Three-dimensional evaluation of age-related changes in root canal curvature and dentin thickness in mandibular first molars using micro-computed tomography.

This study aimed to investigate the age-related alterations in mesial roots of mandibular first molar in terms of root canal curvature values, dentin thickness, interorifice distance, deviation from apical foramen, and location of apical foramen using a three-dimensional curvature measurement method and micro-computed tomography (micro-CT). Forty-five mesial roots of mandibular first molars from three age groups (Group 1: ≤ 30 years, Group 2: 31-59 years, Group 3: ≥ 60 years) were scanned using micro-CT. The central axis of each mesiobuccal and mesiolingual canal was analyzed using cubic B-spline curves to calculate canal curvature. Dentin thickness, deviation of apical foramen from the anatomical apex, and the location of apical foramen in mesiobuccal and mesiolingual canals were measured and recorded. Statistical analyses, including one-way ANOVA, Mann-Whitney U, Kruskal-Wallis and Pearson's correlation tests, were performed to assess age-related differences in curvature, interorifice distance, and dentin thickness with a 5% significance threshold. No statistically significant differences in root canal curvature were observed across the three age groups (p > .05), although a slight increase in curvature was noted in Group 3. Interorifice distance was significantly lower in Group 2 (p < .05), but no significant relationship was found between mesiobuccal curvature and interorifice distance. Dentin thickness, however, showed significant variations: Groups 1 and 2 exhibited thinner mesial dentin (2-6 mm levels), while Group 3 demonstrated greater distal dentin thickness (5-8 mm levels) (p < .05). Apical foramen location and deviation remained consistent across age groups (p > .05), predominantly situated centrally on the root surface. While root canal curvature did not vary significantly with age (p > .05), dentin thickness showed notable age-related differences (p < .05). A significant correlation was observed between the mesiolingual canal curvature and interorifice distance, but no such correlation was found for the mesiobuccal canal. A significant age-related increase in dentin thickness in both the mesiobuccal and mesiolingual canals underscores the impact of secondary dentin deposition, which is probably uniform as the root canal curvature seems to remain relatively stable across the lifespan in mandibular first molars.