title: Relationship between number of proximal contacts and survival of root canal treated teeth.
abstract: OBJECTIVE
  The present study tested the hypothesis that having two proximal contacts (PCs) at access is associated with improved survival of root canal treated (RCT) teeth, controlling for important presenting conditions, endodontic variables and restorative factors.
  
  
  METHODS
  A treatment database at the University of Iowa College of Dentistry was used to identify permanent teeth undergoing obturation between 1 July 1985 and 31 December 1987. The list was restricted to teeth of patients with at least one dental visit in each two-year interval from 1985 to 1996, and a simple random sample of 280 patients (n = 400 teeth) was selected. Dental charts, radiographs, and computerized databases were examined to ascertain variables of interest and to verify study inclusion criteria. Kaplan-Meier survival estimates were generated for the 221 teeth satisfying study inclusion criteria. Multivariate Cox models were developed, with standard errors adjusted to account for clustering of teeth within patients.
  
  
  RESULTS
  The final Cox model showed that teeth with < or =1 PC at access were lost at a rate three times that of teeth with 2 PCs (hazard ratio = 3.1; 95% confidence interval = 1.9-5.1), controlling for tooth type, presence of radiographic caries at access, and presence of a crown before or after obturation.
  
  
  CONCLUSIONS
  Because RCT teeth with two PCs at access experienced substantially better survival than teeth with fewer than two PCs, the influence of PCs on prognosis should be recognized during treatment planning. Future research should employ prospective study designs, capture additional variables, and provide data to support endodontic treatment decisions.
authors.affiliation: Department of Dental Ecology, School of Dentistry, University of North Carolina, CB #7450, Chapel Hill, NC 27599, USA. dan_caplan@unc.edu
authors.forename: D J
authors.initials: DJ
authors.lastname: Caplan
authors.forename: J
authors.initials: J
authors.lastname: Kolker
authors.forename: E M
authors.initials: EM
authors.lastname: Rivera
authors.forename: R E
authors.initials: RE
authors.lastname: Walton
mesh_terms: D006801:Humans; D011379:Prognosis; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D016019:Survival Analysis; D016388:Tooth Loss / Q000209:etiology*; D019553:Tooth, Nonvital / Q000150:complications* / Q000473:pathology*