Apoptosis in physiological root resorption of primary teeth.

Background: During physiological root resorption of deciduous teeth, apoptotic cell death triggered by physiological processes might play a role in physiological root resorption in addition to collagen destruction. Little information has been obtained about the sequence of events and the mechanism responsible for the physiological death of pulp tissue cells. Aim: This study evaluated apoptotic cell death in the pulp tissue of deciduous teeth that showed various levels of physiological root resorption. The role of apoptosis in pulp tissue elimination during the physiological resorption of deciduous teeth was also examined. Materials and Methods: For orthodontic reasons, 12 healthy permanent teeth and the pulp of 34 healthy deciduous teeth showing signs of early and advanced root resorption were extracted. To detect apoptotic cells in the pulp tissue, the terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) method and transmission electron microscopy (TEM) were used. The apoptotic index (AI) values of the study groups were determined using the TUNEL method. This technique required calculating the Apoptag positive(+) fibroblast cell ratio in accordance with the total number of cells. Results: No statistically significant differences were found for the AI values of each study group (p>0.05). Apoptosis was detected in the vascular endothelial cells, the mononuclear inflammatory cells, and the odontoblasts of the connective pulp tissue. In the pulp tissue, evaluated using TEM, various pulp cells were observed at distinct stages of apoptosis. Conclusion: The similarity between the AI values for both study groups suggested that in early and advanced stages of resorption, apoptosis may contribute to the regulation of the pulp cell population in a way that does not relate to the physiological process of deciduous teeth root resorption.