Clinical and ultrastructural study of the natal tooth: enamel and dentin assessments.

A natal tooth, the lower left central primary incisor, extracted from a twenty-eight-day-old boy was the subject of a clinical and ultrastructural (S.E.M., T.E.M., H.R.T.E.M.) study. The right one having been lost shortly after birth, the places of the natal teeth were taken by two hyperplastic structures which disappeared one year later, ejecting two little pearls of hard tissue. Scanning electron microscopic investigation of the extracted natal tooth showed a reduced enamel thickness corresponding to the development stage of the tooth as well as the absence of Hunter-Schreger bands and of an outer prism-free layer probably related with amelogenesis perturbations. Transmission electron microscopy disclosed characteristic ultrastructure of the enamel rods, the morphology of the enamel crystals evaluated by their width-to-thickness ratio taking logically place between fetal and adult enamel. A central dark line, which is thought to be in relation to the initial growth process, was observed in enamel crystals. Dentin aspects did not reveal significant perturbations compared to normal primary teeth.