In vitro wear device for determining posterior composite wear

Background. An in vitro device has been developed to predict the long-term clinical performance of posterior composite resins. in contrast to most sys tems, it is based on three-bodied wear the type of wear generated by food b olus during mastication. Methods. The authors wear-tested two groups of materials that included post erior composite resins, a castable ceramic, an amalgam and an unsalinated c omposite resin. After the wear-testing device concluded 400,000 cycles, the authors evaluated replicas of restoration surfaces for material loss. They used scanning electron microscopy to determine the mechanism of wear. Results. The authors detected considerable differences in wear among the va rious materials included in the study. All of the differences, however, fel l within the range of results obtained from the positive and negative contr ols (unsilanated composite resin and ceramic, respectively). A comparison o f the in vitro wear values with the wear values obtained from a series of o ngoing clinical studies at the same institution revealed a high level of ag reement. Furthermore, replicas of the laboratory-tested composite resin sam ples revealed the same wear patterns as those generated from clinical resto rations. The variation coefficients for then vitro data generally did not e xceed 5 percent, whereas those for the clinical data commonly averaged 20 p ercent. Conclusions. Based on the results of this study, the authors conclude that the in vitro testing device is reliably capable of predicting long-term cli nical wear values. The results obtained after 92 hours of wear testing corr elated closely with those obtained after three years of clinical testing. Clinical Implications. Long-term clinical studies are both time-consuming a nd expensive. Reliable in vitro wear-testing techniques allow manufacturers to develop or modify composite resin systems in considerably shorter perio ds.