Causes, natural history, and incidence of salivary stones and obstructions.

Uncertainty about the causes and natural history of salivary stones (sialoliths) and other obstructions is being dispelled by clinical and experimental research. Sialoliths are now shown to be secondary to chronic obstructive sialadenitis. Microscopic stones (sialomicroliths) accumulate during secretory inactivity in normal salivary glands and produce atrophic foci by obstruction. Microbes ascend the main salivary duct during secretory inactivity and proliferate in atrophic foci and cause spreading inflammation, leading to inflammatory swelling and fibrosis that can compress large ducts. This leads to stagnation of secretory material rich in calcium that precipitates onto degenerating cellular membranes to form a sialolith.