Differences in volume and surface of mandibular condyles among adult patients with skeletal classes I, II, and III

Object: The aim of this study was to evaluate the condylar volumes among a group of 14 to 20 year old pre-orthodontic asymptomatic patients with different skeletal classes. The designation of the volumetric value of a solid has recently become important because it can define by a single number the shape and the surface of an object. By means of a 3D segmental reconstruction, we have been able to define the volumetric value of the facial structure while taking in account its structural cavities, including the nasal cavity, the oral cavity, and the maxillary sinus. Materials and Methods: 60 young adult Caucasian patients scheduled to receive orthodontic treatments due to overcrowded teeth were included in this study. In order to be included patients had to be free of TMD symptoms, tooth agenesis, presence of posterior occlusal stop. They had not to be submitted to ortognathic surgery, and were not extreme brachycephalics and dolichocephalic.. All patients were examined with a Cone Beam (Iluma). The cephalometric analysis was performed with Dolphin 3D using Dicom files acquired through CBCT. The calculation of the condylar volume and of the condylar surface was done with Mimics software. Results: Within and among each skeletal class, we found statistically significant differences between the volumes and the surfaces of the mandibular left and right condyles. Patients with a skeletal class III showed values of the condylar volume and condylar surface significantly higher than patients belonging to the other two skeletal classes. The measurements of the condylar surface had wider ranges and higher standard deviations than the measurements of the condylar volumes. Discussions: The observed differences could be related to the different muscle tone. In support of this observation comes a study by F. Festa et al (2006) that showed how the sEMG activity of the masseter and of the anterior temporal at resting were significantly higher in skeletal class III subjects as compared to subjects in class I and II. However it is important to emphasize that both the class and the type of facial skeleton affect the volume of the condyle. In fact, in another study F. Festa et al (2006) observed how the sEMG activity of the masseter, the anterior temporal, and of the upper trapezius and posterior cervical at mandibular rest position was higher in low angle subjects as compared to high angle and normal angle subjects. This higher sEMG activity may be responable for the volume of the condyle. Conclusions: With this study we have been able to identify an association between condylar volume and skeletal class. In all groups, the measurements of the condylar surfaces presented a inter-individual variability higher than the measurements of the condylar volumes; this may be due to the existence of microscopical abnormalities (small cavities and sulci) that are able to influence the measurements of the condylar surface.but are not able to significantly influence the measurements of the condylar volume.