A salivary gland stone (sialolith) is a calcified mass that develops within the duct system of a salivary gland. This common condition, known as sialolithiasis, occurs when mineral deposits crystallize from the saliva. The mouth contains three major pairs of salivary glands—the parotid, submandibular, and sublingual glands. Sialoliths may form in any of these glands, but they are found most frequently in the submandibular glands, located beneath the jaw, accounting for up to 90% of all cases.
Identifying Sialolithiasis
The presence of a salivary stone often becomes evident through a characteristic set of symptoms, most notably pain and swelling of the affected gland. These symptoms tend to be cyclical, worsening dramatically when a person is eating or anticipating food. This phenomenon, sometimes called “mealtime syndrome,” occurs because the thought or consumption of food triggers the glands to produce a large volume of saliva.
When the stone obstructs the duct, the stimulated saliva cannot flow freely into the mouth and backs up into the gland, causing swelling. The swelling usually subsides slowly after the meal as the saliva is gradually reabsorbed or leaks past the obstruction. If the blockage is complete, a person may also experience a dry mouth or a feeling of tenderness and pressure under the tongue or near the ear, depending on the gland involved. In some cases, a small stone may cause no symptoms until it is incidentally discovered on a dental X-ray.
Primary Factors Leading to Stone Formation
Sialoliths are mineral concretions, primarily composed of calcium phosphate and calcium carbonate, similar to bone or teeth. The formation process begins when calcium salts precipitate around an organic core, or nidus, which can be made of inspissated mucus, sloughed-off epithelial cells, or bacteria. Reduced saliva flow and changes in saliva composition are the central mechanisms that allow this precipitation to occur.
Reduced salivary flow is a major predisposing factor because it allows minerals to become more concentrated. This effect is compounded in the submandibular gland because its duct is long, features an upward curvature, and the gland produces a more viscous and alkaline saliva. The combination of sluggish flow, a long duct, and alkaline pH fosters an environment where calcium and phosphate salts are more likely to crystallize.
Dehydration contributes significantly to this process by reducing the overall fluid content in the body, making saliva thicker and more mineral-dense. Several classes of medications can mimic this effect by reducing saliva production, a side effect known as xerostomia. These include anticholinergics (found in certain bladder control and psychiatric drugs), some antihistamines, and blood pressure medications.
While sialolithiasis is not typically caused by systemic issues with calcium metabolism, certain underlying conditions may increase the risk. Chronic inflammation or infection within a salivary gland can contribute organic debris, which serves as a nidus for stone formation. Furthermore, conditions such as gout (involving uric acid buildup) or hyperparathyroidism (affecting calcium regulation) have been linked to an increased incidence of salivary stones due to altered salivary chemistry.
Managing and Preventing Stones
The initial management of salivary gland stones aims at encouraging the stone to pass spontaneously. Promoting increased saliva flow is a primary goal, achieved through the use of sialogogues—substances that stimulate salivary production, such as sour candies or lemon juice. Maintaining hydration helps thin the saliva, making it less viscous and easier to propel through the duct.
Patients are advised to massage the affected gland to help dislodge the stone and to apply moist heat to the area to reduce pain and swelling. If a bacterial infection, known as sialadenitis, develops due to the obstruction, a course of antibiotics may be necessary. These conservative measures are effective for many small stones, which may pass into the mouth on their own.
For stones that are too large or too deeply lodged to pass naturally, minimally invasive procedures are the preferred intervention. Sialendoscopy involves inserting an endoscope into the salivary duct to visualize the stone, allowing small stones (typically under five millimeters) to be retrieved using a basket. Larger, more impacted stones may require fragmentation using extracorporeal shockwave lithotripsy (ESWL) or a combined surgical approach. Removal of the gland is reserved only for cases of persistent recurrence or severe, irreversible gland damage.