Enamel protection of resin composite containing hydrated calcium silicate by microleakage simulation

Abstract Background. The gaps at the margins of restorative composite resin can increase as the carious process occurs underneath the materials, causing further demineralization along the tooth cavity wall. The aim of this study was to evaluate the effects of restorative resin composite containing hydrated calcium silicate (hCS) filler on enamel protection against demineralization by simulating microleakage between the test material and teeth in a cariogenic environment. Methods. The experimental resin composites were composed of 70 wt% filler, which was mixed with a glass filler and hCS in a weight ratio of 70.0% glass (hCS 0), 17.5% hCS + 52.5% glass (hCS 17.5), 35.0% hCS + 35.0% glass (hCS 35.0), and 52.5% hCS + 17.5% glass (hCS 52.5). A light-cured experimental resin composite disk was positioned over a polished bovine enamel disk, separated by a 30-µm gap, and immersed in artificial saliva with pH 4.0 for 15, 30, and 60 days. After the immersion period, the enamel disk was separated from the resin composite disk and evaluated using a microhardness tester, atomic force microscopy, and polarized light microscopy. The opposing sides of the enamel and resin composite disks were observed using scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS). Results. The enamel surface showed a significant increase in microhardness, decrease in roughness, and remineralization layer as the proportion of hCS increased (P < 0.05). In the SEM image, enamel surface with hCS 35.0 and 52.5 after all experimental immersion periods showed a pattern similar to that of a sound tooth. Conclusions. The results demonstrated that increasing the hCS filler level significantly increased the prevention effect of enamel demineralization compared to restorative resin composites containing conventional dental glass filler. Despite some microleakage exposed to a cariogenic environment, these novel composites may be promising dental biomaterials for protecting teeth against demineralization and preventing secondary caries around the restorations.