Prevalence and correlation of C-shaped root canals of mandibular premolars and molars in Eastern Chinese individuals

Abstract Background To investigate the prevalence, correlation, and differences of C-shaped root canals (CSRCs) morphology in permanent mandibular premolars and molars in Eastern Chinese individuals using cone-beam computed tomography (CBCT). Methods A total of 8000 mandibular premolars and molars CBCT images from 1000 patients (692 females and 308 males) were collected. The prevalence, correlation, bilateral/unilateral presence, morphology of CSRCs, level of canal bifurcation, sex differences, and location of radicular grooves (RGs) were evaluated. The correlation between the prevalence of CSRCs and RGs in different tooth positions and age groups was analyzed. Results The prevalence of CSRCs in mandibular first premolars (MFPs), mandibular second premolars (MSPs), mandibular first molars (MFMs) and mandibular second molars (MSMs) were 10.25%, 0.25%, 0.55% and 47.05%, respectively. There was no correlation between the presence of CSRCs in mandibular premolars and molars. The prevalence of CSRCs in MFPs of males was higher than that in females, while CSRCs in MSMs of females were higher than that in males (P < 0.05). The bilateral symmetry presence of CSRCs in MSMs was significant but not in MFPs. RGs were predominantly found on the mesiolingual surface of premolars and the lingual surface of molars. There was no significant difference in the prevalence of CSRCs in different types of RGs in premolars. The incidence of CSRCs was significantly lower in the non-bifurcation group. Conclusions There was a high prevalence of CSRCs in MFPs and MSMs in the Eastern Chinese population, but there was no correlation. The symmetry of CSRCs was significant in MSMs but not in MFPs. The prevalence of CSRCs in MFPs of males was higher than that in females, while the prevalence of CSRCs in MSMs of females was higher than that in males. In the process of RCT of teeth with CSRCs, CBCT should be taken if necessary, and the treatment should be carried out with the aid of a microscope. Clinicians should pay special attention to CSRCs.