ABSTRACT
OBJECTIVES: This study aimed to evaluate the effect of fractional radiation on the mechanical properties of fluoride-releasing materials. MATERIALS AND METHODS: High-viscosity glass ionomer cement (F9), resin-modified glass ionomer cement (F2), glass hybrid restoration (EQ), and bioactive composite (AC) were divided into 3 subgroups: 0, 35, and 70 Gy fractional radiation doses. The specimens were subjected to surface roughness, Vickers microhardness, and compressive strength tests. The chemical components and morphology of the tested specimens were observed via energy dispersive spectroscopy and scanning electron microscopy. The data were analyzed using two-way ANOVA with Bonferroni post hoc analysis. RESULTS: After exposure to fractional radiation, the surface roughness increased in all the groups. F9 had the highest surface roughness, while AC had the lowest surface roughness within the same radiation dose. The Vickers microhardness decreased in F9 and EQ. The AC had the highest compressive strength among all the groups, followed by F2. More cracks and voids were inspected, and no substantial differences in the chemical components were observed. CONCLUSIONS: After fractional radiation, the surface roughness of all fluoride-releasing materials increased, while the Vickers microhardness of F9 and EQ decreased. However, the compressive strength increased only in F2 and AC.
ABSTRACT
OBJECTIVE: The purpose of this study was to evaluate the microhardness and mineral composition alterations in enamel and dentine after radiotherapy. MATERIALS AND METHODS: Forty human maxillary premolar teeth (20 pairs) were assigned to nonirradiated and irradiated groups, the latter irradiated by fractional radiation to achieve a total dose of 70 Gy. Microhardness measurement was performed on a Knoop microhardness tester. Chemical components were analyzed using energy dispersive spectroscopy and Fourier transform Raman spectroscopy. The morphology was observed using a scanning electron microscope. The microhardness data were analyzed using a paired t-tested and one-way repeated analysis of variance (ANOVA), and the mineral composition data using related-samples Wilcoxon signed rank test and related-samples Friedman's two-way ANOVA by ranks. RESULTS: The irradiated teeth had a significantly lower microhardness in both enamel and dentine compared with the nonirradiated teeth. The irradiated dentine at 50 µm from the external tooth surface at the cemento-enamel junction showed the lowest microhardness compared with other locations. There was no statistically significant difference in calcium:phosphate ratio and chemical components. There was a reduction in protein:mineral ratio in dentine and at the cemento-enamel junction after irradiation. The irradiated teeth exhibited crack lines at the dentine-enamel junction and in dentine. CONCLUSION: Fractional radiation reduced microhardness in both enamel and dentine. The cervical dentine exhibited the highest microhardness reduction compared with other enamel and dentine locations.
ABSTRACT
Objective: The aim of this study was to compare five toothpastes in terms of alteration of surface roughness and colour of red-wine-stained human enamel over time after brushing simulation. Methods: Stained specimens were randomly divided into five groups (n = 8): Oral-B Gum and Enamel (C), ZACT Stain Fighter (ZW), Colgate Optic White Volcanic Mineral (CW), Oral-B 3D White Luxe Fresh Breath (3DW), and Thepthai (TW). The colour and surface roughness of the specimens were measured after brushing simulation for four durations; two weeks, one month, six months, and twelve months. Abrasive particles in toothpaste were inspected under a scanning electron microscope. Results: Surface roughness was increased in the specimens that underwent brushing simulation in all groups (p < 0.05). ZW (6.33 ± 0.98 µm) exerted the most changes in surface roughness for all durations. Other groups showed similar surface roughness at each time point. ΔE00 and ΔL were increased in all groups until twelve months; however, there were no significant differences between C (ΔE00 = 30.17 ± 4.16, ΔL = 38.19 ± 4.34), CW (ΔE00 = 24.25 ± 10.52, ΔL = 31.12 ± 11.00), and TW (ΔE00 = 29.00 ± 3.96, ΔL = 36.68 ± 4.53) at any time period. Moreover, ZW (ΔE00 = 45.6 ± 8.01, ΔL = 53.03 ± 6.71) and 3DW (ΔE00 = 43.6 ± 7.33, ΔL = 51.03 ± 6.47) exhibited a substantial change and were statistically differed from the other groups after four-weeks. Various characteristics of abrasive particles were inspected under SEM. Conclusion: All five toothpastes increased the surface roughness altered the colour of red wine-stained human enamel over time.
