Study of dentinal tubule architecture of permanent upper premolars: evaluation by SEM

Dentinal tubules are the means by which the pulp and mineralised tissues surrounding the dentine (enamel and cementum) communicate. Through these tubules external agents can damage the pulp and subsequently the periodontal ligament. Given the importance of dentinal tubules, the authors evaluated the numerical density, shape, and individual surface area of tubule openings and the percentage of dentine occupied by these. Eight permanent upper premolars were studied using scanning electron microscopy (SEM). In the crown, the external surface of the dentine was evaluated at the dentino-enamel junction and the internal surface at the pulp chamber wall. At the cervical, middle and apical thirds of the root, the external surface was evaluated at the cemento-dentinal junction and the internal surface at the root canal wall. The results showed that numerical density of tubule openings is significantly greater (p < 0.05) at the cervical third of the dentine, at its junction with the cementum and at the pulpal chamber wall, with respect to other areas evaluated. The individual surface area of each opening varied from 5.72 microns 2 in the dentine of the pulpal chamber wall to 0.97 micron 2 in the dentine of the apical third of the root canal wall. The percentage of area occupied by the dentinal tubules per mm2 of dentine was significantly higher (p < 0.01) at the internal dentinal surface as compared to the external. The shape of the tubule openings was found to be circular in the crown and became more irregular as the apical third of the root was approached.