3-Rooted Maxillary First Premolars: An Ex Vivo Study of External and Internal Morphologies

Abstract Introduction This study aimed to analyze the external and internal morphologies of 3-rooted maxillary first premolars using cone-beam computed tomographic (CBCT) imaging. Methods Fifty-six three-rooted maxillary first premolars were imaged by CBCT imaging and classified into 4 groups on the basis of external root morphology. Internal morphologic features, including the shapes of the buccal and palatal orifices and distances of bifurcation of the buccal-palatal and mesiobuccal-distobuccal root canals from the cementoenamel junction (CEJ), were measured. Results The teeth were classified into 4 groups on the basis of external morphology: group A, separation of the buccal and palatal roots with bifurcation of the former into the mesiobuccal and distobuccal roots ( n  = 22); group B, fusion of 2 buccal roots with the palatal root being separate ( n  = 19); group C, complete or partial fusion of the distobuccal and palatal roots ( n  = 9); and group D, fusion of all 3 roots ( n  = 6). The buccal orifice was mainly triangular/heart shaped. The distance of bifurcation of the buccal-palatal root canals from the CEJ in group A differed significantly from those in groups B and C ( P P Conclusions The external and internal morphologies of 3-rooted maxillary first premolars vary considerably.