Using
lipid histochemical and microradiographic methods, the distribution of
lipids and the inorganic component in different areas of
salivary calculi was investigated. Two main groups of
lipids were found, i.e. hydrophilic
phospholipids and hydrophobic
lipids. The hydrophilic
phospholipids were shown to be composed mainly of phosphosphingosides and of the hydrophobic
lipids cholesterol was demonstrated. Phosphosphingosides were localized in more or less lamellar zones as also in large homogeneous areas. In some cases the
calculi were surrounded by a structureless non-mineralized zone exhibiting a strongly positive reaction for phosphosphingosides.
Cholesterol was found in isolated band-formed areas. Phosphosphingosides and
cholesterol were especially prevalent in areas showing a low or slight degree of mineralization. In areas showing a high degree of mineralization the corresponding
lipids gave a weak or absent histochemical reaction. After
EDTA-decalcification, however, an increase in the concentration of
lipid was noticed in high mineralized areas, indicating a masking process. The influence of various factors on the presence and distribution of different
lipids was discussed.