Orthodontic Treatment with Clear Aligners and The Scientific Reality Behind Their Marketing: A Literature Review

Comparison of anxiety, pain, and quality of life in individuals with mild or moderate malocclusion between conventional fixed orthodontic treatment versus Invisalign: a randomised clinical trial

BACKGROUND

We evaluated anxiety, pain, and oral-health-related quality of life in individuals treated with conventional fixed appliances (Group A) and clear aligners (Group B) for moderate malocclusion during the initial phase of orthodontic treatment.

METHODS

Sixty individuals, separated into Group A (n = 30) and Group B (n = 30), were included in the study. They completed the Anxiety Levels, Oral Health Impact Profile-14, and Oral Health Related Quality of Life - United Kingdom/Surveys after the application of attachments on days 0 (T1), 10 (T10), and 20 (T20). Their pain levels were evaluated with the Visual Analogue Scale on days 0, 2, and 6 in the 2nd and 6th hours and on the 1st, 3rd, 7th, 14th, and 21st days.

RESULTS

Per the VAS questionnaire, pain levels in the 2nd hour, 6th hour, 1st day, and 3rd day were significantly lower in Group B than in Group A. In the OHIP-14 survey results, the comparison between Group A and Group B showed a significant difference only on the 1st day. The STAI and OHRQoL-UK survey results did not differ significantly between the groups.

CONCLUSIONS

We found no significant difference between the two groups in terms of anxiety levels, and pain among individuals in Group A was higher than in Group B only at the beginning of the treatment. No significant differences were observed in terms of individuals' quality of life.

TRIAL REGISTRATION

NCT06133296 (retrospectively registered)- Registration Date:15/11/2023.

Orthodontic treatment in adults: Challenges, outcomes, and factors affecting compliance and satisfaction

BACKGROUND

The demand for orthodontic treatment among adults has witnessed a substantial rise in recent years. This study aims to explore the complexities of adult orthodontics, focusing on challenges faced, treatment outcomes, and the influence of factors such as age, gender, and education on patient compliance and satisfaction.

METHODS

A multi-dimensional approach was employed, combining a review of clinical records with structured patient surveys. Descriptive statistics summarized demographic characteristics, treatment duration, and orthodontic problems addressed. Inferential statistics included Pearson correlation, Chi-squared tests, and analysis of variance to examine age compliance, gendersatisfaction, and education-orthodontic problem relationships. Qualitative analysis enriched findings, and statistical software facilitated data processing.

RESULTS

The analysis revealed a statistically significant negative correlation between age and compliance (r = -0.28, P < 0.05), indicating that younger participants demonstrated higher compliance rates. Gender emerged as a significant factor influencing patient satisfaction (P = 0.024), with females reporting notably higher levels of satisfaction than males. Furthermore, participants with advanced education levels (Master's/Ph.D.) were significantly more likely to have orthodontic issues related to malocclusion (P = 0.041).

CONCLUSION

The study provides an insight into the multi-dimensional aspects of adult orthodontics, recognizing the challenges, compliance, and satisfaction levels. Tailored approaches considering age, gender, and education are essential. This research contributes to a deeper understanding of orthodontic treatment in adults and its potential implications for enhanced patient care.

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.

Influence of pain duration and severity on oral health-related quality of life and patient satisfaction during adult treatment with clear aligners

BACKGROUND

This study aims to compare the impact of pain on quality of life and patient satisfaction during treatment with aligners.

METHODS

Ninety-four subjects in active treatment were invited to answer self-reported questions concerning pain severity and duration, occurrence of other signs and symptoms, and level of satisfaction with their treatment. Also, the OHIP-14 questionnaire was applied to assess patients' OHRQoL.

RESULTS

Ninety-four patients (49 women and 45 men) answered the survey. Pain duration of 1-3 days was reported by 69.1% of patients (n = 60). For those who reported pain (n = 84), it was considered mild severity by 42.9% and moderate by 52.4%. Almost sixty-four percent of the sample were very satisfied with the aligner's aesthetics (n = 60) and forty-nine percent were satisfied with treatment in general (n = 46). Mean OHIP-14 score was 3.36 ± 2.54. OHRQoL was significantly associated with pain severity, whereas patients who reported having experienced moderate pain presented a significantly higher mean OHIP-14 score than those who reported having experienced mild pain (3.92 ± 1.93 and 2.69 ± 2.83, respectively; p = 0.036). The "psychological discomfort" OHIP-14's domain was the most influenced by the level of pain.

CONCLUSION

Pain severity significantly influenced OHRQoL, in adult patients under treatment with clear aligners. However, high levels of patient satisfaction were reported, regardless of pain duration or severity.

Effect of material composition and thickness of orthodontic aligners on the transmission and distribution of forces: an in vitro study

OBJECTIVES

To investigate the effects of material type and thickness on force generation and distribution by aligners.

MATERIALS AND METHODS

Sixty aligners were divided into six groups (n = 10): one group with a thickness of 0.89 mm using Zendura Viva (Multi-layer), four groups with a thickness of 0.75 mm using Zendura FLX (Multi-layer), CA Pro (Multi-layer), Zendura (Single-layer), and Duran (Single-layer) sheets, and one group with a thickness of 0.50 mm using Duran sheets. Force measurements were conducted using Fuji® pressure-sensitive films.

RESULTS

The lowest force values, both active and passive, were recorded for the multi-layered sheets: CA Pro (83.1 N, 50.5 N), Zendura FLX (88.9 N, 60.7 N), and Zendura Viva (92.5 N, 68.5 N). Conversely, the highest values were recorded for the single-layered sheets: Duran (131.9 N, 71.8 N) and Zendura (149.7 N, 89.8 N). The highest force was recorded at the middle third of the aligner, followed by the incisal third, and then the cervical third. The net force between the incisal and cervical thirds (FI-FC) showed insignificant difference across different materials. However, when comparing the incisal and middle thirds, the net force (FI-FM) was higher with single-layered materials. Both overall force and net force (FI-FM) were significantly higher with 0.75 mm compared to those with a thickness of 0.50 mm.

CONCLUSIONS

Multi-layered aligner materials exert lower forces compared to their single-layered counterparts. Additionally, increased thickness in aligners results in enhanced retention and greater force generation. For effective bodily tooth movement, thicker and single-layered rigid materials are preferred.

CLINICAL RELEVANCE

This research provides valuable insights into the biomechanics of orthodontic aligners, which could have significant clinical implications for orthodontists. Orthodontists might use this information to more effectively tailor aligner treatments, considering the specific tooth movement required for each individual patient. In light of these findings, an exchangeable protocol for aligner treatment is suggested, which however needs to be proven clinically. This protocol proposes alternating between multi-layered and single-layered materials within the same treatment phase. This strategy is suggested to optimize treatment outcomes, particularly when planning for a bodily tooth movement.

