title: Friction of conventional and silica-insert ceramic brackets in various bracket-wire combinations.
abstract: OBJECTIVE
  To compare the level of friction resistance (FR) of conventional and silica-insert ceramic brackets using various bracket-wire combinations and angulations.
  
  
  METHODS
  Four types of ceramic brackets were examined: (1) polycrystalline alumina bracket (PCA-C), (2) polycrystalline alumina bracket with a stainless steel (SS) slot (PCA-M), (3) polycrystalline alumina bracket with a silica layer (PCA-S), and (4) monocrystalline sapphire bracket (MCS). A conventional SS bracket was used as the control. The static and kinetic FR in four bracket-wire angulations (0 degrees, 5 degrees, 10 degrees, and 15 degrees) was examined using SS and beta-titanium (beta-Ti) orthodontic wires, 0.019 x 0.025 inches in size, under elastic ligature in the dry state.
  
  
  RESULTS
  The FR generated by the PCA-S bracket was significantly lower than that generated with the other ceramic brackets, and was similar to that of the SS bracket. The PCA-S bracket showed the lowest FR with both the SS and the beta-Ti wires at zero bracket angulation. The FR to sliding increased rapidly and nonlinearly when the bracket wire angulation was >5 degrees. The PCS-S bracket showed the lowest FR from 5 degrees to 15 degrees of angulation. The MCS bracket demonstrated the highest increase in FR from 0 degrees to 15 degrees of angulation, showing the highest FR at 15 degrees of angulation.
  
  
  CONCLUSIONS
  PCA-S showed minimal FR among the ceramic brackets, and was comparable to the conventional SS bracket. The silica layer and rounded edges of the ceramic slot lowered FR considerably.
authors.affiliation: Yonsei University, Department of Orthodontics, College of Dentistry, Seoul, South Korea.
authors.forename: Jung-Yul
authors.initials: JY
authors.lastname: Cha
authors.forename: Kyung-Suk
authors.initials: KS
authors.lastname: Kim
authors.forename: Chung-Ju
authors.initials: CJ
authors.lastname: Hwang
mesh_terms: D000537:Aluminum Oxide; D002516:Ceramics; D003799:Dental Stress Analysis; D017276:Friction; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D012822:Silicon Dioxide; D013193:Stainless Steel; D013499:Surface Properties; D014025:Titanium
chemical_list: D013193:Stainless Steel; D012822:Silicon Dioxide; D014025:Titanium; D000537:Aluminum Oxide