Photopolymerized resins: surface hardness variation in relation to time of polymerization and setting.

The authors studied the superficial hardness of composite resins cured for two different times: 20 and 40 seconds of light exposure. The hardness values were read immediately and 24 hours after polymerization. A significant increase in hardness was observed with 40 s exposure as compared to 20 s. Hardness values were significantly higher at 24 h than immediately after polymerization.