Three-dimensional evaluation of musculoskeletal in Class II and Class III patients

To evaluate and compare dimensional morphology of masseter and medial pterygoid muscles and mandibular skeletal parameters between subjects with skeletal Class II and Class III.

The sample consisted of 13 patients with skeletal Class II and 10 patients with skeletal Class III prior to the start of combined orthodontic treatment and orthognathic surgery with correspondence to definite inclusion and exclusion criteria. Magnetic resonance imaging was performed for mandibular muscles and following 2D and 3D measurements were done: cross-sectional area (CSA), thickness, width, longitudinal dimension and volume. 3D multi-slice computed tomography investigation was performed for the assessment of skeletal mandibular parametres and following measurements were done: height of mandibular ramus, length af mandibular corpus, overall mandibular length, intergonial width. All the measurements were done bilaterally. Data were analyzed using descriptive statistics, t-test, and correlation coefficients.

It was found that values of all mandibular and medial pterygoid measurements were higher in Class III subjects with statistical significance (p<0.05). There was a tendency of all masseter variables to be higher in Class III patients. Positive correlations were found between muscles' volume and CSA in both groups, muscles' volume and all mandibular parameters in Class II group, CSAs and all mandibular variables except intergonial width in Class II group. Overall symmetry was observed between left and right sides in all muscular and mandibular measurements in both groups.

The data were acquired using two different imaging techniques - MRI and MSCT that can be mentioned as a novelty in this field of research. Remarkable differences were observed between study groups for both skeletal and muscular measurements.