title: Torsional strength of computer-aided design/computer-aided manufacturing-fabricated esthetic orthodontic brackets.
abstract: OBJECTIVE
  To fabricate orthodontic brackets from esthetic materials and determine their fracture resistance during archwire torsion.
  
  
  METHODS
  Computer-aided design/computer-aided manufacturing technology (Cerec inLab, Sirona) was used to mill brackets with a 0.018 × 0.025-inch slot. Materials used were Paradigm MZ100 and Lava Ultimate resin composite (3M ESPE), Mark II feldspathic porcelain (Vita Zahnfabrik), and In-Ceram YZ zirconia (Vita Zahnfabrik). Ten brackets of each material were subjected to torque by a 0.018 × 0.025-inch stainless steel archwire (G&H) using a specially designed apparatus. The average moments and degrees of torsion necessary to fracture the brackets were determined and compared with those of commercially available alumina brackets, Mystique MB (Dentsply GAC).
  
  
  RESULTS
  The YZ brackets were statistically significantly stronger than any other tested material in their resistance to torsion (P < .05). The mean torques at failure ranged from 3467 g.mm for Mark II to 11,902 g.mm for YZ. The mean torsion angles at failure ranged from 15.3° to 40.9°.
  
  
  CONCLUSIONS
  Zirconia had the highest torsional strength among the tested esthetic brackets. Resistance of MZ100 and Lava Ultimate composite resin brackets to archwire torsion was comparable to commercially available alumina ceramic brackets.
authors.forename: Najla
authors.initials: N
authors.lastname: Alrejaye
authors.forename: Richard
authors.initials: R
authors.lastname: Pober
authors.forename: Russell
authors.initials: R
authors.lastname: Giordano Ii
mesh_terms: D000537:Aluminum Oxide; D002516:Ceramics; D003188:Composite Resins; D017076:Computer-Aided Design; D003722:Dental Alloys / Q000737:chemistry; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D004548:Elasticity; D004868:Equipment Failure; D004955:Esthetics, Dental; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016382:Orthodontic Appliance Design / Q000379:methods; D009967:Orthodontic Appliances; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D019415:Torque; D015040:Zirconium
chemical_list: D003188:Composite Resins; D003722:Dental Alloys; C485633:In-Ceram Zirconia; C452079:paradigm MZ100; D003776:Dental Porcelain; D013193:Stainless Steel; C074543:Cerec; C070870:In-Ceram; D015040:Zirconium; D000537:Aluminum Oxide
keywords: Bracket; Esthetic; Orthodontic; Strength; Torsional; Zirconia