Definition: An anatomical landmark created by the superimposition of the floor of the nasal cavity and the border of the maxillary sinus.
Location: Most commonly found superior to the maxillary canine apex. Sometimes it will be more distal and superior to the first premolar apices.
Edge: Well-defined, corticated.
Shape: Inverted Y.
Number: Single (one per side). 🙂
(click to enlarge)
Y line of Ennis
Y line of Ennis (yellow lines) created by floor of nasal cavity (straight radiopaque line) and border of maxillary sinus (curved radiopaque line) superior to the maxillary canine.