Efeito de nanopartículas de sílica funcionalizadas com fosfato na formulação de sistemas adesivos

Abstract

This study investigated the effect of the incorporation of phosphate-grafted-silica nanoparticles (SiO2-POOH) on dentin bond strength and the physical-chemical properties of model one-step self-etching adhesive (1-SEA). Phosphate was grafted onto the silica nanoparticles through the free radical polymerization of the acid phosphate monomer (Methacryloyloxyethyl Dihydrogen Phosphate / Bis (methacryloyloxyethyl) Hydrogen Phosphate - HEMA-P), in an alcoholic medium. The resulting SiO2-POOH was characterized by using FTIR spectroscopy, TGA, and a TEM micrograph. The SiO2-POOH were added to 1-SEA with three HEMA-P concentrations (0, 20 and 40% wt.), as the control group an unfilled 1-SEA were formulated. The formulated 1-SEAs were evaluated for microshear bond strength to dentin and classified according to failure mode. Additionally, morphological analysis of bonding interface, contact angle, degree of conversion, rate of polymerization, and the cohesive strength were evaluated. Statistical comparisons were conducted at a 5% significance level. The grafting reaction of SiO2-POOH was confirmed by FTIR and TGA. 1-SEA containing SiO2-POOH had significantly higher shear bond strength values than the non-SiO2-POOH adhesives (p = 0.001), except for 1-SEA with 0% of HEMA-P that did not exhibit bonding to the dentin. Compared with its correspondent unfilled 1-SEA, the addition of SiO2-POOH improved the dentin wettability by decreasing the contact angle and, increasing the degree of conversion and rate of polymerization. The cohesive strength, in contrast, was not affected by SiO2-POOH. In conclusion, the SiO2-POOH addition could be used to produce 1-SEA with enhanced dentin bond strength without harming the other properties that were investigated.