The microscopic distribution of tetracycline in human teeth.

The distribution of tetracycline fluorescence was studied in a random collection of 378 teeth extracted in 1976 in Farmington, Connecticut, using ultra-violet microscopy of longitudinal ground sections. The sample consisted of 4 deciduous molars and the following numbers of permanent teeth: 72 incisors, 41 canines, 63 premolars, 26 first molars, 24 second molars, and 148 third molars. Narrow fluorescent lines reflecting short regimens of drug administration and broad bands corresponding to long term administration were identified in the dentin and tabulated in relation to their anatomical position. Fluorescence in the cementum was also noted. Of all the teeth, 33.3% exhibited tetracycline changes in either the dentin, the cementum, or both. There were 89 affected third molars. These had a mean of 3.1 (+/- 2.9) fluorescent dentin lines per tooth as well as many broad bands, largely in the root region. The teeth were subjected to an estimation of age in order to segregate those teeth whose dentin had formed prior to the advent of tetracycline usage. When this was done, the corrected incidence of tetracycline affected teeth in the collection was 45.4%. The observations show that American teeth have been extensively affected by tetracycline. The location of fluorescent markings appear to reflect reluctance to use this drug during the developmental period when cosmetic effects could result. Markings clearly indicate heavy usage of tetracycline during a later period of development corresponding to third molar root formation.