A study on the root canal morphology of primary molars by high-resolution computed tomography

Background/purpose: High-resolution computed tomography (μCT) was used to construct three-dimensional (3D) morphology of root canal systems of primary molars. Materials and methods: Twenty-nine extracted primary molars, including eight maxillary first molars, 10 maxillary second molars, two mandibular first molars, and nine mandibular second molars, without obvious root resorption were used. A μCT device was used to scan the teeth. Data were processed to reconstruct 3D images. Roots and root canal systems were analyzed from 3D images of the teeth and cross-sectional μCT images at different root levels. Results: In primary molars, numbers of roots and root canals varied from two to three and three to four, respectively. Maxillary molars exhibited more one-canal than two-canal roots, yet there were equal numbers in mandibular molars. Fusion between the distobuccal and palatal roots in maxillary molar was common with a greater prevalence in maxillary first molars. More ovoid root canal outlines were found apically. Root canal outlines remained consistent from one level to the next in 76% of the roots. Conclusion: This study showed the complexity of root canal system in primary molars. Understanding variations in root canal systems would improve the interpretative capability for correct diagnoses.