title: PDL regeneration via cell homing in delayed replantation of avulsed teeth.
abstract: BACKGROUND
  This study was aimed to investigate whether regeneration of periodontal ligament (PDL) like tissue could be promoted by stromal cell-derived factor-1 (SDF1) and bone morphogenetic protein-7 (BMP7) induced cell homing in delayed replantation of avulsed teeth.
  
  
  METHODS
  Canine mandibular premolar teeth were first extracted and air-dried for 2 h followed by complete detachment of their PDL tissues. The crown and pulp of the teeth were also removed. Twenty-four roots divided into two groups (n = 12/group) were used for the following in vivo transplantation. The roots of Group A were treated with 17 % EDTA for 24 h to achieve demineralization, and then coated with SDF1 and BMP7 supplemented collagen solution. The roots of Group B were similarly treated except being coated with a pristine collagen solution. The above roots were transplanted in the sockets that formed previously during tooth extraction. At 6 months' post-operation, PDL-like tissue composed of spindle-shaped cells, capillaries and highly organized collagen fibers was observed in the interstitial space between the avulsed root surface and surrounding alveolar bone in Group A. The neo-fibers inserted deeply and perpendicularly into the cementum and adjacent bone. The periodontium-like characteristics of the neo-tissue was confirmed by immunohistochemical staining for collagen I, fibronectin and osteocalcin.
  
  
  RESULTS
  A high incidence of PDL re-establishment as 42 % was achieved for samples of Group A. However, no PDL-like tissue was found but root ankylosis and replacement resorption as well as inflammatory resorption was observed in the replanted roots of Group B.
  
  
  CONCLUSIONS
  It can be confirmed that avulsed teeth could be successfully rescued even in delayed transplantation to avoid dentoalveolar ankylosis or replacement resorption via the current developed cell homing method.
authors.affiliation: Department of Pediatric Dentistry, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, No. 639, Zhi Zao Ju Road, Shanghai, 200011, China. zhuwenting0731@126.com.
authors.forename: Wenting
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Department of Pediatric Dentistry, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, No. 639, Zhi Zao Ju Road, Shanghai, 200011, China. lucy1591961@126.com.
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Pediatric Dentistry, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, No. 639, Zhi Zao Ju Road, Shanghai, 200011, China. 8645282@qq.com.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: School of Chemical Engineering, East China University of Science and Technology, No. 130, Mei Long Road, Shanghai, 200237, China. cenlian@hotmail.com.|National Tissue Engineering Center of China, No. 68, East Jiang Chuan Road, Shanghai, 200241, China. cenlian@hotmail.com.
authors.forename: Lian
authors.initials: L
authors.lastname: Cen
authors.affiliation: Department of Pediatric Dentistry, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, No. 639, Zhi Zao Ju Road, Shanghai, 200011, China. shdrwangjun@outlook.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
mesh_terms: D000818:Animals; D004285:Dogs; D007150:Immunohistochemistry; D010513:Periodontal Ligament / Q000378:metabolism / Q000502:physiology*; D012038:Regeneration; D014084:Tooth Avulsion / Q000601:surgery*; D014090:Tooth Replantation