Effect of gamma irradiation on the wear behavior of human tooth dentin.

OBJECTIVES: The objective of this study was to evaluate the effect of gamma irradiation on the wear behavior of human tooth dentin in terms of possible alterations in crystallinity, grain size, and composition. MATERIALS AND METHODS: Human premolars (n = 19) were collected to obtain the perpendicular or parallel to the direction of the dentin tubule specimens. Each specimen was subjected to 60 Gy of gamma irradiation, in daily increments of 2 Gy. The nanoscratch tests were conducted. The scratch traces were observed via scanning electron microscope (SEM) and surface profilometer. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to investigate the alteration of crystallography and chemical composition of dentin after irradiation. The change of surface microhardness (SMH) was also evaluated. RESULTS: The nanoscratch results showed that the friction coefficient of dentin after irradiation became higher, and the depths and widths of scratch were greater than that of dentin before irradiation. Additionally, irradiation decreased the crystallinity of dentin and induced the formation of bigger crystals. The carbonate/mineral ratio was increased. Furthermore, a significant reduction in microhardness after irradiation was observed. The main damage mechanisms consisted of the formation of delamination and crack in both the specimens cut perpendicular and parallel to tubule dentin after irradiation. CONCLUSION: Irradiation affected directly the wear behavior of tooth dentin, accompanied by the alterations in crystallography, chemical composition, and surface microhardness of dentin. CLINICAL RELEVANCE: This would help extend understanding the influence of irradiation on dentin and provide suggestions for selecting more suitable materials for irradiated tooth.