| Both apical periodontitis (AP) and tooth loss are among the most damaging dental diseases affecting humans. Only a few cross-sectional studies have been done as to RCT quality and post-operative AP in North America. Tooth loss has rarely been studied using survival analysis. The effect of AP and RCT on loss of individual teeth also has received little attention. This dissertation consists of two studies. The aims of Study One were to develop an explanatory model to evaluate the association between RCT quality and post-operative AP, and to assess whether and how this observed association is modified by the presence of pre-operative AP. The aims of Study Two were to determine a predictive model for tooth loss and assess the role of endodontic involvement in tooth loss after controlling for other established risk factors.; The study population was from the Veterans Administration Dental Longitudinal Study (VADLS). Study One followed 609 teeth that received RCT at some time after baseline until the next examination cycle to determine the presence of post-operative AP. The main exposure variables were extension and density of the root filling (indicators of RCT quality). Generalized Estimating Equations (GEE) were used to determine the relationship between extension, density and post-operative AP, while controlling for various covariates. Multivariate logistic regression models revealed that with adjustment for pre-operative AP, defective density was associated with an increased risk of post-operative AP (RR=3.0, 95% CI=1.3, 7.1), while pre-operative AP was the most significant risk factor (RR=29.2, 95% CI=13.6, 63.0).; Study Two followed 18,798 teeth present at baseline until the date of tooth loss or the end of the study, whichever came first. The outcome was time to tooth loss. Multivariate marginal proportional hazards models revealed that, in addition to periodontal status and caries, both AP status and RCT status persisted as independent significant predictors for tooth loss (P<0.01) after controlling for tooth type, number of proximal contacts, number of teeth at baseline, age, education level, and current smoking history. Traditional indicators of oral hygiene and plaque level may not be as important as other factors in predicting time to tooth loss. |
