silicon and prisma-fil

The degrees of in vitro three-body wear resistance of a hybrid, a small-particle, and a microfilled composite were determined after water storage for up to 24 months. The hybrid composite was the most wear-resistant, while the microfilled composite showed the most wear. The hybrid composite showed no loss of wear resistance as a result of water storage. The small-particle composite showed a decrease in wear resistance after water storage only when tested with silicon carbide abrasive. The wear resistance of the microfilled composite decreased following water storage when tested with either a soft (CaCO3) or a hard (SiC) abrasive. For all composites, the soft abrasive was not capable of causing preferential wear of the polymer matrix, as observed on in vivo specimens. Instead, the filler particles became flattened, with minimal loss of interparticle substance. The hard abrasive did cause preferential wear of the matrix. All composites absorbed water and leached silicon during water storage, indicating that the filler-polymer bond was attacked by hydrolytic degradation. Scanning electron microscopic evaluation of the three-body wear specimens indicated that the in vitro wear method did not duplicate in vivo wear conditions (e.g., the hard abrasive caused excessive wear and chipping of the filler particles in vitro, a pattern that was not usually observed in vivo). Filler-polymer de-bonding was observed on in vivo specimens of all the composites, while it was found only on the in vitro microfilled composite specimens. These findings suggest that filler dislodging is a complex process that cannot be simulated with the in vitro wear method used in this study, not even after prolonged water storage.

Topics: Analysis of Variance; Bisphenol A-Glycidyl Methacrylate; Composite Resins; Drug Storage; Hydrolysis; Materials Testing; Microscopy, Electron, Scanning; Particle Size; Silicon; Surface Properties; Time Factors; Urethane; Water

After the gross reduction and fine finishing of a composite resin restoration, selecting a system to create the smoothest polish is difficult because high magnification is necessary to compare the surface roughness. The surfaces of four anterior and posterior composite resins were compared using a Mylar strip, an unfilled resin as a glaze, polishing with three rubber polishers, and three different manufacturers' series of disks. This study suggested that pairing a specific composite resin with a matching polishing system produced the smoothest surface. Because of the differences in the size, shape, number of filler particles, and the type of resin, one system was incapable of creating the smoothest surface for all composite resins.

Topics: Acrylic Resins; Aluminum Oxide; Analysis of Variance; Bisphenol A-Glycidyl Methacrylate; Carbon; Carbon Compounds, Inorganic; Composite Resins; Dental Materials; Dental Polishing; Equipment Design; Evaluation Studies as Topic; Methacrylates; Polymethacrylic Acids; Polyurethanes; Resin Cements; Rubber; Silicon; Silicon Compounds; Surface Properties