Which statement correctly describes cusp tips projection on a receptor?

• A. Cusp tips project away from the receptor
• B. Cusp tips project toward the receptor
• C. Cusp tips are at the receptor edge
• D. Cusp tips are not visible on the receptor

Answer: (B)

In radiography, the image you get is a shadow of the tooth formed on the receptor by the X-ray beam. The part of the tooth that is closest to the receptor casts a shadow nearest to that receptor surface, while parts farther away cast shadows toward the opposite edge of the image. The cusp tips sit on the occlusal surface near the crown and are the closest points to the receptor in a typical intraoral view, whereas the root apices are farther away. So the cusp tips appear projected toward the receptor on the image.