Effect of radiotherapy on the surface roughness and microhardness of contemporary bioactive restorative materials

The aim of this in vitro study was to evaluate the effect of radiotherapy on the surface microhardness and roughness of different bioactive restorative materials.

A total of 60-disc specimens (5 mm × 2 mm) were performed in four groups (n = 15 each) from Equia Forte HT, Cention N, Activa Bioactive Restorative, and Beautifil II. Following the polishing procedure (600, 1000, 1200 grit silicon carbide papers), all specimens were irradiated at 2 Gy per fraction, five times a week for a total dose of 70 Gy in 30 fractions over 7 weeks. Before and after the irradiation, the specimens were analyzed regarding the surface roughness and microhardness. Surface morphology was also analyzed by scanning electron microscopy. Kruskal-Wallis test, Wilcoxon test, and paired sample t-test were used for statistical analysis.

Significant differences were found after radiation with increased mean roughness of both Cention N (p = 0.001) and Beautifil II (p < 0.001) groups. In terms of microhardness, only the Beautifil II group showed significant differences with decreased values after radiation. There were statistically significant differences among the groups' roughness and microhardness data before and after radiotherapy (p < 0.05).

The effect of radiotherapy might differ according to the type of the restorative material. Although results may differ for other tested materials, giomer tends to exhibit worse behaviour in terms of both surface roughness and microhardness.

In patients undergoing head and neck radiotherapy, it should be taken into consideration that the treatment process may also have negative effects on the surface properties of anti-caries restorative materials.