Submandibular fossa depth in relation to the mandibular canal and alveolar crest: a retrospective cross-sectional CBCT study analyzing side-specific and sex-based variations.

An accurate preoperative evaluation of mandibular anatomy is essential before placing dental implants safely in the posterior region, where the submandibular fossa and proximity to the inferior alveolar nerve present serious risks. A precise preoperative evaluation of the mandibular anatomy is essential. This retrospective cross-sectional study evaluated the depth of SF using cone beam computed tomography (CBCT) and its correlation to the mandibular canal (MC) and alveolar crest (AC) in 200 adults (116 males, 84 females). Measurements were performed using the I-CAT Vision software and Intraclass Correlation Coefficient was used for the confirmation of intra- and interobserver reliability. Statistical analyses included Pearson correlations, t-tests, linear mixed-effects models (to account for bilateral correlations), multivariable regression and Benjamini-Hochberg false discovery rate correction. When controlling for within-subject correlation, sex differences remained significant on the right (β = 0.24, p = 0.009) but not the left (p = 0.081). Right side showed a weak negative correlation between SF depth and MC distance (r = -0.189, p = 0.007, r2 = 0.036), but this was not observed on the left side (p = 0.404). A lower MC position on the right was associated with higher SF depth (p = 0.027, q = 0.089). No relation with AC height. Despite sex- and side-related differences, the effect size is very weak (r = -0.189) and thus not suitable for prediction. Fossa depth was not a predictor of alveolar crest height, nor did it replace MC position evaluation. Sex and side specific anatomical risk varies, thus quadrant specific evaluation is necessary. These findings do not support standardized planning or SF depth alone as a clinical predictor. Instead, direct, independent CBCT measurements of both SF depth and MC distance at each implant site are necessary. Still, accurate 3D visualization of the SF-MC relationship is important to reduce the risk of lingual perforation and nerve injury. However, this visualization should be based on direct measurements rather than inferred correlations.