Influence of Inorganic Fillers Fraction on Properties of Composite Resins

Objectives: The purpose of this study was to evaluate the influence of inorganic fillers fraction on degree of conversion (DC%), hardness (VHN) and thermal decomposition by differential scanning calorimetry (DSC) of nanofilled, universal and nano hybrid composite resins. Methods: The samples (n=33) were made in a metallic mould (ISO 4049) for DC (%), VHN and (DSC) with Filtek Supreme XT and Z-250, TPH3 at color A2. Their filler weight content and morphology was determined by thermogravimetric analysis (TG) and scanning-electron microscopy (SEM). One LED was used (LEC 1000, 400 mW/cm2) during 40 seconds. For DC%, the samples were pulverized, pressed with KBr and analyzed in a FT-IR Spectrophotometer (Bomen). The DSC and TG measurements were performed in a TA Instruments DSC 2910 and a Netzsch TG 209 (heating rate of 10ºC/min). Ten milligrams of each uncured and cured composite resin were weighed and the experimental conditions were: 25°C as initial, and 300°C for the final temperatures for DSC and 700ºC for TG measurements. The VHN was performed on the top and bottom surfaces, using a MMT-3 Hardness Tester (50 gf load, 30 seconds). Analysis of Variance (ANOVA) and Tukey's test was performed for the DC (%) and VHN measurements (p>0.05). Results: The mean values and standard deviation (±sd) for DC (%) and Vickers hardness were, respectively: Filtek-Supreme XT: (%) DC: 53.0; (±2.0); VHN: (T) 72.1 (±1.67), (B) 54.75 (±5.66); Filtek Z-250: (%) DC: 51.38 (±2.78); VHN: (T) 72.56 (±1.71), (B) 71.01 (±0.92) and TPH3: (%) DC: 49.0 (±5.0); VHN: (T) 53.65 (±2.13), (B) 43.38 (±1.99). The decomposition and the crystallization of the Filtek Z-250 composite resin were in higher temperatures. Conclusions: Nanofilled resin shows properties at least as good as those of universal hybrids and could thus be used for the same clinical indications as well as for anterior restorations.