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.

Numerical biomechanical finite element analysis of different trimming line designs of orthodontic aligners: An in silico study

BACKGROUND

A finite element model was used to investigate the effect of different designs and thicknesses of orthodontic aligner margins on their biomechanical behavior.

METHODS

A three-dimensional data set of an upper jaw was imported into the 3-matic software. The upper right central incisor tooth (Tooth 11) was separated from the remaining model, and its periodontal ligament and surrounding bone were designed. Aligners were designed with four different trimming lines (scalloped, straight, scalloped extended, straight extended), each with four different thicknesses (0.3, 0.4, 0.5, and 0.6 mm). The models were imported into a finite element package (Marc/Mentat). A linear elastic constitutive material model was applied. A facial 0.2 mm bodily malalignment of tooth 11 was simulated.

RESULTS

The maximum resultant force was in the range of 1.0 N to 2.2 N. The straight trimming designs deliver higher resultant forces compared with scalloped trimming designs. Increasing the aligner thickness and/or extending the aligner edge beyond the gingival line leads to an increase in the resultant force. All designs showed an uneven distribution of the normal contact forces over the tooth surface with a predominant concentration toward the cervical third and distal third, particularly with the extended trimming designs. All designs showed uncontrolled tipping of the tooth.

CONCLUSIONS

Based on the current model outcomes, the use of a straight extended trimming line design for aligners is favored because of its positive impact on force distribution and, consequently, the control of tooth movement.

CLINICAL RELEVANCE

These findings provide aligner companies and orthodontists a valuable biomechanical evidence and guidance to enhance control over tooth movement and therefore optimize treatment outcomes. This can be achieved by trimming the edges of aligners with a straight extended design and selecting the appropriate aligner thickness.

Clear Aligners in Pediatric Dentistry: A Scoping Review

Today not just adults but also children are affected by their looks and appearance. Their facial and dental appearance primarily influence how they present themselves in the outside world. Poor esthetic appearance at any age, especially when it comes to children, affects their psychological status. In earlier times, correction of dentition used to be done with crude methods, after which came the concept of braces, which were fixed on the labial surfaces. Even with these, the patients are equally concerned with their looks throughout the treatment, and thus neither adults nor children are eager to use the standard metallic-looking orthodontic gear. To tackle this problem, researchers have developed several solutions, and clear aligners are the modern and aesthetic answer. For effective tooth movement into the desired position, thin, transparent, plastic aligners known as invisible aligners are used, which are created using the computer-aided design/computer-aided manufacturing (CAD-CAM) technology. These aligners are analogous to the splints that cover the clinical crowns as well as the marginal gingiva. The treatment requires proper patient motivation as there can be poor compliance by patients. However, it can offer greater dental hygiene, comfort, and an excellent aesthetic experience during treatment. This review highlights the history of fabrication of clear aligners, examining the efficacy, advantages, and disadvantages of transparent aligners for pediatric patients and also dentists. It weighs aspects like aesthetic appeal, comfort, oral hygiene, treatment predictability, and practice efficiency when comparing transparent aligners, like Invisalign, to conventional orthodontic treatments. It also ascertains the applicability and worth of clear aligners in contemporary orthodontic practice, while examining patient happiness, compliance, and overall treatment results.

Clear Aligners in the Growing Patient: A Systematic Review

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

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

OBJECTIVES

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

CLINICAL RELEVANCE

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

Impact of Orthodontic Treatment on the Incidence of Dental Caries in Adolescents: A Prospective Cohort Study

BACKGROUND

Orthodontic treatment is a widely embraced intervention aimed at enhancing dental aesthetics and correcting malocclusions among adolescents. However, concerns persist regarding its potential impact on oral health, particularly on the development of dental caries. This study aimed to systematically investigate the relationship between orthodontic treatment and the incidence of new carious lesions among adolescents.

METHODS

A prospective cohort design involving adolescents aged 12-18 years was employed. A total of 82 patients met the inclusion criteria. In addition, an age-matched control group of 82 participants who did not undergo orthodontic treatment was included. The study included both a treatment group undergoing orthodontic treatment (braces or aligners) and an age-matched control group that did not undergo any orthodontic intervention. Demographic characteristics, orthodontic treatment details, and oral hygiene practices were documented at baseline and throughout the study period. Dental examinations at six-month intervals post-treatment were conducted to track the incidence and progression of carious lesions.

RESULTS

The demographic characteristics, baseline oral health status, orthodontic treatment details, and oral hygiene practices were comparable between the treatment and control groups. Post-orthodontic treatment assessment revealed a slightly higher incidence of new carious lesions in the treatment group (14.6%) than in the control group (9.8%), although this difference was not statistically significant (p = 0.15). Dental examinations at six-month intervals demonstrated a gradual increase in caries incidence over time in both groups, with no substantial disparities observed.

CONCLUSIONS

This study provides a comprehensive examination of the relationship between orthodontic treatment and the incidence of new carious lesions among adolescents. While a trend towards higher caries incidence in the treatment group was observed, the difference was not statistically significant. These findings contribute to the existing body of knowledge and emphasize the need for ongoing research to guide clinical practice.

Physiochemical and mechanical characterisation of orthodontic 3D printed aligner material made of shape memory polymers (4D aligner material)

OBJECTIVES

To conduct a physiochemical and mechanical material analysis on 3D printed shape-memory aligners in comparison to thermoformed aligners.

MATERIALS AND METHODS

Four materials were examined, including three thermoformed materials: CA Pro (CP), Zendura A (ZA), Zendura FLX (ZF), and one 3D printed material: Tera Harz (TC-85). Rectangular strips measuring 50 × 10 × 0.5 mm were produced from each material. Five tests were conducted, including differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), shape recovery tests, three-points bending (3 PB), and Vickers surface microhardness (VH).

RESULTS

DSC recorded glass transition temperatures (Tg) at 79.9 °C for CP, 92.2 °C for ZA, 107.1 °C for ZF, and 42.3 °C for TC-85. In DMA analysis at 20-45 °C, a prominent decrease in storage modulus was observed, exclusively for TC-85, as the temperature increased. Notably, within the temperature range of 30-45 °C, TC-85 exhibited substantial shape recovery after 10 min, reaching up to 86.1 %, while thermoformed materials showed minimal recovery (1.5-2.9 %). In 3 PB test (at 30, 37, 45 °C), ZA demonstrated the highest force at 2 mm bending, while TC-85 exhibited the lowest. Regarding VH at room temperature, there was a significant decrease for both ZA and ZF after thermoforming. ZA had the highest hardness, followed by ZF and TC-85, with CP showing the lowest values.

CONCLUSIONS

TC-85 demonstrates exceptional shape memory at oral temperature, improving adaptation, reducing force decay, and enabling, together with its higher flexibility, extensive tooth movement per step. Additionally, it maintains microhardness similar to thermoformed sheets, ensuring the durability and effectiveness of dental aligners.

