Root morphology and alveolar bone phenotype of maxillary second molars in patients with periodontitis: a cross-sectional study.

BACKGROUND: Tooth anatomy is a key factor in periodontitis, and existing evidence has largely focused on premolars. The maxillary second molar (MSM), which is frequently affected and therapeutically challenging, remains substantially underexplored. This study aims to evaluate the root morphology and alveolar bone phenotype of the MSM in relation to periodontal parameters, aiming to identify high-risk anatomical sites and inform personalized management. METHODS: This cross-sectional study included patients diagnosed with periodontitis at the Affiliated Hospital of Hangzhou Normal University between January 2022 and January 2025. Periodontal clinical parameters, including probing depth (PPD), clinical attachment loss (CAL), root furcation involvement (FI), and others, were recorded for all patients. Cone-beam computed tomography was used to assess alveolar bone loss (ABL), root concavity (angle and depth), root trunk length, root proximity, and adjacent third molars (M3s). Data were analyzed using SPSS, with p < 0.05 considered statistically significant. RESULTS: The study included 319 patients (173 females and 146 males) with 576 MSMs aged 18 to 80 years (mean 43.5 ± 12.34 years). Triple-rooted (TR) morphology was most prevalent (55.21%, 318/576), followed by double-rooted (DR, 24.65%), single-rooted (SR, 19.44%), and quadruple-rooted (QR, 0.69%) morphologies. Both the angle and depth of root concavity were positively correlated with CAL and ABL. In the DR- and TR-types, inter-root proximity may serve as a potential risk indicator for FI. Thicker alveolar bone correlated with lower odds of stage III/IV and grade B/C periodontitis. The presence of adjacent M3s was associated with increased distal PPD, CAL, and ABL in MSMs. CONCLUSIONS: Our findings indicate that the specific root morphology and alveolar bone phenotype of MSMs are significantly associated with periodontitis. Anatomical features such as root concavity, inter-root proximity, and adjacent maxillary third molars may serve as potential risk indicators for localized periodontal destruction.