Jaw Growth and Development in Class II Division I Malocclusion Children Using the Myobrace® Muscle Function Appliance

Class II Division I malocclusion is common in pediatric orthodontics, and is often associated with malocclusion and poor muscle functionality. However, research on post-treatment changes in maxillomandibular dimensions, excluding normal development influences, is limited. Therefore, this study aimed to investigate the effects of Myobrace® appliance and targeted muscle functional training on maxillomandibular dimensions in children with Class II Division I malocclusion, compared to directed oral muscle training alone.

This retrospective study included 96 children with Class II Division I malocclusion. Based on the treatment method, the patients were divided into two groups: the treatment group (patients who underwent treatment with the Myobrace® muscle function appliance combined with directed muscle functional training for one year) and the control group (patients who received only directive oral muscle training for one year). The growth changes in jaws in both groups were assessed through X-ray cephalometry and plaster casting.

The Sella-Nasion to A point angle (SNA) had increased (p > 0.05), and the maxilla length increased, with significant differences between the two groups (p < 0.05). Furthermore, after intervention, there was a significant increase in mandibular length (p < 0.05). There was a slight decrease in the S-Co value indicating the position of the mandibula. However, this change was not significant, indicating that the mandibula didn't move forward after treatment. The angle between the Frankfort Horizontal Plane and mandibular planes (MP-FH) increased after treatment (p > 0.05), and there were increasing trends on the Y axis, posterior heights, and anterior heights, and these changes were statistically significant (p < 0.05). Additionally, we observed a significant increase in the dental arch (p < 0.05) in the treatment group compared to the control group. This finding suggested that the Myobrace® appliance can promote dental arch growth.

Myobrace® appliance effectively boosts dental arch growth while correcting Class II Division I malocclusion. However, it may be limited in cases of Class II Division I with high-angle, maxillary protrusion, or severe mandibular retrusion, emphasizing the significance of assessing patient characteristics to ensure optimal improvement.