title: Factors affecting the long-term stability of orthodontic mini-implants.
abstract: BACKGROUND
  The placement and removal torques of mini-implants were evaluated as an index of implant stability. We examined factors affecting the initial and long-term stability of mini-implants.
  
  
  METHODS
  We measured the placement and removal torques of 134 mini-implants placed in buccal posterior alveolar bone and assessed the relationships among placement and removal torques, placement period, age, sex, and cortical bone thickness. The mini-implants were machine-surfaced, 1.6 mm in diameter and 8 mm long. A torque screwdriver was used to measure the peak torque values.
  
  
  CONCLUSIONS
  The placement and removal torques averaged approximately 8 and 4 N cm, respectively. A torque of 4 N cm suggests sufficient anchorage capability for mini-implants. No significant correlation between placement and removal torques was found. Placement torque was significantly related to age and cortical bone thickness in the maxilla, whereas removal torque was not significantly related to placement period, age, sex, or cortical bone thickness.
authors.affiliation: Department of Orthodontics, Division of Clinical Research, Dental Research Center, School of Dentistry, Nihon University, Tokyo, Japan. motoyoshi@dent.nihon-u.ac.jp
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Motoyoshi
authors.forename: Miwa
authors.initials: M
authors.lastname: Uemura
authors.forename: Akiko
authors.initials: A
authors.lastname: Ono
authors.forename: Kumiko
authors.initials: K
authors.lastname: Okazaki
authors.forename: Toru
authors.initials: T
authors.lastname: Shigeeda
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Shimizu
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000539:Alveolar Process / Q000473:pathology; D001863:Bone Screws; D015921:Dental Implants; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008334:Mandible / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D008875:Middle Aged; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D016348:Osseointegration / Q000502:physiology*; D010027:Osteotomy / Q000295:instrumentation; D012737:Sex Factors; D013314:Stress, Mechanical; D013499:Surface Properties; D014057:Tomography, X-Ray Computed; D019415:Torque; D055815:Young Adult
chemical_list: D015921:Dental Implants