Cracked Teeth: Distribution, Characteristics, and Survival after Root Canal Treatment

Introduction: The aims of this study were to analyze the distribution and characteristic features of cracked teeth and to evaluate the outcome of root canal treatments (RCTs) for cracked teeth. The prognostic factors for tooth survival were investigated. Methods: Over the 5-year study period, 175 teeth were identified as having cracks. Data were collected regarding the patients' age, sex, tooth type, location and direction of cracks, probing depth, pulp vitality, type of restoration, cavity classification, opposing teeth, and previous endodontic treatment history. Cracked teeth were managed via various treatment methods, and the 2-year survival rate after RCT was analyzed using the Kaplan-Meier method in which significance was identified using the log-rank test. Possible prognostic factors were investigated using Cox multivariate proportional hazards modeling. Results: One hundred seventy-five teeth were diagnosed with cracks. Most of the patients were aged 50-60 years (32.0%) or over 60 (32.6%). The lower second molar was the most frequently (25.1%) affected tooth. Intact teeth (34.3%) or teeth with class I cavity restorations (32.0%) exhibited a higher incidence of cracks. The 2-year survival rate of 88 cracked teeth after RCT was 90.0%. A probing depth of more than 6 mm was a significant prognostic factor for the survival of cracked teeth restored via RCT. The survival rate of root-filled cracked teeth with a probing depth of more than 6 mm was 74.1%, which is significantly lower than that of teeth with probing depths of less than 6 mm (96.8%) (P = .003). Conclusions: Cracks were commonly found in lower second molars and intact teeth. RCT was a reliable treatment for cracked teeth with a 2-year survival rate of 90.0%. Deep probing depths were found to be a significant clinical factor for the survival of cracked teeth treated with RCT.