Prevalence of C-shaped Configurations in the Mandibular First and Second Premolars: A Cone-beam Computed Tomographic In Vivo Study.

Introduction: The mandibular premolar C-shaped anatomy has been presented as a complex morphology to be treated. The objective of this retrospective observational study was to evaluate and characterize, in in vivo conditions, the incidence of these morphologies using cone-beam computed tomographic (CBCT) technology.

Methods: Mandibular premolar CBCT samples were collected from a preexisting database. All teeth were analyzed in 3 planes (axial, coronal, and sagittal), and the C-shape classification was performed at 3 different axial levels (coronal, middle, and apical). C-shape presence and configuration were recorded as well as the number of roots, the presence of a radicular groove, and Vertucci classification. The Z test for proportions was used to analyze the differences between independent groups. Intraobserver reliability was tested using the Cohen kappa test.

Results: Two thousand twelve mandibular premolars were included in this study. A prevalence of C-shaped morphologies was noted in 2.3% and 0.6% of mandibular first and second premolars, respectively. This clinical condition was mostly unilateral. The C-shaped configuration (C1 and C2) was found mainly in the middle axial level. Its presence was uncommon in the apical level and null in the coronal level; 61.5% of all mandibular first premolar C shapes were identified in Vertucci type V roots. Differences were observed among sex, teeth, and Vertucci root configuration at P < .05.

Conclusions: Although the mandibular premolar C-shaped anatomy has a low prevalence ratio, a clinician should be aware of its existence, mainly when treating roots with Vertucci type V configuration. The prevalence was statistically higher in first premolars and males.