Evaluation of rat incisor mesenchymal cells in bleomycin injected animals fixed by immersion or perfusion.

Bleomycin was administered to four groups of rats in a single intravenous injection of 25 mg/kg, 50 mg/kg, 75 mg/kg and 100 mg/kg, respectively. The animals were killed by perfusion or by decapitation followed by immersion fixation at 24 h and 5 days after injection. Sections were made of maxillary incisors and evaluated by light microscopy. Bleomycin produced a transitory arrest of dividing cells resulting in an apparent synchronization of the cell population. Necrotic cells were found within the basal pulp and the preodontoblasts at 1 day observation time. After 5 days a dentinal lesion was observed at the two highest dose levels and the necrotic areas were filled in by proliferating adjacent cells. A better quality of fixation, especially of cells surrounded by dentin, was observed in perfusion fixed animals but the fixation procedure did not influence the alterations found in experimental animals.