INCREMENTAL LINES IN HUMAN DENTIN AS REVEALED BY TETRACYCLINE LABELING

Abstract

Separation distance between pairs of tetracycline lines in the dentin of human extracted permanent teeth casts doubt upon the generally accepted 16 .mu.m rhythm of dentin apposition. Ground sections from 43 extracted human permanent canines and premolars, in which there were more than 2 tetracycline lines in the dentin, were studied with a Nikon, Sur-F fluorescent microscope. The distance between neighboring tetracycline lines in the dentin formed in relation to the same group of odontoblasts was measured along the path of the dentinal tubules on enlarged photomicrographs. Each of the tetracycline lines in the various parts of the tooth pursues a characteristic course, and the differences of the mean values of distances between the lines in different parts of a tooth are statistically significant. The secretory activity of an odontoblast apparently varies considerably during its life cycle. Odontoblast secretion and migration as a general rule start slowly, reach a peak and then slow up as dentin production nears completion. The activity of a particular odontoblast varies with the type of tooth.