A laser speckle contrast analysis (LSCA) study of the effect of curing irradiance on composite polymerization kinetics

The kinetics of resin composite polymerization plays an important, though not well understood, role it the development of shrinkage stress and the resultant integrity of the final restoration. In this report we investigate the effect of curing irradiance on the polymerization kinetics using a dynamic light scattering technique known as laser speckle contrast analysis (LSCA). Thin layer samples are considered with focus given to the effect of sample thickness on the rate results obtained with this method. We present results for the intensity fluctuation rate as a function of irradiance for two statistical models of intensity decorrelation: Lorentzian and Gaussian. Results indicate that the rate of scatterer motion varies approximately with the square root of irradiance, which agrees well with theory and previous results in the literature. Our results suggest that dynamic light scattering techniques, and LSCA in particular, provide an effective, non-contact means of assessing polymerization kinetics.

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