Pages 630-636, Language: EnglishLuo, Y. / Lo, Edward C. M. / Fang, Daniel T. S. / Wei, Stephen H. Y.Objective: The aim of this investigation was to evaluate the clinical performance of a new compomer restorative system, Dyract AP, placed in combination with Non-Rinse Conditioner and Prime & Bond NT in permanent posterior teeth. Method and materials: Fifty Class II and 41 Class I restorations were placed in 39 patients by 1 dentist. The restorations were evaluated directly, with modified US Public Health Service criteria, and indirectly, with color slides and polyvinyl siloxane impressions, at baseline and 6 months and 1 year after placement. Preoperative and 1-year postoperative bitewing radiographs were also taken. Results: All 82 restorations available for 1-year evaluation were in situ. No postoperative sensitivity or pulpal problems were reported. Four Class II restorations (4.9%) failed because of partial fracture or recurrent caries. The percentages of Alfa score for each criterion were color match, 95.1%; marginal discoloration, 57.3%; marginal integrity, 35.4%; anatomic form, 98.8%; and surface texture, 91.5%. The average wear rate of Dyract AP was low (18.5 ± 11.7 µm at 6 months and 35.7 ± 13.6 µm at 12 months). Conclusion: The excellent handling characteristics, the good clinical performance, and the improved wear resistance suggest that this compomer will provide reliable direct tooth-colored restorations in stress-bearing areas.