FRONZA BM * 1 , AYRES APA 1 , PACHECO RR 1 , AMBROSANO GMB 1 , BRAGA RR 2 , RUEGGEBERG FA 3 , M GIANNINI 1 1 Dentistry School, State University of Campinas, Piracicaba, Brazil 2 Dentistry School, University of São Paulo, São Paulo, Brazil 3 College of Dental Medicine, Georgia Regents University, Augusta, EUA *[email protected] OBJECTIVES MATERIALS AND METHODS The aims of this study were to investigate the polymerization shrinkage stress (PS) and the influence of depth on biaxial flexural strength (FS) and elastic modulus (MO) of four bulkfill and one regular composites. The hypothesis tested were that (1) the bulkfill composites would have lower PS values; (2) there would be no difference in mechanical properties at different depths for bulkfill composites, while to the conventional composite these properties would be reduced with increasing depth. Herculite Classic Kerr Tetric EvoCeram Bulk Fill Ivoclar Vivadent Filtek Bulk Fill 3M ESPE Sure6ill SDR Flow Dentsply EverX Posterior GC Group H Group S Group E Group T Group F RESULTS FS at different depths did not present statistically significant differences for all bulkfill composites, suggesting an uniform polymerization throughout the material. In general, MO of the top disc was higher than that located at the bottom for all materials tested. Regarding PS, values observed for most bulkfill materials were similar to the regular composite. Only one bulkfill composite showed lower PS. Acknowledgement: FAPESP (2013/05247-4) #2197 0.5 mm 1 mm 1.5 mm 2 mm 2.5 mm 3 mm 3.5 mm 4 mm a b b b c Discshaped specimens (0.5 thickness x 6 mm diameter) were fabricated using a set of eight Teflon molds, simulating a polymerization depth of 4 mm. Composites (n = 8) were light activated according to manufacturers` instructions. These procedures were performed in a lightproof room with controlled temperature of 21 o C. Specimens dimensions were measured and each disc was tested in the pistonring biaxial test coupled to universal testing machine at 1.27 mm/min until failure. Maximum load was recorded for each specimen, and elastic modulus was determined from the linear portion of each stress/strain curve. Polymethyl methacrylate rods with 4 mm diameter were used as substrate. Surfaces were sandblasted with alumina particles followed by silane and resin bond. The composites (n = 5) were inserted between them with space fixed at 0.8 mm, determining a volume of 6.8 mm 3 (CFactor: 1.3). An extensometer was a-ached to the rods and the composite was lightac6vated for 10 seconds. Force development was monitored for 10 minutes from the beginning of lightac6va6on and the maximum nominal stress was calculated (MPa) by dividing the maximum force value recorded by the crosssec6on of the rods.