Micro-CT Assessment of Dentin Mineral Density and Furcation Morphology in Primary First and Second Molars.

Background/Objectives: The furcation region of primary molars is a critical anatomical zone with high clinical relevance in endodontics and restorative dentistry due to its proximity to the pulp chamber and potential accessory canal communications. This study aimed to quantitatively evaluate and compare dentin mineral density in the crown and furcation regions, as well as furcation structure thickness, maximum dentin thickness, and volume, between primary first and second molars using micro-computed tomography. Methods: Thirty-eight extracted primary molars (19 first and 19 second molars) with physiological root resorption affecting less than two-thirds of the root length were included. Teeth were scanned using a SkyScan 1272 micro-CT system. Mineral density was calibrated using 0.3 and 1.25 g/cm3 hydroxyapatite phantoms. Morphometric parameters of the furcation dentin were analyzed with CTAn software. Statistical analysis was performed using non-parametric tests (p < 0.05). Results: Dentin mineral density was significantly lower in the furcation region compared to the crown in both first (median: 1.64 g/cm3, IQR: 1.62-1.68 vs. 1.84 g/cm3, IQR: 1.82-1.90) and second molars (1.71 g/cm3, IQR: 1.70-1.73 vs. 1.96 g/cm3, IQR: 1.93-1.96) (p < 0.001). Second primary molars showed significantly higher mineral density, greater furcation structure thickness (1.50 mm vs. 1.30 mm), maximum dentin thickness (1.86 mm vs. 1.53 mm), and furcation dentin volume (80.8 mm3 vs. 46.2 mm3) than first molars (all p < 0.05). Accessory canals were detected in 15.79% of specimens. Conclusions: This study demonstrates significantly lower mineralization in the furcation region compared to coronal dentin in primary molars, with first molars exhibiting lower mineral density and thinner furcation structure than second molars. These anatomical and compositional differences highlight the furcation area as a vulnerable zone and suggest the potential value of considering tooth-specific approaches in clinical management. Further clinical studies are warranted to evaluate the implications for treatment outcomes.