The following occlusal radiograph shows:
Intraoral Radiography
Sialoliths in the anterior two-thirds of the submandibular duct are typically imaged with a cross-sectional mandibular occlusal projection. The posterior portion of the duct may be demonstrated with an over-the-shoulder occlusal projection view, where the directing cone is placed on the shoulder and the central ray is directed in an anterior direction through the angle of the mandible, with the patient’s head rotated back and tilted to the unaffected side.
Parotid sialoliths are more difficult to demonstrate than the submandibular variety owing to the tortuous course of Stensen’s duct around the anterior border of the masseter and through the buccinator muscle. 
As a rule, only sialoliths anterior to the masseter muscle can be imaged on an intraoral image. To demonstrate sialoliths in the anterior part of the duct, an intraoral image receptor is stabilized with a holder inside the cheek, as high as possible in the buccal sulcus and over the parotid papilla. The central ray is directed perpendicular to the center of the receptor.
Key Concept
Submandibular calculus
Parotid  calculus
Sublingual calculus
None of the above