Fluoride-incorporated apatite coating on resin-based composite via laser-assisted rapid pseudo-biomineralization

Abstract

A thin-layer of fluoride-incorporated hydroxyapatite (FAp) is useful as an acid-resistant antibacterial mineralized coating to protect a tooth surface. Recently, we achieved rapid and area-specific FAp coating on the surfaces of human tooth substrates via precoating with a light-absorbing agent, indocyanine green, followed by laser irradiation in a fluoride-containing supersaturated calcium phosphate solution. In the present study, this FAp coating technique was applied to a substrate of resin-based composite (RBC), an artificial material with no biomineral component. Similar to the case of tooth substrates, a mineralized layer consisting of needle-like FAp crystals was formed on the RBC surface after laser irradiation for 3 min. The needle-like crystals increased in size with increasing laser power. In the absence of fluoride ions in the supersaturated solution, a layer consisting of plate-like octacalcium phosphate crystals was formed on the RBC surface. The present FAp coating technique was finally applied to an RBC-restored tooth substrate. Cross-sectional analyses revealed that the boundary region between the tooth and RBC was coated and sealed with a mineralized layer. The present FAp coating technique is potentially a new tool to seal the tooth–RBC boundary and reduce the risk of secondary caries associated with RBC restorations.