Technique for simple apatite coating on a dental resin composite with light-curing through a micro-rough apatite layer.

Tooth root surfaces restored with dental resin composites exhibit inferior biocompatibility. The objective of this study was to develop a simple technique for coating apatite onto a resin composite to improve its surface biocompatibility. First, we fabricated a polymer film coated with a micro-rough apatite layer and pressed it (coating-side down) onto a viscous resin composite precursor. As a result of light-induced curing of the precursor through the overlaid film, the micro-rough apatite layer was integrated with the resin composite and, thus, transferred from the polymer film surface to the cured resin composite surface as a result of the difference in interfacial adhesion strength. The transferred apatite layer attached directly to the cured resin composite without any gaps at the microscopic level. The adhesion between the apatite layer and the cured resin composite was so strong that the layer was not peeled off even by a tape-detaching test. The flexural strength of the resulting apatite-coated resin composite was comparable to that of the clinically used resin composite while satisfying the ISO requirement for dental polymer-based restorative materials. Furthermore, the apatite-coated resin composite showed better cell compatibility than the uncoated resin composite. The present apatite coating technique is well suited for dental treatment because the coating is applied during a conventional light curing procedure through simple utilization of the apatite-coated polymer film in place of an uncoated film. The proposed technique represents a practical evolution in dental treatment using light-curing resin composites, although further in vitro and in vivo studies are needed.