Final answer:
The radiopaque 'Y' in the maxillary canine region is the junction of the border of the maxillary sinus and the floor of the nasal cavity.
Step-by-step explanation:
The radiopaque 'Y' seen in dental imaging, in the maxillary canine region, represents the junction of the border of the maxillary sinus and the floor of the nasal cavity. The maxillary bone or maxilla, forms a significant part of the upper jaw, holds the upper teeth, and also contributes to the structure of the orbits and the hard palate. This bone serves as the floor of the nasal cavity and contributes to separating the oral and nasal cavities.