[Three-dimensional assessment and study on temporomandibular joint and the maxillary characteristics of skeletal Class Ⅲ mandibular deviation patients].

PURPOSE: To study the temporomandibular joint morphology and position and the maxillary characteristics of skeletal Class Ⅲ mandibular deviation patients with vertical disproportion in bilateral gonions.

METHODS

Overall 79 adult patients with skeletal Class Ⅲ malocclusions were selected. Craniofacial spiral CT scanning was performed, and three-dimensional reconstruction of the temporomandibular joint(TMJ) was carried out by using ProPlan CMF3.0 three-dimensional analysis software. The patients were divided into two groups according to the deviation degree of the mentum: symmetric group (the S group: n=24) and deviation group (n=55). The deviation group was divided into two subgroups according to whether there was vertical disproportion in bilateral gonions, i.e., ASV group: there were vertical differences in bilateral gonions(n=27), and ASNV group: there was no vertical difference in bilateral gonions (n=28). Seven condylar morphological and position indicators and nine maxilla-related indicators were measured. SPSS 22.0 software package was used for statistical analysis.

RESULTS

In deviation group, the condylar length on the deviated side was shorter than the opposite side, the difference value between the two sides was greater than the symmetric group, and there were asymmetry and different degrees of disproportion in the three-dimensional direction in the maxilla. In ASV group, the angle of the condylar axis to the horizontal plane on the deviated side was smaller and the anteroposterior diameter of the condyle was smaller. In ASV group, the mediolateral dimension of condyle on the deviated side were smaller. From variance analysis and multiple comparisons, the difference of condylar length on both sides in ASV group and ASNV group was greater than that in the symmetric group. There were asymmetries in the maxillae in ASV group and ASNV group, and the maxillary width on the deviated side was greater than that on non-deviated side. Transverse maxillary disproportion was more likely to occur in the ASNV group. The vertical maxillary disproportion on both sides in ASV group was larger than that in ASNV group and S group, and the deviated side was smaller than the opposite side.

CONCLUSIONS

The TMJ morphology and position of skeletal Class Ⅲ mandibular deviation patients with vertical disproportion in bilateral gonions and the maxillary asymmetry in the three-dimensional direction require attention in the diagnosis and conceptual design of surgical-orthodontic treatment.