Response of the rat incisor dental tissues to penetration of the labial alveolar bone in preparation of a surgical window.

The orderly formation of rod and interrod enamel containing precisely-oriented hydroxyapatite crystallites requires a high degree of cellular cooperation. This work examines the susceptibility and response of the rat incisor enamel organ and enamel to mechanically-induced trauma. Such trauma is induced by drilling through the labial alveolar bone of the rat incisor in preparation of a surgical window for a micro-injection technique (McKee and Warshawsky, 1984). The drilling ruptures the enamel organ and removes the underlying enamel. Various experiments indicate that the enamel lesion is a result of aspiration by the rotating bur. The histology of the enamel lesion is described. Several morphological changes which may indicate attempted repair are noted as the lesion moves incisally with time due to the eruption of the tooth. It is concluded that the rat incisor enamel organ is an extremely sensitive cellular system, that if sufficiently disturbed is not capable of restablishing the cellular relations necessary to produce a new enamel layer.