Effects of hydroxyapatite nanoparticle on remineralization of artificial root caries in vitro

An in vitro pH cycling model was used to evaluate the effect of nano-hydroxyapatite on the remineralization of artificial root caries. Sound human teeth fragments obtained from the cervical portion of the root were immersed in a demineralization solution for 96 h at 37°C to induce artificial root caries lesions. The demineralized samples were pH-cycled through treatment solutions, acidic buffer and neutral buffer for 8 days at 6 cycles per day. The samples were subsequently evaluated using a microhardness tester and scanning electron microscope (SEM). Nano-hydroxyapatite (nano-HA) and fluoride significantly increased the microhardness of the lesions (p < 0.05) when compared to a control group. SEM revealed nano-HA adhered to the dentin surface densely and some of them even covered the openings of dentin tubules. We concluded that nano-HA positively affects the demineralization and/or remineralization processes of artificial root caries lesions and may be a promising agent for non-invasive root caries therapy.