Characterization of low-shrinkage dental composites containing methacrylethyl-polyhedral oligomeric silsesquioxane (ME-POSS).

Abstract

The aim of this study was to characterize low-shrinkage dental composites containing methacrylethyl-polyhedral oligomeric silsesquioxane (ME-POSS). Four experimental composites were manufactured, two of which contained organic matrixes of BisGMA-TEGDMA (70/30 wt% - BGC) and BisEMA-TEGDMA (80/20 wt% - BEC). The two other experimental composites replaced BisGMA and BisEMA with 25 wt% of ME-POSS (BGP and BEP). The composites also contained 70 wt% of 0.7 µm silanized BaBSi particles. The following properties were evaluated: Degree of conversion (DC%), volumetric polymerization shrinkage (VS%), polymerization shrinkage stress (Pss), flexural strength (FS), Flexural modulus (FM), hardness (KHN), water sorption (W_sp), water solubility (W_sl), diffusion coefficient (D), and wear. The DC% was not influenced by the presence of ME-POSS, with BEC (75.6%) and BEP (74.8%) presenting higher DC% than BGC (60.6%) and BGP (55.6%). The ME-POSS-containing composites (BGP and BEP) presented significantly lower VS% and Pss. The FS ranged from 92.7 to 142.0 MPa and the FM from 3.6 to 10.3 GPa. ME-POSS did not influence the KHN. BEC and BEP presented lower W_sp and W_sl when compared to BGC and BGP. D ranged from 1.0 × 10^-6 to 7.4 × 10^-6 cm² m^-1. Incorporation of ME-POSS significantly decreased the wear for both binary matrices (p < 0.05). With the exception of FS and FM for BGP, the incorporation of ME-POSS decreased the VS% and Pss without jeopardizing the other properties of the experimental dental composites.