title: Fixed partial prostheses supported by 2 or 3 implants: a retrospective study up to 18 years.
abstract: OBJECTIVE
  The purpose of this study was to evaluate and compare the long-term performance of fixed partial prostheses supported by 2 or 3 implants.
  
  
  METHODS
  All patients treated with fixed partial prostheses supported by either 2 or 3 implants during the period 1985 to 1998 were included in this retrospective report. Annual clinical follow-up examinations were performed, with special attention to stability of the prostheses and peri-implant and occlusal conditions. Radiographic examination was performed when the prostheses were delivered (year 0) and subsequently at 1-year, 5-year, and 10-year examinations.
  
  
  RESULTS
  A total of 178 patients had received fixed partial prostheses (FPPs) during this period of whom 123 (77 women and 46 men) were available for follow-up (mean age = 65 years, range 32-91). These 123 patients received a total of 146 implant-supported FPPs (63 two-implant- and 83 three-implant-supported) supported by 375 implants. The mean observation periods for the 2- and 3-implant-supported restorations were 9.6 years and 9.4 years (range, 5 to 18 years), respectively. Survival rates for the 2- and 3-implant-supported prostheses were 96.8% and 97.6%, respectively. The implant survival rate after loading was 98.4% for both groups. The mean bone loss at the 5-year follow-up was 0.3 mm for the 2 groups. No significant differences in bone loss (P > .05), implant failure rate (P > .05), or incidence of mechanical complications (P > .05) were found between the 2 prosthesis designs. The complications differed, significantly, with more loose gold and abutment screws in the 2-implant-supported group (P < .05) and more porcelain fractures in the 3-implant-supported group (P < .05).
  
  
  CONCLUSIONS
  The 2-implant-supported partial prostheses exhibited long-term clinical performance comparable to prostheses supported by 3 implants.
authors.affiliation: Department of Prosthetic Dentistry, Postgraduate Dental Education Center, Orebro, Sweden. alf.eliasson@orebroll.se
authors.forename: Alf
authors.initials: A
authors.lastname: Eliasson
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Eriksson
authors.forename: Anders
authors.initials: A
authors.lastname: Johansson
authors.forename: Ann
authors.initials: A
authors.lastname: Wennerberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016301:Alveolar Bone Loss / Q000000981:diagnostic imaging*; D019094:Dental Prosthesis, Implant-Supported / Q000009:adverse effects / Q000706:statistics & numerical data*; D019232:Dental Restoration Failure; D003830:Denture, Partial, Fixed / Q000009:adverse effects / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008336:Mandibular Diseases / Q000000981:diagnostic imaging; D008439:Maxillary Diseases / Q000000981:diagnostic imaging; D008875:Middle Aged; D017060:Patient Satisfaction / Q000706:statistics & numerical data; D011859:Radiography; D012189:Retrospective Studies; D011795:Surveys and Questionnaires; D016019:Survival Analysis