Density and diameter of dentinal tubules in etched and non-etched bovine dentine examined by scanning electron microscopy

Bovine teeth have been widely used in studies focusing adhesion to dentine over the last years. However, little is known about main structural aspects of bovine dentine, especially regarding density and diameter of its tubules. Thirty bovine incisors were randomly divided into two groups. In group I, teeth were cross-sectioned at three depths: outer, middle and inner. The dentinal surfaces were etched with 35% phosphoric acid for 90 s. In group II, the teeth were fractured at the same three depths. All the specimens were processed and examined in a Jeol 6100 SEM. Fifteen micrographs from each depth were obtained for the two groups at a magnification of 2500×. To determine the diameter of the dentinal tubules, the LEICA Q500 MC software was used. All the results were statistically processed in the EXCEL® software. The dentinal tubules were wider at the outer regions (GI: 5.21 ± 0.64 μm; GII: 2.30 ± 0.09 μm) than that at the inner regions (GI: 2.71 ± 0.72 μm; GII: 1.77 ± 0.06 μm). Tubular density was higher at the inner regions (50 310 ± 11 178 tubules/mm2) than that at the outer regions (18 772 ± 2951 tubules/mm2). In addition, the peritubular dentine was wider at the outer depth than at the inner one. Our results showed that bovine dentine possesses some structural aspects different from those previously reported for human dentine, mainly related to the diameter of dentinal tubules and to the thickness of peritubular dentine at the several depths.