Selenium anion substitution in hydroxyapatite: chemo-mechanical effects compared with root canal dentin

The objective of this study was to assess the effect of selenium substitution on the chemical and mechanical properties of synthesized hydroxyapatite and compare them with natural dentin. Additionally, this study aimed to compare the properties of synthetic and natural hydroxyapatite to determine if laboratory-synthesized hydroxyapatite could serve as a viable substitute for natural hydroxyapatite. Four groups were analyzed: natural dentin (ND-treated and ND-untreated) and synthetic hydroxyapatite (SD-Treated and SD-untreated), each with 10 samples. Samples were exposed to selenium acid for 2, 5, and 10 min, with saline as a control. Selenium content was measured using ICP-MS, and Vickers microhardness testing was performed. Solubility was assessed in 0.1 M butyric acid (pH 4.4) for 24 h at 37 °C with 100% humidity. Selenium concentrations were significantly higher in ND-treated subgroups than in SD-treated subgroups (P < 0.05), mirroring trends observed in surface microhardness. ND-treated groups also exhibited significantly lower solubility compared to other groups. The results suggest a correlation between selenium levels and dentin's mechanical properties. However, synthesized hydroxyapatite may not be an ideal in vitro model for evaluating dentin fortification.