. Secondly, the clear aligner machining process is conducted to verify the registration effectiveness. Before machining, the path is generated based on the well registered gingival curve. After full registration, the tool path is calculated by establishing a local coordinate system between the workpiece and the tool to avoid interference. This path is calculated and generated as an executable program for ABB industrial robots. Finally, the robot was used for flexible cutting of clear aligners and was able to extract products, ensuring the effectiveness of the proposed research. This method can effectively solve the limitations of traditional milling path planning under such complex conditions.

Exploring publications in 3 major orthodontic journals: A comparative bibliometric analysis of two 10-year periods (2002-2011 and 2012-2021)

INTRODUCTION

This study aimed to perform a bibliometric analysis examining contributing countries and collaborative networks, authors and collaborative relationships, the performance of the institutions, and cocited journals and references in 3 major orthodontic journals (American Journal of Orthodontics and Dentofacial Orthopedics, European Journal of Orthodontics, and Angle Orthodontist) over two 10-year periods (2002-2011 and 2012-2021).

METHODS

In this study, 4432 publications in the first decade and 4012 publications in the second decade were quantitatively analyzed and visualized using visualization software such as VOSviewer (Leiden University, Leiden, Netherlands), CiteSpace (Drexel University, Philadelphia, Pa), and Scimago Graphica (SCImago Lab, Spain).

RESULTS

Institutions in the United States had the highest number of publications through the 2 decades, whereas Brazil, South Korea, and China achieved significant improvements in performance in the second decade compared with the first. Closer collaborative networks among scholars were revealed in the second decade. The cocitation analysis of the journals showed that highly cited journals included more professional orthodontic journals in the second decade than in the first decade.

CONCLUSIONS

Bibliometric analysis of publications in 3 major orthodontic journals over two 10-year periods revealed a trend of diversification in countries and institutions participating in publishing, international collaborations, and collaboration networks among authors in the field of orthodontics during the 2 decades.

Three-dimensional assessment of virtual clear aligner attachment removal: A prospective clinical study

INTRODUCTION

In digital dentistry, virtual attachment removal (VAR) optimizes clear aligner therapy by enhancing efficiency for refinements and enabling prefabricated retainer production through the removal of attachments from a digital scan before the clinical removal of clear aligner attachments. This prospective clinical study aimed to evaluate the accuracy of VAR in the maxillary arch.

METHODS

A total of 110 teeth were analyzed from a sample of 54 maxillary scans from 25 subjects. Models with attachments were virtually debonded using Meshmixer (Autodesk, San Rafael, Calif) and superimposed over the control group in MeshLab. Vector Analysis Module (Canfield Scientific, Fairfield, NJ) was used to calculate and analyze 3-dimensional Euclidean distances on the buccal surfaces between the superimposed models. Statistical analysis was performed using SPSS (version 23.0, IBM, Armonk, NY). The Shapiro-Wilkes (α = 0.05) test determined a nonnormal distribution of results. The Kruskal-Wallis (α = 0.05) was used to determine differences between different tooth types and the number of attachments.

RESULTS

The VAR protocol showed no statistical differences in the root mean square between different tooth segments with an overall tendency for inadequate attachment removal. No difference between the groups was found regarding the number of attachments when used as a main factor.

CONCLUSIONS

The VAR technique is precise enough for the fabrication of retainers from printed dental models in a clinical setting and is not affected by the number of attachments on the tooth.

Class II Correction and Crowding Treatment Using In-House Direct Printed Clear Aligners: A Literature Review and Case Report

Clear aligner therapy has significantly improved orthodontic treatment by offering patients a more aesthetically pleasing option compared to traditional braces. This literature review and case report specifically focus on the effectiveness of directly printed clear aligners in treating Class II malocclusions and crowding. Class II malocclusions are characterized by excessive overjet, which often results from skeletal or dental discrepancies between the upper and lower jaws. Crowding refers to the lack of space for teeth within the dental arch, leading to misalignment and potential functional issues. The review and case report highlight the increasing importance of directly printed clear aligners in modern orthodontics and provide clinicians with a valuable tool to effectively address complex malocclusions and crowding while also meeting patient needs for discretion and comfort. Further research is necessary to validate the long-term stability and outcomes of directly printed clear aligner therapy in various orthodontic cases. A detailed case report demonstrates the successful treatment of a patient with Class II malocclusion and mild crowding using directly printed clear aligners. Treatment outcomes include improvements in dental alignment, occlusion, and facial aesthetics, showcasing the effectiveness of this innovative approach.

Comparative Analysis of Braces and Aligners: Long-Term Orthodontic Outcomes

Objectives

The purpose of this retrospective study was to evaluate the long-term results of orthodontic treatment with traditional braces and Invisalign, with a particular emphasis on treatment length, patient satisfaction, correction of malocclusion, and long-term stability.

Methods

Between 2020 and 2022, individuals who had orthodontic treatment at a tertiary care center had their data analysed. Patients with mild to severe malocclusions treated with conventional braces or Invisalign between the ages of 12 and 18 met the inclusion criteria. Assessments were done on results, length of treatment, degree of malocclusion, and long-term stability. With significance set at P < 0.05, statistical analyses comprised t-tests for treatment duration and Chi-square testing for malocclusion correction.

Findings

The mean treatment time for Invisalign was much shorter (18 months) than for conventional braces (24 months) (P < 0.001). With 88-90% success rates, both techniques demonstrated remarkable success rates in malocclusion treatment. Even though Invisalign was associated with a somewhat greater percentage of relapse instances, the difference was not statistically significant (P > 0.05).

Conclusion

In conclusion, Invisalign showed a much shorter treatment period than conventional braces, yet both showed excellent malocclusion correction. The choice of modality should be based on patient satisfaction, treatment objectives, and case complexity, taking into account the trade-offs between treatment length and potential variations in long-term stability.

Predicting Outcome in Clear Aligner Treatment: A Machine Learning Analysis

Background/Objectives: Machine learning (ML) models predicting the risk of refinement (i.e., a subsequent course of treatment being necessary) in clear aligner therapy (CAT) were developed and evaluated. Methods: An anonymized sample of 9942 CAT patients (70.6% females, 29.4% males, age range 18-64 years, median 30.5 years), as provided by DrSmile, a large European CAT provider based in Berlin, Germany, was used. Three different ML methods were employed: (1) logistic regression with L1 regularization, (2) extreme gradient boosting (XGBoost), and (3) support vector classification with a radial basis function kernel. In total, 74 factors were selected as predictors for these methods and are consistent with clinical reasoning. Results: On a held-out test set with a true-positive rate of 0.58, the logistic regression model has an area under the ROC curve (AUC) of 0.67, an average precision (AP) of 0.73, and Brier loss of 0.22; the XGBoost model has an AUC of 0.67, an AP of 0.74, and Brier loss of 0.22; and the support vector model has a recall of 0.61 and a precision of 0.64. The logistic regression and XGBoost models identify predictors influencing refinement risk, including patient compliance, interproximal enamel reduction (IPR) and certain planned tooth movements, for example, lingual translation of maxillary incisors being associated with the lowest risk of refinement and rotation of mandibular incisors with the highest risk. Conclusions: These findings suggest moderate, well-calibrated predictive accuracy with both regularized logistic regression and XGBoost and underscore the influence the identified factors have on the risk of refinement in CAT, emphasizing their importance in the careful planning of orthodontic treatment and the potential for shorter treatment times, less patient discomfort, and fewer clinic visits. Identification of at-risk individuals could support tailored clinical decision-making and enable targeted interventions.

