Biomedical subjects

F C Driessens

Publications and source records attributed to F C Driessens.

At least 37 records · Page 2Linked to original sources

PubMed1991

The distribution of magnesium in developing rat incisor dentin.

Previous studies have shown that rat incisor dentin contains a considerable amount of magnesium that is distributed heterogeneously. The cementum-related dentin, especially its incisal portion, is richest in magnesium. It was the purpose of the present study to investigate the changes that occur in the magnesium content during dentin maturation. Cross-sections were prepared from rat incisors at the apical, middle, and incisal levels. By means of an electron microprobe, tracings were made of the Ca-, Mg-, and P- signal frequencies. Comparison of corresponding dentin layers within and between the cross-sections showed that the Mg/P molar ratio was always higher in the cementum-related dentin (CRD) than in the enamel-related dentin (ERD) and increased from the apex toward the incisal edge. Especially in the incisal cross-section, an increase in Mg/P was found from the older (peripheral) toward the younger (central) dentin layers. As the Mg/P ratio varied from 0.07 to 0.33, the Ca/P ratio was found to fluctuate from 1.48 to 1.15. The two ratios appeared to be highly correlated (r = -0.97; p less than 0.001), suggesting that Mg replaces Ca and is bound to phosphate.

Animals↗

PubMed1991

Influence of fluoride and carbonate on in vitro remineralization of bovine enamel.

The influence of fluoride, carbonate, and fluoride in combination with carbonate on the in vitro remineralization of bovine enamel was investigated with the use of a sandwich technique. After demineralization, enamel slices were subjected for 610 h to remineralizing solutions with 0.03 or 1.0 ppm fluoride. At each fluoride level, either 0, 1, 10, 20, or 25 mmol/L carbonate was tested. After 0, 22, 62, 126, 192, 329, and 610 h of remineralization, contact microradiographs were made by Cu K alpha-radiation. At 0.03 ppm fluoride, carbonate had an inhibiting influence on remineralization. At 1.0 ppm fluoride, the inhibiting influence of carbonate changed into a stimulation of remineralizatization at 20 and 25 mmol/L carbonate. At 0, 1, and 10 mmol/L carbonate, fluoride had an inhibiting influence on remineralization. The differences in remineralization between the groups were explained by events concerning crystal growth, i.e., different types of minerals might have precipitated with differences in precipitation rates, and retardation of a precipitation step might have occurred under the various remineralization conditions. There was a mutual influence of fluoride and carbonate on the remineralization process. We conclude that the composition of the remineralizing solution with respect to fluoride and carbonate concentrations is important for the remineralization process.

Animals↗

PubMed1991

Acid-susceptibility of lesions in bovine enamel after remineralization at different pH values and in the presence of different fluoride concentrations.

Artificial caries lesions were created in sound bovine enamel slices demineralized at pH 5.0. The lesions were then remineralized at either pH 5.5 or pH 6.8 in solutions containing either 1.5, 15, or 50 mumol/L fluoride. The remineralized slices were then demineralized at pH 5.0 for investigation of acid-susceptibility by means of quantitative microradiography. The results indicated that fluoride, incorporated during the preceding remineralization, had a retarding effect on the demineralization after remineralization, and that for the lowest concentration of fluoride in the remineralizing solution, the inhibitory influence of fluoride depended on the pH of the remineralization solutions used.

Acids↗

PubMed1991

The effect of 2-O-stearoyl-glycerol 1,3-bisphosphate on the demineralization of dental enamel in vitro.

Parts of the buccal and lingual enamel surfaces of sound human third molars were treated with a test compound, and the non-treated parts served as control. After the treatment both parts were demineralized, and the artificial caries lesions were analyzed by means of quantitative microradiography. Treatment during only 1 minute with an aqueous solution of 1.5 mmol/l of the surface active compound 2-O-stearoyl-glycerol 1,3-bisphosphate (Glydip) resulted in a decrease in the rate of enamel demineralization by about 60%. When Glydip was dissolved in a toothpaste/water slurry it inhibited the demineralization by about 30%. When the enamel was covered by a salivary pellicle prior to the application of the slurry, the inhibition of the demineralization disappeared. However, when Glydip was applied in an aqueous solution, the presence of a salivary pellicle did not interfere with the decreasing effect of Glydip on the demineralization. It is concluded that Glydip has promising properties for its use as an anti-caries agent, in combination with fluoride.

Dental Caries↗

PubMed1990

Zinc deficiency-induced changes in the lipid composition and ultrastructure of rat incisor teeth.

The lipids and ultrastructure of the forming, maturing and erupted parts of incisors were compared in rats fed a zinc-deficient diet for 28 days, pair-fed rats and control rats. The lipid levels in the forming portions of zinc-deficient incisors were 30-50% below control levels and were associated with longer Tomes' processes in the secretory ameloblasts, porosities in the forming enamel and fewer malachite green-aldehyde-phospholipid aggregates in the predentine. No marked structural changes were seen in the erupted portions of the teeth, although variations in lipid composition were detected both in the maturing and erupted parts. No differences were found between teeth from the 3 groups of animals for Na, Mg, Cl, Ca and P signals with the electron microprobe.

