MICRORADIOGRAPHIC AND ELECTRON-MICROSCOPIC OBSERVATIONS OF THE ENAMEL-COVERED DENTIN IN RAT MOLARS

The enamel-covered primary and secondary coronal dentin in the molars of 90-day-old and 360-day-old rats was examined using microradiography. Some preparations were subsequently examined by transmission and scanning electron microscopy (TEM and SEM). Fractured dentine surfaces and methacrylate casts of the tubular system in the primary dentine were also examined with SEM. No microradiogrpahic evidence of a hypermineralized peritubular matrix, such as that seen in man and other species, was seen in either young or old rats. TEM and SEM confirmed the microradiographic findings. The tubule obliteration and extensive intraluminal mineral deposits, which have been reported in the enamel-free coronal dentin of the rat molar, were not seen in the enamel-covered coronal dentin, but some evidence of tubule obliteration was seen in the secondary dentine.