Occlusal contact changes in patients treated with clear aligners: A retrospective evaluation using digital dental models

INTRODUCTION

This study used digital intraoral scans to evaluate how clear aligner treatment affects occlusal contacts and to determine the influence of sex and age on contact changes. Results were compared with contact changes that occur during fixed appliance therapy.

METHODS

Patients included in this study were treated in a University setting and private practice. Inclusion criteria were a Class I malocclusion treated nonextraction with clear aligners and the presence of pretreatment and posttreatment digital intraoral scans. Scans were imported into specialized software, and occlusal contacts were analyzed. The effects of age and sex on contact changes during clear aligner treatment were determined. Changes in occlusal contacts were compared with changes that occur during nonextraction treatment of patients with a Class I relationship using fixed edgewise appliances.

RESULTS

A total of 45 clear aligner patients fit the eligibility criteria. Clear aligner treatment reduced the percentage of tight, near, and approximating contacts, whereas the percentage of open and no contacts increased. These changes in occlusal contacts were greater for the older age group studied. Genderinfluenced occlusal contact changes in the anterior dentition only where the decrease in near contacts and increase in open contacts were greater for males. These results for patients treated with clear aligners were similar to those for patients treated with fixed appliances; both treatment modalities reduced close occlusal contacts at the time active treatment was completed.

CONCLUSIONS

These results indicated that when clear aligners or fixed appliances are used to treat a Class I malocclusion, the resulting occlusion immediately after debonding is not as "tight" as it was at pretreatment.

A Bibliometric Analysis of Clear Aligner Treatment (CAT) From 2003 to 2023

Clear aligner treatment (CAT) has been evolving over the past two decades. This study aims to conduct a comprehensive and up-to-date bibliometric analysis of publications related to CAT, presenting the research trends, landscapes, and hot spots in this field. All publications were retrieved from the Web of Science Core Collection from 2003 to 2023. In addition to a general analysis of research landscapes, the following items were analyzed, i.e., countries, institutions, authors, journals, publications, and keywords. A total of 1031 relevant publications were included in this study. From 2003 to the present, the number of publications and citations in this field showed an increasing trend. Italy led in terms of publication counts, and Sichuan University in China had the highest publication counts among institutions. In total, 33 scholars had published a minimum of 10 articles, and the collaborations among them were mostly within each country. The American Journal of Orthodontics and Dentofacial Orthopedics published the most relevant publications. "Predictability of tooth movements," "influencing factors for clinical efficacy," "biomechanics," and "patients' perception and periodontal health" stood out as the core research focus on CAT. Our study identified the most influential countries, institutions and authors, and their cooperative relationships, and detected hot research topics on CAT, calling for more high-quality international collaborative research in the future.

Clear aligner therapy practice among orthodontists in the United Kingdom and the Republic of Ireland: A cross-sectional survey of the British Orthodontic Society membership

OBJECTIVE

To investigate clear aligner therapy (CAT) practice among orthodontists in the British Orthodontic Society (BOS).

DESIGN

A cross-sectional online survey.

METHODS

An electronic survey was distributed to members of the BOS in 2022. The survey comprised questions regarding respondent demographics, general use of CAT, the choice of proprietary CAT appliances, CAT planning, case selection, treatment protocols and orthodontist-reported CAT problems.

RESULTS

Overall, there were 233 (19.5%) respondants with the majority (n = 121, 53.1%) being female. Most respondents reported practising in England (n = 171, 74.7%). The majority (n = 177, 77.3%) indicated that they used CAT in their practice, with 48.1% (n = 81) treating 1-20 patients with CAT annually. The most frequently prescribed CAT system was Invisalign (n = 138, 81.2%). One to three changes to the initial digital treatment plan were made by 72.9% (n = 121) with final tooth positions being the most common reason for adjustment (64.4%). Most (n = 97, 60.3%) rarely or never performed premolar extractions with CAT. Of the respondents, 23 12.7%) reported that they always or mostly used a remote monitoring system in conjunction with CAT, with a wide range of aligner change protocols reported. The median number of months required to complete non-extraction CAT reported by the respondents was 12. Most respondents (n = 77, 51.7%) did not feel that CAT provides superior outcomes compared with fixed appliance therapy.

CONCLUSION

CAT practice varied widely among the surveyed orthodontists. A predilection for the use of Invisalign and utility in less severe cases was noted.

Photopolymerizable semi-crystalline polymers for thermally reversible, 3D printable cast molds

OBJECTIVES

This study demonstrates the use of photopolymerization to create semi-crystalline linear polymers suitable for thermally reversible materials in dental cast moldings produced from 3D printing.

METHODS

An aromatic diallyl, aliphatic dithiol chain extender, and monofunctional thiol were used in a photoinitiated system. The photopolymerization and crystallization kinetics as a function of chemistry and temperature were investigated using spectroscopy and calorimetry. These insights were used to realize vat photopolymerization-based 3D printing of functional objects that could be remotely melted and thereby removed using induction heating.

RESULTS

The addition of monothiol was shown to decrease the polymer molecular weight which correspondingly increased the crystallization rate. Photopolymerization kinetics are independent of temperature while crystallization was slowed as the temperature approaches the melting point of the materials. Through inclusion of chromium oxide, semicrystalline materials could be melted through induction heating. These materials were implemented in vat photopolymerization 3D printing to realize high-resolution objects that could be used as releasable dental molds following printing and induction heating.

SIGNIFICANCE

This work demonstrates a proof-of-concept methodology to realize directly printable, thermally reversible semicrystalline materials for potential use as dental molding materials.

Effect of attachment flash on clear aligner force delivery: an in vitro study

BACKGROUND

The introduction of auxiliaries such as composite attachment has improved the force delivery of clear aligner (CA) therapy. However, the placement of the attachment may give rise to a flash, defined as excess resin around the attachment which may affect CA force delivery. This in vitro study aims to determine the differences in the force generated by the attachment in the presence or absence of flash in CA.

MATERIALS AND METHODS

Tristar Trubalance aligner sheets were used to fabricate the CAs. Thirty-four resin models were 3D printed and 17 each, were bonded with ellipsoidal or rectangular attachments on maxillary right central incisors. Fuji Prescale pressure film was used to measure the force generated by the attachment of CA. The images of colour density produced on the films were processed using a calibrated pressure mapping system utilising image processing techniques and topographical force mapping to quantify the force. The force measurement process was repeated after the flash was removed from the attachment using tungsten-carbide bur on a slow-speed handpiece.

