Tooth decay can be induced by many oral bacteria such as Streptococcus mutans (S. mutans), Streptococcus sobrinus (S sobrinus) and so on. However, S. mutans is commonly found- in the human oral cavity and is a significant contributor to tooth decay. Since now, S. mutans can be detected by either some biochemical tests or molecular methods
however, biochemical tests are less sensitive than molecular methods such as polymerase chain reaction (PCR) and real-time PCR Thus, in this study, primers were used in PCR to amplify a sequence of the gtfB gene of S. mutans. The results showed that S. mutans prevalence of patient was 89,47 percent. The lipopolysaccharide from S. mutans induced apoptosis of pulp cell derived from decayed tooth. The nuleus defragment was detected in dentin damaged tooth and pulp damaged tooth and not detected in normal tooth and enamel damage tooth. The result of single cell gel electrophoresis assay showed that DNA defragment observed in pulp damaged tooth (39,1 percent) was higher than dentin damged tooth (24,36 percent) and normal tooth (2,746 percent). RT-PCR was applied to detect the transcript expression of bax, bel-2. and osteopontin transcript. The RT-PCR result demonstrated that pulp damaged tooth and dentin damaged tooth lost the balance in the expression of bax (proapoptotic gene) and bel-2 (antiapoptotic gene). Bel-2 and osteopontin transcripts were not detected in pulp damaged tooth and dentin damaged tooth. Osteopontin is also antiapoptotic gene. Cell derived from dentin damaged tooth and pulp damaged tooth highly expressed apoptotic properties. Dentin damaged tooth and pulp damaged tooth did not express osteopontin, thus extracellular matrix surrounding pulp cell would not be contributed by osteopontin protein.