The crystal chemistry of submandibular and parotid salivary gland stones

The mineral composition of 38 human salivary gland stones was described qualitatively on the basis of X-ray diffraction and chemical analysis. In 32 submandibular stones, hydroxyapatite was the most frequently observed phase with a magnesium-substituted whitlockite co-phase (octacalcium phosphate was rarely present). In six parotid gland stones, apatite, magnesium substituted whitlockite and octacalcium phosphate were noted to be the major crystalline phases. Brushite was rarely found in either submandibular or parotid stones. This is the first report of octacalcium phosphate in salivary gland stones. All stones had ash weights ranging from 75--80%, but their Ca/P ratios could not be used to predict the crystalline phases present. Whitlockite was observed more frequently in the central regions of the submandibular stones than in the outer crusts. Possible explanations for the presence of each of these phases are discussed.