| In the dental clinical practice, the commonest restorative materials are metal, composite resin and ceramics. But all three kinds have disadvantages. Metallic alloy is unesthetic and can trigger corrosion. Composite resin is not wear-resistant and its color is unsteady. Ceramics is brittle, easy to break and can't be used in the posterior region of the dentition. The fiber-reinforced composite(FRC) materials are new kinds of materials, are composed of fiber and composite resin.They has both strength and esthetics and can meet the need of dentiton restoration. The fibers have 4 kinds: carbon fiber, aramid Kevlar fiber, glass fiber, polyethelene fiber. At present, glass fiber is most widely used. Polyethelene fiber is organic fiber and is only used recently. At the present time,there are still controversies on the reinforcing effect of Polyethelene fiber. Nowadays there are few articles on the study of FRC materials and no report of study on the polyethelene fiber in our country, the objective of this study is to investigate if the Ribbond polyethylene fiber has an reinforcing effect on the polymethyl methacylate.Material and Methods 1 Mould fabrication: wax specimen was fabricated into 50X 5 X 2mm shape and was placed into flask. Then the flask was opened and the wax was removed. 2 Specimen fabrication: 1PMMA group: 2 portion of PMMA powder and 1 portion of PMMA liquid was mixed, then was poured into the mould and polymerized with pressure. Later the specimen was taken out and measured to inspect if the width and thickness were even. 10 specimens were made in this group. (2)Wire group: 48mm long wire was cut. 2 portion of PMMA powder and 1 portion of PMMA liquid was mixed and then was poured into the mould. The wire was placed into the certain place. Later the PMMA was polymerized with the same pressure. The specimen was taken out and measured to inspect if the width and thickness were even. 10 specimens were made in this group. (3)Ribbond group: 48mm long Ribbond ribbon was cut and precautions were taken to prevent from ribbon polluting. 2 portion of PMMA powder and 1 portion of PMMA liquid was mixed and was poured into the mould. Then the ribbon was placed into the certain place. Later the PMMA was polymerized with the same pressure, the specimen was taken out and measured to inspect if the width and thickness were even. 8 specimens were made in this group. 3 Testing of mechanicalproperty: A three-point bending test was used to measure the flexural strength and flexural modulus of specimens according to GB9341-88 standard. Then the data were analyzed with a one-way analysis of variance.Results The flexural strength of chemical-cured PMMA group was 51.383 ± 2.761MPa and the flexural modulus was 1791.200± 113.762MPa; The flexural strength of stainless steel wire group was 58.725±1.218MPa and the flexural modulus was 2092.760 ±120.275MPa; The flexural strength of Ribbond polyethylene fiber group was 80.975 ±2.580MPa and the flexural modulus was 2866.525 ±107.509MPao The one-way analysis of variance showed that the results were significant (P<0.001). Newman-Keuls method showed that the differences among all groups were significant(P<0.05).Conclusion 1 The stainless wire can raise the flexural strength and flexural modulus of polymethyl methacylate. 2 The Ribbond polyethylene fiber can raise the flexural strength and flexural modulus of polymethyl methacylate. 3 There is statistical difference between the reinforcing effect of stainless wire and that of Ribbond polyethylene fiber, the reinforcing effect of Ribbond polyethylene fiber is better than that of stainless wire. |
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