effect of preheat repetition on color stability of methacrylate and silorane-based composite resins

Background. the aim of this study was to investigate the effect of preheating methacrylate- and silorane-based composite resins on their color stability up to 40 times at 55‒60°c. methods. seventy-six methacrylate and silorane-based composite resin samples, with a diameter of 10 mm and a height of 2 mm, were divided into 4 groups (n=19). after the samples were prepared, their color parameters were determined using a reflective spectrophotometer. the composite resin samples were separately stored in a solution of tea for 40 consecutive days. then the samples underwent a color determination procedure again using a spectrophotometer and color changes were recorded. finally two-way anova was used to study the effect of composite temperature on its staining (p<0.05). independent-samples t-test was used to evaluate changes in conversion rates of preheated composite resin samples compared to non-heated samples at p=0.005 and p=0.029 for silorane-based and z250 composite resin samples, respectively. results. both composite resin type (p=0.014) and preheating (p<0.001) had significant effects on δe. conclusion. repeated preheating of methacrylate- and silorane-based composite resin samples, up to 55‒60°c for 40 rounds, resulted in more color changes compared with unheated composite resin samples. after storage in a solution of tea the color change rate in the composite resin samples of silorane-based was higher than the z250 composite resin samples.