title: [A comparative study on apexification using different kinds of materials in dogs].
abstract: OBJECTIVE
  To compare the efficacy of hydroxyapatite (HA), calcium hydroxide (CH) and Vitapex on root formation of immature teeth of dogs.
  
  
  METHODS
  Sixteen roots of permanent incisors in two dogs (about five to six months old) were used. After the pulpectomy, roots were randomly divided into four groups. Group A, B and C were experimental groups and filled with HA, CH and Vitapex, respectively. Group D was control group and filled with AH plus. The changes of root length and apical areas were measured by cone beam CT(CBCT), meanwhile, paraffin sections with hematine-eosin (HE) staining were used to observe the shape of root tips; frozen sections with alkaline phosphatase (ALP) staining were used to observe the osteoplastic activity of cells.
  
  
  RESULTS
  1) CBCT showed that four weeks later, all roots in every groups became longer (P < 0.05), and the apical areas in three experimental groups decreased (P < 0.05). However, eight weeks later, high density image could be detected in every root. 2) Histological examination showed that there was no inflammation in every group, and after four weeks, none of apicals were closed, but partial cementum and peridental membrane had extended into canals. After eight weeks, a complete cementum barrier and an intensive distribution of positive cells of ALP staining could be seen in group A, however, some spaces could be seen in the cementum barrier of group B and C, which were filled with periodontal membranes, and the positive cells of ALP staining were dispersed. Moreover, scattered cementum, cementoid and abundance fiber or blood vessels could be seen in group D, in which ALP staining was negative.
  
  
  CONCLUSIONS
  The root formation of immature teeth can go on after pulpectomy when there is no inflammation, the tissue source is probably the periodontal membrane, and HA which can induce root formation faster is a better material in the apexification.
authors.affiliation: Dept. of Conservative Dentistry and Endodontics, The Affiliated Hospital of Stomatology, Chongqing Medical University, Chongqing Research Center for Oral Diseases and Biomedical Science, Chongqing 401147, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Huang
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.forename: Maode
authors.initials: M
authors.lastname: Xiao
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D000818:Animals; D056624:Apexification; D002126:Calcium Hydroxide; D003739:Dental Cementum; D004285:Dogs; D010513:Periodontal Ligament; D012387:Root Canal Filling Materials; D012828:Silicones; D014092:Tooth Root
chemical_list: D012387:Root Canal Filling Materials; D012828:Silicones; C029584:calcium hydroxide, iodoform, silicone oil drug combination; D002126:Calcium Hydroxide