title: Long-term survival of primary root canal treatment carried out in a dental teaching hospital.
abstract: OBJECTIVE
  This study aimed to examine clinically and radiographically the survival of primary root canal treatment completed in a dental teaching hospital between 10 and 20 years previously.
  
  
  METHODS
  A data collection form was used to collate all information obtained from the written patients' records along with the results from clinical and radiographic examination of 608 teeth, out of a total of 986 randomly selected teeth that had been root filled in the Prince Philip Dental Hospital (PPDH), Hong Kong, between 1981 and 1989. The criteria for failure were extractions (except for documented nonendodontic reason), retreatments and presence of a periapical radiolucency. The survival function of the treated teeth was plotted against the calculated date of failure using the Kaplan-Meier (K-M) method. Covariables were examined further by Cox Regression analysis with a backward stepwise method.
  
  
  RESULTS
  A total of 314 teeth (52%) were either documented or deemed to have failed after examination. The median survival time was 111 months. Cox Regression analysis indicated that the survival of root-filled teeth was significantly influenced by the tooth type, preoperative periapical status and the type of coronal restoration. The survival function declined with time, with a rapid drop in the first 18 months or so. The rate at which failures occurred appeared to slow down with a longer observation time.
  
  
  CONCLUSIONS
  There was a nonlinear decline in the cumulative survival probability of primary root canal treatment. Tooth type, preoperative periapical status and type of post and final restoration significantly affected the long-term survival of the treated teeth.
authors.affiliation: Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, Hong Kong. spcheung@hkusua.hku.hk
authors.forename: G S P
authors.initials: GS
authors.lastname: Cheung
authors.forename: T K
authors.initials: TK
authors.lastname: Chan
mesh_terms: D003442:Crowns / Q000706:statistics & numerical data; D003740:Dental Clinics; D019232:Dental Restoration Failure; D005260:Female; D005500:Follow-Up Studies; D006784:Hospitals, Teaching; D006801:Humans; D008297:Male; D011176:Post and Core Technique / Q000706:statistics & numerical data*; D016016:Proportional Hazards Models; D012390:Root Canal Therapy / Q000706:statistics & numerical data*; D016019:Survival Analysis