Synchrotron Radiation (SR) Wide-angle X-ray Diffraction (WAXD) and Small-angle X-ray Scattering (SAXS) techniques were used to assess microstructure of bovine enamel white-spot lesions (WSL) evaluated in a 10-day pH cycling model comprising three different dentifrice groups: (A) 0.21% NaF plus TCP (Clinpro Tooth Crème), (B) 1.1% NaF plus TCP (Clinpro 5000), or (C) 0% NaF (Tom’s of Maine) dentifrice. Each day consisted of four 2-minute treatments, one 4-hour acid challenge (pH=5.0), and immersion in artificial saliva (pH=7.0) between these events. These specimens were also examined with cross-sectional microhardness, digital light microscopy and FE-SEM (field emission scanning electron microscope), and demonstrated the remineralization model effected changes in subsurface microstructure. X-ray diffraction data from WAXD and SAXS were collected on enamel slab cross-sections extending from 0 μm to 150 μm, in 6 μm microbeam increments. A primary outcome of this observational study was that simultaneous WAXD and SAXS measurements were able to resolve significant differences (ANOVA, Student’s t-test, p<0.05) between the effects of the two fluoridecontaining dentifrices on subsurface lesion microstructure. In particular, enamel lesions treated with 1.1% NaF dentifrice group manifested an abundance of nanometer-sized crystallites, while treatment with the 0.21% NaF dentifrice produced larger apatite-like crystals. While the presence of fluoride in both cases promoted regularity in crystal size and orientation, this was not observed for lesions treated without fluoride. Altogether, our observations demonstrate the pathological processes for remineralization are markedly influenced by the presence and concentration of fluoride, the microstructural characteristics of which can be distinguished using the simultaneous WAXD and SAXS technique.

Thin films of HfO2 were fabricated on a p-Si(001) substrate using double pulse excitation (DPE) pulsed laser deposition (PLD) with KrF excimer and Nd:YAG lasers, and using conventional Nd:YAG laser PLD under two typical oxygen pressures (7.3 × 10-2 and 7.3 × 10-1 Pa). At 400°C or higher temperatures, the films are crystalline; at less than 400°C, they are amorphous. At higher oxygen pressures, DPE-PLD was effective against droplets. Then the surface morphology and electrical insulation properties of thin films were improved. At lower pressure, DPE-PLD was ineffective.

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