Avaliação do efeito de diferentes tempos de fotoativação e da interposição de matriz de silicone na estabilidade de cor das resinas compostas

Abstract

Introduction- The techniques of photoactivation and composite resin restoration construction can influence the behavior of composite resins over time. Objective- To evaluate the color stability of composite resins using the guided restoration technique under different transparent addition silicones and two different photoactivation times. Materials and methods- A total of 120 cylindrical specimens (6mm x 1.5mm) were manufactured using two composite resins: Opallis Conventional EA3 (FGM, Brazil) (n=60) and Opallis Flow A3 (FGM, Brazil) (n=60). The experimental groups that were to undergo the restorative technique using a transparent silicone matrix were divided into three subgroups: control (without a matrix) (n=20), Silic One Clear Body (FGM, Brazil) (n=20), and Elite Transparent (Zhermarck, Italy) (n=20). The conventional composite resin was photoactivated for 20 seconds and the flowable resin for 40 seconds, according to the manufacturer's recommendations. Subsequently, an additional photoactivation of 20 seconds (20s+20s and 40s+20s) was performed in half of the groups (n=10). Another 120 specimens, with the same dimensions, were then manufactured using the conventional resin Opallis Conventional EA3 (FGM, Brazil) and photopolymerized under different exposure times: 20s (n=60) and 40s (n=60). Both groups were further subdivided for polymerization using a transparent addition silicone matrix, Silic One Clear Body (FGM, Brazil), with two different thicknesses: control (without a matrix) (n=20), 2mm (n=20), and 4mm (n=20). For each matrix group, two different photoactivation times were used: 20s (n=10) and 20s+20s (n=10) or 40s (n=10) and 40s+20s (n=10). In both studies, the total color variation (ΔE) was assessed using a reflection spectrophotometer (UV-2600, Shimadzu), considering the parameters of the CIELab* system, the initial color was registered and recorded again after 15 days. Levene’s and Shapiro-Wilk tests were used to evaluate, respectively, data homogeneity and normality; and a Tukey's test was performed as the post hoc test. Results-The analysis of the reflection spectrophotometer results showed no significant differences (p≤0.05) in most groups when comparing the types of resins. However, in the case of the flowable resin associated with the Elite matrix, additional photopolymerization improved color stability. No statistically significant differences were observed in color stability when testing matrix thickness in most groups. A polymerization time of 20 seconds was sufficient without the matrix or when using a 2mm matrix. When using a 4mm matrix, a photoactivation of 40 seconds is recommended, either in a single exposure with the matrix in place or in two 20-second stages, with and without the matrix, respectively. Conclusion- Conventional and flowable resins exhibit similar behavior regarding color stability. The manufacturer’s recommended photoactivation time should be followed; however, an additional exposure time may enhance the color stability of these resins, especially when transparent matrices are interposed during the guided restoration technique.