Electron Probe Micro-analysis for Subsurface Demineralization and Remineralization of Dental Enamel

Chu, J.S.; Fox, Jeffrey L.; Higuchi, William I.; Nash, W. P.

doi:10.1177/00220345890680010401

Cited by 10 publications

(6 citation statements)

References 23 publications

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“…The profile of deposition in the CPP-ACFP-treated enamel showed that the bulk of the fluoride was incorporated into the body of the lesion matching the area that had the greatest increase in mineral density. In previous studies examining the uptake of fluoride into enamel, fluoride was found to localise in the outermost surface layer (approximately 10 m) [Petersson et al, 1976;Chu et al, 1989]. The greater depth of fluoride incorporation shown in the current study is likely to be attributed to the higher activity gradient of the neutral ion HF 0 at pH 5.5 driving it deeper into the lesion.…”

Section: Discussionsupporting

confidence: 53%

Enamel Subsurface Lesion Remineralisation with Casein Phosphopeptide Stabilised Solutions of Calcium, Phosphate and Fluoride

et al. 2008

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Casein phosphopeptide stabilised amorphous calcium phosphate (CPP-ACP) and amorphous calcium fluoride phosphate (CPP-ACFP) solutions have been shown to remineralise enamel subsurface lesions. The aim of this study was to determine the effect of ion composition of CPP-ACP and CPP-ACFP solutions on enamel subsurface lesion remineralisation in vitro. CPP-bound and free calcium, phosphate and fluoride ion concentrations in the solutions were determined after ultrafiltration. The ion activities of the free ion species present were calculated using an iterative computational program. The mineral deposited in the subsurface lesions was analysed using transverse microradiography and electron microprobe. CPP was found to stabilise high concentrations of calcium, phosphate and fluoride ions at all pH values (7.0–4.5). Remineralisation of the subsurface lesions was observed at all pH values tested with a maximum at pH 5.5. The CPP-ACFP solutions produced greater remineralisation than the CPP-ACP solutions at pH 5.5 and below. The mineral formed in the subsurface lesions was consistent with hydroxyapatite and fluorapatite for remineralisation with CPP-ACP and CPP-ACFP, respectively. The activity gradient of the neutral ion pair CaHPO₄⁰ into the lesion was significantly correlated with remineralisation and together with HF⁰ were identified as important species for diffusion.

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Section: Discussionsupporting

confidence: 53%

Enamel Subsurface Lesion Remineralisation with Casein Phosphopeptide Stabilised Solutions of Calcium, Phosphate and Fluoride

et al. 2008

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“…Analysis of Mineral Fluoride by Electron MicroprobesThe method of electron microprobe analysis has been discussed in detail by Chu et al 14 Some modifications were made. The surface of the cross section was polished ultrasonically with 1.0-µm diamond paste for 6 h and then coated by a thin layer of carbon.…”

Section: Methodsmentioning

confidence: 99%

“…The amount of fluoride associated with the mineral can be determined by an electron microprobe technique 14 and the mineral density can be measured by an X-ray microradiography method. 15 Therefore, based on the measured composition of solid mineral as a function of time and position, a model independent data analysis (MIDA) technique, previously established in our laboratory 16,17 can be applied to calculate the intercrystalline solution composition as a function of position and time in the microenvironment during demineralization.…”

Section: Introductionmentioning

confidence: 99%

Calculation of Intercrystalline Solution Composition during in Vitro Subsurface Lesion Formation in Dental Minerals†

