Introduction: Gamma radiation is usually used, as a primary or supplementary
treatment, for oral cancer patients. Aim: The present work was undertaken to investigate,
in vitro, the effect gamma irradiation of a cumulative dose of 60 Gy (20 Gy/day over
three days) on enamel and dentin microhardness before and after demineralization
and remineralization. Materials and methods: Ten healthy freshly extracted human
third molars were used in this study. The teeth specimens were cut perpendicular to
their occlusal surface into two halves. Half of the specimens were gamma-irradiated
to a dose of 60 Gy (20 Gy/day). The data involved the measurement of VHN Vickers
microhardness on both radiated and non-irradiated. Results: The results indicated that
the mean microhardness values of the non-irradiated enamel samples were decreased
after gamma irradiation, and were significantly decreased after demineralization;
meanwhile, the microhardness values of the demineralized non-irradiated enamel
samples were significantly increased after remineralization. The results showed that
the microhardness of the demineralized non-irradiated dentin samples was increased,
and that the microhardness of the gamma-irradiated dentin samples was slightly
decreased. Conclusions: gamma-irradiation had significant effect on enamel and dentin
microhardness values and had significant decrease effect on demineralization of enamel
while had significant increase by remineralization.