Morphology of the mineralizing front and observations of reparative dentine following induction and inhibition of dentinogenesis in the rat incisor

An extra oral approach was made to 26 pairs of Wistar rat incisors and a small bur used to expose the pulps which were then dressed with either calcium hydroxide paste (Pulpdent) zinc oxide-eugenol cement (Kalzinol) or a triamocinolone acetonide/tetracycline containing cement (Ledermix). Animals were sacrificed at 7 days, incisors removed, a window cut to the pulp opposite the site of exposure, soft tissues removed with 7% NaOCl for 30 minutes before teeth were dehydrated in graded concentrations of acetone and gold coated for examination under SEM. Calcium hydroxide produced rapid complete repair with a remarkably regular formation of calcospherites, except for a zone of relative inhibition perforated by nutrient canals at the periphery of each lesion. Both zinc oxide-eugenol and triamcinolone acetonide cements inhibited both bridging of the defect created by the exposure and dentine formation in the surrounding pulpal wall. Data was grouped according to the degree of hard tissue repair. The results were statistically significant (Chi-square p < or = 0.001). This method demonstrated qualitative and quantitative differences in the repair process resulting from chemical variations in the dressings applied.