Abstract:

BACKGROUND: Cranial base angle is related to the formation of sagittal dentoskeletal type, and the effect of occlusal plane or posterior occlusal plane on the formation of sagittal dentoskeletal type remains controversial.

OBJECTIVE: To compare the importance of occlusal plane inclination and posterior occlusal plane inclination in determining the formation of sagittal dentoskeletal type, and to explore the combined influence of the cranial base angle and posterior occlusal plane inclination on the formation of sagittal dentoskeletal type, and its correlation.

METHODS: The study was implemented in accordance with the ethical requirements of Hospital of Stomatology, Southwest Medical University. Patients and their guardians signed the informed consents. Totally 207 lateral cephalograms from patients (100 males and 107 females, aged 12-20 years) were selected. Dentoskeletal landmarks and subsequent measurements were performed and analyzed using Uceph software and SPSS 17.0 software, respectively. The samples were classified as three sagittal dentoskeletal types according to the anteroposterior dysplasia indicator (APDI) value: class I, class II, and class III. The SNK and LSD methods were used for comparison among the three groups. The Pearson correlation coefficient analysis was used to analyze the correlation between skull base angle (NSBa angle), occlusion plane (FH-OP), posterior occlusion plane (FH-POP) and other related measurement indexes. Descriptive statistical methods were used to group occlusal plane inclination, posterior occlusal plane inclination and skull base angle, and the two-sample t-test was used to compare relevant bone and tooth indexes. Four dentoskeletal groups were established according to the posterior occlusion plane inclination and skull base angle: small skull base angle-flat posterior occlusion plane group (S-F), small skull base angle-steep posterior occlusion plane group (S-S), large skull base angle-flat posterior occlusion plane group (L-F), large skull base angle-steep posterior occlusion plane group (L-S). Intergroup comparison was completed using crossover one-way analysis of variance.

RESULTS AND CONCLUSION: The skull base angle was significantly smaller in the class III group than the class I and II group. Significantly higher posterior occlusion plane inclination was observed in the class II group than the class I and III groups. No differences were found in the APDI and ANB between occlusal plane groups. Significant differences in the ANB angle and APDI value were shown on the small skull base angle-flat posterior occlusal plane group and the large skull base angle-steep posterior occlusal plane group. These results indicate that among the factors affecting the formation of sagittal dentoskeletal type, the posterior occlusal plane is more representative than the occlusal plane. The curvature of the skull base and the inclination of the posterior occlusal plane affect the formation of sagittal dentoskeletal type. During the formation of sagittal dentoskeletal type, there may be some compensatory mechanisms between the curvature of the skull base and the posterior occlusal plane.

Key words: cranial base angle, occlusal plane, skeletal frame, malocclusion