CLINICAL RELEVANCE

The 3D printed aligner material with shape memory characteristics (4D aligner) has revolutionized the orthodontic aligner field. It showed mechanical properties more suitable for orthodontic treatment than thermoforming materials. Additionally, it offers enhanced control over aligner design and thickness, while optimizing the overall workflow. It also minimizes material wastage, and reduces production expenses.

Clear aligner therapy versus conventional brackets: Oral impacts over time

Background

The objective is to compare the impact of clear aligner treatment (CAT) versus conventional fixed appliance treatment (FAT) on oral health-related quality of life (OHRQoL) among adults at five-time points: pretreatment (T0), 1 week (T1), 1 month after (T2), and 6 months after (T3) treatment initiation, and in the long-term follow-up (T4).

Materials and Methods

Search terms were based on Medical Subject Headings (MeSH) and non-MeSH. Potentially eligible studies compared OHRQoL in clear aligner (CA) and fixed appliance (FA) patients. In February 2023, Scopus, Web of Science, Cochrane, and PubMed were searched for published studies. Nine out of 94 shortlisted papers were eligible for a systematic review. Of these nine papers, five studies were considered for a meta-analysis.

Results

At T0, CA and FA patients had similar oral health impact profile (OHIP)-14 questionnaire scores with a standard mean difference (SMD) of 0.105 (confidence interval [CI]: -1.029-1.48). The SMD of the OHRQoL related to T1, T2, and T3 was -3.119 (CI: -0.145, 0.355), -1.527 (CI: -5.597, -0.64), and - 2.331 (CI: -1.906, -1.148). T4 showed no difference between groups (SMD = 0.007, CI: CI: -4.286, -0.376). Regarding the OHIP-14 domains, functional limitations remained consistent in both groups across all time intervals. Psychological discomfort exhibited a notable difference only at T2. Throughout the treatment, CAT showed significantly lower levels of physical, psychological, and social disability, as well as handicap, though these differences did not persist beyond T4. Notably, physical pain was the sole domain that remained elevated in the FAT group up to T4.

Conclusion

During the 1st day of the orthodontic treatment, both the CA and FA groups had comparable OHRQoL statuses. However, as time passed, the CA group notably improved their OHRQoL compared to the FA group. Interestingly, after a year or the completion of treatment, both groups eventually reached similar OHRQoL levels. Nevertheless, it is worth noting that FA patients continued to experience more physical pain even a year later.

Oxidative Stress and Natural Products in Orthodontic Treatment: A Systematic Review

In recent years, orthodontics, a specialized branch of dentistry, has evolved considerably in terms of both techniques and materials used. Aimed at correcting dental malocclusions and craniofacial anomalies, it improves the functionality and aesthetics of the face and oral cavity. However, orthodontic treatment, in its developmental stages, may induce oxidative stress (O.S.) phenomena, with an increase in the production of reactive oxygen species (ROS), damaging the dental and periodontal tissues involved, affecting the short-, medium- and long-term results. Studies on the antioxidant effects of natural products (e.g., resveratrol, green tea, turmeric, etc.) in the medical field have aroused considerable interest in recent years. A systematic literature review was conducted on the PubMed, Scopus, and Web of Science databases using natural products (N.P.s), O.S., and orthodontic as keywords. The study aims to consider the determinants of the increase in ROS occurring during orthodontic treatment and the possibility of natural products being able to control and neutralize biochemical phenomena by restoring the physiological process in which the balance between the production of ROS and the ability of the body's antioxidant system to neutralize them is in favor of the latter.

Predictability of Dental Distalization with Clear Aligners: A Systematic Review

The current review aims to evaluate the scientific evidence relating to the effectiveness of treatment with clear aligners (CAs) in controlling distalization orthodontic tooth movement. "Orthodontics, aligners" and "distalization" were the search terms used on the Scopus, Web of Science and Pubmed databases with the Boolean operator "AND". The results of the last ten years of research were 146 studies; of these, 19 publications were included for this review. The distalization movement is possible with invisible masks alone, but the risk of losing anchorage in the anterior sectors is very probable. The stability of the results and the reduction of unwanted effects can be guaranteed by the use of skeletal anchoring devices and interproximal enamel reduction (IPR), with which compensations are obtained to reduce the initial overjet. Temporary anchorage devices (TADs) can be used to manage posterior anchorage after distalization of maxillary molars with aligners. This hybrid approach has demonstrated the greatest orthodontic success. TADs are useful aids to provide direct and indirect skeletal anchorage. The opposite effect must be considered when planning dental distalization, especially of the molars, in patients with large overjet, and corrective measures or the use of auxiliaries may be necessary to prevent midcourse corrections. This systematic review provides a critical evidence-based assessment of the predictability of dental distalization with CAs, an ever-evolving orthodontic technique.

Comparison of efficacy between MBT preadjusted edgewise appliance and clear aligner therapy among class I crowding cases: A randomized controlled trial

Background

To compare the efficacy of McLaughlin Bennett Trevisi (MBT) appliance and Clear Aligner Therapy (CAT) among nonextraction Class I crowding cases.

Methods

The study sample (60 patients) was allotted into two equal groups (30 patients each) using block randomization wherein Group 1: treated with 0.018" MBT appliance and Group 2: treated with CAT for correction of malocclusion. At the end of treatment (T1), treatment duration, chairside time, laboratory time, number, and type of appointments were noted from treatment record cards. For comparing the acceptability among patients treated with both modalities at T1, the patients were interviewed regarding the comfort and ease of using an appliance with a questionnaire-based survey.

Results

The median number of nonscheduled/emergency and finishing stage appointments was significantly higher in Group 1 compared to Group 2 (P-value <0.001). The median duration of treatment at the scheduled, finishing, and overall appointments, was significantly higher in Group 1 compared to Group 2 (P-value <0.001). The median chairside time of all appointments was significantly higher in Group 1 compared to Group 2 (P-value <0.001). The experience with treatment and overall acceptability was significantly higher in Group 2 compared to Group 1 (P-value <0.001). However, mean laboratory time per aligner fabrication in Group 2 was 30.26 ± 3.45 min against no laboratory time consumed in Group 1.

Conclusions

CAT significantly reduces treatment duration, chairside time, number of nonscheduled/emergency, and finishing stage appointments in nonextraction Class I crowding cases. Prospective studies with 3D aligner systems are recommended to add further evidence in this regard.

Clinical Trials Registry-India Registration No

CTRI/2018/04/013301.

Periodontal health status, oral microbiome, white-spot lesions and oral health related to quality of life-clear aligners versus fixed appliances: A systematic review, meta-analysis and meta-regression

Objective

: Assess and evaluate the different indicators of oral health-related quality of life (OHRQoL) among patients treated with clear aligners (CAs) versus those treated with conventional fixed orthodontics (FAs).

