Investigation of apoptosis in healthy and inflamed pulp tissue

When caries occurs in tooth hard tissue due to pathogenic microorganisms and is left untreated, these microorganisms and their by-products progress to the pulp tissue, causing reversible inflammation at first, then irreversible inflammation and ultimately cell death. Cell death occurs for two main reasons: apoptosis and necrosis. Apoptosis is a physiological process that also occurs in healthy tissues and ensures tissue sustainability. The aim of our study was to investigate the apoptosis (programmed cell death) process in inflamed pulp tissue depending on the severity of inflammation. In this study, caspase-9, cytochrome-c and TUNNEL, which are the basic parameters of apoptosis, were analyzed immunohistochemically in pulp tissue from healthy (n=10), reversible (n=10) and irreversible (n=10) pulpitis teeth. For histopathologic examinations, pulp cells were sectioned and hematoxylin-eosin stained and inflammation markers were scored. Immunostaining was performed for caspase-9, cytochrome-c and TUNEL analysis. After all procedures, the sections were examined and evaluated under a light microscope. All scoring values in the study were subjected to normality test with Shapiro-Wilk. Differences between groups were evaluated by Kruskal-Wallis analysis, pairwise comparisons were evaluated by Mann-Whitney U analysis and intergroup correlation was evaluated by Spearman's rho analysis at p=0.05 confidence interval. Markers of inflammation such as hemorrhage, edema, necrosis, fibrosis and calcification were significantly higher in irreversible pulpitis compared to other groups (p<0.05). There was a high correlation between hemorrhage and necrosis, inflammation and edema and TUNNEL analysis. Although caspase-9 was higher in irreversible pulpitis compared to the other groups, there was no statistically significant increase (p>0.05). TUNEL analysis results increased statistically significantly with all other markers depending on the severity of inflammation (p<0.05). In our study, we think that the number of cells that go to apoptosis increases depending on the severity of inflammation and damaged cells can be eliminated in the tissue, thus regeneration may be possible.