The effects of irradiance and exposure time on the surface roughness of bulk-fill composite resin restorative materials

OBJECTIVES: To evaluate the surface roughness of 4 different bulk-fill resin-based composites cured using different irradiance levels. METHODS: This in vitro study was performed in February 2017 to August 2017 at the College of Dentistry, King Saud University. Twenty-four specimens were prepared from each of the bulk-fill materials [Tetric N-Ceram (TNC), SonicFill (SF), Smart Dentin Replacement (SDR), and Filtek Bulk-Fill (FB)] using a brass metal mold, resulting in a total of 96 specimens, cured using a Bluephase N light curing unit. Half of the total number of specimens (N=48) were cured using high-power irradiance (1200 mW/cm(2)) for 20 seconds, while the remaining half (N=48) were cured using low power irradiance (650 mW/cm(2)) for 40 seconds. After 24 hours, baseline surface roughness of each specimen was analyzed using a profilometer, then polished using Sof-lex abrasive disks, and the surface roughness of all groups was assessed. RESULTS: Post-polished SonicFill cured at high irradiance had the highest mean surface roughness (0.23±0.03), whereas pre-polished Smart Dentin Replacement (0.11±0.01) and SonicFill (0.11±0.02) cured at low irradiance had the lowest mean surface roughness. CONCLUSION: High curing irradiance (1,200 mW/cm(2)) had no positive influence on the surface roughness of Filtek Bulk Fill and Tetric N-Ceram bulk-fill RBCs compared with lower curing irradiance (650 mW/cm(2)). However, the difference of curing irradiance significantly affected the surface roughness in SDR and sonic fill RBCs.