Accelerating the Curing of Resin Composite at the Cavity Floor

Abstract

Objective: The aim of this study was to evaluate the effect of a slow-start curing method on accelerating the curing of different shade resin composites at the cavity floor. Materials and Methods: Clearfil AP-X or Photo Clearfil Bright resin composite was placed in a Teflon mold. Then the resin composite was polymerized using one of two light curing techniques: 1) conventional curing method: 600mW/cm^2 for 60s, or 2) slow-start curing method: 270mW/cm^2 for 10s+interval for 5s+600mW/cm^2 for 50s. After light curing, Knoop hardness number (KHN) was measured at the top and bottom surfaces of the resin specimens. Results: A greater KHN was observed at the top surface of the resin composite than at the bottom surface with the conventional curing method for both resin composites and shade (p<0.05). The slow-start curing method showed a statistically greater KHN at the base of the resin composite than at the top surface for Photo Clearfil Bright (shade A3) (p<0.05). The same KHN at the top and base surfaces of the resin composite was recorded when using Clearfil AP-X and Photo Clearfil Bright (shade B4) (p<0.05). Conclusions: The slow-start curing method accelerated the curing of resin composite at the bottom surface. The light-curing resin composite has the property of increasing the contrast ratio during polymerization showed accelerating the curing at the cavity floor. It was suggested that this type of resin composite compensates the polymerization contraction stress.