Color stability of resin matrix restorative materials as a function of the method of light activation.

The purpose was to investigate the influence of curing devices and curing times on the yellow value (b-value) of composites, ormocers and compomers after performing a suntest (EN ISO 7491). Eight samples of Charisma (CH), Durafill (DU), Definite (DE), and Dyract AP (DY) each were light cured with Translux Energy (tungsten halogen light) for 20, 40 or 60 s and with Apollo 95-E (plasma light) for 3, 10 or 20 s. All samples were subjected to a suntest. Before and after the suntest the yellow values (b-values) were determined and the change (Delta b) was calculated. When cured with Translux Energy for 20 and 40 s DU, CH, and DY revealed significantly negative Delta b-values. The b-value of DE remained nearly constant. When cured for 60 s, DU and DE shifted to more yellow while CH and DY still bleached a little. When cured with Apollo 95-E, a dramatic bleaching process of all materials investigated occurred after the suntest (significant negative Delta b). It may be concluded that the bleaching of composites, ormocers and compomers depends on (i) the used light curing device and (ii) the chosen curing times. The tungsten halogen light provided highly significantly superior results.