Biodegradation of commercial dental composites by cholesterol esterase

The research literature suggests that current dental polymeric composites are not chemically inert at the material/biological interface. Several studies have investigated the process of "biodegradation" on dental composites in the presence of enzymes, by monitoring changes in weight loss and surface hardness properties. However, it is hypothesized that these methods can provide an erroneous measure of biochemically induced degradation, since they are less sensitive to molecular events and lack the ability to provide chemical information. Knowledge of the latter is important because it relates to the biological significance of biodegradation, i.e., the identification and quantification of released compounds that may be capable of influencing cell, bacteria, or enzyme function. It was the objective of this study to compare three methods (weight loss, surface micro-hardness, and liquid chromatography combined with mass spectrometry) for their ability to measure the effect of enzyme-induced biodegradation on three commercial composite resin materials. The enzyme was cholesterol esterase, and the composites were Silux Plus XL, Z100 A2 (3M), and TPH XL (L.D. Caulk). Biodegradation was readily detected by liquid chromatography, and its sensitivity was shown to be substantially greater than that of weight loss or surface hardness measurements, although surface hardness measurements did show some agreement with liquid chromatography data. The data also indicated that the levels and distribution of released degradation products can vary substantially from one product to the next, and that this merits further investigation if the potential impact of different commercial restorative materials on cell and bacteria function is to be assessed.