title: Influence of microgap location and configuration on peri-implant bone morphology in nonsubmerged implants: an experimental study in dogs.
abstract: OBJECTIVE
  It is unknown whether different microgap configurations can cause different peri-implant bone reactions. Therefore, this study sought to compare the peri-implant bone morphologies of two implant systems with different implant-abutment connections.
  
  
  METHODS
  Three months after mandibular tooth extractions in six mongrel dogs, two oxidized screw implants with an external-hex connection were inserted (hexed group) on one side, whereas on the contralateral side two grit-blasted screw implants with an internal Morse-taper connection (Morse group) were placed. On each side, one implant was inserted level with the bone (equicrestal) and the second implant was inserted 1.5 mm below the bony crest (subcrestal). Healing abutments were inserted immediately after implant placement. Three months later, the peri-implant bone levels, the first bone-to-implant contact points, and the width and steepness of the peri-implant bone defects were evaluated histometrically.
  
  
  RESULTS
  All 24 implants osseointegrated clinically and histologically. No statistically significant differences between the hexed group and Morse group were detected for either the vertical position for peri-implant bone levels (Morse equicrestal -0.16 mm, hexed equicrestal -0.22 mm, Morse subcrestal 1.50 mm, hexed subcrestal 0.94 mm) or for the first bone-to-implant contact points (Morse equicrestal -2.08 mm, hexed equicrestal -0.98 mm, Morse subcrestal -1.26 mm, hexed subcrestal -0.76 mm). For the parameters width (Morse equicrestal -0.15 mm, hexed equicrestal -0.59 mm, Morse subcrestal 0.28 mm, hexed subcrestal -0.70 mm) and steepness (Morse equicrestal 25.27 degree, hexed equicrestal 57.21 degree, Morse subcrestal 15.35 degree, hexed subcrestal 37.97 degree) of the peri-implant defect, highly significant differences were noted between the Morse group and the hexed group.
  
  
  CONCLUSIONS
  Within the limits of this experiment, it can be concluded that different microgap configurations influence the size and shape of the peri-implant bone defect in nonsubmerged implants placed both at the crest and subcrestally.
authors.affiliation: Department of Prosthodontics, Propaedeutics, and Dental Materials, School of Dentistry, Christian-Albrechts-University at Kiel, Germany. dw@max-17.de
authors.forename: Dietmar
authors.initials: D
authors.lastname: Weng
authors.forename: Maria José Hitomi
authors.initials: MJ
authors.lastname: Nagata
authors.forename: Matthias
authors.initials: M
authors.lastname: Bell
authors.forename: Luiz Gustavo Nascimento
authors.initials: LG
authors.lastname: de Melo
authors.forename: Alvaro Francisco
authors.initials: AF
authors.lastname: Bosco
mesh_terms: D016301:Alveolar Bone Loss / Q000209:etiology* / Q000473:pathology; D000818:Animals; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous / Q000009:adverse effects / Q000379:methods*; D015921:Dental Implants; D017267:Dental Prosthesis Design / Q000009:adverse effects*; D004285:Dogs; D020007:Implants, Experimental; D016348:Osseointegration
chemical_list: D015921:Dental Implants