In vitro study by fluorescence microscopy and microradiography of tetracycline-tooth interaction.

The administration of tetracycline to the growing child may cause discoloration and hypoplasia in developing teeth. Whether tetracycline may also cause changes in fully mineralized enamel and dentin, is still a matter of discussion. The present investigation examines the in vitro reaction between tetracycline chloride and enamel and dentin of extracted human teeth. Specimens were immersed in 0.5 mg/ml to 20 mg/ml aqueous tetracycline solutions. After 24 hr the specimens were sectioned and studied by fluorescence microscopy and microradiography. The tetracycline solutions, which were all very acidic, were found to cause 1) demineralization of enamel and dentin, 2) incorporation of fluorescent material in enamel and, notably, dentin; and 3) formation of yellow, rhombohedral crystals on dental surfaces, especially in the more concentrated solutions. No fluorescence was seen in totally demineralized dentin. The findings indicate that the incorporation of tetracycline into enamel and dentin is caused by physiochemical processes that may take place regardless of the developmental stage of the mineralized tissues.