Association of molar interradicular distance and angulation with periodontal disease severity: a cross-sectional study.

This retrospective cross-sectional study evaluated associations of molar interradicular distance (IRD) and tooth angulation with clinical and radiographic indicators of periodontitis severity in 316 patients. IRD at the cemento-enamel junction (R0), mid-root (R1), and apical third (R2), along with premolar-molar (α) and molar-molar (β) angulation, bone loss (BL), horizontal and vertical furcation bone loss (h-BL and v-BL), and bone-loss pattern, were measured by cone-beam computed tomography (CBCT). Generalized estimating equation (GEE) models adjusted for age, sex, and plaque index (PI) and accounted for within-patient clustering of tooth-level observations. Mandibular molars had wider IRD at all three levels and greater β than maxillary molars (all p < 0.001). In the maxilla, wider R0 and R2 were associated with greater distal clinical attachment loss (CAL) of first molars, whereas R0-R2 were positively associated with mesial probing depth (PD) of second molars (all p < 0.05). β showed negative associations with maxillary CAL and mesial bleeding on probing (BOP) of second molars (p < 0.05). In the mandible, wider R0-R2 were associated with greater distal PD and CAL of first molars (all p < 0.05), and β was positively associated with distal CAL of first molars (p = 0.005). Wider R0 and R2 were also associated with greater distal BL in maxillary first molars (p < 0.01); R0 was associated with v-BL and a vertical bone-loss pattern in maxillary first molars, whereas R0 and R1 were associated with a vertical bone-loss pattern in mandibular first molars (p < 0.05). Overall, IRD and molar angulation showed heterogeneous, site-specific associations with clinical and radiographic periodontal parameters. These cross-sectional findings support interpreting IRD and angulation as adjunctive anatomical correlates of local disease expression rather than primary etiologic determinants or stand-alone predictors of periodontitis.