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Results for “Dental Enamel Permeability”

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At least 19 recordsLinked to original sources
PubMedDate not supplied

[The effect of calcium glycerophosphate and Remodent on the dental enamel permeability in dogs with fluorosis].

In 14 dogs aged 6 months with severe fluorosis, the authors studied the effects of intake of calcium glycerophosphate and local remodent application on 45Ca enamel incorporation and the depth of its penetration into the dental hard tissues. The treatment led to a substantial decrease in both enamel 45Ca accumulation and the depth of its penetration under severe fluorosis. Combined use of the drugs was more beneficial in terms of enamel 45Ca permeability.

Animals↗
PubMed1990

Effect of X-ray irradiation on the permeability of bovine dental enamel.

To estimate permeability properties of bovine dental enamel, complex impedance measurements and radioisotope diffusion experiments were carried out before and after X-ray irradiation (single dose, 72 Gy) of enamel specimens. Neither impedance measurements nor diffusion experiments showed significant changes in permeability.

Animals↗
PubMed1984

A phenomenological interpretation of the frequency-dependent impedance behaviour of bovine dental enamel.

The permeability of dental enamel can be estimated by means of diffusion measurements with radio-isotopes. Because of the low intrinsic permeability of enamel membranes, determination via this route may take two weeks. A much faster electrochemical method is presented, in which the real and imaginary part of the membrane impedance are measured at discrete intervals in the frequency-range 1 Hz-1 MHz. Using the principles of network-analysis, a phenomenological interpretation of these electrochemical data in terms of a 6-parameter model is given. The model contains R0, the intrinsic membrane resistance, R infinity, the residual membrane resistance and the four parameters, necessary to describe the postulated enamel diffusion impedance, which bears strong resemblance to the Warburg impedance. Starting from this model, optimal estimates (with standard-errors) of a membrane's R0 and vmax (the log of the frequency where the imaginary part of the membrane impedance is maximal) were derived. These parameters were predictors of the permeability of enamel.

Animals↗
PubMed1986

Measurement of the permeability of dental enamel and its variation with depth using an electrochemical method.

To investigate the permeability of the dental enamel of erupted and unerupted human pre-molars and its variation with depth, we determined the resistivity of successive 100-micron-thick layers. The electrical resistance of halved tooth crowns at zero Hertz, which according to Scholberg et al. (1982, 1984) is inversely related to the permeability, was measured before and after removal of successive enamel layers from the outer surface toward the dentino-enamel junction (D.E.J.). The resistivity of the successive enamel layers increased from the D.E.J. toward the outer surface in approximately the same way in erupted as well as in unerupted pre-molars, except within the outermost layer of 100 to 200 microns thickness. The resistivity of this layer in erupted pre-molars was considerably higher than that in unerupted pre-molars, which may be due to post-eruptive mineralization.

Adolescent↗
PubMed1989

Albumin interaction with caries-like lesions in bovine enamel.

The exposure of bovine enamel to an albumin-containing demineralizing solution results in penetration of protein into the porous enamel. Washing of this albumin-containing enamel results in a complete (low pretreatment albumin concentrations) or partial removal of the albumin (pretreatment concentrations greater than or equal to 200 micrograms/ml-1). Subsequent exposure to increasing salt concentrations of fluoride, phosphate, calcium or chloride shows a partial removal of albumin at fluoride or phosphate concentrations of 75 mM while complete removal occurred at 150-200 mM fluoride or phosphate. Exposure to either calcium or chloride, even at 3 M concentrations, showed a negligible albumin release. It is proposed that protein removed at high fluoride or phosphate concentrations is bound by a strong interaction between protein-carboxyl groups and calcium on the surface of the enamel mineral. The partial removal of albumin released at low fluoride or phosphate concentrations indicates an enamel-albumin interaction by means of Ca-bridging between protein-carboxyl groups and mineral phosphates. Finally, it is suggested that salt-free washing removes albumin that has lost its native form upon binding to the partially dissolved crystallites of the enamel. It is concluded that enamel is mainly protected from demineralization by the inhibitory effects of protein penetrated into the pores, in addition to possible protection by the pellicle on the surface.

Albumins↗
PubMed1990

Comparison of the iodide permeability test, the surface microhardness test, and mineral dissolution of bovine enamel following acid challenge.

