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Repair and retention of snap rings

by:Tronshal     2022-03-21
With the increase of crown and bridge restorations, there are more opportunities to design snap-ring retainers on the abutments with artificial crowns when the removable partial denture is used clinically. After the denture is put into use, the retention force of the retaining ring may decrease and the surface of the crown may be worn due to repeated removal and wearing. The snap ring is made of steel plate stamping or bar turning. The disadvantage of these two process methods is that the material waste is large, the material utilization rate is only about 20%, and the product has large flash and is difficult to file. In view of this situation, we used the principle of steel wire rolling and forming, and trial-produced a snap ring rolling machine. After the 65Mn steel wire was flattened with a pressing wheel, it was rolled and formed by the rolling wheel, and then milled one by one to obtain the finished product. The variation trend of the maximum dislocation force of cobalt-chromium alloy and pure titanium retaining ring in the porcelain crown and the wear of the specific area on the surface of the porcelain crown before and after the experiment were studied. Methods A nickel-chromium porcelain crown was fabricated to simulate the shape of the mandibular first molar, and a cobalt-chromium alloy retaining ring and a pure titanium retaining ring were fabricated on it. After the clasp was in place, the universal tester was used to carry out 1500 repeated removal and wearing experiments. After every 20 times of removal and wearing, the peak value was tested to compare the attenuation of the dislocation force between the clasp and the porcelain crown and use the regression fitting method to make statistics. Scanning electron microscope observation was made to compare the wear of the fixed point area of u200bu200bthe porcelain crown before and after the experiment. Results The retention force of the pure titanium retaining ring decayed linearly within 520 cycles. After that, it tends to be stable, with a mean value of 9.00N. The retention force of the cobalt-chromium alloy snap ring did not decay, with an average value of 9.36N. The difference between the two is statistically significant.
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