Root and canal morphology of maxillary premolars and their relationship with the crown morphology

To investigate the relationship between crown/root size and root/canal morphology of maxillary premolars.

One hundred and thirty-three first (P1) and 110 second (P2) maxillary premolars were used. Mesiodistal and buccolingual diameters and root heights of P1 and P2 were recorded to the nearest 0.01 mm. The number of single and multi-rooted premolars was recorded based on the Turner's classification. Root canal morphology was studied using a clearing technique with Vertucci's classification. Pearson's correlation coefficient was used to analyze the relationship between tooth size and root/canal morphology.

Two-rooted P1 was found in 33.9% of male and 22.5% of female. P2 showed a single root in 85.4% of male and 82.6% of female. In case of P1, the number of root canals (P<0.05) and apical foramina (P<0.01) was significantly different between male and female. P1 crown dimensions were larger in double-rooted teeth than in single-rooted ones. Significant differences were observed in buccolingual (P<0.05) and crown area (P<0.05) in females. Root height was smaller in double-rooted than in single-rooted P1. A similar trend was observed for P2 with a larger crown size in teeth with two apical foramina compared with those with a single foramen.

Two-rooted P1 with two or more apical foramina are more commonly seen in males than in females. For P1, the correlation of number of roots and apical foramina was stronger with buccolingual diameter than with mesiodistal diameter in both genders. P1 and P2 with large crown dimensions tend to have multiple roots and apical foramina.