An Investigation In Vitro Of The Mechanical Properties Of Four Kinds Of Composite Resins For Inlay

Composite resin has been used in China for over 20 years. Because of its beautiful figuration, sturdiness and easy operation performance, it is more and more widely used in the clinic and gradually replacing the silver amalgam. However, due to the composite resins which are filled directly will bring the curing shrinkage, marginal microleakage, pulp irritation and other adverse effects, the inlay technique with the composite resins is more and more popular with doctors and patients. But now in the market there are a wide range of composite resins and people are increasingly concerned about their mechanical properties and fatigue resistance, etc, and looking for the best composite resin on the clinical application.In the study, we respectively measured and comparatively analysed the compression strength,wear resistance, hardness, and fatigue after immersion that the resins was soaked in the artificial saliva at the room temperature of four kinds of composite resins for inlay, which were Ceramage (Japan Shofu Inc. A2B), Surefil (U.S. Dentsply Inc. A2), Solitaire 2 (Germany Heraeus Inc. A2), FiltekTM Z350 (USA 3M Inc. A2), the results would provide the bases for the clinical application of the composite resins. We maked the samples which were demanded according to the testers.Ten specimens of each material were prepared for the compression test. Then the samples were randomly divided into two groups (pre-soaked A group and B group after soaking), A group was immersed in the distilled water at 37℃for twenty-four hours, and B group was respectively immersed in the artificial saliva for two months (replacing the soak solution every seven days) at the room temperature(22℃).We tested the compression strength by the electronic universal testing machine;Five specimens of each material were prepared for wear and embedded in the base, and then they were kept in distilled water for fourteen days at the constant temperature of 37℃.We calculated the weight wear of each material after wear test by the wear tester, and then converted it to the volume wear by the conversion formula after measuring the density of each material by the density formula; Three samples of each material were prepared for hardness test and immersed in the distilled water at 37℃for twenty-four hours, and then placed on the micro-Vickers hardness tester. We tested five values for each specimen;All the data was analyzed by using the statistical software SPSS 17.0 for statistical analysis.The results of the experiment:The ranking of the compressive strength of A group from the biggest to the smallest was:Surefil>Ceramage>Solitaire 2>FiltekTM Z350. The compressive strength of Surefil was significantly higher than the other three resins (P＜0.05), no significant difference was obtained between each two groups of Ceramage, Solitaire 2 and FiltekTM Z350((P>0.05).The ranking of the compressive strength of B group in descending order was:Surefil>FiltekTM Z350>Ceramage>Solitaire 2. There was no significant difference between the composite resins by the One-Way ANOVA (P>0.05). The data of the compression strength between A group and B group of each material was analyzed by the Independent-Samples T Test. No significant difference was obtained for FiltekTM Z350(P>0.05), but for the other three materials, the compressive strengths significantly reduced and the difference had the statistical significance (P<0.05); In the wear test, all samples of FiltekTM Z350 were broken and no data was obtained. There was the significant difference between each two groups of Solitaire 2,Ceramage and Surefil(P<0.05); The ranking of the hardness of four composite resins in decreasing order was:Surefil>FiltekTM Z350>Ceramage>Solitaire 2. Significant difference was found between the materials(P<0.05).We observed the indentation of the specimen by the metallurgical microscope (200 times magnification), the square indentation diagonals of Surefil and FiltekTM Z350 were regular, while the centers of the square indentation of Ceramage and Solitaire 2 collapsed and there were two long diagonals of the indentation.The collapse of Solitaire 2 was the most significant.The conclusions from this experiment were:1. The mechanical properties of Surefil was the best,and it was suitable for the posterior inlay;2. FiltekTM Z350's ability to resist the fatigue damage was better than the other hybrid composite resins;3. The volume wear of Solitaire 2 was the smallest, but its hardness was poor. It suggested that the comprehensive properties of composite resins needed to be further improved;4. The hardness of the composite resins could not replace their wear resistance.According to the experiment we knowed that the mechanical properties of four kinds of materials had their own advantages and disadvantages, we should make the comprehensive consideration and choose the material to obtain the best effects on the clinical application based on their various properties.Through the investigation in vitro,we measured the general mechanical properties of four kinds of composite resins and made the comparative analysis, it provided a theoretical basis for the clinical application.