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

INTRODUCTION: This study aimed to evaluate the efficacy of Invisalign First Phase I treatment compared with tooth-borne rapid maxillary expansion (RME) in mixed dentition patients by examining changes in palatal volume, palatal surface area, and maxillary interdental transverse measurements. METHODS: In this open-label, 2-arm, parallel, randomized controlled trial, patients with a posterior transverse discrepancy ≤6 mm were allocated into the clear aligner therapy (CAT) group (Invisalign First Phase I treatment) and RME group (tooth-borne RME) according to a computer-generated randomization list immediately before the start of treatment. Digital models were obtained before the beginning of the treatment (T0) and at the end of the retention period/treatment (T1) using an intraoral scanner. Palatal volume was measured as the primary outcome, and palatal surface area and intermolar and intercanine transverse widths at the cusps and gingival level were measured as secondary outcomes. Patients and interventionists were not blinded because of the nature of the intervention. RESULTS: Out of 50 patients, 41 (19 males and 22 females; mean age, 8.12 ± 1.53 years) were enrolled and divided into 2 groups: 20 in the CAT group and 21 in the RME group. Two participants did not receive the allocated intervention for different reasons (1 patient discontinued the intervention in the CAT group, and another patient was lost to follow-up in the RME group). Thus, 19 patients (5 males and 14 females; mean age, 8.48 ± 1.42 years) were analyzed from the CAT group, and 20 patients (12 males and 8 females; mean age, 7.83 ± 1.19 years) from the RME group. Regarding intragroup comparisons, all outcome measures significantly increased from T0 to T1 in both groups. In terms of intergroup comparisons, there were no significant differences in the variation (Δ) of outcome measures between the 2 groups from T0 to T1, except for the intermolar width at the gingival level (P <0.005). The change in palatal volume was 532.01 ±540.52 mm³ for the RME group and 243.95 ± 473.24 mm³ for the CAT group (P = 0.084), with a moderate effect size (d = 0.57). CONCLUSIONS: RME showed trends favoring better outcomes compared with Invisalign First Phase I treatment across all assessed measures. The only parameter that showed statistically significant differences between the 2 groups was variation in intermolar width at the gingival level, suggesting the occurrence of buccal tipping in patients undergoing Invisalign First Phase I treatment. TRIAL REGISTRATION: The trial was registered at ClinicalTrial.gov (no. NCT04760535).

The 50 most-cited articles on clear aligner treatment: A bibliometric and visualized analysis.

INTRODUCTION: Research on clear aligner treatment (CAT) has increased in recent years. In this study, we aimed to perform a bibliometric and visualized analysis to identify and critically assess the 50 most highly cited articles on CAT. METHODS: Web of Science was selected as a data source and consulted until March 2020 to identify all articles potentially relevant to the analysis. All the eligible articles were collected until 50 manuscripts were listed. Article-based parameters, journal-based parameters, and author-based parameters were registered to perform the bibliometric analysis. Keywords were automatically harvested from the selected articles to implement the visualized analysis. RESULTS: The search identified a total of 378 articles; the total number of citations of the selected articles varied from 15 to 112. The average number of citations per year varied from 1.15 to 13.83. The predominant study design was clinical (31.7%). Over the 15 journals in which the most cited articles were published, the American Journal of Orthodontics and Dentofacial Orthopedics published the majority of those included in the list (14) and also received the greatest number of citations (671). A total of 195 authors contributed to the 50 most cited articles; a significant portion of them (26) were unaffiliated with academic institutions. A total of 184 keywords were gathered from the article list. CONCLUSIONS: The number of citations on CAT is expected to grow steadily in parallel with the rising number of research projects. The present work identifies the most influential articles on CAT and their characteristics, placing emphasis on the journals, the authors, and the topics addressed.

The use of conventional transcutaneous electrical nerve stimulation in chronic facial myalgia patients.

