title: Frictional resistances of metal-lined ceramic brackets versus conventional stainless steel brackets and development of 3-D friction maps.
abstract: The frictional resistances of 2 metal-lined ceramic brackets (Luxi and Clarity) were compared with 2 conventional stainless steel brackets (Mini-Taurus and Mini-Twin) in vitro. In method 1, we varied the second-order angulation from 0 degrees to 12 degrees while maintaining the normal or ligature force constant at 0.3 kg; in method 2, we varied the ligature force from 0.1 kg to 0.9 kg while maintaining the angulation at theta = 0 degrees or theta = 11 degrees. The hardware simulated a 3-bracket system in which the interbracket distances were always 18 mm. All couples were evaluated at 34 degrees C using the same size stainless steel archwire (19 x 26 mil) and ligature wire (10 mil). In the passive region, the static and kinetic frictional forces and coefficients of friction were key parameters; in the active region, the static and kinetic binding forces and coefficients of binding were critical parameters. From outcomes of methods 1 and 2, the 4 aforementioned parameters, and a knowledge of the critical contact angle for binding, 3-dimensional friction maps were constructed in the dry and wet states from which the frictional resistances could be determined at any ligature force or second-order angulation. Those 3-dimensional maps show that metal-lined ceramic brackets can function comparably to conventional stainless steel brackets and that 18-kt gold inserts appear superior to stainless steel inserts. As the morphologies of metal inserts are improved, these metal-lined ceramic brackets will provide not only good esthetics among ceramic brackets but also minimal friction among conventionally ligated brackets.
authors.affiliation: Dental Research Center, University of North Carolina, Chapel Hill 27599, USA. rkusy@bme.unc.edu
authors.forename: R P
authors.initials: RP
authors.lastname: Kusy
authors.forename: J Q
authors.initials: JQ
authors.lastname: Whitley
mesh_terms: D000537:Aluminum Oxide; D000704:Analysis of Variance; D002516:Ceramics; D003799:Dental Stress Analysis; D017276:Friction; D006047:Gold Alloys; D016014:Linear Models; D008422:Materials Testing; D008670:Metals; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D013193:Stainless Steel; D017155:Wettability
chemical_list: D006047:Gold Alloys; D008670:Metals; D013193:Stainless Steel; D000537:Aluminum Oxide