Zirconia brackets: an evaluation of morphology and coefficients of friction.
The frictional characteristics of two types of zirconia (Harmony, Hudson Ltd., Sheffield, U.K., and Toray, Yamaura Corp., Tokyo, Japan) brackets were compared with those of polycrystalline alumina (Transcend 2000, Unitek Corp., Monrovia, Calif.) brackets in both dry and wet states. To compare the couples, four arch wire alloys were studied: stainless steel, cobalt-chromium, nickel titanium, and beta-titanium. Under dry conditions, the highest frictional coefficients were seen with the Harmony/beta-titanium couple (uk = 0.64); the lowest values were seen with both Transcend 2000/stainless steel (uk = 0.13) and Toray/cobalt-chromium couples (uk = 0.13). Beta-titanium arch wires produced the highest coefficients of friction against each type of ceramic bracket, except against Toray arch wires in the wet state. The presence of human saliva produced only slight changes in the frictional behavior of zirconia brackets. We conclude that currently available zirconia brackets offer no significant improvement over alumina brackets with regard to their frictional characteristics.
Department of Orthodontics, University of North Carolina at Chapel Hill.
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Keith
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Kusy
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Whitley
D000537:Aluminum Oxide; D000704:Analysis of Variance; D002516:Ceramics / Q000737:chemistry*; D002858:Chromium Alloys; D003799:Dental Stress Analysis; D017276:Friction; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D012044:Regression Analysis; D012463:Saliva; D013193:Stainless Steel; D013499:Surface Properties; D014025:Titanium; D015040:Zirconium
D002858:Chromium Alloys; D013193:Stainless Steel; D015040:Zirconium; D014025:Titanium; D000537:Aluminum Oxide; C028541:zirconium oxide