OBJECTIVES: The aim of this study was to evaluate the efficacy of conventional TENS in women affected by chronic facial myalgia. MATERIALS AND METHODS: The study was performed on 49 women affected by chronic facial myalgia randomly allocated in the TENS group (34 women) and the control group (15 women). The subjective level of pain was assessed by the Visual Analogue Scale indicating the mean (VAS MEAN), the maximum (VAS MAX) and the current intensity of pain (VAS NOW). The level of pain at the muscular palpation sites was assessed by the Pericranial Muscle Tenderness Score (PTS) and the Cervical Muscle Tenderness Score (CTS). The TENS therapy lasted for 10 weeks, and data were collected at baseline, after 5, 10, 15 and 25 weeks. The differences between groups before and after treatment were compared with the Mann-Whitney and the Kolmogorov-Smirnov tests. The intra-group differences were compared with the one-way ANOVA test. RESULTS: The results showed that the VAS MEAN, VAS MAX, PTS and CTS were significantly reduced in the TENS group compared to the control group after 10 weeks of TENS (p < 0.05). The intra-group analysis revealed a decreasing tendency of VAS MEAN, VAS MAX, VAS NOW, PTS and CTS in the TENS group in a 25-week period (p < 0.05). CONCLUSIONS: The study demonstrated the efficacy of conventional TENS in patients with chronic facial myalgia and the decrease in both subjective and objective pain. CLINICAL RELEVANCE: Conventional TENS is a safe, non-invasive, easy-to-administer therapy for chronic facial myalgia.

Sleep bruxism in adolescents: a systematic literature review of related risk factors.

BACKGROUND: Multiple risk factors have been associated to sleep bruxism (SB). Nevertheless, there are still many unsolved issues concerning the etiology of SB that have consequences on the clinical management strategies. OBJECTIVE: Systematically review the literature to assess the relationship between risk factors and SB symptoms in adolescents (age 11-19 years). SEARCH METHODS AND SELECTION CRITERIA: PubMed, Embase, Scopus, Cochrane Oral Health Group's Trial Register and Cochrane Register of Controlled Trials, Web of Science, LILACs, and SciELO were searched to identify all peer-reviewed articles potentially relevant to the review. DATA COLLECTION AND ANALYSIS: The risk of bias was assessed according to the guidelines from the Cochrane handbook for systematic reviews of interventions, with reporting in agreement to the preferred reporting items for systematic reviews and meta-analyses guidelines. RESULTS: Four out of the 4546 initially identified articles were selected. According to the grading of recommendations assessment, development and evaluation assessment (GRADE), the magnitude of agreement was almost perfect for all checklist items. Sleep disturbances, and snoring in particular, headache, jaw muscle fatigue, and tooth wear seem to be associated to SB in adolescents from 11 to 19 years old. LIMITATIONS: Despite the large interest of the scientific community in the field of oral parafunctions, only four articles met the eligibility criteria. Furthermore only associations and not definite cause-effect relationships were highlighted in the selected articles. CONCLUSIONS: Sleep disturbances presented the strongest association with SB while very few occlusal features had a moderate association. As a common sense the investigation of sleep respiratory disorders could be of great help in the management of SB in adolescents.

Diagnostic accuracy and measurement sensitivity of digital models for orthodontic purposes: A systematic review.

INTRODUCTION: Our objective was to assess the accuracy, validity, and reliability of measurements obtained from virtual dental study models compared with those obtained from plaster models. METHODS: PubMed, PubMed Central, National Library of Medicine Medline, Embase, Cochrane Central Register of Controlled Clinical trials, Web of Knowledge, Scopus, Google Scholar, and LILACs were searched from January 2000 to November 2014. A grading system described by the Swedish Council on Technology Assessment in Health Care and the Cochrane tool for risk of bias assessment were used to rate the methodologic quality of the articles. RESULTS: Thirty-five relevant articles were selected. The methodologic quality was high. No significant differences were observed for most of the studies in all the measured parameters, with the exception of the American Board of Orthodontics Objective Grading System. CONCLUSIONS: Digital models are as reliable as traditional plaster models, with high accuracy, reliability, and reproducibility. Landmark identification, rather than the measuring device or the software, appears to be the greatest limitation. Furthermore, with their advantages in terms of cost, time, and space required, digital models could be considered the new gold standard in current practice.