The relationship among the iodide permeability (Ip) test, the surface microhardness (SMH) test, and enamel demineralization chemically analyzed as mineral loss was investigated using bovine enamel blocks. Demineralization periods of 0 (control) and 5, 15, 30, and 45 min using 0.05 mol/l lactate (pH 4.75) were chosen to approximate the acid challenge occurring during the intraoral enamel demineralization test. Mineral loss (Ca and PO4) was found to be directly proportional to dissolution time (r = 0.95). Changes (delta) in Ip and SMH each increased linearly over time (r = 0.58 and 0.64, respectively) and were similarly related to mineral loss (r = 0.60 and 0.65, respectively). The correlation between delta Ip and delta SMH was 0.55. When longer demineralization periods (60, 120, and 240 min) were included, the correlation between delta Ip and delta SMH was 0.68. We conclude that both the Ip test and the SMH test can be used as measures of the early stages of enamel dissolution.

Animals↗
PubMed1996

Methods of assessing erosion and erosive potential.

Methods for use in vitro are reviewed first, classified under the examination of extracted teeth, chemical and physical methods, digital image analysis, scanning electron microscopy and other potentially useful techniques. Methods for recording erosion in laboratory animals are dealt with next, including techniques that can also be used in vitro, Restarski's system and various modifications of it, and digital image analysis. Thirdly the main systems and indices that have been designed for clinical use are arranged under case histories and clinical examination, scales of severity and indices of diagnosis of varying complexity. Finally, some of the main advantages and limitations of the techniques are summarized.

Acids↗
PubMedDate not supplied

Scanning electron microscopy of softened enamel.

After exposing enamel specimens to 0.3% citric acid at pH 3.2 for various times, the acid was titrated to pH 7 before rinsing the specimens in water. After freeze-drying the specimens were examined by scanning electron microscopy. This procedure eliminates artefacts due to drying and mineral precipitation. The results showed that the outer region of softened enamel is much more delicate than previously thought, even after short (5- to 20-min) etching times. Mineral was lost from both prism boundaries and the prism bodies, resulting in a surface presenting thin, separate crystal bundles. In further studies, replicas of subsurface pores, created by resin impregnation, showed the softening depth to be several times greater than is suggested by techniques based on removing the softened enamel by physical forces. The results point to a need for improved methods of measuring softening depth. More importantly, it appears that the outer region of the softened layer remaining after an erosive challenge might be too fragile to resist frictional forces in vivo.

Acid Etching, Dental↗
PubMed1989

Kinetics of acquisition and loss of calcium fluoride by enamel in vivo.

Two in vivo experiments were performed, concerning (1) the kinetics of the acquisition of calcium fluoride on enamel during daily rinses with a solution of 0.023% F as sodium fluoride, and (2) the loss of calcium fluoride from enamel slabs which had been topically treated with a neutral solution containing 0.9% F as sodium fluoride. Enamel slabs were carried in the mouth by 6 volunteers for 8 days in both experiments. Sound and etched enamel were included. (1) During mouthrinses moderate amounts of fluoride were acquired by sound enamel, and more as calcium fluoride than as fluoridated apatite, whereas on etched enamel, more fluoride was deposited as fluoridated apatite. On etched enamel there was also a tendency that the deposition of calcium fluoride levelled out whereas the incorporation of firmly bound fluoride continued. This may indicate that calcium fluoride was transformed into fluoridated apatite, probably through remineralization during pH cycling in plaque covering the etched enamel. (2) After single topical application, it was found that etched enamel initially took up more calcium fluoride than sound enamel, but also lost more during the 1st day of in vivo exposure. The loss of calcium fluoride was arrested after 1-2 days, on sound enamel at 70% and on etched enamel at 40% of the original level. It is suggested that the increased amounts of firmly incorporated fluoride in enamel originated from calcium fluoride on enamel, and that calcium fluoride is an important and clinically significant source of fluoride ions on enamel.

Acid Etching, Dental↗
PubMed1988

Intra-oral retention of fluoride by bovine enamel from amine fluoride toothpaste and 0.4% amine fluoride liquid application.

The purpose of this study was to compare in vivo fluoride accumulation in enamel and in enamel lesions from a single topical fluoride application and daily toothbrushing with a fluoride dentifrice. Amine fluoride preparations were used for both products. Intra-oral appliances with bovine enamel specimens were worn by volunteers during a period of seven weeks. After this period, the specimens were analyzed for fluoride uptake and change in demineralization susceptibility. The results demonstrated that lesions had a high fluoride uptake capacity. Fluoride content values increased by 25-30 micrograms/cm2 during a single topical application, as compared with 10-15 micrograms/cm2 during seven weeks of toothbrushing. About half the fluoride acquired as a result of topical treatment was lost during subsequent exposure to the oral fluids when no further fluoride supplementation was given. The uptake of fluoride by sound enamel was comparatively small, regardless of the use of fluoride dentifrice or application. The presence of mature plaque at the time of fluoride application did not affect the amounts of fluoride delivered. Acid susceptibility tests showed that the enamel solubility exhibited a negative correlation with fluoride content of the specimens.

