title: Effect of Platform Shift/Switch and Concave Abutments on Crestal Bone Levels and Mucosal Profile following Flap and Flapless Implant Surgery.
abstract: BACKGROUND
  Crestal remodeling/bone loss appears to be a common sequel to dental implant placement. Several hypotheses/clinical strategies have been proposed to explain/avert crestal remodeling; however, causative mechanisms remain unclear and the efficacy of these clinical approaches uncertain.
  
  
  OBJECTIVE
  The objective of the present study was to provide a histological account of crestal bone levels and mucosal profile at platform shift/switch and concave abutments following flapless and conventional flap surgery and subcrestal implant placement using a dog model.
  
  
  METHODS
  Four dental implants each were placed in the left/right mandibular posterior jaw quadrants in five adult male Hound/Labrador mongrel dogs using flap surgery with a 1 × 5 mm gap defect or using a flapless approach, both involving placement 2 mm subcrestally and platform shift/switch versus concave abutments. Block biopsies for histological/histometric analysis were collected at 8 weeks.
  
  
  RESULTS
  No significant differences were observed regarding crestal bone levels, with all groups showing mean bone levels above the implant platform. Similarly, crestal bone-implant contact was not significantly different among groups. Moreover, peri-implant mucosal profiles were not statistically different among groups for buccal sites; average mucosal height reached 4.1 to 4.9 mm above the implant platform. Comparison between buccal and lingual sites showed a nonsignificant tendency toward greater crestal resorption at buccal sites, adjusting for other factors. Mean crestal bone-implant contact level approximated the implant platform for lingual sites while consistently remaining below the platform at the buccal sites. Peri-implant mucosal height was significantly higher at buccal than at lingual sites, with the epithelial attachment located a significant distance away from the implant platform at buccal sites.
  
  
  CONCLUSIONS
  The surgical approaches (subcrestal implant placement by flap surgery or a flapless approach) and abutment designs (platform shift/switch or concave) used in this study seem to have a limited impact on crestal remodeling, associated bone loss, and mucosal profile. Bioclinical strategies should be developed to circumvent the limitations of current clinical protocol.
authors.affiliation: Laboratory for Applied Periodontal & Craniofacial Regeneration, Georgia Regents University, Augusta, GA, USA.|Clinica Dental Gamborena, San Sebastian, Spain.
authors.forename: Inãki
authors.initials: I
authors.lastname: Gamborena
authors.affiliation: Laboratory for Applied Periodontal & Craniofacial Regeneration, Georgia Regents University, Augusta, GA, USA.
authors.forename: Jaebum
authors.initials: J
authors.lastname: Lee
authors.affiliation: Laboratory for Applied Periodontal & Craniofacial Regeneration, Georgia Regents University, Augusta, GA, USA.|Section of Periodontology, School of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Tiago
authors.initials: T
authors.lastname: Fiorini
authors.affiliation: Laboratory for Applied Periodontal & Craniofacial Regeneration, Georgia Regents University, Augusta, GA, USA.
authors.forename: Brent A
authors.initials: BA
authors.lastname: Wenzel
authors.affiliation: Laboratory for Applied Periodontal & Craniofacial Regeneration, Georgia Regents University, Augusta, GA, USA.|Peter Schüpbach GmbH, Horgen, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Schüpbach
authors.affiliation: Laboratory for Applied Periodontal & Craniofacial Regeneration, Georgia Regents University, Augusta, GA, USA.
authors.forename: Ulf M E
authors.initials: UM
authors.lastname: Wikesjö
authors.affiliation: Laboratory for Applied Periodontal & Craniofacial Regeneration, Georgia Regents University, Augusta, GA, USA.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Susin
mesh_terms: D016301:Alveolar Bone Loss / Q000601:surgery*; D000818:Animals; D016723:Bone Remodeling; D000044:Dental Abutments; D003757:Dental Implantation; D015921:Dental Implants; D004285:Dogs; D004846:Epithelial Attachment / Q000166:cytology; D008297:Male; D008334:Mandible / Q000601:surgery*; D013524:Surgical Flaps / Q000601:surgery*
chemical_list: D015921:Dental Implants
keywords: alveolar bone; animal models; crestal resorption/remodeling; dental implants; platform shift/switch