title: [A scanning electron microscopic study of root surface following mini-implant anchorage for maxillary incisors intrusion].
abstract: OBJECTIVE
  To establish an animal model for maxillary incisors intrusion with mini-implant as the anchorage and study the effect on the surface morphology of cementum after the force had been given.
  
  
  METHODS
  9 dogs were selected and randomly divided into 5 groups, group I was the control group(1 dog) with no force given; groups II,III,IV,V were experimental groups (2 dogs each). Mini-implants were inserted into the labial alveolar bone between the roots of second and third maxillary incisors on both sides, 100 gram force was imposed on the first and the second incisors on both sides.The animals were sacrificed at the end of 1, 2, 4,12 weeks (activation for 4 weeks,then retention for 8 weeks after force removal) respectively after activation.Scanning electron microscopy was used to examine the surface of the cementum.
  
  
  RESULTS
  In group II, the surfaces of root tip had a little scratch, which was small,confined. In group III, near the apical 1/3 of root, lacunas were fused, but no dentin exposed. In group IV, at the junction of the apical 1/3 and the middle 1/3 of the root, lacunas went deep into the dentin,which were wide and serious. In group V, the surfaces of lacunas were low ,smooth and even.
  
  
  CONCLUSIONS
  As the intrusion goes on, the area of absorption expands from the root tip to neck. Root resorption increases with the duration of the applied force prolonged and repair of the cementum occurs at the resorbed area after force removal.
authors.affiliation: Department of Orthodontics, School of Stomatology, Lanzhou University, Lanzhou 730000, Gansu Province, China. lujj06@lzu.cn
authors.forename: Jia-jing
authors.initials: JJ
authors.lastname: Lu
authors.forename: Tao
authors.initials: T
authors.lastname: Qi
authors.forename: Zhen-lin
authors.initials: ZL
authors.lastname: Ge
mesh_terms: D000818:Animals; D003739:Dental Cementum; D003804:Dentin; D004285:Dogs; D004583:Electrons; D007180:Incisor; D008855:Microscopy, Electron, Scanning; D012391:Root Resorption; D014087:Tooth Movement Techniques; D014092:Tooth Root