Tetracycline as a marker in hard tissue research: effects on enamel formation in rat maxillary incisors.

Tetracycline in low dose is often used as a marker in hard tissue research. A low dose effect on enamel formation has never been proven despite well known toxic reactions in enamel after higher doses. The purpose of the investigation was to evaluate enamel formation in maxillary incisors of rats given a single low dose of a tetracycline with low toxicity, commonly used in research. Eight young rats received an intraperitoneal injection of 2 mg oxytetracycline per 100 g. The rats were terminated after periods between 1 h until 5 days. Undemineralized ground sections were prepared and studied under fluorescence microscopy. Microradiograms were taken to study the degree of mineralization. A diffuse uptake was seen within enamel in areas corresponding to late secretory stage and incisally in maturing enamel with a low mineralization degree. Tendencies of enamel aberrations were seen in all rats. These appeared as splittings within the formed enamel. In conclusion, low toxicity tetracycline disturbs normal amelogenesis, even if administered in low doses. It should therefore be avoided in hard tissue research where enamel formation is studied.