Variation of chin morphology and mandibular incisor length in different facial divergence patterns: New insights from CBCT records

Abstract

AimEvaluate constitutional differences in chin morphology and volume, and mandibular tooth size, between different facial divergence patterns.Materials and MethodsThe sample consisted of 284 pretreatment cone beam computed tomography (CBCT) images of growing and non‐growing patients who were stratified into 4 groups based on mandibular plane inclination to cranial base (SN) angle. Linear and angular measurements were made on the lateral CBCT images: mandibular lateral incisor crown (I‐C) total (I‐A) lengths, the distances between point D (centre of symphysis) and both incisor apex (D‐A) and menton (D‐Me) and between cemento‐enamel junction and menton (CEJ‐Me); chin width at the level of the central incisor apex (CWA) and point D (CWD); and the angles of the anterior and posterior symphyseal slopes. The volume of the symphysis was measured using a specialized 3D imaging software. Group differences and associations between parameters were gauged through the three‐way ANOVA analysis.ResultsI‐C, I‐A, D‐A, D‐Me and CEJ‐Me were greater in the hyperdivergent group (p < .001). CWA and CWD were wider in the hypodivergent group (p = .003). Volume of the chin and inter‐slope angles were similar in all groups (p > .05). The anterior slope angle decreased with hyperdivegence (p < .005) in opposite pattern to the posterior slope angle (p < .005).ConclusionsShape differences in mandibular symphysis were observed between opposite divergence patterns. Mandibular incisors were longer with hyperdivergence and shorter with hypodivergence. However, chin volumes were similar across divergence groups. These findings underline the role of genetic and environmental factors that impact facial growth.