Amines↗
PubMed2000

The chemistry of enamel caries.

The chemical changes which occur during the process of carious destruction of enamel are complex due to a number of factors. First, substituted hydroxyapatite, the main component of dental enamel, can behave in a very complex manner during dissolution. This is due not only to its ability to accept substituent ions but also to the wide range of calcium phosphate species which can form following dissolution. In addition, the composition, i.e., the extent of substitution, changes throughout enamel in the direction of carious attack, i.e., from surface to interior. Both surface and positively birefringent zones of the lesion clearly illustrate that carious destruction is not simple dissolution. Selective dissolution of soluble minerals occurs, and there is the probability of reprecipitation. The role of fluoride here is crucial in that not only does it protect enamel per se but also its presence in solution means that rather insoluble fluoridated species can form very easily, encouraging redeposition. The role of organic material clearly needs further investigation, but there is the real possibility of both inhibition of repair and facilitation of redeposition. For the future, delivering fluoride deep into the lesion would appear to offer the prospect of improved repair. This would entail a delivery vehicle which solved the problem of fluoride uptake by apatite at the tooth surface. Elucidation of the role of organic material may also reveal putative mechanisms for encouraging repair and/or protecting the enamel mineral.

Animals↗
PubMed2004

Biological factors in dental caries enamel structure and the caries process in the dynamic process of demineralization and remineralization (part 2).

Dental caries is a complex disease process that afflicts a large proportion of the world's population, regardless of gender, age and ethnicity, although it does tend to affect more indivduals with a low socioeconomic status to a greater extent. The physicochemical properties of the mineral comprising the tooth surface and subsurface modulate the development, arrestment and remineralization of dental caries. Post-eruption maturation of enamel surfaces and exposed root surfaces is important in order for more susceptible mineral phases to be modified by incorporation of soluble fluoride from the plaque into dental hydroxyapatite. The chemical reactions that occur during acidic conditions when tooth mineral dissolves (critical pH) are determined by the supersaturation of calcium and phosphate within plaque and saliva, as well as if fluoride is present.

Apatites↗
PubMed1999

Laboratory enamel solubility reduction and fluoride uptake from enamelon dentifrice.

The presence of calcium-releasing ingredients in toothpastes containing sodium fluoride is usually avoided to prevent loss of active fluoride due to the formation of the insoluble calcium salt. The purpose of this study was to determine the bio-availability of fluoride from Enamelon Toothpaste (E), which simultaneously supplies fluoride, calcium and phosphate salts from a dual dispensing package. Fluoride uptake into artificially lesioned enamel cores due to the use of the test dentifrice (E) diluted 1:3 in whole human saliva was compared to that from a clinically proven effective sodium fluoride/silica USP reference toothpaste (C) and a non-fluoride control (E-w/o F). Enamel solubility reduction due to the use of E, C and E-w/o F was measured by determining the quantity of phosphate released to lactic acid buffer before and after treatment of the crowns of molars with 1:3 slurries of the dentifrices in water. Fluoride uptakes and enamel solubility reductions were 5031 +/- 158 ppm and 21.6 +/- 2.2% for E, 1915 +/- 39 ppm and 13.6 +/- 2.0% for C, and -3 +/- 2 ppm and 0.8 +/- 1.7% for E-w/o F. The fluoride uptake and enamel solubility reductions from E were significantly greater than from C (p < 0.001, Fisher LSD), and both fluoride-containing dentifrices significantly outperformed E-w/o F (p < 0.001). The laboratory results indicate that the calcium and phosphate salts delivered by the remineralizing Enamelon dentifrice increase the bioavailability of fluoride to substantially exceed that of the clinically proven standard dentifrice.

Analysis of Variance↗
PubMed2005

[In vitro study of the effects of 10-30 % hydrogen peroxide solutions on the surface of human tooth enamel].

The aim of the present study was to investigate the effects of hydrogen peroxide solutions (10-30%) on the enamel surface and the inner structure of human teeth. Prepared enamel samples were exposed to various concentrations of hydrogen peroxide solutions for one hour. Changes in the enamel were analyzed by two different methods. The inner structure was studied by the Ellman's reagent to detect possible changes in the amount of free thiol groups in the remaining organic phase of matured enamel. Surface alterations were imaged by atomic force microscope. Ellman's reaction revealed the presence of three groups of free thiols: one with easy, the second one with medium and the third one with difficult accessibility by hydrogen peroxide. Atomic force microscopy revealed severe alterations on the enamel surface after treatment with both low and high concentration of hydrogen peroxide. Our observations indicated that hydrogen peroxide induced alterations in the surface structure and in the inner phases of mature enamel in both low and high concentrations.

Anti-Infective Agents, Local↗