RESULTS

The intraclass correlation coefficient showed excellent reliability (ICC = 0.96, 95% CI = 0.92-0.98). The average mean force exerted by ellipsoidal attachments with flash was 8.05 ± 0.16 N, while 8.11 ± 0.18 N was without flash. As for rectangular attachments, the average mean force with flash was 8.48 ± 0.27 N, while 8.53 ± 0.13 N was without flash. Paired t-test revealed no statistically significant difference in the mean force exerted by CA in the presence or absence of flash for both ellipsoidal (p = 0.07) and rectangular attachments (p = 0.41). Rectangular attachments generated statistically significantly (p < 0.001) higher mean force than ellipsoidal attachments for flash and without flash.

CONCLUSION

Although rectangular attachment generated a significantly higher force than ellipsoidal attachment, the force generated by both attachments in the presence or absence of flash is similar (p > 0.05).

Clear aligner's adverse effects: A systematic review protocol

With the growing popularity of clear aligners, more patients have chosen to use them instead of traditional orthodontic braces to correct their malocclusions. Clear aligners offer distinct advantages over conventional fixed braces, such as limited aesthetic impact, the convenience of easily removing them for meals, improved accessibility for brushing and flossing, and a treatment approach that avoids the use of metal, minimizing potential irritation to the cheeks and gums. Manufacturers point out a disadvantage that can be administered in this type of treatment. Still, to our knowledge, a comprehensive review of the published literature assessing the adverse/negative effects of clear aligners has not yet been conducted. A systematic review, with or without meta-analysis, will be performed. The inclusion criteria will be studies involving individuals using clear aligners and reporting potential adverse/negative effects during or after treatment. No restrictions about time or language will be applied. The studies screening will be conducted in two stages. Two independent reviewers will initially evaluate the title and abstract under the eligibility criteria. Subsequently, the same two reviewers will examine the articles' full text in-depth. The results will be synthesized in the form of a narrative description and incorporate a meta-analysis if justified. Furthermore, we will present details regarding the sample characteristics, intervention, study objectives, methodologies employed, and primary findings. This study aims to investigate the potential adverse effects and their frequency among orthodontic patients wearing clear aligners. Moreover, the outcomes of this review have the potential to illuminate specific inherent limitations of aligner therapy as a comprehensive orthodontic approach.

Biomechanics of clear aligner therapy: Assessing the influence of tooth position and flat trimline height in translational movements

OBJECTIVE

The present clear aligner therapy (CAT) research focuses on isolating and reporting the biomechanical performance for three separate teeth, three translational movements and two flat trimlines at different heights. By identifying key patterns, the research seeks to inform the development of improved aligner designs, ultimately enhancing the effectiveness of clinical orthodontic treatments.

MATERIALS AND METHODS

In an in vitro setting using the Orthodontic Force Simulator (OFS), the biomechanical response of 30 aligners was investigated on three different teeth of a straight symmetric maxillary dentition (central incisor, canine and first molar). Each tooth was tested under two flat trimline conditions (trimmed at gingival margin, TL0; extended 2.0 mm below, TL2) and for three types of translational movements (palatal translation, mesial translation and intrusion). Forces and moments were reported at the centre of resistance for each displaced tooth as well as the two neighbouring teeth, evaluating a total of 18 distinct scenarios.

RESULTS

Findings indicate significant variability in the biomechanical responses based on tooth location in the arch, trimline height and movement performed. For palatal translations, the palatal force required to perform the movement was observed highest in molar cases, followed by canine and incisor cases, with a notable difference in the distribution of side effects, indicating a strong influence of tooth anatomy and position in the arch. Similarly, in mesial translations and intrusions molars experienced greater forces and moments than the corresponding movements applied on canines and incisors, but uniquely dispersed for each configuration tested. Regarding the shape of the aligner, TL2 consistently showed improved control over orthodontic movements compared to TL0. Neighbouring teeth frequently displayed compensatory reactions up to about half of the intensity observed on the tooth being moved, with notable variations from case to case.

CONCLUSIONS

This research supports fundamental factors impacting CAT: Characteristic patterns in the direction and intensity of forces and moments are associated with each of the three translational movements tested. Tooth anatomy and arch location significantly influence the biomechanical performance of aligners, with an observed trend for molars to display higher forces and moments over canines and incisors, but distributed differently. The height of a flat trimline, specifically TL2, shows enhanced control over orthodontic movements. Additional findings revealed a compensatory activity of neighbouring teeth, which varies based on tooth region and movement type. It potentially could influence CAT outcomes negatively and merits attention in future investigations. These results support a tailored CAT method that improves aligner design for better force application. This method needs to be used alongside, and confirmed by, clinical knowledge. Future research should extend these findings to a wider range of clinical conditions for greater applicability in the day-to-day orthodontic practice.

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.

In vitro assessment of dental erosion caused by clear aligners

The primary objective of this in vitro study was to investigate the erosive potential of enamel under the use of clear aligners (CA), by simulating in vivo conditions experienced by patients who do not remove their CA during the consumption of acidic beverages. In addition, the difference in erosion protection conferred by artificial and human saliva was also evaluated. Sound-extracted human premolars (n = 20) had half of their surfaces protected with acid-resistant nail polish and were randomly distributed into two experimental groups (n = 10): teeth immersed in human saliva or artificial saliva. All teeth had half of their lingual surfaces enclosed by a CA device. The erosive challenges consisted of individual immersion of each sample in citrus acid three times a day, intermediated by immersion in human saliva or artificial saliva for 2 h, during ten days of the erosive protocol. The enamel mineral content was analyzed by high-resolution microtomography. The differential mineral concentration profiles were obtained by subtracting the profile of the mineral concentration of the exposed area and enamel under the CA area from the respective sound area (control). In addition, enamel wear and enamel volume loss were measured. Scanning electron microscopy (SEM) was also performed to analyze the enamel surface. Data were analyzed by two-way ANOVA, followed by the Student-Newman-Keuls test. The enamel wear was higher in teeth immersed in artificial saliva, when compared to human saliva (p < 0.001). The volume loss of the exposed enamel area was lower for tooth immersed in human saliva than in artificial saliva (p < 0.001), during the acid challenge protocol. The use of CA during acid challenges promoted wear and mineral loss of dental enamel, being these changes more pronounced on the enamel surface under the CA. These results open a new path for the development of further studies adopting clinical protocols that promote more accurate responses in the clinical practice during orthodontic treatment.

Evaluation of the Quality and Reliability of YouTubeTM Videos Created by Orthodontists as an Information Source for Clear Aligners

Objective

This study aimed to evaluate the quality, reliability, and content usefulness of videos created by orthodontists on clear orthodontic aligners.

Methods

Videos were screened using YouTubeTM by conducting a search for "Invisalign". After a preliminary evaluation of the first 250 results, 61 videos that met the selection criteria were scored and their length, days since upload, and numbers of views, likes, dislikes, and comments were recorded. These data were used to calculate the interaction index and viewing rate. Video reliability was assessed using a five-item modified DISCERN index, and video quality was assessed using the Video Information and Quality Index. A 10-item content usefulness index was created to determine the usefulness of the video content. Descriptive statistics of the parameters were calculated, and correlation coefficients were calculated to evaluate the relationships between the parameters.

