IADR Abstract Archives

Effect of Irradiance on the Rate of Resin Polymerization

Objectives: Curing lights are becoming more powerful and curing times are getting shorter. The degree of polymerization of dental resins can be determined from microhardness recordings, or by calculating the degree of conversion from Fourier Transform Infrared Spectroscopy (FTIR) recordings. This study investigated the effects of irradiance on the rate of polymerization and hardness while delivering the same amount of energy to the resin composite.

Methods: Tetric Evoceram A2 was cured on a Tensor 27 FTIR machine which had a temperature controlled Attenuated Total Reflectance detector to maintain the composite at 35oC. The SmartLite IQ2 (delivering 750 mW/cm2) and a Bluephase G2 curing light (delivering 3000 mW/cm2) were used to cure the specimens. The degree of conversion was monitored in real time for the first 60 seconds and the polymerization rates were compared. After 2 hours, the specimens were removed and the Knoop microhardness was measured at 9 locations at the top and bottom of the specimens. Three specimens were made with each light and the results were compared using ANOVA and paired t-tests (α=0.05).

Results: There was a difference in rate of polymerization between the two lights, but there was no significant difference in the final degree of conversion and the Knoop hardness. When used for 5 seconds, the Bluephase G2 produced the same degree of conversion and Knoop microhardness values as the SmartLite used for 20 seconds. However, the rate of polymerization was significantly faster for the Bluephase G2.

Conclusion: The Bluephase G2 is a powerful LED curing light delivering four times the irradiance of the SmartLite IQ2. Five seconds of light curing with the Bluephase G2 produced similar degree of conversion and Knoop microhardness values to the SmartLite IQ2 used for 20 seconds. NSERC, NORTH and Dalhousie University supported this study.


IADR/CADR General Session
2008 IADR/CADR General Session (Toronto, Ontario, Canada)
Toronto, Ontario, Canada
2008
38
Dental Materials 6: Polymer-based Materials - Physical Properties and Performance
  • Felix, Christopher M.  ( Dalhousie University, Halifax, NS, Canada )
  • Price, Richard Bengt  ( Dalhousie University, Halifax, NS, Canada )
    • Oral Session
    Resin Polymerization
    07/02/2008