25 - Analysis of Indirect Restorative Materials Submitted to Different Conditioning Protocols

Abstract

The aim of this study was to evaluate the influence of hydrofluoric acid application time and concentration on bond strength and surface morphology of three indirect restorative materials. Samples measuring 4x4x0.8 mm were obtained from three materials (lithium monosilicate reinforced by zirconia - Celtra Duo, nanoceramic resin - Lava Ultimate and hybrid ceramic - Vita Enamic). These materials were conditioned with hydrofluoric acid at concentrations of 5% or 10% for 20, 40, 60 or 90 seconds. In addition, a control group was adopted, in which no conditioning was performed, totaling 9 groups for each material. The analysis of bond strength was performed using the microshear test (n=6). For this purpose, cylinders of Variolink Esthetic LC resin cement were made on the conditioned samples, using a silicone matrix. The test was performed in a mechanical testing equipment, in which the samples were fixed and with the aid of an orthodontic wire, tension was applied to the cylinders. Bond strength data were submitted to two-way ANOVA and Tukey's test (α=0.05). The surface microstructure of each material was observed through images obtained by the technique of scanning electron microscopy (SEM) (n=2). Celtra Duo presented better bond strength values when subjected to etching with 10% hydrofluoric acid for 40, 60 and 90 seconds. For Lava Ultimate, better results were obtained with application of 10% acid concentration for 20 and 40 s, while Vita Enamic showed better results after application of 5% hydrofluoric acid for 40 and 90 seconds and at 10% for 20 and 40 s. Through the images obtained by the technique of scanning electron microscopy (SEM) it was possible to observe the appearance of irregularities on the surface of each material evaluated after conditioning. The evaluated restorative materials showed different behaviors after conditioning protocols with hydrofluoric acid, therefore, the professional must adopt the best hydrofluoric acid concentration and time protocol for each specific material in order to obtain a satisfactory and effective adhesive procedures.