Objective: The purpose of this study was to use survival analysis to evaluate the long-term treatment outcome of first-time, nonsurgical root canal therapy performed in a dental teaching hospital and to identify factors that might affect that outcome.
Study design: One-tenth of all teeth treated between 1989 and 1994 were sampled. Patients were invited to return for a recall and were examined both clinically and radiographically. Any teeth that had been extracted or retreated or that were associated with a periapical radiolucency or presented with clinical signs and symptoms were deemed to have failed. An adjusted date of failure was calculated in the survival analysis by means of the Kaplan-Meier method. Ten covariables were further analyzed with the Cox regression model by using a backward stepwise regression method.
Results: Of 550 sampled teeth, 251 were examined. The mean observation period was 74 months. The failure rate was 44% (n = 111), with a median survival time of 113 months (mean, 91 months). Use of the Cox Regression model revealed that tooth type was significant in affecting the survival time of the treatment. Radiographic presence of voids in the apical and middle thirds of root canal fillings was associated with a significantly lower mean survival time than the presence of voids found in the coronal third or no void at all. The use of a calcium hydroxide dressing after initial treatment was associated with a longer survival time than failure to use medication or dressing with Ledermix alone.
Conclusion: Simple calculation of percentages did not provide sufficient information on the treatment prognosis. The survival of first-time root canal therapy was significantly influenced by the tooth type, radiographic location of voids in the root canal filling, and the intracanal medicament used.