Laypeople's perceptions of frontal smile esthetics: A systematic review.

INTRODUCTION: The emphasis on dental esthetics has increased in recent years. There are, however, differences in esthetic perceptions among professional and lay groups. The aim of this comprehensive review was to update previous reviews and answer the following research question: Can lay thresholds for acceptance of smile esthetic anomalies be defined? METHODS: A systematic search in the medical literature (PubMed, PMC, NLM, Embase, Cochrane Central Register of Controlled Clinical trials, Web of Knowledge, Scopus, Google Scholar, and LILACs) was performed to identify all peer-reviewed articles reporting data regarding evaluations of laypeople's perceptions of dental esthetic factors. RESULTS: Of the 6032 analyzed articles, 66 studies were selected for the final review process. Among the selected articles investigated perceptions of diastema, 15 analyzed modifications in tooth size and shape, 8 considered incisor positions, 15 evaluated midline discrepancies, 16 investigated buccal corridors, 26 analyzed gingival display and design, 3 considered lip height, and 20 investigated miscellaneous factors. Threshold values were identified for the following features: diastema (0-2 mm), tooth size and shape of incisor position, midline discrepancy (0-3 mm), buccal corridors (5-16 mm), gingival exposure (1.5-4 mm), occlusal canting (0°-4°), and overbite (2-5 mm). Furthermore, few other smile characteristics were found to be significantly associated with perception of smile aesthetics, even though any threshold could be detected. CONCLUSIONS: On the basis of the obtained results, threshold values for the main features of smile and dental esthetics could be identified. Limitations of the present study were the heterogeneity of data which made it impossible to perform a meta-analysis, and the lack of information about sample selection and selective outcome reporting.

Periodontal health during clear aligners treatment: a systematic review.

BACKGROUND: Clear aligner treatment (CAT) has been cited as a safe and comfortable orthodontic procedure for adult patients. However, the available evidence is scarce. OBJECTIVE: To perform a systematic review of the existing literature in order to assess periodontal health during CAT. SEARCH METHODS AND SELECTION CRITERIA: Pubmed, Pubmed Central, National Library of Medicine's Medline, Embase, Cochrane Central Register of Controlled Clinical trials, Web of Knowledge, Scopus, Google Scholar, and LILACS were searched from January 1945 to September 2014 to identify all peer-reviewed papers potentially relevant to the review. DATA COLLECTION AND ANALYSIS: After duplicate selection and extraction procedures, the risk of bias was assessed according to the Centre for Reviews and Dissemination criteria, and a 3-point grading system, as described by the Swedish Council on Technology Assessment in Health Care (SBU), was used to rate the methodological quality of the selected papers. A PICOS table was used for data extraction. RESULTS: Five relevant articles were selected from the 1247 identified articles. The level of evidence was moderate for all the studies. A significant improvement of the periodontal health indexes was revealed, in particular when CAT was compared to fixed appliances. No periodontal CAT adverse effects were observed in the selected studies. CONCLUSIONS: Periodontal health indexes were significantly improved during CAT. The results of this review should be interpreted with some caution because of the number, quality, and heterogeneity of the included studies.

Psycho-Neurological Status in Children with Malocclusions and Muscle Pressure Habits.

