title: Histologic evaluation of root response to intrusion in mandibular teeth in beagle dogs.
abstract: BACKGROUND
  The purpose of this article was to histologically evaluate root resorption and repair after orthodontic intrusion with different force magnitudes and fixed anchorage.
  
  
  METHODS
  A randomized split-mouth repeated-measure design was used. Intrusive forces were applied for 98 days to the mandibular second, third, and fourth premolars of 8 mature beagle dogs. Two miniscrew implants were used as anchorage to apply constant intrusive forces of 50, 100, or 200 g per tooth. Demineralized sections of each tooth were stained and histologically studied for root resorption. Multilevel statistical procedures were used to evaluate the results.
  
  
  RESULTS
  Root resorption was present in all teeth, independent of the force applied. Significant differences were found between root regions, with the apices and the interradicular regions the most affected and with dentin involvement at the furcation. There was cementum repair in 24.14% of the lacunae. Light constant intrusive forces between 50 and 200 g showed no significant differences in the amount of resorption produced. Resorption was more frequently seen at the level of the apices and the furcation.
  
  
  CONCLUSIONS
  Orthodontically induced root resorption is not clinically significant after application of continuous intrusive forces between 50 and 200 g. Moreover, there is no relationship between root resorption, the position of posterior mandibular teeth in the arch, and the amount of intrusive force applied.
authors.forename: Juan I
authors.initials: JI
authors.lastname: Ramirez-Echave
authors.forename: Peter H
authors.initials: PH
authors.lastname: Buschang
authors.forename: Roberto
authors.initials: R
authors.lastname: Carrillo
authors.forename: P Emile
authors.initials: PE
authors.lastname: Rossouw
authors.forename: William W
authors.initials: WW
authors.lastname: Nagy
authors.forename: Lynne A
authors.initials: LA
authors.lastname: Opperman
mesh_terms: D000539:Alveolar Process / Q000473:pathology; D000818:Animals; D001641:Bicuspid / Q000473:pathology*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D003722:Dental Alloys / Q000737:chemistry; D003739:Dental Cementum / Q000473:pathology; D003804:Dentin / Q000473:pathology; D004285:Dogs; D008334:Mandible; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation; D009969:Orthodontic Wires; D010513:Periodontal Ligament / Q000473:pathology; D011897:Random Allocation; D012391:Root Resorption / Q000473:pathology; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D019227:Tooth Apex / Q000473:pathology; D019237:Tooth Cervix / Q000473:pathology; D014087:Tooth Movement Techniques; D014092:Tooth Root / Q000473:pathology*; D014945:Wound Healing / Q000502:physiology
chemical_list: D003722:Dental Alloys; D013193:Stainless Steel