title: Effect of placement angle on the stability of loaded titanium microscrews: a microcomputed tomographic and biomechanical analysis.
abstract: BACKGROUND
  The aim of this study was to evaluate the impact of the placement angle on the stability of loaded microscrews.
  
  
  METHODS
  Forty-eight microscrews were placed at 4 angles ( 30°, 50°, 70°, and 90°) into the tibiae of 12 beagles, loaded with a force of 2 N immediately, and maintained for 8 weeks. Microcomputed tomography and pullout tests were used for morphometric and biomechanical analyses, respectively.
  
  
  RESULTS
  All microcomputed tomography parameters and the peak loads at extraction of the microscrews were influenced by the placement angles of the microscrews. The higher microcomputed tomography parameters and the peak load at extraction were measured at angles from 50° to 70°. Oblique and vertical placement angles resulted in reduced stability of the loaded microscrews (P <0.05).
  
  
  CONCLUSIONS
  To achieve the best stability of microscrews, a placement angle of 50° to 70° is advisable.
authors.affiliation: State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Lixing
authors.initials: L
authors.lastname: Zhao
authors.forename: Zhenrui
authors.initials: Z
authors.lastname: Xu
authors.forename: Xing
authors.initials: X
authors.lastname: Wei
authors.forename: Zhihe
authors.initials: Z
authors.lastname: Zhao
authors.forename: Zhi
authors.initials: Z
authors.lastname: Yang
authors.forename: Linkun
authors.initials: L
authors.lastname: Zhang
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.forename: Tian
authors.initials: T
authors.lastname: Tang
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D001863:Bone Screws; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D004285:Dogs; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008422:Materials Testing; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation* / Q000379:methods; D016382:Orthodontic Appliance Design; D016348:Osseointegration / Q000502:physiology; D011897:Random Allocation; D013314:Stress, Mechanical; D013499:Surface Properties; D013977:Tibia / Q000601:surgery; D014025:Titanium / Q000737:chemistry*; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: D001672:Biocompatible Materials; D003764:Dental Materials; D014025:Titanium