Non-nutritive sucking behaviors such as finger- and tongue-sucking, tongue thrust, lips- or cheek-sucking, nail-, lip- or tongue-biting and other pressure habits represent risk factors for malocclusion. The association between psycho-neurological disorders and different types of malocclusion in children with sucking habits was long studied. During neurological examination, many children with sucking habits are diagnosed as Minimal Cerebral Dysfunction or Attention Deficit Hyperactivity Disorder (ADHD) bearers. The aim of this study is to assess the psycho-neurological status and motor disorders in children with malocclusion and normal occlusion. 135 children, aged between 8 and 12 years old, were examined, 42 children with normal occlusion and 93 children with different types of malocclusion. Besides clinical examination, all children were studied by the following psychoneurological methods: 1) Parent's Questionnaire, 2) Diagnostic interview Kiddie-Sads 3) Physical and Neurological Exam for Subtle Signs and 4) stabilometric tests. This study shows as in presence of dentofacial anomalies, pressure habits, ADHD reports significant effects on the functional state of the motor system: increases are noted in all basic parameters of statokinesiograms (crossed distance, sway area and ellipse surface), which lead to increased physiologic energy costs to maintain the vertical position of the body.

Reliability of a portable device for the detection of sleep bruxism.

OBJECTIVES: The aim of the study was to assess the repeatability in detecting sleep bruxism (SB) episodes by combined surface electromyography and heart rate (HR) signals recorded by a compact portable device (Bruxoff®). SB episodes are preceded by a sudden HR change. Thus, HR detection increases the precision of automatic detection of SB. MATERIALS AND METHODS: Ten healthy subjects (five women and five men; 30.2 ± 11.02 years) were selected for the study. Rhythmic masseter muscle activities, constituting the basic pattern of SB, were detected during three nights of recording during three different weeks with the Bruxoff device. RESULTS: The two-way ANOVA was not significant for SB episodes per night, SB episodes per hour, and heart frequency: no significant differences were observed during the three different nights of recording for each of the abovementioned variables (P > 0.05). The intraclass correlation coefficient showed a good reproducibility for SB episodes per night (69 %), SB per hour (74 %), and heart frequency (82 %). A poor reproducibility was revealed for the number of masseter contractions (53 %). The Pearson analysis showed the absence of a significant correlation between the number of masseter contractions per night and the number of SB episodes per night (r = -0.02, P = 0.91). CONCLUSIONS: The Bruxoff device showed a good reproducibility of measurements of sleep bruxism episodes over time. CLINICAL RELEVANCE: These findings are important in the light of the need for simple and reliable portable devices for the diagnosis of SB both in the clinical and research settings.

Effectiveness of a fixed anterior bite plane in Class II deep-bite patients.

Orthodontic treatment of patients with distoclusion combined with dental deep bite and linguo version of the front upper teeth is one of the most difficult forms of malocclusion to treat to a functional and morphological optimum. Our objective was to analyze the efficacy of a fixed anterior bite plane appliance to disclude the teeth and correct this type of malocclusion. At the Department of Orthodontics MSUMD (Moscow State University of Medicine and Dentistry), we proposed the use of a fixed anterior bite plane for the effective treatment of patients with distoclusion combined to a dental deep bite. This appliance was used in 35 patients aged 11 to 15 years (13.2 +/- 1.2) with distoclusion combined with deep bite in a therapeutical approach that also involved an osteopathic correction. The appliance permitted the correction of the distoclusion by discluding the posterior teeth, allowing eruption of the molars and premolars which improved the occlusal plane line (Curve of Spee) and changed the inclination of the upper incisors which liberated the mandible from its retruded position. We also noted an effect on the postural status of the patient.

Short-Term Effects of 3D-Printed Occlusal Splints and Conventional Splints on Sleep Bruxism Activity: EMG-ECG Night Recordings of a Sample of Young Adults.

