Preliminary investigation to the mechanism of anterior occlusal plane canting in orthodontic treatment

Objective To explore the mechanism of anterior occlusal plane canting (AOPC)during orthodontic treatment. Methods 37 patients presented with AOPC after orthodontic alignment were selected as study group, another 31 patients who showed no AOPC after orthodontic treatment and received no AOPC correction during orthodontic treatment were selected as control group. The incidence of pre-treatment AOPC, symmetricity of dentition and treatment planning were investigated. Results ① 59.5% of the patients in study group and 12.9% in control group showed primary AOPC before treatment, the difference is significant with chi-square test (P<0.05). ② 48.4% of the patients in control group, 63.7% in primary AOPC group and 60% in secondary AOPC group showed dentition asymmetry before orthodontic treatment, but the difference between groups is not significant by chi-square test (P<0.05). ③ Taking the symmetricity of both the dentition and treatment planning into consideration, 19.4% of the patients in control group, 45.5% in primary AOPC group and 86.7% in secondary AOPC group showed non-conducive treatment planning to dental arch symmetry correction, the difference between groups is significant by chi-square test (P<0.05). Conclusions AOPC before treatment and non-conducive treatment planning to dental arch symmetry, but not dentition asymmetry itself contribute to AOPC during orthodontic treatment. Significant difference between left side and right side saggital and vertical anchorage might be related to the occurrence of AOPC during orthodontic treatment. Key words: Anterior occlusal plane canting; Mechanism; Dentition asymmetry; Treatment planning