Results

The mean reliability score was 2.75±1.02 (out of 5), and the total quality score was 11.80±3.38 (out of 20). The total content usefulness index was quite low, with a mean score of 2.52±2.14 (out of 10). Interaction index and viewing rate were positively correlated with reliability score (r=0.463, p<0.01; r=0.295, p<0.05) and total quality score (r=0.365, p<0.01; r=0.295, p<0.01, respectively). The reliability score was positively correlated with the total quality score (r=0.842, p<0.01) and total content usefulness index (r=0.346, p<0.01).

Conclusion

Videos about orthodontic aligner treatment have average reliability and quality but largely insufficient content.

The use of clear aligners in orthognathic surgeries: a case series

Pre- and postoperative fixed orthodontic appliances are the customary and standard practice for patients with treatment planned for undergoing orthognathic surgery. Traditionally, most patients undergoing orthognathic surgeries are in their late teens. Although these patients still compose the greatest pool of the orthognathic surgery population, many patients seek orthognathic surgery later in life. This older patient population often has different concerns and goals than the younger patient population. One of these concerns is often the aesthetic appearance of fixed appliances and the time required to wear these appliances pre- and postoperatively. Today, removable orthodontic appliances consisting of a series of clear aligners have gained immense popularity due to their aesthetic appeal over traditional braces. Additional benefits of removable orthodontic appliances include improved oral hygiene leading to a decreased risk of gingivitis. Whereas clear aligner systems are commonly used in the nonsurgical orthodontic population, there has been limited use of Invisalign in the orthognathic surgery population. In this article, we present a case series of 5 patients who successfully underwent orthognathic surgery using clear aligners for pre- and postoperative orthodontic treatment.

The Role of Interproximal Reduction (IPR) in Clear Aligner Therapy: A Critical Analysis of Indications, Techniques, and Outcomes

Interproximal reduction (IPR) has become a standard practice in orthodontic treatment, particularly in the clear aligner therapy. It became an integral part of the digital plan when using clear aligners. Given the irreversible nature of IPR, precise planning and performance is essential. This article aims to analyze and summarize the existing literature on IPR in the context of clear aligners. The goal is to help clinicians to gain essential knowledge for safely and effectively navigating IPR. The review critically examines different perspectives found in the literature, covering indications, methods, and outcomes. Topics exploring the impact of IPR on treatment outcomes include space gaining, addressing tooth size discrepancies, tooth shape adjustments, resolving malocclusion, and enhancing aesthetics. Emphasizing precision of the procedure by the clinician and awareness of contraindications, the article also discusses the impact of IPR on patients. This includes considerations like increased pulp temperature, susceptibility to cavities due to changes in enamel roughness, effects on soft tissues, and post-IPR tooth sensitivity.

Predictability of Orthodontic Space Closure Using Invisalign Clear Aligners: A Retrospective Study

Introduction Clear aligners have demonstrated success in achieving complex tooth movements. However, orthodontists have faced challenges related to the predictability of clear aligners. This retrospective study aimed to assess the predictability of ClinCheck® accuracy in space closure before and after Invisalign® treatment and to identify factors associated with the need for refinement. Methods Patient records from one private clinic in Makkah, Saudi Arabia, were analyzed, and a sample of 55 adult patients who had spacing and underwent Invisalign treatment were included. Data on demographic and orthodontic variables were collected, and a chi-square test was conducted to examine the association between the requirement for refinement and demographic as well as clinical/orthodontic factors. Furthermore, the initial and final space measurements were compared using paired t-tests across various demographic and clinical/orthodontic variables. Results After completing the treatment, 70.9% (N=39) of the cases did not require any orthodontic refinement. The mean final space measurement was higher for males compared to females (0.7 mm and 0.4 mm, respectively), individuals who received treatment in the upper compared to lower arch (0.5 and 0.4 mm, respectively), those with moderate compared to mild spacing (0.5 and 0.1 mm, respectively), and those with class III compared to class I Angle classification (0.9 and 0.3 mm, respectively). Additionally, patients with severe spacing had a significantly higher probability of requiring refinement compared to patients with mild spacing (adjusted odds ratio = 20.9; p < 0.05). Conclusion The study emphasizes the significance of careful patient selection and treatment planning, suggesting that orthodontists should consider overcorrecting in space closure when using clear aligners, especially in cases with more significant spacing.

Surface wear of attachments in patients during clear aligner therapy: a prospective clinical study

BACKGROUND

This prospective clinical study aimed to quantitatively evaluate the surface wear of attachments and investigate the associated risk factors. Additionally, the wear values and regions of three types of commonly used attachments were explored.

METHODS

Participants were recruited from the population of patients who received clear aligner therapy from October to December 2022. Intraoral scanning was performed on eligible participants before treatment (T0), immediately after initial bonding of attachments (T1), and at 2 months (T2), 4 months (T3), 6 months (T4), and 8 months (T5) after starting treatment. The attachment volume, average depth and regions of attachment wear were measured using superimposed digitized models. The Kruskal-Wallis test was performed to compare data between multiple groups. Multiple linear regression analyses were performed to evaluate risk factors for the volume of attachment wear.

RESULTS

A total of 47 patients with 617 attachments were included. As treatment time increased, the attachment volume decreased significantly (P = 0.003). The initial attachment volume was positively related to the volume of attachment wear (β = 0.527, P < 0.001). The volume of attachment wear was significantly greater in females than in males (β = 0.147, P = 0.020) and in optimized attachments than in conventional attachments (β = 0.308, P < 0.001). The wear of 3-mm rectangular attachments progressed from edges to buccal surfaces, with the deepest wear at corners of gingival edges; the wear of the optimized attachments was primarily located on surface ridges. The wear volume ratio of the optimized root control attachments was significantly greater than that of the 3-mm rectangular attachments at T3 (P = 0.011), T4 (P < 0.001), and T5 (P < 0.001).

CONCLUSIONS

The volume of attachment wear increased gradually with treatment time. Sex, attachment type, and initial attachment volume were risk factors for the volume of attachment wear. The deepest wear regions of 3-mm rectangular attachments were at the corners of gingival edges, while the deepest wear regions of optimized attachments were at surface ridges. Four months after treatment, optimized root control attachments showed more relative wear than 3-mm rectangular attachments.

Effects of clear aligners on the vertical position of the molar teeth and the vertical and sagittal relationships of the face: a preliminary retrospective before-after clinical trial

INTRODUCTION

Despite the popularity of clear aligners, their predictability has not been assessed adequately. Moreover, no study has investigated their effects on numerous dentomaxillary variables. Therefore, this study was conducted for the first time, assessing several new or controversial items. The aim of the study was to evaluate the effects of clear aligners on the vertical position of the molar teeth and the vertical and sagittal relationships of the face.

