| PrefaceComposite resin material have a increasing development since Bowen RL, an American scholar, invented the dental composite resin in 1962 in which BIS - GMA resin was taken as the matrix and silica as the filling. They developed from the conventional type characterized by large granular to the ultraminiature type characterized by minor granular, then to the mixed type bearing the advantages of both large and minor granular. Composite resin materials have been applied on prosthetic clinic widely. They are used for not only the dental filling but also the fabrication of the crown as well as pontic teeth. Since the movement of mastication produces huge pressure, composite resin materials must have perfect adhesion, aesthetics and mechanical functions as well as high wear resistance.In the present report, we study the abrasion of three kind of composite resin materials and enamel under different loads and experimental conditions. We used abrasion - testing machines made by metal institute of china science academy and observed the surface which had been abraded. The purpose of this study is to analyses the effects of different factors on the abrasion of composite resin and enamel and find the appropriate resin materials for clinic.Materials and MethodsThree composite resin materials evaluate in this study included Sculpture, a hybrid composite resin from Jeneric/entron co. U. S. A; Pekulux, the light solidified resin with microfiller from kulzer co. Germany; and Bayer, the heat solidified resin dental from Heraeus co. Shanghai. Enamel materials are from fresh extracted teeth for ortho-dontia and the opposite occlusion which is matched by rotative steel and 37. 5mm in diameter is obtained from mental institute.The specimens of prosthetic were formed to the shape of cylinder, 4. 66mm in diameter, 3. Omm in height. According to the manufacturers' directions. Surfaces were then polished by abrasive paper (granulation 400) after. The specimens were solidified, invested and attached firmly on the wear - testing machine.The specimens conducted the sliding abrasion experiments on the wear - testing machines with 73 rotations per minute, which lasted for 3 hours under 4 kinds of experimental conditions including flour adding group, water adding group, abrasive materials adding group as well as dry abrasion group and 3 kind of loads including 1.5kg, 3.0kg and 4.5kg.The specimens were dealed with absolute alcohol for 30min before and after the experiment and measured. The mass by photoelectrical scale, then we selected a sample of abrasion from each material and observed the surface structure under the gold phase microscope as well as photographed them.ResultsUnder the same experimental condition , the abrasion increased with the raise of the load, and there were significant difference in statistic analysis.Under the different experimental conditions, the experiment shown the similar abrasion tendency.The greatest volume of the abrasion appeared in abrasive material adding group, then dry abrasion group, water adding group and the least abrasion appeared in flour adding group. Consistent significant difference ( P < 0. 05 ) existed among different kind of experimental condition, wear resistance of several materials was different, ie, enamels was the largest, Sculptures was larger than that of Bayer. And Pekulux's was the lest.DiscussionThe wear occurred in oral cavity included three - body wear process as well as two - body wear process. These two processes were both existed in clinic. The study in vitro usually used different amalgams to imitate the effect of food friction agents during the process of wear and the friction agents added played a role in delaying or acceleration wear. This study used flour, abrasive materials and water as the friction agent. The experiment showed that the volume of the abrasion was the lest in these materials due to the addition of flour, and was the most due to the addition of abrasive. We considered that flour acted as the lubricant which resulted in... |
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