title: Bone level changes at axial- and non-axial-positioned implants supporting fixed partial dentures. A 5-year retrospective longitudinal study.
abstract: OBJECTIVE
  The aim of this study was to retrospectively analyze the potential influence of implant inclination on marginal bone loss at freestanding, implant-supported, fixed partial dentures (FPDs) over a 5-year period of functional loading.
  
  
  METHODS
  The material comprised 38 periodontally treated, partially dentate patients with a total of 42 free-standing FPDs supported by implants of the Astra Tech System. Mesio-distal inclination of the implants in relation to a vertical axis perpendicular to the occlusal plane was measured with a protractor on standardized photographs of the master cast. The two tail quartiles of the distribution of the implants with regard to the implant inclination were defined as axial-positioned (mean 2.4 degrees; range 0-4 degrees) and non-axial-positioned implants (mean 17.1 degrees; range 11-30 degrees), respectively. For FPDs supported by two implants, both the mesial-distal and buccal-lingual inter-implant inclination was measured. The primary outcome variable was change in peri-implant bone level from the time of FPD placement to the 5-year follow-up examination. Comparison between axial- and non-axial-positioned implants was performed by the use of a Mann-Whitney U-test. Spearman's correlation analysis was used to analyze relationships between inter-implant inclination (mesial-distal and buccal-lingual) and 5-year bone level change on the FPD level.
  
  
  RESULTS
  The 5-year mean bone level change amounted to 0.4 mm (SD 0.97) for the axial and 0.5 mm (0.95) for non-axial-positioned implants (P>0.05). For the FPDs supported by two implants, the mean inter-implant inclination was 9.2 degrees (1-36 degrees) in the mesial-distal direction and 6.7 degrees (0-24 degrees) in the buccal-lingual direction. Correlation analysis revealed lack of statistically significant correlation between inter-implant inclination (mesial-distal and buccal-lingual) and 5-year bone level change (r=-0.19 and r=-0.32, respectively).
  
  
  CONCLUSIONS
  The study failed to support the hypothesis that implant inclination has an effect on peri-implant bone loss.
authors.affiliation: Department of Periodontology, Institute of Odontology, The Sahlgrenska Academy at Göteborg University, Göteborg, Sweden.
authors.forename: Theofilos
authors.initials: T
authors.lastname: Koutouzis
authors.forename: Jan L
authors.initials: JL
authors.lastname: Wennström
mesh_terms: D016301:Alveolar Bone Loss / Q000209:etiology*; D003758:Dental Implantation, Endosseous / Q000379:methods; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003779:Denture Design; D003830:Denture, Partial, Fixed; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007576:Jaw, Edentulous, Partially / Q000534:rehabilitation / Q000601:surgery; D008137:Longitudinal Studies; D008297:Male; D008334:Mandible / Q000601:surgery; D008437:Maxilla / Q000601:surgery; D008875:Middle Aged; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants