Comparison of the number and diameter of dentinal tubules in human and bovine dentine by scanning electron microscopic investigation

Detailed information on dentine structure is essential for interpreting data from investigations on dentine-adhesive materials. The purpose here was to compare the number and diameter of dentinal tubules at similarly prepared surfaces of bovine permanent central incisors and human deciduous and third molars. In bovine teeth, crowns and roots were used; in human samples only the crowns were investigated. Tubule density in the middle layer was higher in bovine root (BR) dentine (number of tubules per mm 2±SD: 23,760±2453) than in human deciduous (HD) (18,243±3845), human permanent (HP) (18,781±5855), and bovine coronal (BC) (17,310±2140) dentine. The corresponding values for the deep layer were 23,738±4457 (BR), 24,162±5338 (HD), 21,343±7290 (HP), and 20,980±4198 (BC). No significant differences were found for the number of dentinal tubules in bovine coronal dentine compared to the dentine of human deciduous and permanent molars. The mean diameter of bovine dentinal tubules was slightly, but not significantly, higher than in human dentine (middle layer/deep layer±SD): BC, 2.85 μm±0.18/3.50 μm±0.33; BR, 3.10 μm±0.33/3.23 μm±0.30; HD, 2.55 μm±0.16/2.82 μm±0.28; HP, 2.65 μm±0.19/2.90 μm±0.22. These findings demonstrate that corresponding coronal dentine layers of human deciduous and permanent molars, and of bovine central incisors, are not significantly different in their number of tubules per mm 2 and their tubule diameter, whereas tubule density in bovine root dentine is significantly higher. These results suggest that provided standardized preparations are used, bovine incisor crown dentine is a suitable substitute for human molar dentine in adhesion studies.