title: Evaluation of optimal length and insertion torque for miniscrews.
abstract: BACKGROUND
  The purpose of this article was to test the theory that short miniscrews will decrease the possibility of damaging the root, but the failure rate will increase.
  
  
  METHODS
  One hundred eighty-six miniscrews (diameter, 1.3 × 5 mm, n = 63; 6 mm, n = 62; 7 mm, n = 61) were placed in 105 consecutive patients. Multislice computed tomography and cone-beam computed tomography scans were taken before and after miniscrew placement. Insertion torque was measured at miniscrew placement.
  
  
  RESULTS
  The success rate of the miniscrews in the maxilla (93.4%) was higher than that in the mandible (70.3%). A significantly lower success rate with 5-mm miniscrews was observed compared with 6-mm and 7-mm miniscrews in the mandible. Miniscrews placed in less than approximately 3.8 mm of bone and those within 1.4 mm of the root had significantly higher failure rates. Miniscrews placed with insertion torque greater than 10 Ncm had a tendency for a lower success rate.
  
  
  CONCLUSIONS
  The optimum lengths of miniscrews of a diameter of 1.3 mm are 5 mm in the maxilla and 6 mm in the mandible. They should be placed at a distance from the root with insertion torque less than 10 Ncm for safe orthodontic anchorage without failure.
authors.affiliation: Division of Orthodontics and Dentofacial Orthopedics, Graduate School of Dentistry, Tohoku University, Sendai, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Suzuki
authors.forename: Toru
authors.initials: T
authors.lastname: Deguchi
authors.forename: Hisako
authors.initials: H
authors.lastname: Watanabe
authors.forename: Masahiro
authors.initials: M
authors.lastname: Seiryu
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iikubo
authors.forename: Takashi
authors.initials: T
authors.lastname: Sasano
authors.forename: Koji
authors.initials: K
authors.lastname: Fujiyama
authors.forename: Teruko
authors.initials: T
authors.lastname: Takano-Yamamoto
mesh_terms: D000293:Adolescent; D000328:Adult; D001641:Bicuspid / Q000000981:diagnostic imaging; D015519:Bone Density / Q000502:physiology; D001863:Bone Screws; D054893:Cone-Beam Computed Tomography / Q000379:methods; D003724:Dental Arch / Q000601:surgery; D004868:Equipment Failure; D004869:Equipment Safety; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000601:surgery; D008437:Maxilla / Q000601:surgery; D008963:Molar / Q000000981:diagnostic imaging; D061330:Multidetector Computed Tomography / Q000379:methods; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D009969:Orthodontic Wires; D013314:Stress, Mechanical; D013499:Surface Properties; D016019:Survival Analysis; D014092:Tooth Root / Q000000981:diagnostic imaging; D019415:Torque; D055815:Young Adult