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G J Flim

Publications and source records attributed to G J Flim.

6 recordsLinked to original sources
PubMed1978

Diffusion of fluoride ions in dental enamel at pH 7.

The penetration and uptake of both radioactive (18F) and stable fluoride (19F) in bovine enamel were investigated. Buffered pH 7 NaF solutions were employed. Penetration profiles of both 18F and 19F in enamel were determined by using a sectioning technique. 18F and 19F concentrations decreased exponentially with increasing penetration distance. The uptake of 18F in enamel can be described by a power function of the immersion time, with an average power of 0.76. The results agree reasonably with our previously published theoretical model for the diffusion in enamel, based on simultaneous diffusion in enamel pores and in the hydroxyapatite crystallites. The diffusion coefficients of fluoride ions in enamel obtained from the application of the model to the results presented here, were: D = 0.9 x 10(-17) cm2/s in the crystallites and D' = 3.3 x 10(-10) cm2/s in the enamel pores. An average penetration depth of fluoride ions at pH 7.0 of 8 micron in 4 hours has been calculated.

Animals↗
PubMed1977

The temperature dependency of 45Ca diffusion in bovine enamel.

The diffusion of 45Ca ions in sound bovine enamel at pH 7.0 was studied as a function of temperature in the range 20 degrees-40 degrees C. The experimental data show that the diffusion is governed by two processes with activation energies of about 0.7 and 1.3 eV respectively. These values are considerably larger than the activation energy of calcium ion diffusion in water (0.2 eV). The diffusion process with the activation energy of 1.3 eV is dependent upon the calcium concentration in solution. A model based on the complex pore structure of enamel and on interactions of diffusing ions with the enamel constituents is discussed.

Animals↗
PubMed1977

Diffusion of 45Ca in bovine enamel.

The penetration of 45Ca ions into whole bovine enamel from an aqueous solution was studied as a function of the Ca content in the solution. A sectioning technique was employed to measure the penetration of 45Ca into the enamel. Probably only Ca ions occupying surface positions in the hydroxyapatite crystallites participate in the exchange process at the solution-enamel interface. The fraction of Ca ions participating in the exchange was 2% of the total number of Ca ions. Two different diffusion processes occur; firstly, a process governed by a diffusion coefficient, D1 ranging from about 5 x 10(-14) to 2 x 10(-12) cm2/s and strongly dependent on the calcium concentration in the solutions; and secondly a process with a concentration-independent diffusion coefficient, D2, with a value of 2.8 x 10(-12) cm2/s. It is assumed that the 2 diffusion types correspond to intra- and interprismatic transport, respectively. A model based on the pore structure of dental enamel and on surface charges on hydroxyapatite crystallites is discussed.

Animals↗