title: Periodontal repair in dogs: gingival tissue occlusion, a critical requirement for GTR?
abstract: BACKGROUND
  Design criteria for guided tissue regeneration (GTR) devices include biocompatibility, cell occlusion, space maintenance, tissue integration, and ease of use. Previous studies have established the importance of wound stabilization and space provision during the early healing sequel for successful GTR outcomes as well as evaluated biocompatibility, tissue integration, and clinical manageability of various biomaterials. The importance of cell or tissue occlusion has yet to be established. The objective of this study was to evaluate the role of tissue occlusion as a critical determinant for GTR outcomes.
  
  
  METHODS
  Routine, critical size, 5-6 mm, supra-alveolar, periodontal defects were created around the mandibular premolar teeth in six young adult Beagle dogs. Space-providing expanded polytetrafluoroethylene (ePTFE) membranes, with (macroporous) or without (occlusive) 300- microm laser-drilled pores, 0.8 mm apart, were implanted to provide for GTR. Treatments were randomly assigned to left and right jaw quadrants in subsequent animals. The gingival flaps were advanced to cover the membranes and sutured. The animals were euthanized at 8 weeks postsurgery for histologic and histometric analysis.
  
  
  RESULTS
  Three animals experienced wound failure within 2-3 weeks postsurgery resulting in exposure and removal of the occlusive ePTFE membranes. All defect sites, irrespective of membrane configuration or history of membrane exposure and removal, exhibited substantial evidence of periodontal regeneration including a functionally oriented periodontal ligament. To evaluate the biologic potential of GTR devices, only animals without wound failure and membrane removal were included. Alveolar bone regeneration for animals receiving occlusive and macroporous ePTFE membranes averaged (+/-sd) 3.2+/-1.1 versus 2.0+/-0.4 mm (p=0.3113). Cementum regeneration was enhanced in defect sites receiving the occlusive ePTFE membrane compared to the macroporous membrane (4.7+/-0.4 versus 2.3+/-0.2 mm; p=0.0167). Ankylosis was observed in one animal. Limited root resorption was observed in a second animal.
  
  
  CONCLUSIONS
  Tissue occlusion does not appear to be a critical determinant for GTR. However, tissue occlusion may be a requirement for optimal GTR. Moreover, macroporous space-providing devices may increase the predictability of clinical GTR therapy.
authors.affiliation: Department of Periodontology, Temple University School of Dentistry, Philadelphia, PA 19140, USA. ulf.wikesjo@temple.edu
authors.forename: Ulf M E
authors.initials: UM
authors.lastname: Wikesjö
authors.forename: Won Hee
authors.initials: WH
authors.lastname: Lim
authors.forename: Robert C
authors.initials: RC
authors.lastname: Thomson
authors.forename: W Ross
authors.initials: WR
authors.lastname: Hardwick
mesh_terms: D016301:Alveolar Bone Loss / Q000601:surgery; D000818:Animals; D001861:Bone Regeneration; D003238:Connective Tissue / Q000502:physiology; D003739:Dental Cementum / Q000502:physiology; D004285:Dogs; D004847:Epithelial Cells / Q000502:physiology; D005881:Gingiva / Q000502:physiology; D016557:Guided Tissue Regeneration, Periodontal / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008567:Membranes, Artificial; D009779:Occlusive Dressings; D010513:Periodontal Ligament / Q000502:physiology; D011138:Polytetrafluoroethylene; D016062:Porosity; D012038:Regeneration; D014945:Wound Healing / Q000502:physiology*
chemical_list: D008567:Membranes, Artificial; D011138:Polytetrafluoroethylene