Factors related to loss of root canal filled teeth.

This case-control study characterized factors related to loss of root canal filled (RCF) teeth among members of the Kaiser Permanente Dental Care Program, a dental health maintenance organization based in Portland, Oregon. Individuals were identified who were enrolled continuously from January 1, 1987, through December 31, 1994, underwent initial root canal therapy on a permanent tooth (excluding third molars) in 1987 or 1988, had a clinical examination within two years after endodontic access, and were at least 21 years old at access. Patients who lost the RCF tooth by December 31, 1994, were defined as cases (n = 96); those who did not were defined as controls (n = 120). Computerized data, dental radiographs, and chart entries were reviewed to ascertain variables of interest, and multivariable logistic regression was used to describe differences between the groups. RCF teeth of cases had fewer proximal contacts at access than RCF teeth of controls (odds ratio = 2.7; 95% Cl = 1.4, 5.1). Cases were older (odds ratio = 1.4; 95% Cl = 1.1, 1.9 per 10-year increase) and more likely to have had a facial injury than controls (odds ratio = 3.6; 95% Cl = 1.2, 10.5). Cases also had more missing teeth (odds ratio = 1.5; 95% Cl = 1.0, 2.1) and more plaque (odds ratio = 1.7; 95% Cl = 1.0, 2.6). Conditions evident during treatment planning may help dentists assess patients' chances of losing an RCF tooth.