How Much Energy Does a Class I Restoration Receive?

Methods: The irradiance received by a Class I restoration in tooth #2.7 was measured using a spectroradiometer. To simulate clinical reality, the tooth was located in a mannequin attached to a dental chair. After obtaining appropriate Ethics Committee approval, 20 volunteers cured the simulated restoration. Three curing lights were used for the following times: Optilux401 (20s), SmartLiteIQ2 (20s), BluephaseG2 (5s). The irradiance (mW/cm²) received by the restoration was recorded throughout the light curing process to calculate the total energy (J/cm²) delivered by each volunteer. The critical amount of energy required for the bottom surface of 2mm of Filtek Supreme A2B to reach 80% of the hardness at the top surface was calculated.

Results: The critical amount of energy required for the bottom surface of Supreme A2B to reach 80% of the hardness reached at the top was 10 J/cm². In 20 seconds the Optilux401 and the SmartLiteIQ2 delivered on average 7.5 and 9.7 J/cm² respectively, and in 5 seconds the BluephaseG2 delivered 9.1 J/cm². The amount of energy delivered by the 20 volunteers ranged from 5 to 12 J/cm². Analysis of variance showed there was a significant difference in the total energy delivered by the three lights (p<0.05). When the curing times were doubled to 40s and 10s, then all the volunteers delivered an adequate amount of energy.

Conclusion: Dental restorations receive less energy than is possible due to errors in positioning the light guide over the restoration. To adequately cure Filtek Supreme A2B, the BluephaseG2 light should be used in the mouth for ten seconds, and the SmartLiteIQ2 or the Optilux401 should be used for 40 seconds. NSERC, NORTH and Dalhousie University supported this study.