Tomographic Evaluation of the Internal Morphology of Mandibular Premolars

o evaluate by cone beam computed tomography (CBCT) the internal morphology of mandibular premolars in a population attended in School of Dentistry, University of Buenos Aires, between March-December 2023, to establish their typology according Vertucci's classification and determine the height of bifurcation in the root canal. A total of 791 mandibular premolars were studied. Inclusion criteria: teeth with closed apex, absence of root resorption and endodontic treatment. Variables recorded: number of teeth, typology and length bifurcation in relation to the apex. Canals were evaluated in axial plane: cervical cut: 3 millimeters from the amelocementary junction, apical cut: 3 millimeters from the apex and middle cut: middle distance between anterior readings. To analyze apex-bifurcation distance, two lines A and B were drawn on sagittal section, passing through apex and bifurcation respectively. A perpendicular to previous ones gave the measurement in millimeters. Categorical variables were described by absolute frequencies and percentages with 95% confidence interval. Bifurcation length was expressed as mean ± SD. Chi-square tests and two-factor factorial ANOVA were used to analyze the results (p < 0.05, significant). Distribution according Vertucci's typology was not uniform, for total mandibular premolars (p < 0.05) and for first (p < 0.05) and second (p < 0.05). In the three ca- ses, type I predominated: 80 % (CI95: 77 % to 83 %), 72 % (CI95: 68 % to 76 %) and 88 % (CI95: 84 % to 91 %), respectively. Bifurcation length varied significantly between typologies (p < 0.05), but there was no significant difference between mandibular first and second premolars (p = 0.06). There was no interaction between typology and tooth type (p = 0.06). Bifurcation length in types II, III and V was 8.7 ± 2.2, 4.6 ± 1.4 and 7.6 ± 1.8, respectively. Mandibular premolars have additional canals. If preoperative radiograph shows atypical anatomy, CBCT is indicated to determine the anatomical complexity of tooth to be treated. KEY WORDS: endodontics, mandibular premolars, root morphology, computed tomography.