Introduction: The purpose of this study was to assess the prevalence of apical periodontitis in root canal-treated teeth from the Korean population and to evaluate the relationship between the quality of root canal fillings and coronal restorations and the periapical status of these teeth.

Methods: Full-mouth periapical radiographs at the Dental Hospital of Yonsei University, Seoul, South Korea, were examined. A total of 1030 endodontically treated teeth restored with full veneer crown-type restorations were evaluated by 2 independent examiners. Teeth were classified as healthy or diseased according to the periapical status. The quality of endodontic treatment and coronal restorations were also classified via radiographic and clinical evaluation. The data were analyzed using the chi-square test and logistic regression.

Results: Forty-one percent of all endodontically treated teeth were classified as diseased. Approximately 35.6% of the teeth had endodontic treatments that were rated as adequate. The diseased teeth rate for cases with adequate endodontic treatment was 24.5%, which was significantly lower when compared with teeth with inadequate endodontic treatment (49.9%). The number of teeth with adequate coronal restorations was 706 (68.5%). Teeth with adequate coronal restorations had a significantly decreased prevalence of diseased teeth (34.7%) compared with teeth with inadequate coronal restorations (54.3%). Teeth with both adequate root fillings and restorations showed a significantly better outcome (82.3%) than the others, and teeth with both inadequate root fillings and restorations showed a significantly worse outcome (41.2%) than the others.

Conclusions: Data from this Korean population showed a relatively high prevalence of apical periodontitis. The quality of endodontic treatment and coronal restorations were of equal importance and were strong independent predictors of the periapical status.