Frequency of Root Canal Isthmi in Human Permanent Teeth Determined by Cone-beam Computed Tomography

Introduction: This study evaluated the frequency of root canal isthmi (RCIs) in human permanent teeth by using cone-beam computed tomography. Methods: A sample of 1400 teeth of 618 patients (394 women; mean age, 43.4 years) was selected. RCIs were detected longitudinally on 0.1-mm/0.1-mm axial slices of cone-beam computed tomography images of roots scanned from the pulp orifice to the apex, and findings were classified into 7 categories according to RCIs beginning and end: (1) both in the Cervical third, (2) begin in the cervical third and end in the middle third, (3) begin in the cervical third and end in the apical third, (4) both in the middle third, (5) begin in the middle third and end in the apical third, (6) both in the apical third, or (7) no isthmus. A chi(2) test with Yates correction or the Fisher exact test was used to analyze categorical variables, described as frequencies (%). The Student t test was used to compare quantitative variables. Results: RCI is a common anatomic structure in human permanent teeth, except in maxillary anterior teeth. Conclusions: The higher frequencies of RCIs (87.9%) were found in mandibular first molars. The frequencies of RCIs according to mean age and tooth group were not significantly different (P>.05), except in mandibular central incisors. RCIs were less frequent among older patients.