Effect of water storage and additional polymerization on the color parameters of flowable resin composites

Tooth colored dental restorative materials should maintain their chromatic properties throughout their service period. The aim of this study was to examine the possible color changes of flowable resin composite filling materials following water storage. The effect of additional light curing on color stability of restorative materials was also investigated.

Six brands of light-cured flowable resin composites of the same shade (A3) were prepared from two groups generated by curing for 20 or 60 seconds. The initial color parameters of the flowable composite samples were measured with a dental colorimeter according to the CIELAB color scale, and the samples were stored in distilled water at 37°C. Following 2 weeks' water storage, the measurements were repeated. The color differences (ΔE*(ab)) were calculated according to the CIELAB formula. Statistical differences between the measurements were analyzed by ANOVA and Duncan's tests.

No initial color variation between the samples cured for 20 seconds and 60 seconds was perceptible (ΔE*(ab)<3.3). However, after 2 weeks' water storage, a noticeable color change, ΔE*(ab)>3.3, was detected in Eco-flow, Filtek Supreme and Grandio samples in both polymerization groups.

Flowable resin composites may exhibit a significant color change as a result of water storage. Sixty seconds exposure period does not influence the final color.

Clinicians should be aware of color shifts in flowable resins.