Animals↗

PubMed1990

Influence of fluoride on in vitro remineralization of artificial subsurface lesions determined with a sandwich technique.

Remineralization experiments of bovine enamel with subsurface lesions were carried out with the use of a sandwich technique. The remineralizing solutions contained no or 2 ppm fluoride added to the solution. The amount of remineralization was determined after remineralization periods up to 324 by means of quantitative microradiography. After 84 h the group with fluoride showed significantly (p less than 0.05) less remineralization than the nonfluoride group. This inhibition of fluoride on the remineralization may be explained by the inhibiting effect that fluoride at certain concentrations has on the crystal growth of apatites.

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↗

PubMed1990

Is systemic treatment of osteoporosis and mandibular resorption possible?

It is argued that mandibular resorption can be considered as osteoporotic in nature. This calls for a systemic approach in its treatment. One aspect mostly neglected is the tendency of bone to bind calcium and phosphate ions. A direct measure for this tendency is the difference in pH between the bone extracellular fluid and blood plasma with octocalcium phosphate. Calculation of these degrees of saturation of about 2000 data of blood plasma compositions given in the literature learned that calcitonin injections, estrogen replacement and magnesium supplementation increase the tendency of bone to bind calcium and phosphate ions and, hence, should be used in the therapy of mandibular resorption and of bone resorption in general.

Bone Resorption↗

PubMed1990

Aluminium in tooth pastes and Alzheimer's disease.

Epidemiological studies from Norway and England suggest a relation between the frequency of Alzheimer's disease and the concentration of aluminium in the drinking water. Estimates, made in this study, show that the role of aluminium from tooth pastes may be even more important than that from the drinking water. For that reason we determined in samples of tooth pastes taken from the BENELUX market which brands contained aluminium. This appeared to be the case for about 22% of the brands which according to the manufacturers cover about 60% of the market.

Aluminum↗

PubMed1990

[The use of aluminum-containing toothpaste and its potential risk].

Epidemiological studies from Norway and England suggest that there is a relation between the frequency of Alzheimer's disease and the concentration of aluminum in the drinking water. A recent Dutch study suggests further that the role of aluminum from tooth pastes may be even more important than that from drinking water. For this reason we determined in samples from the Belgian market which tooth pastes contained aluminium oxyhydroxide as abrasive. This happened to be the case in 5 out of 27 brands. It is not know to us which part of the market these tooth pastes represent.

Aluminum Hydroxide↗

PubMed1989

Plasma calcium difference between man and vertebrates.

1. Literature data about the plasma content of total calcium, ionized calcium and inorganic phosphate in healthy animals and man of different age and sex were collected. 2. It was established that under normal conditions ionized calcium is about 45% of total calcium. 3. The degree of saturation of these blood samples with respect to octocalcium phosphate OCP was calculated. 4. In young animals and man the blood plasma has a higher degree of saturation than in adult animals and man. 5. The blood plasma of healthy animals is supersaturated with respect to OCP during their whole life. 6. However, the blood plasma of healthy human adults is slightly undersaturated with respect to OCP.

Age Factors↗

PubMed1989

Effects of surface-active compounds on the demineralization of dental enamel.

Slices of bovine enamel and intact human enamel were treated with (a) a two-step treatment consisting of phytate followed by hexadecyl amine, or (b) 2-O-stearoylglycerol-1,3-diphosphate (Glydip), or (c) phosphatidic acid. The effect of these agents on the rate of caries lesion formation and on the permeability of dental enamel was quantitatively determined. Glydip had the most pronounced effect on lesion formation and showed a strong inhibiting effect on the rate of demineralization, combined with a reduction of the permeability. The results indicate that at least a part of the effect of Glydip on the demineralization was caused by a reduction of the rate of dissolution of the enamel mineral. The reduction in permeability may have had an additional effect.

Amines↗

PubMed1989

The influence of fluoride on in vitro remineralization of bovine enamel.

Remineralization experiments using bovine enamel were carried out with 2 ppm fluoride or no fluoride added to the remineralizing solutions. The group without fluoride showed (quantitative microradiography) significantly more remineralization in the first 50 microns of the lesion than the fluoride group. It is suggested that fluoride may inhibit remineralization.

Animals↗

PubMed1989

A systemic approach to the oral problem of mandibular resorption.

It is argued that mandibular resorption can be considered as osteoporotic in nature. This calls for a systemic approach in its treatment. One aspect mostly neglected is the tendency of bone to bind calcium and phosphate ions. A direct measure for this tendency is the difference in pH between the bone extracellular fluid and blood plasma. This pH difference is directly reflected by the degree of saturation of blood plasma with octocalcium phosphate. Calculation of these degrees of saturation of about 2000 data of blood plasma compositions given in the literature indicates that calcitonin injection, estrogen replacement and magnesium supplementation increase the tendency of bone to bind calcium and phosphate ions and hence should be used in the therapy of mandibular resorption and of bone resorption in general.

