Objectives: We assessed the impact of type of tooth on the outcome of root canal treatment (RCT) according to factors potentially weakening the prognosis such as preoperative apical periodontitis (AP) and treatment modality (primary or secondary RCT).
Materials and methods: We scrutinized patient documents including pre- and postoperative radiographs of 640 permanent teeth receiving non-surgical RCT at Helsinki University Clinic in 2008-2011. Of teeth, 44% were molars, 32% premolars, and 24% anterior teeth. Patients' mean age was 51.5 years; 51% were male. AP was present in 60.5% of teeth preoperatively. We used the periapical index (PAI) to assess the radiographs and defined radiographically "healthy" and "healing" cases as successful. Statistical evaluation included chi-squared tests, Fisher's exact tests, t tests, and logistic regression modeling.
Results: The overall success rate (SR) was 84.1%; 88.3% for primary and 75.5% for secondary RCT (p < 0.001). The SRs for anterior teeth, premolars and molars were 85.6%, 88.8%, and 79.7%, respectively. Teeth with and without AP had SRs of 77.3% and 94.5%, respectively (p < 0.001). The RCTs were more likely to succeed in anterior teeth and premolars than in molars (OR 1.7; 95% CI 1.1-2.7) and in females than in males (OR 1.9; 95% CI 1.2-3.1).
Conclusions: Apart from existing AP and retreatment scenario, also, the type of tooth and gender had a significant influence on the outcome of RCT in this study.
Clinical relevance: The prognosis of RCT varies by type of tooth; special attention should be given to RCT of molar teeth.
Keywords: Endodontic; Outcome; Periapical index (PAI); Root canal treatment; Tooth type.