Wang

Fox

Baig

et al. 1996

Journal of Pharmaceutical Sciences

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Applications of a novel technique to calculate intercrystalline solution composition during enamel demineralization are presented. Bovine tooth enamel blocks and carbonated apatite (CAP) compressed disks were demineralized in an in vitro subsurface lesion system. The demineralization medium was a 0.1 M acetate buffer at pH 4.5, containing calcium, phosphate, and fluoride (0.5 ppm). Mineral samples were demineralized for various times, and fluoride profiles and mineral density profiles of these samples were determined by electron microprobe and X-ray microradiography, respectively. A model independent data analysis (MIDA) technique uses these data along with the differential equations for mass transfer and permits calculation of the local intercrystalline solution composition profiles inside the porous mineral matrix as functions of time and position. The invariance in diffusivity with time as calculated in the analysis was taken as an indicator of the physical reasonableness of the method. Current outcomes suggest that it is the sharp gradient of fluoride concentration in the intercrystalline solution which causes the formation of subsurface lesions. Since the driving force for mineral dissolution is a function of solution composition, a gradient of this driving force is consequently formed. Using a compressed disk of carbonated apatite powder as a model for block enamel excluded the possibility of the existence of a gradient of mineral composition which could also cause a gradient of the driving force for mineral dissolution. An FAP surface complex hypothesis is consistent with the current view that fluoride in the intercrystalline solution has a stronger inhibition effect on the dissolution of mineral than does fluoride in the mineral phase. With the help of the MIDA technique, calculated results indicate that the mechanism of the formation of subsurface lesions is dynamically controlled by the intercrystalline solution composition.

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“…The bulk solution ionic activity product was calculated by the method described by Fox (1977 fluoride (200-33,400 pug fluoride/g hydroxyapatite) was chosen as the fluoride standard for the electron probe micro-analyzer. The procedure for preparation of these powder standards as described by Chu et al (1989) was followed. The chemical composition of the deposited material was close to that of FAP.…”

Section: Methodsmentioning

confidence: 99%

“…Sample preparation. The procedure for the finishing of thin cross-sections of enamel from successive dissolution experiments was followed as described by Chu et al (1989). The samples, along with fluoride standards, were coated in a vacuum evaporator with a uniform layer of carbon (-20 nm) to eliminate charge build-up on the surface of the sample during electron bombardment.…”

Section: Methodsmentioning

confidence: 99%

Quantitative Study of Fluoride Transport During Subsurface Dissolution of Dental Enamel

1989

Self Cite

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Previous studies using bovine dental enamel as a model have shown that surface and subsurface dissolution of enamel may be governed by micro-environmental solution conditions. We have now investigated the demineralization phenomenon more rigorously with the primary objective of developing a method for deducing solution species concentration profiles as a function of time from appropriate experimental data. More specifically, in this report, a model-independent method is described for determination of the pore solution fluoride gradients in bovine enamel during subsurface demineralization. Microradiography was used to determine the mineral density profiles, and an electron microprobe technique to determine total fluoride (F) profiles associated with the enamel. In each case, matched sections of bovine enamel were exposed to partially saturated acetate buffers at pH = 4.5 containing 0.5 ppm F for various periods of time (from six to 24 hours). The treated enamel was found to have an intact surface layer and subsurface demineralization. The extent of the demineralization and the depths of the lesions increased with time in all cases. The data were first used to calculate (a) the total F gradients in the enamel at various times, and (b) the local uptake rate of F as a function of time and position. Then, by manipulation of the equations describing the uptake and transport of F, we calculated the pore diffusion rate of F and the micro-environmental solution F concentration in the aqueous pores as a function of time and of distance from the enamel surface. It was also possible to calculate an intrinsic F diffusion coefficient in the pores, which was about 1.0 X 10(-5) cm2/sec, in good agreement with reported values. 14C-sucrose uptake and release experiments with identically prepared demineralized enamel sections were also conducted to provide an independent check on the assumed dependence of porosity on mineral density. The results of this investigation, especially the outcomes relative to this new method for determination of pore solution F gradients during acid attack of the dental enamel, should be valuable in future studies of the mechanism(s) of the action of F in inhibiting dental enamel demineralization.

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Electron Probe Micro-analysis for Subsurface Demineralization and Remineralization of Dental Enamel

Cited by 10 publications

References 23 publications

Enamel Subsurface Lesion Remineralisation with Casein Phosphopeptide Stabilised Solutions of Calcium, Phosphate and Fluoride

Enamel Subsurface Lesion Remineralisation with Casein Phosphopeptide Stabilised Solutions of Calcium, Phosphate and Fluoride

Calculation of Intercrystalline Solution Composition during in Vitro Subsurface Lesion Formation in Dental Minerals†

Quantitative Study of Fluoride Transport During Subsurface Dissolution of Dental Enamel

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