Caries Prevention After Surface Reaction-Type Prereacted Glass Ionomer Filler-Containing Coating Resin Removal from Root Surfaces

Severe periodontal diseases cause root exposure, and there is no established method for the protection of exposed root surfaces. PRG Barrier Coat is a coating material with bioactive prereacted glass ionomer filler (hereafter, filler). However, the material can be detached in some clinical situations. We evaluated the effects of PRG Barrier Coat removal on root dentin demineralization under simulated oral cavity pH conditions. Five extracted human teeth were prepared, and three 200-mu m-thick single sections were obtained from each tooth. The polished surfaces, except the outer surface, were covered with a wax coating. PRG Barrier Coat (BC group) or Fuji III (FIII group), a glass ionomer cement, was applied to the root surfaces of one section each from each tooth and removed after 24 h. The remaining sections were included as a control group. Then, all specimens were subjected to pH cycling (pH 6.8-4.5) for 6 weeks. All specimens were observed using transverse microradiography images obtained weekly during pH cycling, which were used for integrated mineral loss assessments. Fluoride and calcium levels in each specimen were also evaluated at 5 weeks using a proton-induced gamma emission/proton-induced X-ray emission system. The control group surfaces and the BC and FIII group subsurfaces showed demineralization at 5 weeks, while an outer surface remineralization layer formed in the BC group. In the BC group, subsurface demineralization was observed at week 1, and it disappeared at week 6. There were no significant differences in IML values before and during pH cycling in the BC and FIII groups. Furthermore, fluorides penetrated the root surfaces of specimens in both groups. These findings suggest that PRG Barrier Coat and FIII supplemented the root surface with fluoride and inhibited demineralization, which can facilitate caries prevention for approximately 1 to 6 months.