Cone-beam computed tomography overestimates critical dentin thickness in the danger zone: implications for structural risk assessment

To investigate whether cone-beam computed tomography (CBCT) overestimates dentin thickness within the mandibular molar danger zone, a structurally vulnerable region critical for tooth integrity and restorative decision-making, by comparing CBCT measurements with high-resolution micro-computed tomography (micro-CT) as the reference standard.

Thirty-six mandibular first molars underwent CBCT and high-resolution micro-CT. Dentin thicknesses at predefined danger/safety zones of mesiobuccal, mesiolingual, and distal canals were measured 4 mm apical to the furcation. Bland-Altman analysis, paired comparisons, and intraclass correlation coefficients were performed.

CBCT measurements consistently overestimated dentin thickness by 0.10-0.14 mm compared with micro-CT. Mean dentin thickness within the danger zone ranged from 0.98 to 1.07 mm and was lower than that of the safety zone (p<0.003). High intra- and inter-observer agreement was observed, indicating reproducible measurement performance.

CBCT systematically overestimates dentin thickness of the danger zone. Although the observed bias was identified under ex vivo conditions, it may influence the radiographic interpretation of structurally vulnerable regions and should be considered when CBCT measurements are used to support oral rehabilitation planning.