title: Novel bone substitute material in alveolar bone healing following tooth extraction: an experimental study in sheep.
abstract: OBJECTIVE
  Electrospun cotton wool-like nanocomposite (ECWN) is a novel synthetic bone substitute that incorporates amorphous calcium phosphate nanoparticles into a biodegradable synthetic copolymer poly(lactide-co-glycolide). The objectives of this study were to develop a tooth extraction socket model in sheep for bone graft research and to compare ECWN and bovine-derived xenograft (BX) in this model.
  
  
  METHODS
  Sixteen cross-bred female sheep were used. Bilateral mandibular premolars were extracted atraumatically. Second and third premolar sockets were filled (Latin-square allocation) with BX, ECWN or left unfilled. Resorbable collagen membranes were placed over BX and selected ECWN grafted sockets. Eight sheep per time period were sacrificed after 8 and 16 weeks. Resin-embedded undemineralised sections were analysed for descriptive histology and histomorphometric analyses.
  
  
  RESULTS
  At 8 weeks, there were with no distinct differences in healing among the different sites. At 16 weeks, osseous healing followed a fine trabecular pattern in ECWN sites. Non-grafted sites showed thick trabeculae separated by large areas of fibrovascular connective tissue. In BX grafted sites, xenograft particles were surrounded by newly formed bone or fibrovascular connective tissue. There were no statistically significant differences in bone formation across the four groups. However, ECWN sites had significantly less residual graft material than BX sites at 16 weeks (P = 0.048).
  
  
  CONCLUSIONS
  This first description of a tooth extraction socket model in sheep supports the utility of this model for bone graft research. The results of this study suggested that the novel material ECWN did not impede bone ingrowth into sockets and showed evidence of material resorption.
authors.affiliation: Private Periodontal Practice, Auckland, New Zealand.
authors.forename: Jinyi
authors.initials: J
authors.lastname: Liu
authors.affiliation: Clinic of Preventive Dentistry, Periodontology and Cariology, University of Zürich, Zürich, Switzerland.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Schmidlin
authors.affiliation: Clinic of Preventive Dentistry, Periodontology and Cariology, University of Zürich, Zürich, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Philipp
authors.affiliation: Institute for Chemical and Bioengineering, ETH Zurich, Zurich, Switzerland.
authors.forename: Nora
authors.initials: N
authors.lastname: Hild
authors.affiliation: Department of Oral Sciences, University of Otago, Dunedin, New Zealand.
authors.forename: Andrew
authors.initials: A
authors.lastname: Tawse-Smith
authors.affiliation: Department of Oral Sciences, University of Otago, Dunedin, New Zealand.
authors.forename: Warwick
authors.initials: W
authors.lastname: Duncan
mesh_terms: D000539:Alveolar Process / Q000473:pathology*; D000818:Animals; D018786:Bone Substitutes; D002130:Calcium Phosphates; D008853:Microscopy; D053758:Nanoparticles; D010012:Osteogenesis; D034561:Sheep, Domestic; D014081:Tooth Extraction; D020390:Tooth Socket; D014945:Wound Healing
chemical_list: D018786:Bone Substitutes; D002130:Calcium Phosphates; C519480:amorphous calcium phosphate
keywords: animal; biomaterials; bone substitutes; extraction socket; wound healing