METHODS

This preliminary retrospective before-after non-randomized clinical trial was performed on 168 observations of 84 patients (33.60±9.28 years, 54 females) treated with 0.75mm Invisalign appliances. Pretreatment and posttreatment values were measured for: mandibular plane angle, occlusal plane angle, Y-Axis, ANB, facial angle, lower anterior facial height, overbite, and the distances of the molars from the palate and mandibular plane were measured. The alterations in parameters caused by treatment (delta values) were calculated for each measurement. Effects of treatment and some parameters on delta values were analyzed statistically (α=0.05).

RESULTS

Mean±SD of ΔMP-FH, ΔOP-FH, ΔY-Axis, ΔLAFH, ΔNPog-FH, ΔANB, ΔOverbite, ΔSNB, Δ6-PP, Δ7-PP, Δ6-MP, and Δ7-MP were respectively 0.11±1.61, 0.80±1.56, 0.15±1.18, 0.07±0.91, -0.22±1.25, 0.03±0.62, 0.04±1.15, -0.06±1.14, -0.36±0.94, -0.32±1.14, 0.19±0.96, 0.18±1.10. Only the alterations in OP-FH, 6-PP, and 7-PP were significant (P≤0.011). Age, sex, treatment duration, or pretreatment mandibular plane angle were not correlated with any delta values. However, the pretreatment occlusal plane angle was negatively correlated with ΔOP-FH and ΔY-Axis. Crowding was correlated negatively with ΔOP-FH and ΔY-Axis and positively with ΔNPog-FH. Overjet was negatively correlated with ΔANB and ΔOverbite (P≤0.035).

CONCLUSIONS

Invisalign intruded first/second maxillary molars and increased the occlusal plane angle. Age, sex, and treatment duration were not correlated with post-treatment anatomic alterations.

Effect of clear aligner type on maxillary full-arch intrusion: 3D analysis using finite element method

BACKGROUND

Vertical maxillary excess (VME) is one of the most common reasons for seeking orthodontic treatment. Total intrusion with aligners is a promising alternative to surgery in some cases. Considering the elastic deformation of aligners, this study aimed to evaluate the possible desirable and undesirable teeth displacements during full maxillary arch intrusion using clear aligners and temporary anchorage devices (TADs).

METHODS

The maxillary arch and clear aligners were modeled in SolidWorks. Four aligner brands including Leon, Duran, Duran Plus, and Essix Plus were selected based on their material properties. Anterior and posterior intrusion forces of 80 and 300 g were applied from attachments between the canines and first premolars and between the first and second molars, respectively. Vertical and anteroposterior tooth displacements were determined.

RESULTS

The greatest intrusion was recorded at the buccal of the second molar, followed by the first molar. The lowest value was measured at the palatal of the molars with all aligners except Duran, which indicated minimal intrusion in the central incisor. All teeth were mesially displaced at the incisal/occlusal except incisors that moved distally. All apices showed distal movement.

CONCLUSIONS

Total intrusion using clear aligners may be accompanied by other tooth movements, including buccal tipping and mesial-in rotation of the molars, retrusion of incisors, and mesial movement of other teeth.

Chemical-Physical Characterization of PET-G-Based Material for Orthodontic Use: Preliminary Evaluation of micro-Raman Analysis

OBJECTIVES

 Orthodontic treatment with clear thermoplastic aligners is in great demand by patients especially for aesthetics. Any alterations in the chemical composition of the thermoplastic material for aligners, subjected to the oral environment and exposure to various commonly used substances, could influence the desired orthodontic movement decreasing the predictability of the treatment. The objective of this study was to determine the chemical-physical characterization by micro-Raman spectroscopy of a thermoplastic material based on polyethylene terephthalate glycol (PET-G) used for the manufacture of Lineo aligners (Micerium Lab, Avegno, Italy) subjected to different staining beverages and cleaning agents.

MATERIALS AND METHODS

 Twenty-two thermoformed PET-G samples were immersed to various substances of daily use for 10 and 15 days (coffee, tea, Coca-Cola, red wine, colloidal silver disinfectant, nicotine, artificial saliva, cigarette smoke, and different combinations of saliva with some of the previous solutions). Subsequently, the chemical-physical characterization was investigated by micro-Raman spectroscopy.

RESULTS

 The analysis of the spectra acquired for all the specimens showed no difference in the exposure to the different solvents at 10 and 15 days. Furthermore, having ascertained the heterogeneous surface morphology of the PET-G material due to thermoforming, various deposits were present on all the samples whose consistency and concentration depended on the substance used.

CONCLUSION

 The spectroscopic investigations have provided a precise and detailed analysis of the qualitative and structural data of the PET-G material under examination. No significant structural modifications of the thermoplastic polymer were found after immersion in different solutions in the exposure times adopted.

Impact of various aligner auxiliaries on orthodontic activity: A systematic review and network meta-analysis

Background

It is imperative to analyze the forces and moments produced by various auxiliaries in order to select the optimal attachments and, eventually, to maximize the efficacy and efficiency of orthodontic therapy. Through this investigation, we aimed to highlight the impact of various aligner auxiliaries on orthodontic activity in patients undergoing orthodontic treatment on a pre/post treatment protocol basis.

Methods

After a thorough search of the online journals, a total of 482 documents were found using keywords such as "Orthodontic Treatment", "Aligner Auxiliaries", "Elastic Ligatures" and "Tooth Movement." The database research, elimination of duplicate studies, data extraction and risk of bias were performed by the authors independently. This systematic review and network meta-analysis included prospective studies and clinical trials to evaluate research that had looked at the impact of various aligner auxiliaries on orthodontic activity in patients undergoing orthodontic treatment.

Results

Eight investigations of varying designs were selected for this review. The majority of investigations revealed that aligner auxiliaries significantly improve anterior root torque, rotation, and mesio-distal (M-D) movement, as well as posterior anchoring. They also significantly improved anterior root rotation. However, few studies have presented inconsistent or non-statistically significant findings.

Conclusion

Auxiliaries for aligners also appear to improve extrusion and other orthodontic movements, but there is insufficient evidence to support these claims. No research has examined posterior bucco-lingual expansion or tilting. Clarification of the effect of attachments and their related variables requires additional clinical investigations.

Advancements in Clear Aligner Fabrication: A Comprehensive Review of Direct-3D Printing Technologies

Clear aligners have revolutionized orthodontic treatment by offering an esthetically driven treatment modality to patients of all ages. Over the past two decades, aligners have been used to treat malocclusions in millions of patients worldwide. The inception of aligner therapy goes back to the 1940s, yet the protocols to fabricate aligners have been continuously evolved. CAD/CAM driven protocol was the latest approach which drastically changed the scalability of aligner fabrication-i.e., aligner mass production manufacturing. 3D printing technology has been adopted in various sectors including dentistry mostly because of the ability to create complex geometric structures at high accuracy while reducing labor and material costs-for the most part. The integration of 3D printing in dentistry has been across, starting in orthodontics and oral surgery and expanding in periodontics, prosthodontics, and oral implantology. Continuous progress in material development has led to improved mechanical properties, biocompatibility, and overall quality of aligners. Consequently, aligners have become less invasive, more cost-effective, and deliver outcomes comparable to existing treatment options. The promise of 3D printed aligners lies in their ability to treat malocclusions effectively while providing esthetic benefits to patients by remaining virtually invisible throughout the treatment process. Herein, this review aims to provide a comprehensive summary of studies regarding direct-3D printing of clear aligners up to the present, outlining all essential properties required in 3D-printed clear aligners and the challenges that need to be addressed. Additionally, the review proposes implementation methods to further enhance the effectiveness of the treatment outcome.

