Evaluation of temporomandibular joint, masticatory muscle, and brain cortex activity in patients treated by removable functional appliances: a prospective fMRI study

OBJECTIVES

The aim of this study is to evaluate the effects of functional orthodontic appliances on the masticatory muscles, temporomandibular joint (TMJ), and brain to determine whether using functional appliances full-time or only at night yields different results.

METHODS

16 patients with Class II malocclusion were included in this study. Eight patients were instructed to wear their appliances (monoblock/twinblock) full-time and the other eight patients were instructed to wear them at night while sleeping. An additional 10 patients with Class II malocclusion were later included as a pre-treatment control group. Signal intensity ratios (SIR) of TMJ structures and morphological evaluations of the masticatory muscles were done for all patients. Functional MRI (fMRI) data were also obtained from the patients while performing chewing and biting movements.

RESULTS

ANB angle was reduced significantly in both the full-time and night wear groups, by values of 1.17° and 1.35°, respectively (p < 0.05). MRI showed that SIRs were significantly increased in both groups in the masticatory muscles, retrodiscal pad, condylar process, and articular disc (p < 0.05). Both resting and task-based fMRI evaluation revealed significant increases in blood oxygen level dependent signals in several regions of the brain in both groups (p < 0.05).

CONCLUSIONS

The cephalometric and MRI findings of this study indicate that the treatment effects were similar for both wear schedules. Functional appliances should be regarded not as simple devices that treat Class II malocclusion through skeletal and dental correction alone, but as exercise devices that lead to neuromuscular changes by facilitating muscle adaptation and activating various brain regions.

Class II functional appliance treatment and dynamic three-dimensional mimic muscle evaluation

BACKGROUND

Functional appliances have skeletal and dentoalveolar treatment effects, but knowledge on their effect on facial expressions is limited.

OBJECTIVE

To analyse changes in facial expressions, using three-dimensional (3D) mimic muscle evaluation, in growing children with Class II malocclusion and large overjet, undergoing functional appliance treatment.

METHODS

Fifteen growing children with Class II division 1 malocclusion, selected prospectively, had dynamic 3D recordings of facial expressions prior to and 12 months after commencing functional appliance treatment. Facial expressions recorded were smile and lip pucker, and the movements of the oral commissures were analysed, as well as mouth width and its symmetry. A control group of fifteen age- and sex-matched growing children without immediate need for orthodontic treatment had similar recordings prior to and after a 12-month observation period.

RESULTS

In the treatment group, the Class II malocclusion in all children improved after 12 months of functional appliance wear. With regard to movements of the oral commissures, the initial recordings of the treatment group did not show any significant differences to the control group for neither smile nor lip pucker. Differences were noted however when looking at mouth width asymmetry, where this tended to become more symmetrical in the functional appliance treatment group, during rest and during smiling, while it became more asymmetrical in the untreated control group.

CONCLUSION

The use of removable functional appliances in children with Class II division 1 malocclusion may have a positive effect on mouth width symmetry when smiling, making it more symmetrical.

A finite element study comparing Advansync® and Twin Block in mandibular anterior repositioning

OBJECTIVE

This study aims to utilize the finite element method (FEM) to compare the dentoalveolar and mandibular effects associated with anterior mandibular repositioning using AdvanSync® (ADV) and Twin Block (TB).

METHODS

A patient with Class II skeletal malocclusion and mandibular retrognathism was selected. A TB appliance was subsequently applied. Computed Tomography (CT) scans were acquired at the beginning of treatment (T1) and 8 months later (T2). Concurrently, a numerical TB model was validated through FEM simulations, which were compared with the T2 results. The ADV appliance was virtually simulated to evaluate stress and deformation on the condyle, symphysis, first lower molar and lower central incisors.

RESULTS

Both simulations demonstrated significant mandibular advancement. However, ADV led to less incisor proclination and more molar intrusion compared to TB. ADV exhibited increased stress in the lower molar area, while TB had higher stress in the lower incisor region. Stress and deformations in the condyle and mandibular symphysis were similar in both simulations, with the highest stress observed at the condylar neck and the lowest at the upper pole of the condylar head.

CONCLUSIONS

Both appliances achieved similar levels of mandibular advancement, with greater proclination of the lower central incisors and more widespread distribution of stress and molar intrusion when using ADV compared to TB.

