X-ray diffraction and scanning electron microscope investigations of fluoride-treated dentine in man

Root surfaces of human teeth and powdered dentine were treated in vivo and in vitro with 2 per cent neutral and acidulated (0.1 M H₃PO₄) NaF solutions for varying periods. The root surfaces were examined by scanning electron microscopy (SEM) and the ashed dentine powder by X-ray diffraction. Fluoride determinations were carried out in the F-treated material. CaF₂ formation was detected up to a maximum amount of 0.7 per cent in the dentine powder following a 5-day treatment with acidulated NaF solution. The SEM micrographs revealed granular precipitates mainly in the peritubular and intertubular regions, decreasing as a function of the fluoride release following the washing effects of oral fluids in vivo and saline immersion in vitro. Precipitated fluoride compounds blocking mechanically or labile fluoride in the organic matrix of dentine blocking biochemically the transmission of stimuli are suggested as desensitization factors.