Experimental Studies in Calcification

Abstract

The effect of single injns. of strontium chloride on the dentin of the rat incisor was studied histologically. Sr produced changes in the dentin of a definite pattern consisting of (a) a calciotraumatic line, (b) a hypocalci-fied layer and (c) a hypercalcified layer of dentin. Measurements showed that the hypocalcified layer represented the pre-exptl. predentin which had remained uncalcified. The hypercalcified layer was formed immediately following the injn. The border between hypo- and hypercalcified layers of dentin represented the demarcation between pre-exptl. and exptl. dentin and is called the exptl. dentin line. Silver staining showed that the hypocalcified layer had a structure similar to that of old predentin and that the hypercalcified layer, which was intensively stained by hematoxylin, contained fewer fibrils than the normal dentin. A single injn. of Sr is an effective and accurate means of marking the dentino-pulpal border at the beginning of different exptl. procedures. The analysis of the structure of the cal- ciotraumatic layer was used to outline hypothetically the stages of dentinogenesis.