| Metal restorative materials had been widely applied to clinic of restorative dentistry because of their appropriate physical and mechanical functions and biocompatibility. The abrasion problem of metal materials was gradually concerned. In this experiment, we used a kind of rotative abrasion device drived by electric to experiment with 3 kind of metal restorative material. With Ni - Cr alloy, Co - Cr alloy, Titanium, and natural enamel. By the experiment, we compared the loss volume of each material during the experiment, analysed the statistic variances and valuated the abrasion features of materials. Furthermore, we analysed the abradant surface appearance by microphotogra-phy in order to provide evidences for comparing abrasion features. As well as references for selecting restorative materials in clinic. On the other hand, we also discussed study methods of abrasion features.MATERIALS AND METHODSThree kinds of metals used in this study included Ti ( cast titanium for bracing, sofu) , Ni -Cr alloy (cast alloy, containing 8-10% of nickel, 17 to 19 percent of chromium; ADA Verasoft) and Co - Cr alloy ( cast alloy, containing 60 to 65 percent of cobatt and 26 to 28 percent of chromium; ADA Vera PDS). The enamel was obtained from natural dentals, the first bicuspid tooth extracted during the process of dental orthodonics in healthy children. The NiCr18 - 8 steel loop, couple device, and self - coagulating plastic were obtained from the Dental Materials Factory of Shanghai.Each kind of metal was casted to the shape of cylinder, 4. 5mmin diameter, 10mm in height, and then the specimens were polished and invested in self - coagulating plastic according to the uniform shape. The preparation of enamel was the same as that of metals. Before the experiment, specimens were weighed by electric scale whose accuracy is 0.1g. The abrasion experiment conducted on the oral abrasion device which was dived by electric and rotated 73 per minute. The experiment lasted for 3 hours under 4 kind of experimental conditions including dry abrasion group, water adding group, flour adding group and abrasive materials adding group, and 3 kinds of loads including 1. 5kg, 3.0kg, 4.5kg. We experimented parallelly for five times with each metal under the same experimental conditions and loads. After the abrasion experiment, we measured the mass of specimens by electric scale and analysed the variances.RESULTSThe experiment results showed that the loss volume of Ti was the greatest among every group and the loss volume of Ni - Cr alloy and Co - Cr alloy was similar which was severe less than that of Ti. Significant statistic differences existed in the loss volume among Ni - Cr alloy or Co - Cr alloy, Ti and enamel ( P < 0. 05 ) . The same thing existed in the loss volume between Ti and enamel. But significant differences of the loss volume between Ni - Cr alloy and Co - Cr alloy wern t concealed.The loss volume of abrasion was different under the different load. It is the smallest under the load of 1. 5kg and the greatest under the load of 4.5kg. Significant statistic differences of the loss volume a-mong different load of 1.5kg, 3. Okg and 4. 5kg were revealed (P <0.05).Pertaining to the appearance of abradant surfaces, deep and wide grooves existed on the abradant surface of Ti, shallow and narrow grooves appeared on the abradant surfaces of Ni - Cr alloy and Co - Cr alloy, while there was no abrasion on the surface of enamel except for the scorched mark. Under different experimental conditions, the abrasion in dry abrasion group and abrasive materials adding group was greater than that in flour adding group and water adding group.DISCUSSIONMetals and alloy materials had been widely applied to prosthodon-tics clinic. Because of appropriate physical and mechanical functions and biocompatility. Cast Ni - Cr alloy which was belong to high - soluble cast alloy and beared many advantages such as good tensible intensity, elasticity as well as proper hardness was used to fabricate clasps, abuts, bases of removable de... |
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