A Comparative Analysis of Treatment Effects of PowerScope and AdvanSync2 in Class II Division 1 Malocclusion: A Retrospective Study

INTRODUCTION

Fixed functional appliances are widely used for the treatment of retrognathic mandibles in skeletal class II malocclusion. The primary objective of the present investigation was to evaluate and compare the treatment effects induced by PowerScope (American Orthodontics, Sheboygan, WI) and AdvanSync2 (Ormco, Orange, CA). The hypothesis posited that there were no notable disparities in the therapeutic impacts of the two appliances.

MATERIALS AND METHODS

A retrospective study was undertaken involving 90 subjects with retrognathic mandibles. Group 1 was treated with AdvanSync2, group 2 received PowerScope treatment, and group 3 consisted of an untreated class II control sample. Lateral cephalograms were traced at pre-treatment (T0) and post-treatment (T1), to measure various skeletal, dental, and soft tissue parameters. The comparison between the groups was done using analysis of variance (ANOVA) and post-hoc analysis by Tukey's test.

RESULTS

Significant changes were observed in all the parameters, comparing the effects of both appliances to the control group (p < 0.05). AdvanSync2 displayed statistically significant skeletal effects on the maxilla and mandible (p < 0.05). The statistically significant differences were also seen for dental effects such as reduction in overbite and overjet. On the other hand, PowerScope exhibited effects that were not considered statistically significant on the maxilla, instead primarily manifesting dento-alveolar changes that led to a considerable reduction in overbite. In comparison to the control group, both appliances notably produced soft tissue changes.

CONCLUSIONS

Our study rejected the null hypothesis. AdvanSync2 yielded superior skeletal outcomes with greater mandibular advancement, compared to PowerScope, which exhibited enhanced dento-alveolar alterations. AdvanSync2 took less treatment time, compared to PowerScope.

[Early orthodontic/orthopedic treatment in patients with class II sagittal anomalies. A review]

Introduction

Class II sagittal anomalies have a prevalence of between 18-32% of the population. To resolve this type of malocclusion, various therapies have been proposed, some of which involve functional orthodontic or orthopedic appliances. However, it is still a matter of discussion whether the treatments should be started at an early age in patients, or if there are adverse effects that could harm structures of the stomatognathic system.

Objective

To analyze the results obtained from early treatment in patients with Class II sagittal malocclusion through a literature review.

Materials and methods

An advanced search with terms and connectors was carried out in the Medline via Pubmed and Science Direct databases. Inclusion and exclusion criteria were applied for the definitive selection.

Results

Through this search, a total of 5909 articles were collected, of which 23 were considered to meet the criteria established in this review work.

Conclusions

There are orthodontic/orthopedic devices aimed at solving the characteristics of class II sagittal malocclusions, but before planning early treatment it is essential to provide an accurate diagnosis to evaluate the specific type of appliance that is required.

Facial soft tissue changes in adolescent patients treated with three different functional appliances: a randomized clinical trial

INTRODUCTION

Patients with Class II, division 1 malocclusion generally seek treatment to improve facial esthetics. Therefore, the orthodontist needs to know the changes in the soft profile produced by functional appliances.

OBJECTIVE

This study evaluated the soft tissue profile changes in patients treated during the peak of the pubertal growth spurt.

METHODS

Thirty selected patients were randomized into three treatment groups: Twin Block (TB), Herbst with dental anchorage (HDA), and Herbst with skeletal anchorage (HSA). All patients had computed tomographic images: pretreatment (T1) and after 12 months of active treatment (T2). Twenty-four soft tissue cephalometric measures were analyzed. The normality of all data was assessed by the Shapiro-Wilk test. Intragroup comparisons were analyzed using the t-paired test; the inter-group comparisons were determined through ANOVA and the post-hoc Tukey test.

RESULTS

At T1, no significant differences were observed between groups. At T2, in the intragroup comparison, facial soft tissue changes were statistically significant in the three groups for the lower lip, sulcus inferioris, facial soft tissue convexity in HDA group and TB group, and H angle in HDA group and HSA group, and soft tissue pogonium in TB group. In the inter-group comparison, no statistically significant differences were observed.

CONCLUSION

It can be concluded that there were significant changes in soft tissue measurements that benefited Class II, division 1 patient's facial profile treated with the functional appliances Twin Block, Herbst, and Herbst with skeletal anchorage. Nevertheless, no significant differences were detected among the effects obtained by the three treatment protocols.