THE EFFECT OF CURING LIGHT VARIATIONS ON BULK CURING AND WALL-TO-WALLQUALITY OF 2 TYPES AND VARIOUS SHADES OF RESIN COMPOSITES

Objectives. This study evaluated the influence of light intensity and irradiation time variations on the curing efficacy of two types and va rious shades of resin composites and the effect of reduced light inten sity on the preservation of wall-to-wall continuity. Materials and Met hods. Three microfilled composites (in three different shades) and one hybrid composite were used in this study. Polymerization shrinkage, a nd the hardness and adaptation of adhesive restorations in dentin cavi ties were determined at light intensities of 175 and 700 mW/cm(2) and irradiation times of 10 and 60 s. Data were compared using in a genera l linear model analysis. Results. Shrinkage measurements were the indi cation of conversion and conversion rate. Reduced intensity slowed dow n the rate of polymerization but did not reduce the conversion as long as an irradiation time of 60 s was employed. High-energy irradiation caused increased separation of the composite from the tooth structure. On the basis of obtaining optimal conversion and adaption, it was dem onstrated that the irradiation time to be more effective than irradiat ion energy. Significance. Light-cured composites require an understand ing of their structure, pigmentation and irradiation parameters to obt ain optimal performance. High intensity light-curing does not necessar ily lead to optimal quality.