Ultrastructure of the in vitro formation of hydroxyapatite in submandibular saliva of children with cystic fibrosis.

Calcium phosphate, which precipitates in submandibular saliva of patients with cystic fibrosis 
because of elevated calcium concentrations, was shown by electron microscopy to 
transform, on standing in vitro, from amorphous calcium phosphate globules to 
stellar clusters of hydroxyapatite crystals. Amorphous globules appeared to form at 
regular nucleation points on a fine network of unknown nature. Hydroxyapatite 
crystal formation was confirmed by electron diffraction pattern and chemical solubility. 
Zymogen-granule spherules (inclusion bodies), which are present in greatly increased numbers 
in cystic fibrosis submandibular saliva, disintegrated on standing from a homogeneous 
appearance to beaded, hollow spheres. 