Colour changes on curing light-activated anterior restorative resins

With many composite resins operators may notice a change in colour after light curing the restoration. Three types of specimen--a disc, a simulated Class III and a veneer--were made using a series of composite resins. Generally, resins became lighter or more translucent on irradiation. This was not only true for a range of resins from a single company but also the extent of the change was brand dependent. For most resins the opacity decreased with curing and most of this change occurred with a 20 seconds cure. The reflectance was approximately 50 per cent greater for resins placed over a white background than on a dark background for the thin disc specimens.