Morphometric evaluation of Bonwill triangle parameters in relation to mandibular third molar impaction status: a retrospective cone-beam computed tomography study

This study aimed to evaluate the relationship between mandibular third molar impaction status and Bonwill triangle parameters, and to determine whether impacted third molar angulation was associated with Bonwill triangle dimensions. This retrospective comparative cross-sectional study screened 4,021 archived cone-beam computed tomography (CBCT) records and included 136 eligible individuals aged 18–35 years: 68 with bilateral impacted mandibular third molars (IMTM group) and 68 with bilaterally erupted mandibular third molars (EMTM group). Bonwill triangle parameters were measured as intercondylar distance (CR–CL) and right and left condyle–incisal distances (I–CR and I–CL). Impacted third molar angulation was assessed within the IMTM group. Statistical analyses included two-way ANOVA, age-adjusted ANCOVA, and correlation analyses using Pearson and Spearman coefficients. In age-adjusted analyses, the main effect of group was not significant for CR–CL, I–CR, or I–CL measurements ( p = 0.742, 0.646, and 0.202, respectively). A significant sex effect was observed for all Bonwill triangle parameters (all p < 0.001), with higher values in males. No significant group × sex interaction was detected. In the IMTM group, impacted third molar angulation was not significantly correlated with the ipsilateral condyle–incisal distance or the CR–CL distance. Bonwill triangle dimensions were not significantly associated with mandibular third molar impaction status and were not significantly correlated with impacted third molar angulation. However, consistent sex-related differences indicate that these parameters may primarily reflect general mandibular morphometric variation when evaluated using CBCT.