In Situ Investigation on Color change of Resin Composite Restoratives Cured by Two Different Curing Units

Abstract: Purpose: To investigate and compare in situ the effect of halogen and high-performance light emitting diode light curing unit on the colour change of resin composite. Methods: 240 standardized disc-shaped resin composite specimens (4 x 1.5 mm) were prepared;120 using microhybrid composite and 120 using nanofilled composite (60 bleaching shade and 60 enamel shade for each group). Each subgroup of 60 specimens was divided into two subclasses (30 specimens each) one was polymerized using halogen and the other using HP LED. Twenty patients with partial or complete dentures participated after written consent. They were divided into two groups of ten patients. The first group received 80 specimens (10 from each subclass) investigated after one week, then received another 80 investigated after 6 months and the second group received 80 specimens investigated after one year. Colour assessment was performed by correlating data obtained using two methods: (1) A reflectance spectrophotometer. (2) A digital determination method. Data were analysed using ANOVA and Tukey’s post-hoc test. Results: There was no statistically significant difference of mean color change for both curing lights. Good agreement was found between the contemporary spectrophotometer and the digital spectroradiometer at p < 0.001. Conclusions: Biodegradation of resin composite by the oral environmental factor has a direct effect on its optical properties. Discoloration properties of the resin composite are material, shade and time dependant. However, th