title: Subcrestal placement of two-part implants.
abstract: OBJECTIVE
  The aim of the present experiment was to study the healing around two-part implants that were placed in a subcrestal position.
  
  
  METHODS
  Five mongrel dogs, about 2 years old, were included. The mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later two test and two control implants (OsseoSpeed, 3.5 mm x 8 mm) were placed in one side of the mandible. The implants were placed in such a way that the implant margin was located 2 mm apical to the bone crest. In the test implants, the surface modification extended to the implant margin and, thus, included the shoulder part of the implant. Regular abutments with a turned surface (Zebra) were connected to the control implants, while experimental abutments with a modified surface (TiOblast) were connected to the test implants. A plaque control program that included cleaning of implants and teeth every second day was initiated. Four months later the dogs were euthanized and biopsies were obtained and prepared for histological analysis.
  
  
  RESULTS
  The marginal bone level at the test implants was identified in a more coronal position than that at the control implants. In 40% of the test implants, the bone-to-implant contact extended coronal of the abutment/fixture (A/F) border, i.e. in contact with the abutment part of the implant. The connective tissue portion of the peri-implant mucosa that was facing the test abutments contained a higher density of collagen and a smaller proportion of fibroblasts than that at the control sites.
  
  
  CONCLUSIONS
  It is suggested that osseointegration may occur coronal to the A/F interface of two-part implants. Such a result, however, appears to depend on the surface characteristics of the implant components.
authors.affiliation: Department of Periodontology, The Sahlgrenska Academy at Göthenburg University, Göthenburg 405 30, Sweden. maria.welander@odontologi.gu.se
authors.forename: Maria
authors.initials: M
authors.lastname: Welander
authors.forename: Ingemar
authors.initials: I
authors.lastname: Abrahamsson
authors.forename: Tord
authors.initials: T
authors.lastname: Berglundh
mesh_terms: D000539:Alveolar Process / Q000502:physiology / Q000601:surgery*; D000818:Animals; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous / Q000295:instrumentation* / Q000379:methods; D015921:Dental Implants; D017267:Dental Prosthesis Design; D004285:Dogs; D008334:Mandible; D008437:Maxilla; D016348:Osseointegration / Q000502:physiology; D010521:Periosteum / Q000502:physiology / Q000601:surgery; D014945:Wound Healing / Q000502:physiology*
chemical_list: D015921:Dental Implants