Effects of Different Radiation Doses on the Microhardness, Superficial Morphology, and Mineral Components of Human Enamel

Objective: To evaluate the effects of three different radiotherapy doses (20, 40, and 70Gy) on the microhardness, superficial morphology, and mineral content (based on Ca and P values) of three different depths of human enamel (cervical, middle, and occlusal).

Design: Thirty-four third molars were cut, separated, and prepared. Microhardness samples (n=30) were embedded in acrylic resin and then polished, and depths were delimited. Microhardness tests were performed on cervical, middle, and occlusal enamel pre- and post-radiotherapy with a load of 50g for 30s. For the scanning electron microscopy (SEM) analysis (n=4) and energy dispersive X-ray spectroscopy (EDS) (n=12), samples were fixed in a 3% glutaraldehyde solution, washed in 0.1M cacodylate solution, and dehydrated in crescent concentrations of ethanol. Microhardness data were tested for significant differences using a two-way analysis of variance (ANOVA) and Tukey's test (p<0.05), while SEM and EDS were evaluated qualitatively.

Results: The results showed a decrease in microhardness values only in the cervical enamel, regardless of the radiation dose used; no morphological or mineral change was observed.

Conclusion: Radiotherapy can affect the microhardness values of only cervical enamel without compromising the morphological or mineral (Ca and P) content at any depth.