Hybrid treatment of varied orthodontic appliances for a patient with skeletal class II and temporomandibular joint disorders: A case report and review of literature

BACKGROUND

The relation between orthodontic treatment and temporomandibular disorders (TMDs) is under debate; the management of TMD during orthodontic treatment has always been a challenge. If TMD symptoms occur during orthodontic treatment, an immediate pause of orthodontic adjustments is recommended; the treatment can resume when the symptoms are managed and stabilized.

CASE SUMMARY

This case report presents a patient (26-year-old, female) with angle class I, skeletal class II and TMDs. The treatment was a hybrid of clear aligners, fixed appliances and temporary anchorage devices (TADs). After 3 mo resting and treatment on her TMD, the patient's TMD symptom alleviated, but her anterior occlusion displayed deep overbite. Therefore, the fixed appliances with TAD were used to correct the anterior deep-bite and level maxillary and mandibular deep curves. After the levelling, the patient showed dual bite with centric relation and maximum intercuspation discrepancy on her occlusion. After careful examination of temporomandibular joints (TMJ) position, the stable bite splint and Invisible Mandibular Advancement appliance were used to reconstruct her occlusion. Eventually, the improved facial appearance and relatively stable occlusion were achieved. The 1-year follow-up records showed there was no obvious change in TMJ morphology, and her occlusion was stable.

CONCLUSION

TMD screening and monitoring is of great clinical importance in the TMD susceptible patients. Hybrid treatment with clear aligners and fixed appliances and TADs is an effective treatment modality for the complex cases.

Effects of Thermoforming on the Mechanical, Optical, Chemical, and Morphological Properties of PET-G: In Vitro Study

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

Bioceramic micro-fillers reinforce antibiofilm and remineralization properties of clear aligner attachment materials

Introduction: Clear aligners, while offering a more hygienic alternative to fixed appliances, are still associated with challenges including plaque accumulation and enamel demineralization. The aim of the present study was to investigate the antibiofilm and remineralization effectiveness of innovative flowable composite attachments containing bioceramic micro-fillers. Methods: Four experimental attachments were formulated and bonded to human enamel specimens: 3M Filtek Supreme flowable composite (Filtek SF) + 10% bioactive glass 45S5 (BAG), Filtek SF + 30% BAG, Filtek SF + 10% Bredigite (BRT), Filtek SF + 30% BRT. Plaque biofilms were grown on the bonded enamel using a standardized protocol and the biofilm-killing effect was assessed by confocal laser scanning microscopy and scanning electron microscopy. Vickers microhardness was measured to evaluate the remineralization effect of the attachments containing bioceramic fillers after acid challenge. Shear bond test was performed to assess the bonding strength. Results: Attachments with bioceramic fillers significantly inhibited plaque biofilm growth in 3 weeks on enamel, contributing over 20% bacterial cell killing in 10% filler groups and over 30% killing in 30% filler groups. All four experimental groups demonstrated significantly higher microhardness values than the control group without fillers on the attachment side. The shear bonding strength was not compromised in the attachments with micro-fillers. Discussion: Proper incorporation of bioceramic micro-fillers in attachments provides an innovative approach for clear aligner therapy with reinforced antibiofilm and remineralization effects without weakening shear bonding strength.

Predicted and achieved overjet and overbite measurements with the Invisalign appliance: a retrospective study

OBJECTIVES

To determine whether achieved outcome regarding overjet and overbite matched the predicted outcome following treatment with Invisalign (Align Technology, San Jose, Calif) aligner appliances.

MATERIALS AND METHODS

Data including pretreatment, predicted and achieved overjet, and overbite measurements provided by Align's digital treatment facility, ClinCheck Pro, were evaluated. Descriptive statistics, Mann-Whitney U-test, and Wilcoxon rank-sum intraclass correlation (ICC) test results were calculated.

RESULTS

From an initial sample of 600, 355 adult patients satisfied the inclusion and exclusion criteria. ICC scores for data input were excellent. Median (interquartile range [IQR]) age was 30.14 (23.33, 39.92) years and most (n = 259; 72.95%) were women. Almost one-third (n = 101; 28.45%) had undergone extraction as part of their treatment. More aligners were prescribed in the initial digital treatment plan for patients (median, 44; IQR: 35, 51.5; minimum, 17; maximum, 92) undergoing extractions as part of their orthodontic treatment than those who were not (median, 24; IQR: 18.25, 32; minimum, 13; maximum, 85) (P < .0001). Planned changes in overjet differed significantly from achieved outcomes (P < .001). Planned increases in overbite resulted in up to more than twice (222.72%) as much increase than predicted. Planned reduction of overbite achieved 8.69% of its predicted reduction in extraction cases.

CONCLUSIONS

Achieved overjet and overbite measurements differed significantly from the predicted outcomes at the end of an initial sequence of aligners. Planned increases in overbite resulted in greater overbite correction than predicted, particularly in extraction cases. Planned overbite reduction was challenging, especially in patients with extractions.

Biomechanical effects of different staging and attachment designs in maxillary molar distalization with clear aligner: a finite element study

BACKGROUND

In the present study, the effects of distalizations of one and two molars with different step distances and attachment designs have been analyzed.

METHODS

A 3D finite element analysis model has been developed in order to determine the tendency of tooth displacement and stress distribution with clear aligner treatment.

RESULTS

Under the condition of single-molar distalization, when the step distance was set to 0.25 mm, the total displacement was 0.086 mm for central incisors, 0.080 mm for lateral incisors, 0.084 mm for canines, 0.102 mm for the first premolar and 0.076 mm for the second premolar. The von Mises stress of roots and the principal stress of the periodontal ligament was slightly lower than in the control group when the step distance was set to 0.130 mm. Under the condition of two-molar distalization, when the step distance was set to 0.130 mm, the total displacements for central incisors, lateral incisors and canines as well as both the first and second maxillary molars were basically the same as with a distance of 0.250 mm for one-molar distalization. In addition, when the step distance was 0.130 mm with two-molar distalization, the rotation center of the first and second molar was closer to the apex of the root indicating that the smaller step distance led to more bodily movement during the two-molar distalization. However, displacement tendencies of the first molar and the second molar were basically the same whether horizontal or vertical rectangular attachments were added.

CONCLUSIONS

A step distance of moving two molars to 0.130 mm can achieve the same reaction force on the anterior teeth as moving one molar 0.250 mm without effects on horizontal or vertical rectangular attachments.

