In subjects with facial asymmetry, it is generally accepted that the maxillary frontal occlusal plane inclines toward the deviated side of the mandible. However, a few patients with facial asymmetry have their frontal occlusal planes inclined toward the contralateral side of the mandibular deviation. The aim of this study was to elucidate the morphological features of the subjects with mandibular deviation with the frontal occlusal planes inclined toward the contralateral side.
The sample consisted of 40 patients whose Menton was deviated at least 2.0 mm from the facial midline. They were divided into two groups based on the relationship between the side of inclination of the frontal occlusal plane and the side of the mandibular deviation. Group IL consisted of 20 patients whose frontal occlusal plane inclined to the ipsilateral side of the mandibular deviation, while Group CL consisted of 20 patients whose frontal occlusal plane inclined to the contralateral side of the mandibular deviation. Then, we compared the two groups using 1) lateral cephalometric analysis, 2) P-A cephalometric analysis, 3) frontal soft tissue analysis and 4) dental casts analysis.
The following findings were obtained:
1. In Group CL patients, not only the frontal occlusal plane defined by bilateral molar positions, but also the maxilla itself significantly inclined toward the contralateral side of the mandibular deviation.
2. In Group CL patients, the maxillary dental midline was significantly deviated toward the contralateral side of the mandibular deviation.
3. The difference in bilateral mandibular ramus lengths was significantly smaller in Group CL patients.
4. In Group CL patients, the mandibular molar compensation for the mandibular lateral deviation was significantly less than that in Group IL patients.
5. In Group CL patients, both the midline and cant of the upper lip were significantly deviated toward the contralateral side of the mandibular deviation.
6. The incidence of missing or buccolingual version of maxillary premolar teeth was significantly higher in Group CL patients.