title: Complication and failure rates in patients treated for chronic periodontitis and restored with single crowns on teeth and/or implants.
abstract: OBJECTIVE
  To assess the biological and technical complication rates of single crowns on vital teeth (SC-V), endodontically treated teeth without post and core (SC-E), with a cast post and core (SC-PC) and on implants (SC-I).
  
  
  METHODS
  From 392 patients with chronic periodontitis treated and documented by graduate students during the period from 1978 to 2002, 199 were reexamined during 2005 for this retrospective cohort study, and 64 of these patients were treated with SCs. Statistical analysis included Kaplan-Meier survival functions and event rates per 100 years of object-time. Poisson regression was used to compare the four groups of crowns with respect to the incidence rate ratio of failures, and failures and complications combined over 10 years and the entire observation period.
  
  
  RESULTS
  Forty-one (64%) female and 23 (36%) male patients participated in the reexamination. At the time of seating the crowns, the mean patient age was 46.8 (range 24-66.3) years. One hundred and sixty-eight single unit crowns were incorporated. Their mean follow-up time was 11.8 (range 0.8-26.4) years. During the time of observation, 22 biological and 11 technical complications occurred; 19 SC were lost. The chance for SC-V (56) to remain free of any failure or complication was 89.3% (95% confidence interval [CI] 76.1-95.4) after 10 years, 85.8% (95% CI 66-94.5) for SC-E (34), 75.9% for SC-PC (39), (95% CI 58.8-86.7) and 66.2% (95% CI 45.1-80.7) for SC-I (39). Over 10 years, 95% of SC-I remained free of failure and demonstrated a cumulative incidence of failure or complication of 34%. Compared with SC-E, SC-I were 3.5 times more likely to yield failures or complications and SC-PC failed 1.7 times more frequently than did SC-E. SC-V had the lowest rate of failures or complications over the 10 years.
  
  
  CONCLUSIONS
  While SCs on vital teeth have the best prognosis, those on endodontically treated teeth have a slightly poorer prognosis over 10 years. Crowns on teeth with post and cores and implant-supported SCs displayed the highest incidence of failures and complications.
authors.affiliation: Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland.
authors.forename: Kurt
authors.initials: K
authors.lastname: Schmidlin
authors.forename: Natascha
authors.initials: N
authors.lastname: Schnell
authors.forename: Stefanie
authors.initials: S
authors.lastname: Steiner
authors.forename: Giovanni E
authors.initials: GE
authors.lastname: Salvi
authors.forename: Bjarni
authors.initials: B
authors.lastname: Pjetursson
authors.forename: Giedre
authors.initials: G
authors.lastname: Matuliene
authors.forename: Marcel
authors.initials: M
authors.lastname: Zwahlen
authors.forename: Urs
authors.initials: U
authors.lastname: Brägger
authors.forename: Niklaus P
authors.initials: NP
authors.lastname: Lang
mesh_terms: D000328:Adult; D000368:Aged; D002908:Chronic Disease; D003442:Crowns / Q000009:adverse effects*; D015921:Dental Implants / Q000009:adverse effects*; D019232:Dental Restoration Failure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010518:Periodontitis / Q000000981:diagnostic imaging / Q000628:therapy*; D016012:Poisson Distribution; D011176:Post and Core Technique / Q000009:adverse effects; D011859:Radiography; D012189:Retrospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants