An In Vitro Investigation Of Wear Resistance And Hardness Of New Composite Resins

Objectives Evaluate wear resistance and hardness of 3 new composite resins, and analyze the correlation between the hardness of the composites and the amount of wear of them. Observe the surface of the wear patterns of the composites, and analyze the wear mechanisms.Methods 3 new composite resins: Solidex(hybrid composite),Spectrum(hybrid composite)and FiltekTM Z350(nanofilled composite) were researched in this study.The smples of the composites were cured according to the manufacturers′directions.Human enamel served as a control.The specimens prepared for test were form through add cylindrical basic units constituted with selfcuring acrylic resin to every smple.Ten specimens of each material were prepared for wear test and five specimens for hardness test.The specimens were conditioned for two weeks in distilled water at 37℃and subjected to wear testing at 10 MPa contact stress against 304 stainless steel counter-bodies using a refited MG-200 wear machine. Artificial saliva was used as the wear medium. Measur the density of each composite resin. A electronic balance was used to measure the weight of each specimen before and after wear test,calculate the weight loss,and convert it to volume loss by the density of each tested material(the density of enamel according to the literature reported). The surface of the wear patterns of one specimen which was selected randomly from 10 spiese of each tested material after wear testing was examined using a scanning electron microscope(SEM). Vickers hardness was measured for five specimens of each material prepared for hardness test using the Vickers indentation technique with a load of 100g for 15 seconds,and five points of every specimen were measured.The data of wear and hardness were analyzed by Mann-Whitney test and 1-way ANOVA. The relationship between the hardness of the composites and the amount of wear of them was determined by a regression analysis.The level of statistical significance chosen wasα=0.05.Results FiltekTM Z350 showed the lowest volumetric wear and highest Vickers hardness in the composites(P<0.05).No significant differences in wear and hardness were observed between Solidex and Spectrum( P>0.05). Significant differences in wear and hardness were observed between Enamel and the composites (P<0.05).Significant relationships were observed between the hardness of the composites and the amount of wear of them(r=-0.9686)(P<0.05).. Different wear character of the friction surface of the tested materials were observed by SEM. Conclusions Nanofilled composite was superior to the hybrid composite in wear resistance and hardness. Enamel were harder and more wear resistance than any of the composites.Nanofilled composite is a direction of development of the composite materials in the future.