Methods

: An electronic search was performed on the database is Web of Science, Scopus, and Embase databases. Randomized and non-randomized control trials, cross-sectional, prospective cohort and retrospective trials were included. Quality was assessed with risk of bias tool and risk of bias in non-randomised studies. Meta-analyses were performed with random effects models, estimating the standardized and non-standardized mean differences, odds ratio and risk ratio as the measure of effect. The effect on time was determined using a meta-regression model.

Results

: Thirty one articles were included in the qualitative synthesis and 17 in the meta-analysis. CAs had a significantly lower negative impact on QoL, with an "important" effect size, while the influence of time was not significant. Periodontal indicators plaque index (PI), gingival index (GI), probing depth (PD), and bleeding on probing show significantly better values in patients treated with CAs, with moderate to large effect sizes. PI and GI have a significant tendency to improve over time. In microbiological indicators, CAs present a lower biofilm mass without differences in the percentage of patients with high counts of Streptococcus mutans and Lactobacilli bacteria. The risk of white spot lesion onset is ten times lower in carriers of CAs.

Conclusions

: Patients wearing CAs show better periodontal indicators, less risk of white spot development, less biofilm mass and a better QoL than patients with FAs.

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

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Evaluation of the Clinical Variables Affecting Attachment Reproduction Accuracy during Clear Aligner Therapy

BACKGROUND

The purpose of this study was to evaluate some of the clinical variables that influence the accuracy of reproducing the planned attachment shape. The following clinical variables were considered: the template material, type of composite, and pressure application on the template during attachment curing.

METHODS

In this study, the evaluated materials for the thermoplastic transfer template construction are Erkolen 0.8 (polyethylene: PE) and Erkodur 0.8 (polyethylene terephthalate glycol-PET-G), and two types of composite resins: Enaflow (light-curing low-viscosity composite resin) and Enamel plus dentina HRI (light-curing high-viscosity composite resin). Two different light-curing lamps were used: Valo cordless color with no pressure and push light pressure (SCS). The 26 models included in the study were imported into the 3 Shape Ortho System 2022 (ver. 85.0.20 3 Shape, Denmark), and attachments were virtually placed on the dental elements of the first premolar and on both sides of the first upper molars. The accuracy of the attachment reproduction was evaluated through linear and angular evaluations against the reference model (MCAD). Three physical models were obtained: model A (MA), which was printed with attachments; model B (MB) with attachments made with a PE template; and model C (MC) with attachments made with a PET-G template.

RESULTS

The results showed statistically significant differences (p < 0.05) between the PE and PET-G templates with greater precision using the PET-G template. Statistically significant differences (p < 0.05) were found among the high-viscosity composite and low-viscosity composite with pressure curing.

CONCLUSIONS

In light of the obtained data, using a PET-G template is recommended. The pressure application during composite curing reduces the reproduction accuracy with a low-viscosity composite.

Clear Aligner Therapy: Up to date review article

The advantages of Clear Aligners Therapy (CAT) include the braces being virtually invisible, comfortable to wear, and removable for eating and brushing; that way, CAT can be used to treat a wide range of orthodontic issues. In 1999, the company Align Technology introduced the frst commercial clear aligner system called Invisalign. The Invisalign system was initially only available to orthodontists, but later became available to general dentists as well. The system quickly gained popularity among patients who were looking for a more discreet and comfortable alternative to traditional braces. In 2000, Align Technology received FDA clearance for the Invisalign system, which further increased its popularity. The biomechanics of clear aligners involve the use of custom-made tooth aligners that are specifcally shaped to guide teeth into desired positions. These aligners are typically made from flexible materials such as polyurethane or ethylene vinyl acetate and are adjusted to apply the necessary forces for tooth movement. Attachment devices, such as power ridges or buttons, are often used to enhance or assist in specifc tooth movements and for retention of the aligner. The use of attachments allows for the exertion of desired force on the teeth, which is crucial for the success of Clear Aligner Therapy. CAT should be used if patients are concerned about the esthetic appearances of their teeth-for example, actors and other individuals that rely on their appearances in public in a professional context-and if the misalignment is not severe, so that clear aligners can still work. One should not use CAT in cases of severe crowding or spacing issues that require extractions. If the patient has complex jaw discrepancies or skeletal issues or if teeth need to be moved extensively in multiple directions, CAT is likely not going to be strong enough. In conclusion, Clear Aligner Therapy is a safe, effective, and convenient orthodontic treatment option that offers patients a virtually invisible way to achieve a straighter, more beautiful smile. With continued advancements in technology and a growing body of research supporting its effectiveness, the future of Clear Aligner Therapy looks bright.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effect of trimming line design and edge extension of orthodontic aligners on force transmission: A 3D finite element study

OBJECTIVES

To investigate in a numerical study the effect of the geometry and the extension of orthodontic aligner edges and the aligner thickness on force transmission to upper right central incisor tooth (Tooth 11).

METHODS

A three-dimensional (3D) digital model, obtained from a 3D data set of a complete dentulous maxilla, was imported into 3-matic software. Aligners with four different trimming line designs (scalloped, straight, scalloped extended, straight extended) were designed, each with four different thicknesses (0.3, 0.4, 0.5, and 0.6 mm). The models were exported to a finite element (FE) software (Marc/Mentat). A facial 0.2 mm bodily malposition of tooth 11 was simulated.

RESULTS

The maximum resultant force was in the range of (7.5 - 55.2) N. The straight trimming designs had higher resultant force than the scalloped designs. The resultant force increases with increasing the edge extension of the aligner. The normal contact forces were unevenly distributed over the entire surface and were concentrated in six areas: Incisal, Mesio-Incisal, Disto-Incisal, Middle, Mesio-Cervical, and Disto-Cervical. The resultant force increases super linearly with increasing thickness.

CONCLUSIONS

The design of the trimming line, the edge extension, and the thickness of the aligner affect significantly the magnitude of the resultant force and the distribution of normal contact force. The straight extended trimming design exhibited better force distribution that may favor a bodily tooth movement.

CLINICAL RELEVANCE

A straight extended trimming design of an orthodontic aligner may improve the clinical outcomes. In addition, the manufacturing procedures of the straight design are much simpler compared to the scalloped design.

Efficacy of invisible advancement correction for mandibular retraction in adolescents based on Pancherz analysis

BACKGROUND

Mandibular retraction is the main etiological mechanism of class II malocclusion in China and the subsequent distal molar relationship can cause functional discomfort in mastication, breathing and the temporomandibular joint. The use of mandibular advancement (MA) devices has recently emerged as an adolescent mandibular retraction treatment; however, current studies regarding the effect thereof are relatively few, and there is lack of sufficient clinical support.

AIM

To investigate the clinical effect of invisalign MA on the treatment of mandibular retraction in adolescents.

