Occlusal radiograph can locate:
Typically, the occlusal radiograph is especially useful in the following cases:

To locate precisely roots and supernumerary, unerupted, and impacted teeth (this technique is especially useful for impacted canines and third molars).
To localize foreign bodies in the jaws and stones in the ducts of sublingual and submandibular glands.
To demonstrate and evaluate the integrity of the anterior, medial, and lateral outlines of the maxillary sinus.

Ref: ORAL RADIOLOGY Principles and Interpretation,Stuart C. White,Michael J. Pharoah Edition 7 page no 126
Supernumerary teeth
Impacted teeth
Stones in salivary duct
All of the above