Effect of Bleaching Agents on Composite Resins With and Without BIS-GMA.

Abstract Objective to evaluate the change in color, hardness and roughness produced by carbamide peroxide (CP) at two different concentrations on two resins. Materials and Methods 16% or 45% CP was applied to 66 resin discs with and without Bis-GMA. Color was measured with a spectrophotometer, and ΔE ab and ΔE 00 calculated. Microhardness tester and SEM were used. Results In both composites, the a* and b* coordinates tended to red and yellow, respectively, and were significant in the Bis-GMA group (p < 0.05). The ΔE ab and ΔE 00 were higher in the composite with Bis-GMA, regardless of the treatment received (p < 0.05). The microhardness was reduced in both composites regardless of the PC concentration compared to the control (p < 0.05). 45% CP reduced the microhardness in the resin group with Bis-GMA compared to 16% CP (p < 0.001), but was not significant in the resin without Bis-GMA (p = 1). An increase in roughness was directly proportional to the concentration of CP and it was more notable in the composite without Bis-GMA. Conclusions The composite with Bis-GMA showed a greater tendency to darken than the one without Bis-GMA. The surface hardness of the composite was reduced in both composites and was not influenced by CP concentration in the composite without Bis-GMA. Clinical relevance: Bleaching is a common procedure nowadays. It is important to know how how CP affects composites to establish a prognosis of the treatments, both in terms of color change, roughness or hardness.