METHODS

This study included 30 adolescent patients who underwent treatment with the MA appliances from December 2017 to June 2021. The lateral cephalometric data before and after treatment were collected and imported into Dolphin Imaging software. The changes were measured by linear measurement superimposed with lateral cephalometric trajectory based on the Pancherz technology.

RESULTS

There was no significant difference in the length and position of maxilla before and after the treatment. The position of the mandible moved 3.13 mm, the length increased 4.14 mm, the mandibular ramus length increased 4.09 mm, the body length increased 4.25 mm, and the position of the condyle moved 1.03 mm forward after treatment. Additionally, changes in the incisor sagittal position and labial inclination were observed. The position of the upper incisor point moved back 1.33 mm, without statistical difference, the inclination and tooth angle decreased by 3.44° and 4.06°, respectively; the position of the lower incisor point was moved 2.98 mm, and the inclination and tooth angle increased by 2.62° and 1.23°, respectively. Furthermore, changes in the incisor overjet and molar relationship were seen. Overjet decreased by 4.31 mm, of which 1.78 mm was due to dental factors, accounting for 41.3% of the effect as opposed to 58.7% due to skeletal factors. Molar relationship improved 3.87 mm, with 1.34 mm due to dental factors, and dental and skeletal factors were accounted for 34.6% and 65.4% of the effect, respectively.

CONCLUSION

For adolescent patients with mandible retraction, invisalign MA can effectively promote the mandible growth, and it was proven to be mainly due to skeletal effects.

Computer-aided finite element model for biomechanical analysis of orthodontic aligners

OBJECTIVES

To design a finite element (FE) model that might facilitate understanding of the complex mechanical behavior of orthodontic aligners. The designed model was validated by comparing the generated forces - during 0.2-mm facio-lingual translation of upper left central incisor (Tooth 21) - with the values reported by experimental studies in literature.

MATERIALS AND METHODS

A 3D digital model, obtained from scanning of a typodont of upper jaw, was imported into 3-matic software for designing of aligners with different thicknesses: 0.4, 0.5, 0.6, 0.7 mm. The model was exported to Marc/Mentat FE software. Suitable parameters for FE simulation were selected after a series of sensitivity analyses. Different element classes of the model and different rigidity values of the aligner were also investigated.

RESULTS

The resultant maximum forces generated on facio-lingual translation of Tooth 21 were within the range of 1.3-18.3 N. The force was direction-dependent, where lingual translation transmitted higher forces than facial translation. The force increases with increasing the thickness of the aligner, but not linearly. We found that the generated forces were almost directly proportional to the rigidity of the aligner. The contact normal stress map showed an uneven but almost repeatable distribution of stresses all over the facial surface and concentration of stresses at specific points.

CONCLUSIONS

A validated FE model could reveal a lot about mechanical behavior of orthodontic aligners.

CLINICAL RELEVANCE

Understanding the force systems of clear aligner by means of FE will facilitate better treatment planning and getting optimal outcomes.

Comparison of Bond Strength of Orthodontic Brackets Onto the Tooth Enamel of 120 Freshly Extracted Adult Bovine Medial Lower Incisors Using 4 Adhesives: A Resin-Modified Glass Ionomer Adhesive, a Composite Adhesive, a Liquid Composite Adhesive, and a One-Step Light-Cured Adhesive

BACKGROUND This study aimed to compare the bond strength of orthodontic brackets onto the tooth enamel of 120 freshly extracted adult bovine medial lower incisors using 4 adhesives: a resin-modified glass ionomer adhesive, a composite adhesive, a liquid composite adhesive, and a one-step light-cured adhesive. MATERIAL AND METHODS The study group (120 freshly extracted bovine medial lower incisors) was divided into equal subgroups depending on the type of adhesive used to fix the brackets to the tooth enamel (n=30), and then according to the observation time (n=10). Orthodontic brackets were fixed onto the tooth enamel for 24 hours (T1), 3 months (T2), and 6 months (T3) using 4 types of adhesives: resin-modified glass ionomer adhesive Fuji Ortho LC, composite adhesive Transbond Plus Light Cure Band, flowable composite adhesive Transbond Supreme Low Viscosity, and a one-step light-cured adhesive GC Ortho Connect. Shear tests and fracture plane analyses were performed. RESULTS Statistically significant differences at time T1 were noted in the comparison of shear stress values when brackets were fixed with GC Ortho Connect adhesive compared to other adhesives (P<0.05), except for the Transbond Plus adhesive (P>0.05). At time T3, significant statistical differences occurred between GC Fuji Ortho LC and the other 3 adhesives (P<0.05). The fracture analysis showed that, regardless of the time function, adhesive-cohesive fractures without damage to the enamel were the most common for all the assessed materials. CONCLUSIONS Of the adhesives evaluated, GC Ortho Connect appears to be the most appropriate choice for bonding orthodontic brackets to the enamel surface.

Changes of maxillary central incisor and alveolar bone in Class II Division 2 nonextraction treatment with a fixed appliance or clear aligner: A pilot cone-beam computed tomography study

INTRODUCTION

This retrospective clinical study investigated the clinical changes of maxillary central incisor and alveolar bone in Class II Division 2 nonextraction treatment with fixed appliances or clear aligners on the basis of cone-beam computed tomography.

METHODS

Fifty-nine Chinese Han patients with similar demographic characteristics were collected from a conventional bracket group, a self-ligating bracket group, and a clear aligner group. All measurements about root resorption and alveolar bone thickness on the cone-beam computed tomography images were tested. Changes between pretreatment and posttreatment were evaluated by paired-sample t test. The variation among the 3 groups was compared by 1-way analysis of variance.

RESULTS

The resistance center of the maxillary central incisor showed upward or forward movement, and the axial inclination was increased in 3 groups (P <0.0001). Root volume loss in the clear aligner group (23.68 ± 4.82 mm³) was significantly less than that in the fixed appliances group (28.24 ± 6.44 mm³ in the conventional bracket group, 28.17 ± 6.07 mm³ in the self-ligating bracket group) (P <0.05). All 3 groups showed a significant decrease in palatal alveolar bone and total bone thickness at all 3 levels at posttreatment. In contrast, labial bone thickness significantly increased except for crestal level l. Among the 3 groups, the clear aligner group had a prominent increase in labial bone thickness at the apical level (P = 0.0235).

CONCLUSIONS

Clear aligner treatment for Class II Division 2 malocclusions could effectively reduce the incidence of fenestration and root resorption. Our findings will be beneficial to comprehensively understand the effectiveness of different appliances for Class II Division 2 malocclusions treatment.

Effect of Trimming Line Design and Edge Extension of Orthodontic Aligners on Force Transmission: An in vitro Study

OBJECTIVES

To investigate how the stress distribution and forces transmitted from orthodontic aligners to the tooth surface are affected by the geometry and extension of the trimming line.

