title: Peri-implant bone loss as a function of tooth-implant distance.
abstract: OBJECTIVE
  In a retrospective study, the radiographs of 39 patients with Applegate-Kennedy Class I or II in the posterior mandible who had been treated with screw-anchored fixed partial dentures supported by IMZ implants and natural teeth were examined for the presence of radiologically detectable peri-implant bone loss. Furthermore, the results were correlated with a mathematical model.
  
  
  METHODS
  The radiographs of the implants were digitized, and the areas of bone atrophy mesial and distal to the implants were determined semi-automatically. The data obtained were correlated with the distance between the implant and the abutment tooth. The connection between the tooth-supported crown and the implant-supported denture was made with a vertical screw-lock precision attachment. In a mathematical analysis it was assumed that the fixed partial prosthesis was a rigid beam with 3 elastically embedded supports.
  
  
  RESULTS
  The mean distance between the tooth and the first implant was 11.02 mm (SD: 4.24), and between the tooth and the second implant was 20.25 mm (SD: 5.16). Peri-implant bone loss significantly followed a rational function (mesial implant: P = .03, distal implant: P = .02), meaning that, as the tooth-implant distance increased, the area of atrophy became rapidly larger and then diminished gradually. Distances of 8 to 14 mm between the tooth and the first implant and of 17 to 21 mm between the tooth and the second implant were associated with a more pronounced bone loss. These results were also confirmed mathematically.
  
  
  CONCLUSIONS
  A tooth-implant distance of 8 to 14 mm for the first implant and 17 to 21 mm for the second implant should be avoided for implant placement if prosthetic rehabilitation is planned using a fixed partial denture supported by a premolar and 2 IMZ implants in the mandible. Although this investigation was done on IMZ implants only, the results were confirmed by a mathematical model, which indicated that the observed bone loss may be the same in other types of implants placed in the same positions.
authors.affiliation: Department of Oral Surgery, Dental School, University of Vienna, Austria. monika.gottschalk-baron@meduniwien.ac.at
authors.forename: Monika
authors.initials: M
authors.lastname: Baron
authors.forename: Robert
authors.initials: R
authors.lastname: Haas
authors.forename: Werner
authors.initials: W
authors.lastname: Baron
authors.forename: Georg
authors.initials: G
authors.lastname: Mailath-Pokorny
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016301:Alveolar Bone Loss / Q000000981:diagnostic imaging / Q000209:etiology*; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous / Q000009:adverse effects*; D015921:Dental Implants / Q000009:adverse effects*; D019094:Dental Prosthesis, Implant-Supported / Q000009:adverse effects*; D003799:Dental Stress Analysis; D003834:Denture Precision Attachment; D003830:Denture, Partial, Fixed / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible; D008875:Middle Aged; D008962:Models, Theoretical; D009811:Odontometry; D011859:Radiography; D012189:Retrospective Studies
chemical_list: D015921:Dental Implants