Purpose: To study the durability of a recently developed low-shrinkage resin composite, suggested to counter the stress formation in direct resin composite restorations. Materials and Methods: Each of 50 patients received one or two pair(s) of Class II restorations. The first restoration in the pair was a low-shrinkage resin composite (InTen-S) and the second a hybrid resin composite restoration (Point 4). Both restorations were placed with an etch-and-rinse bonding system and an oblique layering technique. A total of 106 restorations, 33 premolar and 73 molars, were placed. The restorations were evaluated annually. Results: At 5 years, 97 restorations were evaluated. Two participants reported slight postoperative sensitivity symptoms for a few weeks after placement. Twelve non acceptable restorations were observed during the 5 years, five InTen-S (10.4%) and 7 Point 4 (14.3%) (not significant). Secondary caries was the main reason for failure (8) followed by composite fracture (2) and tooth fracture (2). Conclusion: The low-shrinkage resin composite showed good durability, but not significantly better than the control resin composite in Class II cavities. Most failures occurred at the last part of the study. Secondary caries was the main reason for failure.

Keywords: clinical trial, composite restoration, posterior, resin, polymerization shrinkage