(1) Background: This study aims to compare the effects of 3D-printed splints and conventional manufactured splints on sleep bruxism (SB) EMG activity. (2) Methods: Twenty-six patients (19 M, 7 F, 25.8 ± 2.6 years) were randomly allocated to a study group (3D splints) and a control group (conventional manufactured splints) and followed for a period of three months with night EMG-ECG recordings. Samples of the involved materials were analyzed for nanoindentation. The outcomes of interest considered were the overall SB index, the total amount of surface masseter muscle activity (sMMA), and general and SB-related phasic and tonic contractions. A statistical evaluation was performed with a confidence interval (CI) between 2.5% and 97.5%. (3) Results: Differences between groups with OAs were observed for general tonic contraction (p = 0.0009), while differences between recording times were observed for general phasic contractions (p = 0.002) and general tonic contractions (p = 0.00001). Differences between recording times were observed for the total amount of sMMA (p = 0.01), for general phasic contractions (p = 0.0001), and for general tonic contractions (p = 0.000009) during night recordings without OAs. (4) Conclusions: Three-dimensional splints seem to have a higher impact on SB-related electromyographic activity but not on the overall sleep bruxism index. The more regular surfaces offered by 3D splints could be related to phasic contraction stabilization.

Impacted Permanent Mandibular Canines: Epidemiological Evaluation.

BACKGROUND: The aim of this study was to evaluate the epidemiology of impacted and transmigrated mandibular canines in a large orthodontic population referred to the University of Turin. METHODS: Panoramic radiographs, intraoral photographs, and dental casts of 2119 patients referred to the Department of Orthodontics at the University of Turin, Italy, between 1995 and 2022 were reviewed. These patients were divided into two groups. Group A included 1479 patients found in the Dental School archive before 2017, more specifically between 1995 and 2017. These patients were examined in order to calculate the prevalence of impacted and transmigrated mandibular canines. From 2017 to 2022, the records of 640 new patients were examined (GROUP B) in order to calculate the incidence of these occurrences. RESULTS: The prevalence of mandibular canine impaction in Group A was found to be 1.7%, with a total of 25 patients having mandibular canine impaction. A prevalence of 0.3% was found for mandibular canine transmigration (Group A). The incidence of mandibular canine impaction was found to be 2%, with a total of 13 patients with mandibular canine impaction (Group B). Mandibular canine transmigration was found in 1 of 640 participants (Group B). CONCLUSIONS: Twenty-five of 1479 patients had impacted mandibular canines, resulting in a prevalence value of 1.7%. The incidence was found to be 2%, with 13 of 640 patients having impacted mandibular canines. These results show higher prevalence and incidence rates of mandibular canine impaction when compared with previously published data.

Comparison of two electric toothbrushes: evaluation on orthodontic patients.

BACKGROUND: The effectiveness of different types of electric toothbrushes in terms of removing bacterial plaque is still a debated issue. The aim of the study was to compare the plaque removal after a single use of two types of electric toothbrushes, sonic and roto-oscillating, in patients with fixed orthodontics. METHODS: Twenty-five subjects with fixed multibrackets appliances were randomly selected. Plaque scores were detected using a fluorescein-based detector. After using the sonic toothbrush with a surfactant-free toothpaste, the plaque scores were detected again. After 3 months, the procedure is performed again following the same methods, using the roto-oscillating toothbrush. For the statistical analysis a Student's t-test using Microsoft Excel 2021 (Microsoft Corp., Redmond, WA, USA) was performed. The differences were considered statistically significant for probability values P<0.05. RESULTS: It can be seen that the brushing carried out with a sonic technology is more effective than the roto-oscillating technology. However, the FMPS, MOPI and OPI indexes do not show differences between the use of the two toothbrushes. The OHI-S index shows a statistically significant difference using the sonic toothbrush with a significance level of 0.05%. CONCLUSIONS: It can be said that both electric toothbrushes are effective for maintaining a good home oral hygiene in patients with fixed orthodontics.

Predictability of orthodontic tooth movement with aligners: effect of treatment design.

