Influence of light intensity on two restorative systems

Objectives: High intensity curing lights are recommended almost universally on the basis of immediate curing depth measurements. Although this single factor is well documented, the influence of light intensity on other parameters has not been investigated extensively. Methods: Two restorative systems were examined with two light intensities in regard to four properties; polymerization shrinkage (density method), flexural modulus and strength (ISO 4049), hardness profiles after post-cure (Vickers), and marginal adaptation in dentine cavities (quantitative margin analysis). Results: The variation in light intensity did not significantly affect curing contraction or post-cure hardness profiles to a depth of 4.5 mm for either resin composite. Significant differences were found in flexural modulus with both restoratives: only one material demonstrated a light intensity-related influence on flexural strength. Marginal gap formation increased in each bonding agent/resin composite pair with increased light intensity. Conclusion: In clinically relevant layer thicknesses, curing a resin composite with a higher intensity light may demonstrate significant disadvantages due to increased shrinkage stress.