2008/06/09 by Frank Mueller, Mueller, Frank, Christian Zeitz +15
Arts and Humanities · Dentistry · Physics and Astronomy · #Cultural Heritage Materials Analysis #Dental materials and restorations #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #X-ray Spectroscopy and Fluorescence Analysis #cond-mat.mtrl-sci
paper · pdf · doi:10.48550/arxiv.0806.1425
9 pages, 5 figures, 1 table
arxiv created 2008/06/09 · openalex publication_date 2008/06/09 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Structural and chemical changes that arise from a fluoridation of synthetic hydroxyapatite in neutral and acidic fluoridation agents are investigated. For synthetic hydroxyapatite (Ca5(PO4)3OH = HAp), the elemental depth profiles were determined by X-ray photoelectron spectroscopy (XPS) to reveal the effect of fluoridation in nearly neutral (pH = 6.2) and acidic agents (pH = 4.2). Due to the high surface sensitivity of the technique, the depth profiles have a resolution on the nm scale. With respect to the chemical composition and the crystal structure XPS depth profiling revealed very different effects of the two treatments. In both cases, however, the fluoridation affects the surface only on the nm scale which is in contrast to recent literature, where a penetration depth up to several microns was reported. Moreover, evidence is given that the actual fluoridation depth depends on the pH value. Recently, a qualitative three layer model was proposed for the fluoridation of HAp in an acidic agent. In addition to the elemental depth profile, as presented also by various other authors, we present a quantitative depth profile of the compounds CaF2, Ca(OH)2 and fluorapatite (FAp) that are predicted by the three layer model. The analysis of our experimental data exactly reproduces the structural order of the model, however, on a scale that differs by nearly two orders of magnitude from previous predictions. Our results also reveal that the amount of Ca(OH)2 and FAp is small as compared to that of CaF2. Therefore, it has to be questioned whether such narrow Ca(OH)2 and FAp layers really can act as protective layers for the enamel.