MATERIALS AND METHODS

Thirty-six aligners were thermoformed from Zendura FLX sheets (0.75 mm thick) and divided into four groups based on the design of the trimming line: Scalloped, Scalloped extended, Straight and Straight extended. Fuji pressure-sensitive films were used for pressure measurement. The pressurized films were scanned and evaluated. Pressures and forces were measured over the entire facial surface of an upper right central incisor (Tooth 11) and at 7 different locations [cervical, middle, incisal, mesio-incisal, mesio-cervical, disto-cervical, and disto-cervical]. In addition, the thickness of the aligners at these 7 sites was measured with a digital caliper.

RESULTS

The active force ranged from (2.2 - 6.9) N, and the average pressure was (1.6 - 2.7) MPa. The highest values were recorded for the (straight extended) design, while the lowest values were recorded for the scalloped design. The forces and stresses were not uniformly distributed over the surface. When the values in each area were compared separately, significant differences were found between the different designs in the cervical area, with the scalloped design transmitting the lowest cervical forces. Aligner thickness was drastically reduced (60-75% thinning) over the entire tooth surface after thermoforming.

CONCLUSIONS

The straight extended design of aligner's trimming line exhibited more uniform force transfer and stress distribution across the surface than the other designs.

CLINICAL RELEVANCE

The trimming line design could have a significant impact on the clinical outcome of orthodontic aligner treatment.

Assessment of the Susceptibility of Aesthetic Orthodontic Brackets to Discoloration

The high aesthetic value of orthodontic appliance elements during treatment constitutes an important factor for an increasing number of adult patients. The aim of this study was to determine whether food dyes could significantly affect the color of both plastic and ceramic orthodontic brackets. Four brands of orthodontic brackets were investigated in the present study. Twenty-five samples of each kind were prepared. Five brackets of each series were stored in pure water, coffee, black tea and red wine for 1 h, 24 h, 7 days and 14 days. Total color change ∆E* of the samples was analyzed after storage with the use of the SpectroShade dental spectrophotometer (MHT, Verona, Italy) according to the CIE L*a*b* color scale. Correlations between bracket brand, kind of food dye and intensity of color change at the significance level p = 0.05 were investigated. After 1 and 24 h of incubation, water had the least influence on the color change of aesthetic orthodontic brackets, and tea had the greatest effect (p = 0.05). After 7 and 14 days of incubation of the samples, water still remained the environment influencing ∆E* change to the smallest extent, whereas storage in red wine changed the color of brackets to the significantly (p = 0.05) highest degree. The degree of discoloration of the assessed brackets depended on the type of material and the storage time in the environment of the individual food dyes (p = 0.05). The results of the present study show that, in the event of contact with food dyes, aesthetic orthodontic brackets discolor, the intensity of which can be influenced by the materials they are made of, the kind of food dye and the time of samples’ storage.

Bonding of Clear Aligner Composite Attachments to Ceramic Materials: An In Vitro Study

Background: We aim to evaluate the effect of surface conditioning, bonding agents and composite types on surface roughness (SR) and shear bond strength (SBS) of clear aligner composite attachments bonded to ceramics. Methods: One hundred and eighty IPS e.max CAD specimens were prepared. For SR, 60 specimens were divided according to surface conditioning (n = 15) into four groups: control, 9.6% hydrofluoric acid (HFA), 37% phosphoric acid (PhA), air abrasion (AA). SR was measured using a Profilometer and Atomic Force Microscopy. For SBS, 120 specimens were divided according to conditioning methods (n = 40) (9.6% HFA and 37% PhA or AA), then according to bonding agents (n = 20) (Assure universal bond (AUB) or Single bond universal (SBU)) and then according to composite type (n = 10): Filtek™ Z350 and Filtek™ Z350 XT flowable composite. SBS was measured using Instron testing machine. Descriptive and group comparison were calculated (p < 0.05). Results: AA had the highest SR, while the control had the lowest SR (p < 0.05). HFA had the highest, but insignificant SBS, followed by AA (p > 0.05). AUB had higher SBS than SBU (p < 0.001). Filtek™ Z350 produced higher SBS than Filtek™ Z350 XT flowable composite (p < 0.01). Conclusion: The combination of AA, AUB, and Filtek Z350 produced the highest SBS, followed by HFA, AUB, and Filtek Z350.

Orthodontic Management of Skeletal Class II Malocclusion with the Invisalign Mandibular Advancement Feature Appliance: A Case Report and Review of the Literature

The treatment of Class II malocclusion due to mandibular retrognathia is one of the most common challenges met in orthodontic practice. When it comes to a growing patient, functional appliances are the optimal way to achieve growth modification by enhancing mandibular growth. Clear aligners have been part of the orthodontic treatment for several decades but until recently they were only used to correct mild malocclusions. In 2017, Align Technology introduced the Invisalign with Mandibular Advancement Feature (IMAF) which replicates the action of functional appliances. As this device is new to clinical practice, there is limited literature on its clinical efficiency. This case report describes the orthodontic management of a 12-year-old male patient having skeletal Class II malocclusion due to mandibular retrognathia. As the patient was experiencing active growth, the IMAF appliance was chosen for his treatment. The IMAF appliance appears to be successful in the treatment of Class II malocclusion with mandibular retrognathism in a growing patient. As with all functional appliances, the correction of the malocclusion is a result of both skeletal and dental effects and the IMAF presents the advantage of producing less proclination of the lower incisors compared to other functional appliances.

Accuracy evaluation of orthodontic movements with aligners: a prospective observational study

Background

Since their introduction in orthodontics, clear aligners have been appreciated by patients, including adults, for their comfort and low aesthetic impact. Despite the enormous mobilization of financial resources all over the world aimed at producing new product lines, few clinical studies or high-quality evidence have been produced regarding the real effectiveness of such treatment. Given the few limited kinds of research on the subject, this study aims to produce and critically evaluate other data, to establish the concrete reliability of clear aligners in orthodontic therapy.

Results

Significant sample sizes were obtained for intrusion, vestibulo/lingual (V/L) crown tipping, and rotation. The overall accuracy for rotation resulted in 86%, ranging from 96% for maxillary central incisors to 70.4% for mandibular first premolars. The intrusion was registered only for anterior teeth; mean predictability was 92%, with the worst result being 86.7% for mandibular canines and the best being 98% for mandibular central incisors. V/L tipping was the most accurate movement: 93.1% of the prescribed movement was completed. Maxillary central incisors showed the lowest accuracy (80.7%), while mandibular central incisors were the highest (97.5%).

