DEVELOPMENT OF INTERGLOBULAR DENTIN IN RAT MOLARS AND ITS RELATION TOMATURATION OF ENAMEL

The development of interglobular dentine in the first upper and lower molars of Wistar rats aged 3, 7, 14, 21, 42 days was examined histoche mically using a lectin, succinyl wheat germ agglutinin (sWGA), which i s specific for N-acetyl-D-glucosamine. sWGA stained the interglobular dentine, predentin and Golgi area of odontoblasts. Interglobular denti ne was not formed in the first molars of 3-day rats, but appeared in t hose of 7-day rats near the enamel-free area. In 14-day rats, interglo bular dentine was present in most areas of the coronal dentine except the cervical area. At the interface between dentine and predentin, num erous sWGA-negative calcospherites were seen, suggesting that the inte rglobular dentine is formed actively there. In 21-day rats, the interl obular dentine was more numerous than in 14-day rats. Interglobular de ntine was present in the cervical root dentine as well as in the coron al dentine, including the cervical area. The distribution of interglob ular dentine in 42-day rats was similar to that in 21-day rats, but fl uorescence of sWGA binding was less intense in the former. Because the development of interglobular dentine appeared to be time and position specific its relation to the stages of ameloblasts was analysed. Thin enamel matrix was formed at cusps in molars of 3-day rats and thickne ss of enamel matrix increased in 7-day rats. In these teeth, the amelo blasts were at the differentiating or secretory stage. The Golgi area and Tomes' processes of the secretory ameloblasts, the cells of interm ediate layer and the enamel matrix were weakly positive with sWGA. The epithelial cells at the enamel-free area were also stained with sWGA. In 14-day rats, most of the ameloblasts in the first maxillary molars were at the maturative stage except in the cervical area, where the a meloblasts were at the transitional stage. sWGA stained the distal bor der and the Golgi area of the maturative ameloblasts as well as the ce lls of the papillary layer. The distal border of the maturative amelob lasts appeared either thick or thin, suggesting a ruffle-end and smoot h-end of the cells. Ameloblasts were absent in the first molars of 21- day rats and the cervical part of the enamel was covered with the stra tified epithelium like that of 42-day rats. The present study has demo nstrated that interglobular dentine contains sWGA-binding glycoconjuga tes and the formation of the interglobular dentine is largely associat ed with the enamel maturation. These results suggest that matrix-to-ce ll interaction is important for the development of interglobular denti ne.