Association of anterior and posterior occlusal planes with different Angle and skeletal classes in permanent dentitions: A lateral cephalometric radiograph study

OBJECTIVES: Malocclusions affect about two-thirds of the population and orthodontic treatment is justified in 65% of these. However, the associations between anterior and posterior occlusal plane (AOP, POP) inclinations and Angle classification are lacking. PATIENTS AND METHODS: In a retrospective study, lateral cephalometric radiograph tracings of 230 previously untreated Caucasians, aged 13 to 49 years, yielded inclines of the bisector occlusal plane, AOP, and POP. All inclinations were referenced to the Sella-Nasion line and the Frankfort horizontal and were assigned to the Angle classification as well as skeletal groups (retrognathic, neutral, prognathic). Quantile regressions were calculated. RESULTS: In the skeletal groups the angles between Sella-Nasion line and both AOP and POP were significantly different between the groups (p < 0.01), showing steep inclines in skeletal class II and flat inclines in skeletal class III. The angles Frankfort horizontal-to-POP and Frankfort horizontal-to-AOP showed the same trends but only the latter differed significantly between the groups (p = 0.02). Among the Angle groups, AOP inclinations did not differ significantly for both reference planes whereas POP inclinations were significantly different (p = 0.01 to Frankfort horizontal, p = 0.02 to Sella-Nasion). Angle class I patients showed the flattest POP. CONCLUSION: Occlusal plane inclines, measured to Sella-Nasion, were more consistent than those referenced to Frankfort horizontal. Sella-Nasion related anterior and posterior occlusal plane inclinations were steep in skeletal class II and flat in skeletal class III patients over all quantiles. Using the Angle classification, anterior and posterior occlusal plane inclinations did not follow this principle.