title: Five-year evaluation of implants placed at extraction and with dehiscences and fenestration defects augmented with ePTFE membranes: results from a prospective multicenter study.
abstract: BACKGROUND
  Barrier membranes have been used to promote bone ingrowth on implants with dehiscences and fenestrations. Membranes also have been used to protect defects adjacent to implants placed at the time of extraction. The concept of guided bone regeneration relates to preferentially allowing cells from bone to migrate into various defects while excluding fibrous tissue and epithelium. The purpose of these procedures is to enhance bone-to-implant contact at the treated sites and to prevent mucosal complications.
  
  
  OBJECTIVE
  The purpose of this article is to report clinical outcomes for implants placed at the time of extraction and augmented with expanded polytetrafluoroethylene (ePTFE) and followed for 5 years. The outcomes for implants with dehiscences and fenestrations augmented with ePTFE barriers and followed up to 5 years also are reported.
  
  
  METHODS
  Four treatment centers participated in this study (Tucson, Gothenburg, Spokane, and Leuven). In the extraction group, teeth were removed for varying reasons, and Brånemark implants were placed and stabilized within the host bone. Defects present at the coronal implant aspect were covered with ePTFE barrier membranes. Flaps were rotated to cover the membrane-treated sites. If exposure of the material occurred prior to second-stage surgery, the membranes were removed. Barriers remaining unexposed were removed at second-stage surgery. The implants were followed up to 5 years. In the fenestration and dehiscence group, implants with exposed threads were augmented with ePTFE barrier membranes. The barriers were removed at appropriate intervals, and the patients were followed up to 5 years. Radiographic measurements were made from nonstandardized periapical radiographs at abutment connection and 1, 3, and 5-year follow-up visits.
  
  
  RESULTS
  Forty patients participated in the extraction group. They received a total of 49 implants. Three implants failed prior to loading. The 5-year cumulative survival rates for implants placed at the time of extraction were 93.9% and 93.8%, respectively, for maxillary and mandibular implants. The average maxillary mesial and distal marginal bone loss (1-5 yr) was 0.3 mm (standard deviation [SD] = 1.5) and 0.3 mm (SD = 1.0). In mandibles, the average mesial and distal bone loss (1-5 yr) was -0.2 mm (SD = 0.5) and -0.05 mm (SD = 0.6), respectively. The dehiscence and fenestration group included 44 patients. Twenty-six were followed for up to 5 years. Eight patients experienced total implant failure. For dehiscences and fenestrations, the cumulative survival rates were 76.8% and 83.8% for maxillary and mandibular implants, respectively. The average maxillary mesial and distal bone loss (1-5 yr) was 0.4 mm (SD = 0.8) and 0.2 mm (SD = 0.9), respectively. In mandibles, the average mesial and distal marginal bone loss was 0.3 mm (SD = 0.9) and 0.3 mm (SD = 0.8), respectively.
  
  
  CONCLUSIONS
  Implants placed at the time of extraction and augmented with ePTFE barrier membranes have favorable long-term predictability. On the other hand, long-term evaluation of implant dehiscences and fenestrations augmented with barrier membranes indicates that they have less favorable 5-year survival rates. Membrane augmentation of these may be questioned.
authors.affiliation: University of Southern California School of Dentistry, Los Angeles, California, USA. branebill@AOL.com
authors.forename: W
authors.initials: W
authors.lastname: Becker
authors.forename: C
authors.initials: C
authors.lastname: Dahlin
authors.forename: U
authors.initials: U
authors.lastname: Lekholm
authors.forename: C
authors.initials: C
authors.lastname: Bergstrom
authors.forename: D
authors.initials: D
authors.lastname: van Steenberghe
authors.forename: K
authors.initials: K
authors.lastname: Higuchi
authors.forename: B E
authors.initials: BE
authors.lastname: Becker
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016301:Alveolar Bone Loss / Q000209:etiology / Q000601:surgery*; D001861:Bone Regeneration; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants / Q000009:adverse effects; D017268:Dental Prosthesis Retention; D019232:Dental Restoration Failure; D005260:Female; D016557:Guided Tissue Regeneration, Periodontal / Q000379:methods*; D006801:Humans; D015993:Life Tables; D008297:Male; D008567:Membranes, Artificial; D008875:Middle Aged; D011138:Polytetrafluoroethylene; D011446:Prospective Studies; D014081:Tooth Extraction; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants; D008567:Membranes, Artificial; D011138:Polytetrafluoroethylene