title: Biologic and mechanical stability of single-tooth implants: 4- to 7-year follow-up.
abstract: BACKGROUND
  Single-tooth implants have been reported to achieve a high level of surgical and prosthetic success. However, close inspection of the literature reveals a paucity of data on the follow-up of single-tooth implants in function for 5 years or more. Since unsplinted implants may be considered to be subject to greater functional stresses, there is a need to report on the long-term biologic and mechanical integrity of such implant-supported restorations.
  
  
  OBJECTIVE
  To report on the long-term follow-up of single-tooth implants, restored and in function for 4 to 7 years.
  
  
  METHODS
  Twenty-seven Astra Tech single-tooth implants were subject to a clinical audit to evaluate implant and prosthetic success as well as response of both hard and soft tissues over a 1- to 4-year follow-up. This current report presents data on the biologic and mechanical integrity of 23 of these single-tooth implants, which have been in function for up to 7 years (mean, 63 mo). Data are provided with respect to implant survival, maintenance of marginal bone levels, soft-tissue health, and the recording of any adverse events, including prosthetic complications.
  
  
  RESULTS
  Only 14 implants in 13 patients were available for review, with no failures for this group of implants. One patient from the original group, who was lost to follow-up, was known to have suffered an implant failure. Furthermore, in accordance with established criteria, the remaining 13 implants that are not included in this report must at this time also be considered as potential failures. As such, the best-case scenario would be a 95.6% success rate for the 23 implants included in this review and the worst-case scenario would be a 60.8% success rate. Mean marginal bone loss measured 0.49 mm mesially and 0.76 mm distally, with a frequency of bone loss of 50%. Soft tissues were clinically healthy. There were few adverse events, with only one case of abutment screw loosening, detected at the 6-year review. In addition, crown decementation was recorded three times in two patients.
  
  
  CONCLUSIONS
  It can be concluded that the Astra Tech single-tooth implant can achieve long-term biologic and mechanical stability when used to restore single missing teeth, over the long-term.
authors.affiliation: Departments of Oral and Maxillofacial Surgery, Charing Cross Hospital, London and Bedford Hospital, Bedford, UK. drnorton@nortonimplants.co.uk
authors.forename: M R
authors.initials: MR
authors.lastname: Norton
mesh_terms: D000328:Adult; D000368:Aged; D016301:Alveolar Bone Loss / Q000209:etiology; D003442:Crowns; D019250:Dental Implants, Single-Tooth / Q000009:adverse effects; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000295:instrumentation; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D013314:Stress, Mechanical; D011795:Surveys and Questionnaires