ION GRADIENTS BETWEEN DENTAL ENAMEL MATRIX AND REGION OF TOMES PROCESSES - A SECONDARY-ION MASS-SPECTROMETRY ANALYSIS IN RATS

During the ameloblast differentiation stages, variations in the compos ition of different elements in the enamel matrix occur. The stages are characterized by a certain composition of elements being transported to, or from, the sites of calcification, forming a number of elemental gradients between hard and soft tissues. Sprague-Dawley rat incisor f ragments, harbouring secretory ameloblasts, were frozen in liquid nitr ogen, dried by sublimation, embedded, ground cut and subjected to quan titative secondary ion mass spectrometry. In addition, rats were perfu sed with an aldehyde, after which the maxillary incisors were extracte d, embedded, ground cut and subjected to secondary ion mass spectromet ry imaging. The ion gradients of C-12, F-19, Na-23, Cl-35 and Ca-44 in the Tomes processes region-enamel matrix interface were mapped. The r esults showed steep elemental gradients between the Tomes processes re gion and the enamel matrix, demonstrating preserved barrier functions after fixation. The gradients of C-12, F-19, Na-23 and Ca-44 were main tained close to, or within, the Tomes processes. The data are in favou r of a theory that the Tomes processes region-enamel matrix interface acts as a selectively permeable barrier. (C) 1998 Chapman & Hall.