Conclusions

The present study provided reassuring data in support of the accuracy of the Invisalign^® system. Vestibulo/lingual tipping was the most predictable movement, while rotation of canines, premolars, and lateral incisors were the least predictable. Intrusion resulted highly predictable up to 2 mm. When careful treatment planning follows a correct diagnosis, together with the use of auxiliary features and refinements, the planned results can be achieved in a clinically successful way. Authors believe that there is a major need for greater samples to overcome bias related to variables if we want to answer the unsolved questions, such as the predictability of severe malocclusions treatment.

Performance of Rigid and Soft Transfer Templates Using Viscous and Fluid Resin-Based Composites in the Attachment Bonding Process of Clear Aligners

Objectives

The study aims at assessing the accuracy of the process of attachment bonding in aligner treatments. The analysis leads to the error estimation in the faithful reproduction of master model attachments using two types of transfer templates and two light-curing resin-based composites usually used in orthodontics.

Methods

The authors have used two transfer templates made of two different materials. The first, named Leone-biocompatible thermoforming material hard/soft, has a lower Young's modulus and is labelled as soft, while the other, named Leone-biocompatible thermoforming material, is marked as rigid. The resin-based composites possess different mechanical and rheological properties. Specifically, Transbond™ XT Light Cure Paste Adhesive, 3M has a higher viscosity than the TetricEvoflow, Ivoclar Vivadent, a flowable nanohybrid composite. The authors attempt to estimate the performance ranking between the four possible couples obtained by combining the two light-curing resin-based composites and transfer templates. Each combination was repeated in six models and compared with twelve master models, resulting in 36 total samples. A 3-D laser scanner is used to generate a digital model of each model. The comparison between digital models is the base for a comparative assessment in terms of relative and absolute error. The relative error is estimated using scalar performance indicators ranging from 0 to 1, where 1 indicates the optimum matching. The absolute error estimated from the mean square error between the coordinates of each digital model yields the reproduction accuracy in micrometer. Furthermore, the authors attempted to assess the error distribution by evaluating the point-by-point difference between the digital models.

Results

This analysis aims at localizing the sources of error in the considered models. The use of Transbond™ XT Light Cure Paste Adhesive, 3M with a rigid transfer template is always associated with significant accuracy and minor dispersion. However, in a few instances, using the soft template or the flowable resin-based composite can lead to bad performances. Significance. The data processing bestowed the following performance ranking from the first with lower reproduction error to the last characterized by the worst performance: (1) attachments bonding with rigid template and Transbond™ XT Light Cure Paste Adhesive, 3M, (2) attachments bonding with soft template and Transbond™ XT Light Cure Paste Adhesive, 3M, (3) attachments bonding with rigid template and TetricEvoflow, Ivoclar Vivadent, and (4) attachments bonding with soft template and TetricEvoflow, Ivoclar Vivadent.

Toxicological Assessment of an Acrylic Removable Orthodontic Appliance Using 2D and 3D In Vitro Methods

Malocclusion is a global health problem, mainly affecting children and adolescents. For this reason, orthodontic treatment must be, on the one hand, safe, non-toxic, and effective and, on the other hand, it must have the best possible esthetic profile. Thus, the use of orthodontic appliances is addressed to all age groups, including young children, for a long period of time, which is why their safety profile is a matter of real interest. For this reason, the purpose of the present study was to evaluate the safety and biocompatibility of an acrylic removable orthodontic appliance made of polymethylmethacrylate and stainless steel alloy made by our team of researchers. To verify the biocompatibility of the medical device, it was immersed in artificial saliva with three different pHs (3, 7, and 10) for a period of ten days. Subsequently, the three types of saliva were tested on human keratinocytes (HaCaT cell line) in terms of viability and modification of cell morphology. Finally, the use of 3D reconstructed human epidermis verified the cytotoxic and irritating potential of the medical device, thus providing relevant information regarding its biocompatibility. The results revealed that by maintaining the orthodontic device in the saliva there is no release of substances with a toxic effect on the human keratinocytes and on the 3D reconstructed human epidermis. There were also no significant changes in cell morphology. In conclusion, it is suggested that the acrylic removable appliance has a safety profile recommended for in vivo use.

Efficacy of clear aligners in producing molar distalization: Systematic review

Objectives:

The aim of this review is to systematically analyze the efficacy of molar distalization using clear aligners in non-growing Class II patients.

Materials and Methods:

A complete search across the electronic database through PubMed, Cochrane, Google scholar, LILACS, and manual search of orthodontic journals were done till 2019. Studies were selected on the basis of PRISMA guidelines.

Results:

A total of four articles were included in this review. The amount of molar distalization reported was 2–3 mm.

Conclusion:

Out of the four studies included. In all the studies a significant amount of distalization was reported. Three retrospective studies concluded that distalization with aligners is the most effective of all tooth movements. One study concluded that aligners effectively achieved distalization with an efficacy of 87%, other two studies concluded that aligners effectively distalized the molars with good control over vertical dimension and mesiodistal tipping.

Clear Aligners in Patients with Amelogenesis and Dentinogenesis Imperfecta

Dentinogenesis imperfecta (DI) and amelogenesis imperfecta (AI) are hereditary abnormalities of dental hard tissues. Dental abnormalities may also be accompanied by symptoms of disorders such as osteogenesis imperfecta. AI and DI have a significant burden on socializing, function, and comfort; therefore, frequent screening and accurate diagnosis is the cornerstone of managing such conditions. Both AI and DI could be treated with many strategies, including restorative, prosthetic, periodontal, surgical, and orthodontics treatment. The interdisciplinary combination of orthodontic, prosthodontic, and periodontic treatment has been proven to improve the prognosis of AI and DI. Regarding orthodontic treatment, the most difficult element of orthodontic therapy may be maintaining a high level of motivation for what might be a prolonged form of treatment spanning several years. There are many forms of orthodontic management for AI and DI, including removable appliances, functional appliances, and fixed appliances. Clear aligner therapy (CAT) contains a broad range of equipment that works in different ways, has different construction processes, and is compatible with different malocclusion procedures. The application of CAT in patients with AI and DI is favorable over the fixed applicants. However, the available evidence regarding the application of CAT in AI is weak and heterogeneous. In this review, we discussed the current evidence regarding the application of clear CAT in patients with AI and DI.