Animals↗

PubMed1988

On the prevention and treatment of calcification disorders of old age.

From several investigations it is known that magnesium oxide or hydroxide therapy causes a considerable delay of kidney stone recurrence in man. Further, it is known that the mortality of populations due to cardiovascular disease in areas with hard drinking water containing more magnesium and having a higher Mg/Ca ratio than soft water, is considerably lower than in soft water areas. In the present study a physiological model for the homeostasis of calcium and phosphate is given. It is shown that and why a slight magnesium deficiency causes the pH of bone extracellular fluid to decrease at or below the pH level of the other body fluids. This decrease makes the other body fluids supersaturated with octocalcium phosphate and this is the prime reason for calcification disorders in the soft tissues. Therefore, the hypothesis is proposed that soft tissue calcifications can be stopped and even prevented by magnesium therapy. However, they are not reversible and treatment with chelate therapy is contraindicated.

Acid-Base Imbalance↗

PubMed1988

Physiology of hard tissues in comparison with the solubility of synthetic calcium phosphates.

On the basis of the composition of the mineral in bone and the saturation level of blood plasma, with respect to slightly soluble calcium phosphates, it is shown that normal tissue fluids are not supersaturated with whole bone but with the minerals of dead bone. The phase controlling solubility in living bone is octocalcium phosphate, and the presence of this phase could regulate the calcium phosphate concentrations of the body fluids by a simple physicochemical equilibrium. It is explained how parathyroid hormone and calcitonine can act on osteocytes in such a way that shifts occur in this physicochemical equilibrium. It is also explained how the mineral of bone is affected by the activity of osteoclasts and osteoblasts during bone turnover. From this knowledge about the physiology of bone mineral, it is possible to predict the behavior of calcium phosphate bioceramics implanted in the body once their true solubility limits are known. Solubility studies have been carried out on hydroxyapatite, oxyhydroxyapatite, octocalcium phosphate, brushite, beta-tertiary calcium phosphate, and magnesium whitlockite. These studies indicate that the resorbabilities for implants of these materials are in the following order: magnesium whitlockite less than hydroxyapatite less than oxyhydroxyapatite less than beta-tertiary calcium phosphate. This order is consistent with data from implant studies now available in the literature.

Body Fluids↗

PubMed1988

Improvement of the caries resistance of human dental roots by a two-step conversion of the root mineral into fluoridated hydroxylapatite.

Roots of extracted human molars were treated for both 10 and 30 min with a saturated solution of dicalcium phosphate dihydrate (DCPD) of pH 2.4 and subsequently with a 5.3 mmol.L-1 solution of sodium fluoride of pH 7.0. The objective of these combined treatments was to convert the highly-soluble root mineral into the less-soluble fluoridated hydroxylapatite, with DCPD as an intermediate, to improve caries resistance. The mineral content of the surface layer was not affected in a significant way. Roots treated in this way were subjected to 50 mmol.L-1 acetate buffer solutions of pH 5.5 and with pIOHA-values of 112, 116, and 122. The proportional reduction of the rate of demineralization (Vdem) of similarly treated roots subjected to buffer solutions of pIOHA 112 and 116 appeared to be equal initially. Since fluoridated hydroxylapatite is insoluble under these conditions, these findings are in agreement with expectations. The reduction of V dem amounted to about 45 and 70% for roots treated for 10 and 30 min, respectively. When roots were treated for 10 and 30 min and then exposed to buffer solutions with a pIOHA 122, reductions of V dem of about 30 and 55%, respectively, were found. Conversion of the root mineral into fluoridated hydroxylapatite can eliminate, in principle, the existing difference in caries susceptibility of the root and of the dental enamel.

Calcium Phosphates↗

PubMed1988

The effect of lactic and acetic acid on the formation of artificial caries lesions.

Fluoride specifically adsorbed to hydroxyapatite reduces the rate of dissolution of hydroxyapatite. Since specific adsorption is a property which anions of all weak acids have in common, it is expected that the anions of lactic and acetic acid will be specifically adsorbed to hydroxyapatite too and in this way will cause a reduction in the rate of dissolution of hydroxyapatite. In order to investigate this, we used the experimental results from Featherstone and Rodgers (1981). Calculations of the rate of increase of the lesion depth in dental enamel per mmol. L-1 of the un-ionized acid revealed that lesion progress was pH-dependent and was lowest at that pH which corresponds with the pK-value of the relevant acid. It is concluded that the anions of lactic and acetic acid are specifically adsorbed to the enamel mineral and in this way reduce the rate of dissolution of the mineral. This suggests that a description of the development of an artificial caries lesion in mathematical terms should include the effect on the rate of dissolution of the mineral of specific adsorption of the relevant acid anions to the mineral.

Acetates↗