BACKGROUNDS: The present study was designed to define: (1) which are the less predictable OTM with Invisalign aligners when the treatment plan is designed by expert operators, (2) if the presence and shape of attachments influence the predictability of OTM and (3) if patients' demographics influence OTM predictability. The sample comprises 79 prospectively recruited patients (mean age 30.8 years; SD 12.0; 23 M, 56 F), treated by expert operators with an average of 27 aligners (SD 15) in the maxillary arch and 25 aligners (SD 11) in the mandibular arch. Post-treatment digital models and final virtual treatment plan models were exported from ClinCheck® software as STL files and subsequently imported into Geomagic Qualify ®software, to compare final teeth positions. The differences were calculated and tested for statistical significance for each tooth in the mesial-distal, vestibular-lingual and occlusal-gingival directions, as well as for angulation, inclination and rotation. In addition, the statistical significance of categorical variables was tested. RESULTS: The lack of correction was significant for all movements and in all group of teeth (P < 0.01) except for the rotation of maxillary first molar. The prescribed OTM, the group of teeth and movement, the frequency of aligner change and the use of attachment influence the outcome. The greatest discrepancies in predicted and achieved tooth position were found for angular movements and rotation of teeth characterized by round-shaped crowns, for a ratio of approximately 0.4° per 1° prescribed. Optimized attachments for upper canines and lower premolar rotation seem not working properly. Second molar movements are mostly unexpressed. Furthermore, changing the aligner every 14 days will reduce the lack of correction of the 12% with respect to 7 days aligner change. CONCLUSIONS: Predictability of orthodontic movement with aligners still has limitations related to the biomechanics of the system: the shape of some attachments and the characteristics of aligner material need to be redefined. However, the results of this study allow to properly design the virtual treatment plan, revealing how much overcorrection is needed and which attachments are most effective.

Effects on Sleep Bruxism Activity of Three Different Oral Appliances: One Year Longitudinal Cohort Study.

BACKGROUND: Different oral appliances (OAs) have been proposed to control sleep bruxism (SB) detrimental effects on the stomatognathic system. OBJECTIVE: The aim of the study was evaluate the effect of different OAs on SB activity and masticatory muscle activity (sMMA) measured by EMG. METHOD: This longitudinal cohort study was conducted on 51 patients (21 M, 30 F, mean age 26,5 ± 3,5) suffering from SB diagnosed with a validated portable EMG-ECG holter and wearing different OAs: occlusal splints, functional appliance with metallic bites and clear aligners followed after 1 week, 1 month, 3 months, 6 months and 12 months from delivery. A control group of 16 non-treated SB patients (6 M, 10 F mean age 27,1 ± 1,4) was used as reference. A multiple regression analysis was performed to estimate the differences between groups. Significance was set as P value <0,05. RESULTS: Occlusal splint reduced sleep bruxism index after 1 week, 3, 6 and 12 months from delivery while functional appliance only after 12 months. Occlusal splints reduced general phasic contractions only in the first week and sleep bruxism-related phasic contractions at 1 week, 3 and 6 months after delivery with no significant reductions after 12 months. Patients wearing clear aligners showed reduction in general tonic contractions after 6 and 12 months. CONCLUSION: Resin and metal bites can reduce sleep bruxism index, while resin bites can reduce sleep bruxism-related phasic contractions. Clear aligners do not influence sleep bruxism index but can reduce tonic contractions.

Variations in athletic performance with occlusal splint in track and field athletes: a randomized clinical trial.

