Stephen H.Y. Wei

Effects of Titanium Tetrafluoride on Human Enamel

Extracted human third molars were treated with a solution of titanium tetrafluoride. Calcium, phosphorus and fluoride microanalysis showed a high fluoride uptake and reduced enamel solubility for the treated surfaces. Scanning electron microscope examination showed the presence of a coating that was only partially removed by treatment with perchloric acid.

Supplemental Fluoride Recommendations for Infants Based on Dietary Fluoride Intake

The fluoride content of human milk, cow’s milk products, and commercially available infant formulas was assessed using a fluoride-ion-specific electrode in conjunction with a reference electrode. Bound fluoride fractions were measured in the same manner following application of a microdiffusion technique. This study showed that infants being fed commercially prepared formulas may be receiving fluoride in excess of recommended optimal daily dosages. Although the infant appears to possess a tolerance to high levels of fluoride, no supplemental fluoride appears to be necessary for infants up to 6 months of age.

Electron Microprobe Analyses of the Remineralization of Enamel

The electron microprobe was used to analyze the calcium and phosphorus concentrations of sound, acid-etched, and remineralized enamel. By use of a weak acetic acid-potassium acetate buffer, it was found that the demineralization probably affected only the first 10 micrometers of the enamel surface. This demineralized enamel was successfully remineralized by the use of a calcifying solution. The changes in calcium and phosphorus concentrations and the Ca/P ratios were determined.

Electron Microprobe Investigations of Stannous Fluoride Reactions with Enamel Surfaces

After immersion for 30 seconds in stannous fluoride, tin and fluorine were detected in enamel. When the enamel was immersed for a longer time, it was etched by stannous fluoride treatment. A second tin-rich zone formed on the enamel surface after prolonged exposure and possibly consisted of Sn3F3PO4 and a hydrated tin compound.

Scanning Electron Microscope Study of Stannous Fluoride-Treated Enamel Surfaces

Scanning electron micrographs showed that the reaction products formed on enamel surfaces increased with prolonged immersion time. Sn3F3PO4 crystals and other amorphous and platelike reaction products were present. These findings corroborate the data obtained from similar samples by electron microprobe analyses.

In vivo microsampling of enamel fluoride concentrations after topical treatments.

A microsampling technique was used to measure enamel fluoride concentrations before, immediately after, 1 week after, and 3 months after an application of an APF or NH4F solution on the maxillary anterior teeth of 63 children. The fluoride treatments were preceded by a 1-min application of 0.05 m H3PO4. It was found that NH4F produced an initial enamel fluoride level much higher than that produced by APF. One week after treatment, the fluoride concentrations produced by NH4F were still higher than those obtained with APF. Three months after treatment there was no difference between the NH4F and APF groups. Both groups, however, were observed to have lower fluoride concentrations than before treatment.

X-Ray Diffraction Analyses of the Reactions Between Intact and Powdered Enamel and Several Fluoride Solutions

The X-ray diffraction patterns of intact enamel treated with various fluoride solutions showed essentially no change in the crystalline structure of hydroxyapatite. The reaction between powdered enamel of various particle size and fluoride solutions showed a predominance of calcium fluoride formation. The substitution of F for OH ions in hydroxyapatite was not detected in the formation of fluorapatite under the experimental conditions.

Surface characterization of the stannous fluoride-enamel interaction

Abstract Infrared internal reflection spectroscopy (IRS) has been employed to characterize the nature of faceted human enamel surfaces subsequent to in-vitro topical treatment with filtered, 10 per cent SnF 2 solution. IRS spectra of treated slabs were compared with reference tin-phosphates and similarly treated samples of enamel powder. It was found that the spectral features of enamel shifted with SnF 2 treatment such that infrared absorption peaks corresponded closely to those of pure Sn 3 F 3 PO 4 . Some interpretations of the experimental data are discussed relative to possible clinical implications.

Analyses of the Amalgam-Tooth Interface Using the Electron Microprobe

The electron microprobe was used to study tooth discoloration caused by old silver amalgam fillings. Oscilloscopic displays were obtained for the distribution of tin, silver, and mercury. In addition, a linear graphic display technic on the Enhancitron was used. The oscilloscopic displays showed the migration of tin from the amalgam into the enamel and dentin as opposed to silver or mercury, or both. These findings confirm that tooth discoloration is due to the presence of tin from the process of corrosion rather than from mercury.

Electron Microprobe and Microhardness Studies of Enamel Remineralization

Enamel samples were demineralized and subsequently remineralized in a calcifying solution. Microhardness, which dropped after acid etching, recovered its hardness in part after remineralization. The mean calcium and phosphorus concentrations of the softened enamel increased after remineralization. The Ca/P weight ratio remained within the range of 2.05 to 2.12 in all enamel samples.