We do not yet know exactly how salivary stones are formed. They are, however, more common in patients suffering from diseases that are associated with changes in the composition of the saliva, such as diabetes, gout and diseases involving an increase in the calcium levels in the blood. Many patients may also have a tendency to stones in other organ systems, such as the urinary or biliary tract (kidney stones and gall stones).
In 80 to 90% of cases, salivary stones occur in the excretory ducts of the submandibular glands. The size of these sediments can range from a few millimetres to several centimetres. They are largely made up of calcium carbonate or calcium phosphate, and also contain a smaller proportion of organic substances.
Salivary stones can often go unnoticed for a long time. It is assumed that they grow somewhere in the range of 1 mm in diameter over the course of a year. The stone only becomes a problem when it blocks the excretory path of the duct, resulting in a build-up of saliva and swelling of the gland. As the impaired flow promotes bacterial growth, a painful salivary gland infection is often the first symptom of salivary stones. Salivary stones are particularly common when the weather is warm, as patients do not drink enough and salivary flow is then reduced.