•Purpose: to describe the morphology of three rooted maxillary premolar and its radiographic features..
•n: 325 1st premolars (3.7% with three canals) and 398 2nd premolars (0.3% with three canals )
• Inclusion criteria; exclusion criteria: not mentioned. •Highlights: •Categories:
•1- Category 1: fusion of all three roots or only the two buccal ones, and a semi-fused or free palatal root.
Its the most difficult category to be radiographically assessed.
•2- Category 2: normal separation of the buccal roots at the level mid-root or apical third, with either a semi fused or free palatal root.
•3- Category 3: normal separation of the buccal roots up to the cervical level, with a free palatal root and a classic tripod appearance.
•A chamber that is not aligned to the usual B-P plane; triangular shaped; too large in M-D direction; eccentric location of orifice (not always) should be scrutinized for a third canal maxillary premolars.