摘要:

In this paper, the demineralization of dental enamel was studied in under-saturated calcium phosphate solutions with different pH and fluoride concentrations. The combined data of the mineral dissolved show a dissolution pattern not significantly different from the stoichiometric hydroxyapatite (HAP) dissolution [Ca/P = 1.72 (0.01)]. However, during the very initial demineralization, calcium is removed preferentially. The rate of demineralization seems to be affected to a greater extent when the solution is supersaturated to CaF2 than to fluorapatite (FAP). This is attributed to a different morphology of the calcium fluoride deposition which effectively blocks the acid diffusion. During demineralization, fluoride is taken up by the enamel; the percentage of fluoride being removed from the solution is correlated with the amount of demineralization.

ISSN:0008-6568    

DOI:10.1159/000260667

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The initial rates of dissolution of synthetic apatites were determined using the rotating disc method. The reactivities of carbonated apatites in acidic media were directly related to their carbonate content. This appeared to be due, in part, to a decrease in the apparent activation energy for dissolution of carbonated apatites. Structurally incorporated fluoride in carbonated apatites at levels up to 1,000 μg/g did not influence the dissolution rates, whereas fluoride at a concentration of 1 μg/ml in the buffer solution reduced the dissolution rates by 20–30%. Apatite dissolution under the experimental conditions was intermediate between transport control and surface chemical control. After 10 min, diffusion processes within the apatite pellets were found to influence the overall dissolution r

ISSN:0008-6568    

DOI:10.1159/000260668

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Release of calcium from synthetic hydroxyapatite or human enamel powder was studied after pretreatment with various low molecular weight mono- or polycarboxylic acids in their acid or salt form. Considerable reductions of calcium release were observed with the salts when the assay was performed under vigorous stirring. This effect was attributed to the existence of weak interactions between adsorbates and adsorbents. The higher adsorption of the salt compared to acid form could be related to the formation of a salt bridge between the apatite surface phosphate groups and the adsorbate carboxylic groups.

ISSN:0008-6568    

DOI:10.1159/000260669

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The effect of surface-active agents (SAA) on fluoride deposition in enamel from topical application was studied in vitro. Preliminary imbibition experiments with blocks of human enamel showed that some SAA increased the fluoride penetration in depth during a 5-min fluoride application. Inclusion of several SAA in the fluoride solutions caused increased deposition of apatitically bound fluoride during a postapplication incubation period. Detailed observations on cetylpyridinium chloride or Lodyne S-110 fluorosurfactant showed that addition of these SAA to solutions of KF at pH 8.5, 7.0, and 5.0 tended to decrease the immediate penetration of fluoride at the acidic pH without compromising fluorapatite formation during the postapplication incubation. The fluorapatite formation was greatly enhanced when Lodyne S-110 was added to a treatment solution of KF with orthophosphate at pH 5. Addition of cetylpyridinium chloride to the currently frequently used acid phosphate fluoride solution increased the ability of this formulation to cause fluorapatite formation in enamel. Both SAA reduced the immediate fluoride penetration from acidic solutions of ammonium fluoride with orthophosphate without compromising postapplication fluorapatite formation and increased fluorapatite formation from application of neutral solutions.

ISSN:0008-6568    

DOI:10.1159/000260670

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The polyphosphates pyro-, tripoly-, trimeta- and hexametaphosphate were bound to hydroxyapatite (HA) in much larger amounts in an H2O-labile (removed by H2O washing) than in an H2O-stable (crystal) compartment. Approximately 1 PO4 group was liberated per polyphosphate molecule bound in both compartments. Incubation of HA containing polyphosphates in the crystal compartment gave rise to the liberation of PO4, most of which came from HA-catalyzed polyphosphate hydrolysis, but some of which came from solubilization of HA and possibly from displacement of crystal PO4 via exchange. Crystal-bound phosphonates (ethanehydroxy-11-diphosphonate and methane diphosphonate) neither hydrolyzed nor exchanged further with crystal PO4. The relative amounts of binding and hydrolysis of the test substances as well as their relative effects in solubilizing HA in H2O, reducing HA acid solubility and inhibiting mineralization and microcrystal aggregation were determined. The results are discussed with respect to known or implied anticaries activity.

ISSN:0008-6568    

DOI:10.1159/000260671

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The extent of abrasion of human enamel caused by tooth brushing was investigated in a laboratory study. The enamel was made radioactive by irradiation in a nuclear reactor. The amount of radioactive material removed by brushing with a 30% toothpaste slurry was quantitatively measured as a function of the number of strokes. A detailed description of the brushing machine, the slurry container, the sampling and the calibration is given. The results showed that from polished enamel initially material is removed fairly rapidly. After 500 strokes the amount abraded away was 12.5 μg cm––2 corresponding to a layer in the order of 0.2 μm. In the range between 500 and 10,000 strokes the rate of abrasion was slower; after 10,000 strokes a layer of about 0.4 μm had been removed. The results indicate a considerable biological variation between the various spe

ISSN:0008-6568    

DOI:10.1159/000260672

出版商:S. Karger AG    

年代:1983

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000260673

出版商:S. Karger AG    

年代:1983

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000260674

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

195 Osborne-Mendel rats were weaned 19 days afterbirth and fed cariogenic diet for 42 days. The control group received no treatment. The study groups received applications of sodium fluoride varnish (Duraphat®) or silane fluoride varnish (Fluor Protector®), or a placebo varnish, either on days 19–21 or on days 25–27. After the experimental period, fluoride content and the release of calcium from the enamel was determined in two upper molars. The fluoride content of enamel was considerably increased in groups treated with fluoride varnishes. More fluoride was taken up from Fluor Protector than from Duraphat. The release of calcium and caries were, however, reduced more by Dur

ISSN:0008-6568    

DOI:10.1159/000260675

出版商:S. Karger AG    

年代:1983

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000260676

出版商:S. Karger AG    

年代:1983

数据来源: Karger