CLINICAL RELEVANCE

Our results provide a theoretical basis and guidance for simultaneously moving two molars backward in clinical practice using a clear aligner.

Assessment of clear aligner accuracy of 2 clear aligners systems

INTRODUCTION

This study compared treatment efficacy for specific tooth movements between 2 clear aligner systems (Clarity [3M Oral Care Solutions, St Paul, Minn] and Invisalign [Align Technology, San Jose, Calif]).

METHODS

The study sample included 47 patients (7 males, 40 females; mean age, 36.57 ± 15.97 years) treated with Invisalign and 37 (4 males, 33 females; mean age, 34.30 ± 16.35 years) treated with Clarity aligners who completed their first set of aligners and had an initial refinement scan. Initial and predicted models were obtained from the initial simulated treatment plan. The first model of the refinement scan was labeled as achieved. SlicerCMF software (version 3.1; http://www.slicer.org) was used to superimpose the achieved and predicted digital models over the initial ones with regional superimposition on the relatively stable first molars. Nine hundred forty teeth in the Invisalign system were measured for horizontal, vertical, and angular movements and transverse width and compared with similar measurements of 740 teeth for the Clarity aligners. The deviation from the predicted was calculated and compared between both systems.

RESULTS

The deviation achieved from the predicted was significant between the groups for the mandibular interpremolar and intercanine widths (P <0.05). Clarity aligners significantly undercorrected rotations compared with Invisalign for the mandibular first premolars, mandibular canines, maxillary canines, and maxillary central incisors. There was no statistically significant difference between the groups for the achieved vs predicted movements in the horizontal and vertical planes (P >0.05).

CONCLUSIONS

The efficacy of clear aligner therapy systems (Clarity and Invisalign) in treating mild and moderate malocclusions was comparable. Deviation of the achieved movements from the predicted was greatest for rotational and vertical movements.

Comparison of the bond strength of five different composites used in the production of clear aligner attachments

AIM

The aims of this study were to measure and compare shear bond strength (SBS) and manipulation time (MT) among five different composite resins (CR; two flowable and three highly viscous) which are used in the production of clear aligner attachments.

MATERIAL AND METHODS

This in vitro experiment study comprised of 150 extracted premolars which were divided into 5 equal groups. Predictor variables were CRs; Tetric Evo Ceram (Ivoclar VivadentAG, Liechtenstein) (Group 1), Tetric NCeram; (Ivoclar VivadentAG, Liechtenstein) (Group 2), Tetric N-Flow (GC Dental Products, Tokyo, Japan) (Group 3), G-aenial Universal Injectable (GC Dental Products, Tokyo, Japan) (Group 4), GC Aligner Connect (GC Dental Products, Tokyo, Japan) (Group 5), respectively. Outcome variables were; SBS and MT for each CR attachment in each group of teeth. Oneway ANOVA was used to compare the groups. Levene's test was used to determine variance homogeneity. In terms of variance homogeneity, Bonferroni tests were used as a post-hoc test for multiple group comparisons.

RESULTS

SBS was statistically different between study groups (p < 0.001). Average SBS values ​​are found to be 16.6 ± 3.6 MPa for Tetric Evo Ceram; 20.7 ± 5.4 MPa for Tetric NCeram; 21.0 ± 4.0 MPa for Tetric N-Flow; 18.9 ± 5.0 MPa for G-aenial Universal Injectable; and 17.4 ± 3.5 MPa for GC Aligner Connect. The values ​​in the Tetric Evo Ceram group were significantly lower than the Tetric N-Ceram group (p = 0.004) and the Tetric N-Flow group (p = 0.001). Mean value of shear bond strength in the GC Aligner connect group were significantly lower than in the Tetric N-Ceram group (p = 0.047) and in the Tetric N-Flow group (p = 0.017). Flowable composite had a significantly shorter manipulation time than the high viscous one; mean 1,08 ± 0,22 min to mean 4,57 ± 0,51 min, respectively.

CONCLUSION

Although SBSs of CRs tested in the study was found to be statistically different, they all quite exceeded the accepted clinically sufficient value of 6-8 MPa. Besides, flowable composite required substantially less time to manipulate than the high viscosity composite.

Digital treatment planning and clear aligner therapy: A retrospective cohort study

OBJECTIVE

To investigate the total number of digital treatment plan (DTPs) and aligners manufactured for clear aligner therapy (CAT) by Invisalign® from initial treatment planning to the completion of CAT.

DESIGN

A retrospective cohort study.

MATERIAL AND METHODS

A total of 30 patients, from each of 11 experienced orthodontists, who commenced treatment over a 12-month period, were assessed regarding the number of DTPs and aligners prescribed from initial planning to completion of CAT. Patients were categorised according to the number of aligners prescribed by the initial DTP into mild (<15), moderate (15-29) or severe (>29).

RESULTS

After the application of inclusion/exclusion criteria, 324 patients (71.9% women; median age = 28.5 years) undergoing non-extraction treatment with the Invisalign® appliance were assessed. The median number of initial DTPs was 3 (interquartile range [IQR] = 2, 1-9) per patient before acceptance by the orthodontist. Most (99.4%) patients required a refinement phase with a median of 2 (IQR = 2, 2-7) refinement plans recorded. A total of 9135 aligners per dental arch, was prescribed in the initial DTP of the 324 patients assessed and 8452 in the refinement phase. The median number of aligners per dental arch prescribed from the initial DTP was 26 (IQR = 12, 6-78) and from the refinement plans was 20.5 (IQR = 17, 0-132).

CONCLUSION

A median of three initial DTPs and two refinement plans were required for patients undergoing non-extraction treatment with the Invisalign® appliance. Patients were prescribed almost double the number of aligners initially predicted to manage their malocclusion.

The effect of passive clear aligners on masticatory muscle activity in adults with different levels of oral parafunction

BACKGROUND

There is limited knowledge of the possible side-effects of clear aligners on jaw function.

OBJECTIVES

To determine the short-term effect of passive clear aligners (PCAs) on masticatory muscle activity (MMA), occlusal discomfort (OD) and temporomandibular disorder (TMD) symptoms in adults with different levels of self-reported oral parafunction.

MATERIALS AND METHODS

Participants were screened for oral parafunctional behaviours using the oral behavioural checklist. Respondents in ≥85th and ≤15th percentiles were invited to participate and allocated to a high (HPF: N = 15) or low (lower parafunction [LPF]: N = 16) parafunction group. Participants underwent a TMD clinical examination; somatisation and somatosensory amplification were assessed by questionnaires; OD and stress were assessed by visual analogue scales. While wearing PCAs, awake-time MMA was assessed three times over 9 days using a wearable electromyography device, along with OD, stress and TMD symptoms.

RESULTS

The wearing of PCAs was associated with a significant decrease in mean contraction episode amplitude in both groups (p = 0.003). OD levels increased and remained raised in all participants after insertion of the PCAs (p < 0.001), more so in the HPF group (p = 0.048). The HPF group had higher somatisation scores (p = 0.006) and reported more TMD symptoms at all time points (p ≤ 0.004). No significant changes in stress or TMD symptoms were found in either group during the study period.

