title: Stability of mini-screws invading the dental roots and their impact on the paradental tissues in beagles.
abstract: OBJECTIVE
  To examine the stability of mini-screws that invade a dental root by measuring the retention period/failure rate, and to illustrate their effects on paradental tissues.
  
  
  METHODS
  Three adult male beagle dogs received 48 orthodontic mini-screws. Half of the mini-screws were implanted to invade the roots, and the rest were placed in the middle of the alveolar bone. Half of the mini-screws were loaded immediately. The retention period of the mini-screws was documented. The dogs were euthanized after 8 weeks, and tissue samples were examined histologically.
  
  
  RESULTS
  The failure rate of the mini-screws that invaded the roots was 79.2%, and that of the mini-screws in the middle of the alveolar bone was 8.3%. The application of force had little effect on the failed mini-screws. Moderately injured roots were repaired with osteoid and/or cementoid tissues with normal periodontal ligaments, followed by recovery of the original configuration.
  
  
  CONCLUSIONS
  Orthodontic mini-screws had a higher failure rate when placed to invade the dental roots. However, minimally damaged dental roots do not adversely affect the healing process.
authors.affiliation: Department of Orthodontics, Kyunghee University, Seoul, Korea.
authors.forename: Yoon-Goo
authors.initials: YG
authors.lastname: Kang
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Young-Jun
authors.initials: YJ
authors.lastname: Lee
authors.forename: Kyu-Rhim
authors.initials: KR
authors.lastname: Chung
authors.forename: Young-Guk
authors.initials: YG
authors.lastname: Park
mesh_terms: D000539:Alveolar Process / Q000473:pathology; D000818:Animals; D001641:Bicuspid / Q000293:injuries / Q000473:pathology; D001863:Bone Screws / Q000009:adverse effects*; D003739:Dental Cementum / Q000473:pathology; D004285:Dogs; D004868:Equipment Failure; D008297:Male; D008963:Molar / Q000293:injuries / Q000473:pathology; D052280:Orthodontic Anchorage Procedures / Q000009:adverse effects / Q000295:instrumentation*; D009969:Orthodontic Wires; D016348:Osseointegration / Q000502:physiology; D010513:Periodontal Ligament / Q000473:pathology; D016300:Radiography, Bitewing; D012391:Root Resorption / Q000000981:diagnostic imaging / Q000209:etiology; D013314:Stress, Mechanical; D013997:Time Factors; D014092:Tooth Root / Q000293:injuries* / Q000473:pathology; D014945:Wound Healing / Q000502:physiology