BACKGROUND: Several studies have been proposed with the aim to demonstrate correlations between the dento-mandibular apparatus and the skeletal muscle system of the human body even in regions distant from the oral cavity. However, a definite conclusion cannot be drawn. The aim of this paper is to demonstrate a possible correlation between dental occlusion and sport performances in track and field athletes. METHODS: Sixteen track and field athletes were enrolled for the study and were randomly divided in three groups: Untreated control group, Placebo group (with a lower plaque without occlusal coverage) and Treated group (with occlusal splint). Changes in sprint and jump performance were assessed on a weekly basis for 5 consecutive weeks, during which athletes had to wear oral devices, except for the first week of baseline, for at least 3 trainings lasting 2 hours per week . All participants performed the countermovement jump (CMJ), the drop jump (DJ), the 10m and 30m sprint tests, always on the same day on the week. RESULTS: No statistically significant difference resulted between Control group and Placebo group and between Control group and Treated group. However, it was possible to observe a clinical improvement of measurements obtained, especially for CMJ, 10m and 30m sprint tests. No variation neither statistical neither clinical was observed in DJ test analysis. CONCLUSIONS: Even if statistically it was not possible to demonstrate an improvement in sport performance, most of the athlete analyzed showed better results during training session with occlusal splint compared to athlete without occlusal splint, in countermovement jump, in 10m and 30m sprint tests.

Are occlusal splints effective in reducing myofascial pain in patients with muscle-related temporomandibular disorders? A randomized-controlled trial.

OBJECTIVES: This study aims to evaluate the effectiveness of upper Michigan occlusal splint (OS) compared to mandibular OS in terms of pain, range of motion (ROM), and muscle activity as assessed by surface electromyography (sEMG) in patients affected by muscle-related temporomandibular disorders (TMD). PATIENTS AND METHODS: In this randomized-controlled trial, a total of 40 adult patients (13 males, 27 females; mean age: 47.2±12.8 years; range, 22 to 56 years) with a diagnosis of myofascial pain, lasting from at least three months on at least one masseter muscle. The patients were randomly allocated into two groups: Group 1 (n=20) using upper Michigan OS and Group 2 (n=20) using mandibular OS. At baseline (T0), at one (T1), three (T2), and six months (T3), the following outcomes were assessed: myofascial pain by Visual Analog Scale (VAS) and ROM of mandible movements, activity of the main masticatory muscles through sEMG. RESULTS: There were no significant intra-group differences in the outcome measures assessed in both groups. However, Group 2 had a significantly higher right lateral mandibular ROM at T2 (7.1±3.1 vs. 9.8±2.3, respectively; p<0.05) and a significantly higher left lateral mandibular ROM at T3 (7.6±3.5 vs. 10.5±2.1, respectively; p<0.05). We found no significant difference in none of the sEMG parameters. CONCLUSION: Our study results suggest that OS, independently from being built on the upper or lower arch, seems to not have significant effects in reducing pain over a six-month period in TMD patients.

Micro computed tomography evaluation of Invisalign aligner thickness homogeneity.

OBJECTIVES: To measure the thickness homogeneity of Invisalign (Align Technology Inc, San José, Calif) aligners with micro-computed tomography (micro-CT) scans. MATERIALS AND METHODS: Starting from micro-CT scanning of 20 different aligners, multiplanar reconstructions were obtained. An orthodontist blinded about the study measured aligner thickness in different regions (molar, canine, incisor) and in different sites (gingival-buccal, buccal, occlusal, lingual, and gingival-lingual). To assess various thicknesses in different aligner sites and regions, the sample was stratified into subgroups and linear regression analysis was performed. RESULTS: Descriptive analysis showed that mean thickness of aligners in the incisor region ranged from 0.582 mm to 0.639 mm, in the canine region from 0.569 mm to 0.644 mm, and in the molar region from 0.566 mm to 0.634 mm. Student's t-tests showed no significant differences in the aligner thickness of different regions when data were stratified by different sites. Student's t-tests showed significant differences in thickness homogeneity for the molar region when the data were stratified by tooth (mean difference = 0.068 mm; 95% confidence interval, 0.009-0.126 mm; P = .024). CONCLUSIONS: Invisalign aligner thickness is characterized by small differences. The only significant difference was revealed in the molar region where thickness of the gingival-lingual edge is significantly thinner than that measured at the occlusal aspect. From a clinical perspective, the results of the present study could be considered to explain the reduced predictability of several orthodontic tooth movements in the molar region.