CONCLUSIONS

PCAs were associated with a decrease in MMA in all participants. HPF individuals had greater somatisation and reported greater discomfort when wearing PCAs than LPF individuals.

The displacement of teeth and stress distribution on periodontal ligament under different upper incisors proclination with clear aligner in cases of extraction: a finite element study

OBJECTIVES

To investigate the displacement of dentition and stress distribution on periodontal ligament (PDL) during retraction and intrusion of anterior teeth under different proclination of incisors using clear aligner (CA) in cases involving extraction of the first premolars.

METHODS

Models were constructed, consisting of the maxilla, PDLs, CA and maxillary dentition without first premolars. These models were then imported to finite element analysis (FEA) software. The incisor proclination determined the division of the models into three groups: Small torque (ST) with U1-SN = 100°, Middle torque (MT) with U1-SN = 110°, and High torque (HT) with U1-SN = 120°. Following space closure, a 200 g intrusion force was applied at angles of 60°, 70°, 80°, and 90° to the occlusal plane, respectively.

RESULTS

CA therapy caused lingual tipping and extrusion of incisors, mesial tipping and intrusion of canines, and mesial tipping of posterior teeth in each group. As the proclination of incisors increased, the incisors presented more extrusion and minor retraction, and the teeth from the canine to the second molar displayed an increased tendency of intrusion. The peak Von Mises equivalent stress (VMES) value successively decreased from the central incisor to the canine and from the second premolar to the second molar, and the VMES of the second molar was the lowest among the three groups. When the angle between the intrusion force and occlusal plane got larger, the incisors exhibited greater intrusion but minor retraction.

CONCLUSIONS

The "roller coaster effect" usually occurred in cases involving premolar extraction with CA, especially in patients with protruded incisors. The force closer to the vertical direction were more effective in achieving incisor intrusion. The stress on PDLs mainly concentrated on the cervix and apex of incisors during the retraction process, indicating a possibility of root resorption.

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

INTRODUCTION

Extrusion of maxillary lateral incisors during aligner treatment is a difficult movement to achieve accurately. Despite recommendations regarding attachment design, few studies and no prospective trials compare predictability among attachments. This study aimed to compare the efficacy between optimized and horizontal attachment designs for achieving maxillary lateral incisor extrusion during clear aligner treatment.

METHODS

The study included maxillary lateral incisors in 3 orthodontic practices requiring at least 0.3 mm of extrusion during the first series of 20-25 aligners in patients aged ≥16 years who were scheduled to begin clear aligner treatment (Invisalign; Align Technology, San Jose, Calif). Teeth were randomly assigned to receive optimized (O), rectangular horizontal nonbeveled (H), rectangular horizontal incisally-beveled (HIB), or rectangular horizontal gingivally-beveled (HGB) attachments. After the first series, a blinded evaluator measured extrusion using superimpositions with initial and predicted models. Linear models determined the difference in the predicted extrusion percentage achieved on the basis of attachment design. Other covariates were patient age, sex, number of trays, and self-reported compliance.

RESULTS

Forty patients (74 teeth) were enrolled, and 38 patients (71 teeth) completed the study. Intraexaminer and interexaminer reliability for extrusion measurements was high (intraclass correlation coefficient, 0.985 and 0.991, respectively). The achieved extrusion was significantly less than predicted (mean, 73%; P <0.0001). The average achieved extrusion was 62%, 79%, 78%, and 78% for O, H, HIB, and HGB attachments, respectively, with H significantly more effective than O (P = 0.0403). Horizontal attachments (H, HIB, and HGB combined) were significantly more effective than O attachments (P = 0.0060), with an average difference in achieved extrusion of 14% of the predicted amount (95% confidence interval, 4-23; estimated 76% vs 62%). Horizontal attachments were an estimated 22% more effective than O attachments for extruding maxillary lateral incisors.

CONCLUSIONS

Horizontal attachments are more effective than O attachments for predicted maxillary lateral incisor extrusion between 0.3 and 2.5 mm. The 3 horizontal attachment designs evaluated performed similarly for achieving predicted extrusion.

TRIAL REGISTRATION

This randomized clinical trial was registered and reported at clinicaltrials.gov (NCT04968353).

PROTOCOL

The protocol was not published before trial commencement.

FUNDING

This study was funded in part by the Alexander Fellowship of the Virginia Commonwealth University School of Dentistry, the Southern Association of Orthodontists, and the Virginia Orthodontic Education and Research Foundation. No funding source influenced the study design, the collection, analysis or interpretation of data, writing of the report, or the decision to submit the article for publication.

In vitro evaluation of a novel fluoride-coated clear aligner with antibacterial and enamel remineralization abilities

OBJECTIVE

To investigate the antibacterial and enamel remineralization performances as well as physicochemical properties and biocompatibility of a fluoride-coated clear aligner plastic (FCAP).

MATERIALS AND METHODS

FCAP and normal clear aligner plastic (CAP) was bought from the manufacturer (Angelalign Technology Inc, China). The FCAP was observed under scanning electron microscopy. Its element composition, resistance to separation, contact angle, and protein adhesion performance were characterized. Colony-forming unit (CFU) count and 3-(4,5)-dimethylthiazol(-z-y1)-3,5-diphenyltetrazolium bromide (MTT) assay were used to evaluate the antibacterial ability of Streptococcus mutans. Fluoride release-recharge patterns were obtained. Apatite formation was evaluated after immersing FCAP in artificial saliva. Enamel remineralization capability was evaluated in the demineralization model (immersing samples in demineralization solution for 36 h) and pH cycling model (immersing samples in demineralization solution and remineralization solution in turns for 14 days). Cell Counting Kit-8 (CCK-8) and live/dead cell staining kits were used for cytotoxicity assay.

RESULTS

The FCAP showed uniformly distributed fluoride and did not compromise protein adhesion performance. CFU count (5.47 ± 0.55 for CAP, 3.63 ± 0.38 for FCAP) and MTT assay (0.41 ± 0.025 for CAP, 0.28 ± 0.038) indicated that the FCAP had stronger antibacterial activity compared with normal CAP (P < 0.05 for both evaluations). The FCAP could release fluoride continuously for 14 days and could be recharged after immersing in NaF solution. The FCAP could induce the formation of hydroxyapatite in artificial saliva and could reduce the microhardness decrease, color change, and mineral loss of enamels in both two models (P < 0.05 for all evaluations). CCK-8 and live/dead cell staining analyses showed that the coating did not compromise the biocompatibility of the clear aligner (P > 0.05 for CCK-8 evaluation).

CONCLUSIONS

The FCAP had antibacterial, fluoride recharge, and enamel remineralization abilities while it did not compromise physicochemical properties and biocompatibility.

CLINICAL RELEVANCE

The FCAP has the potential to prevent enamel demineralization during clear aligner treatment.