Hard tissue of teeth and their calcium and phosphate content in Ambystoma mexicanum (Urodela: Ambystomatidae).

The wall of the pulp cavity, fracture faces and the demineralized surfaces of teeth from larvae and adults of Ambystoma mexicanum were investigated by scanning electron microscopy (SEM). Calcium and phosphate contents were determined by microanalysis. The apical part of the tooth (crown, tooth apex) contains dentin canals. In the larva, these do not reach the enamel-dentin border but end below this border in front of a denser hard substance, possibly enameloid. The pedicel in the adult and the basal portion of the tooth in the larva (base) are without dentin canals. These parts of the teeth are characterized by longitudinally arranged collagen fibres as visualized on the demineralized surfaces. These observations indicate a congruency in early-larval and adult teeth between base and pedicel as well as apex and crown. This partition is also confirmed by the calcium and phosphate values which were identical in larvae and adults. Highest values are found in enamel and lowest values in the tooth-bearing bone. Calcium and phosphate content show a clear difference between dentin and the basal part of the tooth (pedicel and base). The ring-like dividing zone in the adult tooth is less well mineralized.