C-Shaped Second Molars Analysis By CBCT

To assess the prevalence, classification and lingual wall thickness (LWT) of C-shaped second molars in northern China by using cone-beam computed tomography (CBCT). The study encompassed CBCT scans of 2028 second molars from 507 participants. Analysis was conducted using Fan standard to evaluate the prevalence and morphology of C-shaped second molars. The LWT was measured and based on which, Danger degree index was announced and recorded. C-shaped canals were detected in 174 participants, 24.42% of males and 41.72% of females in at least one second molar (P<0.05). The prevalence was significant higher in mandible (P<0.05). With respect to classifications within the cervical, mid, and apical-thirds of the C-shaped mandibular second molars, the most common unit was C1-C1-C1 type (75/294). Regarding LWT, cervical-third>mid-third>apical-third. In mid-third plane, middle < mesial < distal (P<0.05). Notable variations were observed in the mid-third of root, prompting a Danger degree index: I, LWT ≥ 1.0mm; II, 1.0mm > LWT > 0.5mm; III, 0.5mm ≥ LWT. Particularly relevant was the high prevalence of degree III in cervical-C3a-type, at 23.53%, with a significant incidence of degree I in cervical-C4-type, reaching 86.21%. The study highlighted a higher incidence of C-shaped second molars in mandible and female, introducing a Danger degree index depended on LWT analysis, indicating the therapy challenges in different classifications.