Influência de diferentes espessuras cerâmicas na atenuação da luz, nas propriedades mecânicas e de nanoinfiltração de cimentos resinosos autoadesivos

Abstract

The objective of this study was to evaluate the influence of different ceramic thicknesses in the attenuation of the light emitted by the photopolymerizer, in the mechanical properties of nanodarkness (Hi) and elasticity modulus (Ei), and in the nano-infiltration (NI) of self-adhesive resin cements. Six IPS e.max® CAD HT A2 / C14 lithium disilicate ceramic blocks were cut into slices with thicknesses of 1.5mm and 2.0mm; and three self-adhesive cements: Maxcem (MAX), Multilink (MTL) and RelyX U200 (U200). To assess the irradiance emitted by the Radii-Plus® photopolymerizer and attenuate light through ceramic thicknesses and cement films, five measurements were made using a spectrophotometer coupled to an integrating sphere. To evaluate the mechanical properties, 45 healthy human molars were used, which had their occlusal surfaces worn to expose the middle dentin. Then, they were randomly assigned to nine experimental groups (n = 5) depending on the variables: (1) ceramic thickness [0-control, 1.5mm and 2.0mm] vs. (2) self-adhesive cement [MAX, MTL and U200]. Cement restorations were made on the dentin surface and light cured for 40s according to the protocol of each group. After the teeth were prepared and restored, they were cut into slices of approximately 1mm. For the Hi and Ei analysis, two slices were selected and evaluated on the cement layer through a nano-indenter with the aid of a Berkovich tip. Two other slices were selected to assess NI at the interface formed between cement and dentin, using scanning electron microscopy (FEG) with a 1000x magnification. The data were subjected to analysis of variance ANOVA 2 factors and Tukey's test (α = 0.05). The total loss of irradiance emitted by the photopolymerizer with the attenuation of different ceramic thicknesses, was statistically significant (p <0.001). When cement discs were interposed between the ceramics, there was a greater attenuation of the light, especially for the 2.0mm thickness (p <0.001). For all cements used, the increase in ceramic thickness did not significantly decrease the values of Hi (p> 0.05) and Ei (p> 0.05); however, it promoted the highest NI values, statistically significant for all groups (p <0.001). The different ceramic thicknesses significantly influence the attenuation of light and the nano-infiltration of self-adhesive resin cements; however, they did not affect the properties of nanohardness and modulus of elasticity.