Evaluation of the influence of four mandibular planes on the diagnosis of high and low mandibular plane angles

Abstract

Four mandibular planes (MPs) are distinguished different when constituting mandibular plane angle (MPA) with sella-nasion (SN) or Frankfort horizontal (FH) plane, which would make high-MPA or low-MPA selection confusing. This study aimed to determine the impact of four MPs—MP gnathion-to-gonion (MP [G]), MP tangent (MP [T]), MP menton (MP [Me]), and MP gonion-to-menton [Go-Me])—on the diagnosis of high and low MPAs and reveal their association with chin morphology. This cross-sectional study was based on cephalometric lateral radiographs from 321 orthodontic samples. MP (G), MP (T), MP (Me), and MP (Go-Me) were analyzed. Regarding MP-SN and MP-FH angle analyses, there were statistically significant differences in the MPA formed by the MP (T) vs. MP (Me); MP (T) vs. MP (G); MP (Go-Me) vs. MP (G); and MP (Go-Me) vs. MP (Me). The numbers of high-MPA cases screened out by the four MPs were (in descending order): MP (T)-SN/FH > MP (Go-Me)-SN/FH > MP (Me)-SN/FH > MP (G)-SN/FH. Considering low-MPA cases, the descending order was MP (Me)-SN/FH > MP (Go)-SN/FH > MP (T)-SN/FH > MP (Go-Me)-SN/FH. Orthodontists should be aware of the differences in MPAs formed by the MP (T), MP (G), MP (Go-Me), and MP (Me) during diagnosis.