Display of maturation cycles in rat incisor enamel with tetracycline labelling.

Tetracycline was incorporated within seconds of intracardiac injection to form bright yellow fluorescent bands under UV irradiation in maturation zone enamel. The bands were narrow, widening with time. At several hours after subcutaneous injection, the fluorescent bands were wide and of low intensity. It is concluded that tetracycline enters maturing enamel opposite the narrow bands of non-striated border ameloblasts which are probably a main exit route for organic matrix remnants. Tetracycline distribution patterns at hours after injection reflect the diffusion of this substance within enamel and the pattern of its removal, which also occurs in relation to the non-striated border, smooth-ended maturation ameloblasts.