Diagnostic accuracy of panoramic radiographic signs for predicting mandibular canal wall defects: a CBCT-referenced study of impacted mandibular third molars in Yemeni patients

Background Injury to the inferior alveolar nerve (IAN) is an uncommon but consequential complication of mandibular third-molar (MTM) surgery. Panoramic radiographic signs are used to screen for risk, but their diagnostic accuracy remains contested. This study evaluated the diagnostic accuracy of orthopantomogram (OPG) signs against cone-beam computed tomography (CBCT) for detecting mandibular canal (MC) cortical defects in a Yemeni cohort. [3, 5] [7, 9] Methods We performed a retrospective, cross-sectional diagnostic accuracy study. Consecutive cases with ≥ 1 classical OPG high-risk sign (e.g., interruption of the white line, canal diversion/narrowing, root darkening/deflection) underwent CBCT as the reference standard. Two calibrated assessors independently scored OPG signs and CBCT cortical integrity; disagreements were resolved by consensus. Accuracy metrics and associations with age, sex, and impaction type (Winter; Pell & Gregory depth) were analyzed. [1, 2, 32] [3, 37] Results Among 344 MTMs (244 female; 100 male), the MC cortex was intact in 207 (60.17%) and defective in 137 (39.83%). Root position relative to the MC was superior in 128 (73.43% intact), lingual in 150 (63.33% intact), and buccal in 66 (27.27% intact). OPG canal diversion (n = 8) predicted MC defects in all cases (100%), and interruption of the white line was associated with higher defect rates (51.2% defective when the white line was broken) whereas isolated root or canal narrowing/darkening were not. Vertical impactions showed the highest proportion of intact canals (76.92%), compared with mesioangular (43.55%), horizontal (62.71%), and distoangular (51.61%) impactions (all χ² P < 0.001). By depth, high impactions had more intact canals (75.29%) than medium (45.32%) or low (45.71%) (P < 0.001). Age groups showed a trend toward more defects in older patients (18–30 years: 36.54% defective; 31–60: 41.02%; >60: 70%), though overall χ² P = 0.100. [3, 37] [3, 37] Conclusions Among classic OPG signs, canal diversion and interruption of the white line best predicted CBCT-confirmed MC cortical defects. OPG is useful for triage, but CBCT remains the preferred modality for definitive assessment and surgical planning in high-risk MTM cases. [3, 37]