7 - Method for Detecting Calcium Phosphate Mineralization on Dental Composites

Abstract

The purpose of the study is to develop a procedure for determining the in-vitro calcium phosphate mineralization potential of dental composites. A dental material containing Methacrylate-Functionalized Calcium Phosphate (MCP), was studied to determine a procedure to identify and quantify its capacity to create calcium phosphate mineralization. This study used Activa Presto, a dental composite containing 3 wt.% MCP (3MCP), and a control with the same chemical formulation as Presto, but without MCP (0MCP). Using ISO 23317:2007 as a guideline, six cylindrical samples were created with an approximate diameter of 9.5 mm and height of 4 mm. Each sample was fabricated with an embedded nylon thread, which was used to suspend each sample in 25 mL of phosphate buffered saline (PBS) in individual plastic bottles. The samples were stored in a 37 C incubator for time periods of one, two and four weeks, and the PBS solution was replaced twice weekly. Once the designated time period elapsed, the samples were removed from the solution, placed back in the 37 C incubator and desiccated for scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) evaluation. The SEM of the 0MCP sample was uniform throughout. At 3000x magnification the surface was granular and showed no sign of crystal formation. All the SEMs of the 3MCP samples had areas of crystal formation and areas where crystals had not yet formed (nucleation areas). The nucleation areas on the 3MCP sample looked granular, like the control, but EDS revealed a different surface composition. The EDS shows that the 0MCP sample had minimal calcium and phosphorus, elements essential for mineralization. This sample had a high amount of silicon, which comes from the silica inherent in dental composites. The nucleation area of the 3MCP sample had over five times the amount of calcium and phosphorus compared to the control, which indicates that there is an increase in potential for mineralization. The crystal area of the 3MCP sample shows about three times the amount of calcium and phosphorus when compared to the nucleation area, these values confirm the surface has been mineralized. Additionally, silicon was not detectable in this area, which suggests that the crystals are dense, and completely cover the underlying silica in the composite. The results of this study confirm that this procedure is suitable to determine the in-vitro mineralization potential of dental composites.Download : Download high-res image (307KB)Download : Download full-size image