The Biological Effects of 3D Resins Used in Orthodontics: A Systematic Review

Three-dimensional (3D) resin medical-dental devices have been increasingly used in recent years after the emergence of digital technologies. In Orthodontics, therapies with aligners have gained popularity, mainly due to the aggressive promotion policies developed by the industry. However, their systemic effects are largely unknown, with few studies evaluating the systemic toxicity of these materials. The release of bisphenol A and other residual monomers have cytotoxic, genotoxic, and estrogenic effects. This systematic review aims to analyze the release of toxic substances from 3D resins used in Orthodontics and their toxic systemic effects systematically. The PICO question asked was, "Does the use of 3D resins in orthodontic devices induce cytotoxic effects or changes in estrogen levels?". The search was carried out in several databases and according to PRISMA guidelines. In vitro, in vivo, and clinical studies were included. The in vitro studies' risk of bias was assessed using the guidelines for the reporting of pre-clinical studies on dental materials by Faggion Jr. For the in vivo studies, the SYRCLE risk of bias tool was used, and for the clinical studies, the Cochrane tool. A total of 400 articles retrieved from the databases were initially scrutinized. Fourteen articles were included for qualitative analysis. The risk of bias was considered medium to high. Cytotoxic effects or estrogen levels cannot be confirmed based on the limited preliminary evidence given by in vitro studies. Evidence of the release of bisphenol A and other monomers from 3D resin devices, either in vitro or clinical studies, remains ambiguous. The few robust results in the current literature demonstrate the absolute need for further studies, especially given the possible implications for the young patient's fertility, which constitutes one of the largest groups of patients using these orthodontic devices.

Biomechanics of clear aligners: hidden truths & first principles

Over the past two decades clear aligner-based treatment has received remarkableattention from the orthodontic profession and more so from general practitioners.Different companies have emerged using vigorous advertisement to promote theirproducts mainly to patients and clinicians through social media. A variety of concepts,methods, and adjuncts have been introduced to enhance the efficacy andeffectiveness of clear aligners. However, the accuracy of tooth movement (vspredicted) with aligners still hovers around 50%. Fixed appliances fare much better onaccuracy and predictability of treatment. Why is there a discrepancy betweenexpected and actual outcomes? This paper utilizes 'first principles' and the existingevidence to unravel some of the key drawbacks of aligner-based therapy. Severalshortcomings in the biomechanical properties of aligner material (thermoplastics) thataffect clinical performance are discussed. Based on the first principles of alignerbiomechanics, this paper provides clinical insights for improving predictability and effectiveness of aligner therapy.

Clear Aligners: Between Evolution and Efficiency-A Scoping Review

In recent years, clear aligners have diversified and evolved in their primary characteristics (material, gingival margin design, attachments, divots, auxiliaries), increasing their indications and efficiency. We overviewed the brands of aligners used in Italy and reviewed the literature on the evolution of clear aligners based on their characteristics mentioned above by consulting the main scientific databases (PubMed, Scopus, Lilacs, Google Scholar, Cochrane Library). Inclusion and exclusion criteria were established. The data were collected on a purpose-made data collection form and analyzed descriptively. From the initial 580 records, 527 were excluded because they were not related to the subject of the review or because they did not meet the eligibility criteria. The remaining 31 studies were deemed comprehensive for the purpose of the review, although the “gingival margin design” feature and “auxiliaries” tool are not well represented in the more recent literature. Current knowledge on invisible aligners allows us to have a much clearer idea of the basic characteristics of aligner systems. There remains a need to deepen the use of systems other than Invisalign™ to give greater evidence to aligners that are very different based on the characteristics analyzed here and that are very widespread on the market.

The optimal orthodontic displacement of clear aligner for mild, moderate and severe periodontal conditions: an in vitro study in a periodontally compromised individual using the finite element model

Background

Pathologic tooth migration (PTM) is a common complication of mild to severe periodontitis and proper orthodontic treatment is helpful to alleviate periodontal diseases. The goal of this study is to explore an optimal orthodontic displacement of clear aligner using a three-dimensional (3D) finite element model (FEM).

Methods

The cone beam computed tomography (CBCT) data of a patient received invisible orthodontics without diabetes and other systemic diseases were collected. Based on the new classification scheme for periodontal diseases in 2017 (stage I: mild periodontitis, [M1]; stage II: moderate periodontitis, [M2]; stage III: severe periodontitis, [M3]), 3D-FEMs of mandible were established using MIMICS 10.0 and ABAQUS 6.5 softwares. The 3D stress distribution diagrams and stress value of the teeth (left lower incisor, left lower central incisor, right lower lateral incisor, and right lower central incisor) under three different periodontal conditions (M1, M2, and M3) with axial inclination 90° and 100° were obtained by ABAQUS 6.5.

Results

The stress of anterior teeth was concentrated in the teeth neck, and became greater when the periodontal condition was worse. The stress value of anterior teeth and the strain at the top of the alveolar crest are greater as the displacement increasing. The stress value of anterior teeth and the strain at the top of the alveolar crest in axial inclination 100° are relatively great compared to those of axial inclination 90°. For patients with excessively inclined anterior teeth (such as 100°), the optimal orthodontic displacement is 0.18 mm. In order to ensure that alveolar ridge crest is not deformed, the displacement is less than 0.18 mm (strain for 0.165 mm), 0.15 mm (strain for 0.167 mm) and 0.10 mm (strain for 0.117 mm) respectively when alveolar bone is normal, resorption 1/3 or 1/3–1/2.

Conclusions

The optimal orthodontic displacement for patients (M1, M2, and M3) with excessively inclined anterior teeth (axial inclination 100°) is 0.18 mm. To avoid the strain at the top of the alveolar crest, the optimal displacements for M1, M2 and M3 periodontal disease patients are less than 0.18 mm, 0.15 mm and 0.10 mm, respectively.

Relationship between oral health impacts and personality profiles among orthodontic patients treated with Invisalign clear aligners

This within subject clinical experiment assessed oral health impacts before and after Invisalign orthodontic treatment and their relationships with personality characteristics. 50 patients (26 females and 24 males; mean age = 27.62 ± 8.25 years, SE = 1.17, 95% CI = 24.71–29.89 years) were assessed before and after treatment with Invisalign orthodontic treatment. Treatment clinical success was evaluated according defined clinical guidelines. Oral health impacts before and after Invisalign orthodontic treatment were measured via the Oral Health Impact Profile (OHIP). Personality features were measured via the NEO Five-Factor Inventory (NEO-FFI). Probability of α = .05 was utilized to identify significant findings. Females scored less OHIP scores after treatment (had less negative impacts) in comparison to baseline OHIP scores (t = 3.782, df = 25, P = .001, 95% CI of mean difference = 2.750–9.327). Among males, openness scores (R² = .911, B = 5.235, 95% CI for B = 0.062–10.407, t = 2.601, P = .048) were able to predict OHIP scores before treatment; meanwhile, extraversion (R² = .959, B = − 8.224, 95% CI for B = − 14.605–1.843, t = − 3.313, P = .021), openness (R² = .959, B = 21.795, 95% CI for B = 10.737–32.853, t = 5.067, P = .004), and conscientiousness (R² = .959, B = 10.293, 95% CI for B = 4.796–15.790, t = 4.813, P = .005) scores were useful to predict OHIP scores after treatment (R² = .959, P < .05). NEO-FFI scores were not useful to predict OHIP scores before or after treatment among females (P > .05). These findings demonstrate that oral health impacts of Invisalign orthodontic treatment and personality profiles contribution to oral health impacts were different between genders.