Resumo:
Introduction – The clinical performance and physical properties of light-cured resin materials are highly influenced by the degree of monomer-to-polymer conversion. This conversion depends not only on the visible light emitted by the curing device and the photoinitiator system present in the composite resin but also on the amount of light energy delivered to the composite resin. Objective – To conduct an in vitro evaluation of how the angulation of different light-curing units affects color variation of composite resins; and to assess color variation under a transparent addition silicone matrix. Material and Methods – To evaluate color variation, 120 disc-shaped specimens (6mm x 1.5mm) were manufactured using a flowable composite resin (Opallis Flow A3, n=40) and two conventional composite resins (Vittra APS EA3.5, n=40 / Opallis Conventional EA3, n=40), which were subdivided into two light-curing unit groups: Valo Cordless (n=20) and Radii-cal (n=20). Each curing group was further subdivided into two more groups based on the incidence angle (0º, n=10 and 45º, n=10). An additional 120 specimens with the same dimensions were manufactured using a conventional resin (Opallis Conventional® EA3) and light-cured under a transparent addition silicone matrix with three light-curing units (Valo Cordless, n=40; Radii-cal, n=40; and Quazar, n=40). The matrix groups were established (without a matrix, n=20; with a 2mm matrix, n=20) and further subdivided according to curing time: 20s (n=10) and 20s + 20s (n=10). All samples underwent color variation analysis (ΔE). For both tests, ΔE was assessed using a reflection spectrophotometer (UV-2600, Shimadzu), considering the CIELab* color system, the initial color was registered and recorded again after 15 days. Data from both measurements were assessed using Levene's and Shapiro-Wilk's tests with a 5% significance level. Subsequently, to establish multiple comparisons, a three-way ANOVA and a Tukey’s test were performed. Results – In Article 1, some statistically significant differences (p<0.05) were observed: Valo Cordless® showed the lowest total color variation; Opallis Flow® resin exhibited the lowest total color variation; and increasing the tip angulation to 45º led to greater total color variation in the resins Vittra APS® and Opallis Conventional® when Radii-cal® was used. In Article 2, no statistically significant differences were observed in the total color variation (ΔE) when comparing the three tested light-curing units, the presence or absence of a transparent silicone matrix, or the additional curing time. Conclusion – The results indicated that the curing unit angulation and resin type influenced total color variation, with Valo Cordless® showing the best performance. Increasing the angulation to 45º led to greater color variation in some resins. However, the silicone matrix and additional curing time did not significantly affect total color variation.
