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

Myobrace versus twin block in the treatment of class II malocclusion in Children: A systematic review

Background

One of today's largest global problems is malocclusion. We must prevent this through the screening and early treatment of young children, because malocclusion treatment conducted during a child's growth and development stage either the primary or mixed dentition era yields the best outcomes. Functional appliances are usually used during initial orthodontic treatment, such as myobrace and twin block appliances. Myobraces come in various sizes. The size chosen depends on the treatment objectives, which may include correcting class II malocclusions. The twin block appliance is a functional device commonly employed to treat class II malocclusions.

Purpose

This investigation's main goal was to compare the efficacy of the myobrace and twin block appliances in class II malocclusion treatment to select a more appropriate pediatric dentistry device.

Results

A total of 5 articles were selected from 306 articles based on relevant keywords. All selected studies were conducted within the last 10 years.

Discussion

Myobrace and twin block appliances can address overjet issues and achieve significant overjet measurement reductions. This appliance promotes mandibular growth and enhances the facial profiles of individuals with class II malocclusions.

Conclusion

In order to treat individuals with class II malocclusions, the myobrace and the twin block both address skeletal and dentoalveolar discrepancies. But compared to the myobrace, the twin block appliance had more noteworthy outcomes.

Evaluation of mandibular motion in adolescents with skeletal class II division 1 malocclusion during mandibular advancement using clear functional aligners: a prospective study

BACKGROUND

This study aimed to evaluate the characteristics of mandibular protrusive condylar trajectory in adolescents with skeletal Class II Division 1 malocclusion and the changes of condylar trajectory during mandibular advancement (MA) treatment using clear functional aligners.

METHODS

This prospective study consisted of a cross-sectional study and a longitudinal study. In cross-sectional study, sixty-one adolescents were divided into two groups: Class I (n = 30) and Class II Division 1 (n = 31). The condylar trajectory was measured and compared using the Mann-Whitney U test. The longitudinal study was the MA treatment group using clear functional aligner and consisted of 16 participants from Class II Division 1group. The condylar trajectory was collected at three-time points: pre-treatment (T1), during MA treatment at approximately 3 months (T2, 105.6 days average), and at the end of MA treatment (T3, 237.6 days average). The changes at T1, T2, and T3, as well as the symmetry between the left and right condyles across all groups, were examined using the Wilcoxon paired test.

RESULTS

A greater increase in the anteroposterior displacement and space displacement during protrusive movements was observed in the Class II Division 1 group compared with that in the Class I group, with a large difference being observed in the left and right condylar movements. The condylar anteroposterior displacement and space displacement decreased significantly at T2 and increased significantly at T3; however, no significant difference was observed between T1 and T3. A significant difference was observed between the condylar movement on the left and right sides at T1; however, no significant difference was observed at T2 and T3.

CONCLUSIONS

Adolescents with Class II Division 1 malocclusion had higher protrusive capacity than those with Class I. Moreover, their left and right condylar motion was more asymmetric. The range of condyle motion decreased first and then increased during MA therapy, and the left and right condyle movement became more symmetrical, which may be the adaptive response of neuromuscular function to the changes in jaw position.

Association of masseter muscles thickness and facial morphology with facial expressions in children

OBJECTIVE

To evaluate the potential influence of muscular capacity and facial morphology on facial expressions in children.

MATERIALS AND METHODS

A cross-sectional study was carried out on 40 healthy children (ages 9-13), without previous orthodontic treatment. Masseter muscle thickness and anthropometric facial proportions were measured using ultrasound and digital calipers respectively. A three-dimensional infrared face-tracking system was used to register facial expressions. The maximal amplitude of smile and lip pucker (representing maximal lateral and medial commissure movement) were used for analysis. Stepwise regression was used to investigate whether muscle thickness or anthropometric facial proportions were associated with the quantity of commissure movement.

RESULTS

When performing maximal smile, children with thicker masseter muscles were found to have more limited displacement of the commissures (R = 0.39; p = 0.036). When performing lip pucker, children with thicker masseter muscles were found to have greater commissure movement (R = 0.40; p = 0.030). No significant associations were found between anthropometric facial proportions and facial expressions.

CONCLUSION

Masseter muscle thickness seems to be associated with facial expressions in children. Those with thicker muscles show more limited commissure movement when smiling, but greater movement with lip pucker. This indicates that masticatory muscles may serve as a surrogate for mimic muscle activity. Facial morphology of the subjects does not seem to be associated with facial expression.