Tuesday, August 5, 2025
This study investigated the correlation between masseter muscle morphology, occlusion, and TMJ characteristics in adult patients with skeletal Class II malocclusion. Eightty-seven participants were evaluated, divided into four groups based on their skeletal Class II profile. CBCT scans were performed before and after orthodontic treatment, allowing for the assessment of masseter morphology, occlusion, and TMJ variables. Significant intergroup differences were observed in masseter morphology indexes (TMM, CSAMM) and occlusion indices (AU6, AL6, TU6, etc.), as well as TMJ variables (AJS, SJS, etc.). The masseter muscle's morphology was found to significantly influence occlusion and TMJ characteristics, affecting occlusal planes, curves, condylar position, and articular fossa morphology. These findings suggest that masseter muscle function plays a critical role in stomatognathic dysfunction and highlight the importance of CBCT-based muscle assessments in orthodontic planning. Skeletal Class II malocclusion, characterized by mandibular retrusion (70% of cases), results from factors like mandibular underdevelopment and functional issues such as steep occlusion planes. Muscle imbalances and posterior-inferior rotation can contribute to the Class II pattern, while the masseter, a primary masticatory muscle, influences occlusion force distribution. The study's findings inform myofunctional therapy in adult orthodontic care, while BTX-A injections show potential improvements in masseter thickness and molar height. The study was approved by the Clinical Research Ethics Committee, with informed consent provided to participants. All participants were informed of the study's purpose and provided written consent. The sample was divided into four groups based on ANB and MP-SN angles, and CBCT scans were performed on both before and after orthodontic treatment. All data were analyzed using One-Way ANOVA and Pearson correlation. The masseter muscle's thickness and cross-sectional area were measured and analyzed twice, with a one-week interval between measurements. The study highlights the importance of CBCT-based assessments in understanding and improving occlusion and TMJ conditions in Class II patients.
Reference: The effects of masseter muscle morphology on three-dimensional occlusion and temporomandibular joint in adult patients with skeletal class II malocclusion: a CBCT studyLabels: BMC Oral Health
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