Comparative evaluation of hardness and elasticity modulus of tooth-colored materials for dental restoration

Abstract

The aim of this study was to compare Rockwell hardness (HRC) and modulus of elasticity (Young modulus) to different restorative materials. Three commercial composite resins: Filtek Z250 (3M ESPE Co.), Zmack Comp (Zermack SpA, Italy), Kalore (GC Corporation, Japan) and one compomer: Dyract eXtra (Dentsply De Trey Gmbh, Germany) were used. Six samples of each material were obtained by placing them in plastic rings having 5 mm inner diameter and 6 mm high. All composite samples were cured for 40 s using a lamp LEDidition - Ivoclaire Vivadent clinical, Austria. The samples were finished and polished and then stored in distilled water, at room temperature for 48 hours. Rockwell Hardness (HRC) measurements were realized using the UMT-2 Tribometer (CETR). The hardness was automatically calculated from the slope of unloading curve and expressed in GPa and transformed in HRC values (kgf/mm2). Six indentations were performed on diametral direction and mean values were calculated for all tested samples. The device also measured the modulus of elasticity for each sample. Data were analyzed by ANOVA and Mann-Whitney test (significance level of p < 0.05). The mean HRC values were the following: Filtek Z250 > Zmack Comp > Dyract eXtra > Kalore (82.98 > 70.10 > 53.27 > 37.72 kg/mm2). Regarding Young modulus, the rank from highest to lowest as follows: FiltekZ250 > Zmack Comp > Dyract eXtra > Kalore (16.24 > 14.05 > 12.41 > 7.86). The microhydrid composite resins have a significantly higher hardness than nano-hybrid composites or compomers.