title: Effects of repeated sterilization cycles on primary stability of orthodontic mini-screws.
abstract: OBJECTIVE
  To determine if repeated sterilization has deleterious effects on the clinical stability of mini-screws.
  
  
  METHODS
  Thirty each of the following mini-screws were tested: Aarhus (American Orthodontics, Sheboygan, Wisc), VectorTAS (Ormco Corporation, Orange, Calif), Dual-Top (RMO, Denver, Colo), and Ortho Anchor (KLS Martin, Jacksonville, Fla). Controls were sterilized once using a steam autoclave (Statim 5000, SciCan USA, Canonsburg, Pa). Each group of mini-screws was divided into three groups: the control (n = 10) and two test groups (n  =10, each). Test groups were cycled five and 10 times respectively. All screws were inserted into custom-designed synthetic blocks that simulated mandibular bone. Maximum insertion torque and lateral displacement force data were recorded and subjected to statistical testing. Two-way analysis of variance (ANOVA) and three-way mixed ANOVA were used for statistical analyses for maximum insertion torque data and lateral displacement force data, respectively. Level of significance was established at P < .05.
  
  
  RESULTS
  Insertion torque values displayed significant differences between both of the groups and sterilization cycles (P < .05). Significant differences were observed between American Aarhus mini-screws and both RMO and KLS Martin mini-screws. Ormco Vector mini-screws also differed significantly from the KLS Martin mini-screws in this comparison (P < .05). For lateral displacement, there was a significant main effect of groups, F(1,36) = 14.5 (P < .05). Significant differences were observed between American Aarhus mini-screws and all three of the other groups (P < .05).
  
  
  CONCLUSIONS
  The examined groups displayed statistical differences of variable quality that may not affect their clinical stability.
authors.affiliation: Department of Orthodontics, School of Dentistry, The University of Texas Health Science Center at Houston, Houston, TX 77054, USA. sercan.akyalcin@uth.tmc.edu
authors.forename: Sercan
authors.initials: S
authors.lastname: Akyalcin
authors.forename: Holly P
authors.initials: HP
authors.lastname: McIver
authors.forename: Jeryl D
authors.initials: JD
authors.lastname: English
authors.forename: Joe C
authors.initials: JC
authors.lastname: Ontiveros
authors.forename: Ron L
authors.initials: RL
authors.lastname: Gallerano
mesh_terms: D001696:Biomechanical Phenomena; D001863:Bone Screws; D019245:Compressive Strength; D003722:Dental Alloys / Q000737:chemistry; D006801:Humans; D008334:Mandible / Q000033:anatomy & histology / Q000601:surgery; D008422:Materials Testing; D008953:Models, Anatomic; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D033081:Shear Strength; D013227:Steam; D013242:Sterilization / Q000379:methods*; D013314:Stress, Mechanical; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry; D019415:Torque
chemical_list: D003722:Dental Alloys; D013227:Steam; D014025:Titanium