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Biomedical subjects

D Slop

Publications and source records attributed to D Slop.

At least 19 recordsLinked to original sources
PubMed1992

Load dependency and reliability of microhardness measurements on acid-etched enamel surfaces.

The load dependency of hardness measurements was investigated on sound and demineralized enamel samples. For all samples investigated, the Knoop hardness number (KHN) varied as a function of the applied load. Higher loads enhanced indenter penetration into the test surface. The variation in KHN values observed in demineralized enamel, both surface-softened and surface-etched, was explained by a decrease in porosity as a function of depth. The reading error for indentations made on surface enamel etched with 37% phosphoric acid gel for 30 s was found to be slightly elevated compared to indentations made on a polished sound enamel surface. It was concluded that the surface microhardness technique can be used for the longitudinal investigation of etched surface enamel.

Acid Etching, Dental↗
PubMed1992

Comparison of salivary fluoride concentrations after administration of a bioadhesive slow-release tablet and a conventional fluoride tablet.

The in-vitro and in-vivo fluoride release of bioadhesive, slow-release tablets prepared from a mixture of polyethylene glycol polymers, containing 0.1 mg of fluoride as NaF was studied, and their ability to sustain fluoride levels in saliva were compared with conventional fluoride tablets with the same fluoride content. In-vitro release experiments showed that the bioadhesive tablets needed 8 h to release all their fluoride compared with less than 1 h for the conventional fluoride tablets. In-vivo, the bioadhesive tablets had a retention period of 6 h and could sustain a salivary fluoride level of more than 10 microM above the baseline for 7 h. The conventional fluoride tablets achieved a peak concentration of 0.5 mM directly after dissolution in the mouth, but the fluoride level could not be sustained for longer than 1 h. A good agreement was found between the in-vitro swelling behaviour of the bioadhesive tablets and their in-vitro and in-vivo release characteristics and their in-vivo retention time.

Adult↗
PubMed1992

[Prevention of alveolar bone loss].

This article describes the bone resorption and remodeling of the edentulous jaw, starting right after extraction of teeth. This resorption is a physiological process, but can be influenced by wearing dentures. Load on the mucosa and disturbed blood circulation of the mucosa caused by the denture gives an additional bone resorption. The prevention of bone resorption can be executed in saving teeth or roots as long as possible. But when the jaw is already edentulous it is necessary to create an optimal function and load-dividing of the denture and regular controls are indicated. From time to time the denture has to be rebased or relined due to the changes in contour of the jaw. Also a daily massage of the mucosa after cleaning the denture is advisable to restore a normal blood circulation.

Alveolar Bone Loss↗
PubMed1991

A comparative study of the lead and cadmium content of surface enamel of Belgian and Kenyan children.

Acid etch surface enamel microbiopsies were performed on teeth from 378 children aged 6-12 years; 318 of the children lived in Belgium, an industrialized country, and 60 lived in a rural part of Kenya. In addition to lead and cadmium, calcium and phosphorus were also quantitatively determined in the etch solutions. Calcium was chosen as an internal reference for the expression of the lead and cadmium concentrations and for the assessment of the etch depth. The mean lead level in surface enamel of the Belgian children was approximately eight times higher than that of the Kenyan children. The cadmium levels were not significantly higher. An appropriate regression model taking into account differences in etch depth showed that a significant decrease of lead and cadmium with etch depth occurred and that a significant correlation between lead and cadmium in surface enamel existed for the Belgian cohort. Moreover, the same mean calcium/phosphorus ratios were obtained for the Belgian and Kenyan surface enamel samples, and were found not to play a significant role in the calibration of the lead and cadmium levels.

Belgium↗
PubMed1991

Acid-etched enamel surfaces after 24 h exposure to calcifying media in vitro and in vivo.

The remineralization of acid-etched enamel lesions is investigated in this study both in vitro and in vivo over periods of 24 h. In an initial study, samples of etched bovine enamel were subjected in vitro to treatment with synthetic calcifying solutions, or were exposed to saliva by means of an intraoral appliance. Alterations in hardness of the enamel surface were measured by indentation techniques. In a second study the suitability of an impression technique for investigating the surface relief induced by an acid-etch procedure was investigated. Extracted human incisors were used to make SEM observations of eteched areas and corresponding sections of impressions. Subsequently, six subjects were selected for a clinical evaluation of the impression technique. Although a significant decrease in indentation length (increase in hardness) was observed for etched enamel lesions treated with calcifying solutions in vitro, no evidence for any such change was observed in samples exposed to the influence of saliva when investigated by the indentation and impression techniques.

Acid Etching, Dental↗
PubMed1991

Model for assessment of lead content in human surface enamel.

Acid etch surface enamel microbiopsies were taken in vitro and in vivo and analyzed for lead using electrothermal atomic absorption spectrometry. The in vitro samples were obtained from subjects resident in an urbanized region in Belgium or from a region close to a nonferrometal industrial plant. The smaller set of in vivo samples were all from subjects resident in an urbanized region. Using a regression tree approach it was possible to identify in a stepwise manner factors that contributed to the variation of lead in the samples. For the in vitro as well as in vivo samples, the etch depth, tooth type, and age of the subjects were identified as significant factors but sex and dental arch quadrant were not. The residual lead levels obtained after regression with the significant factors were better distributed with much lesser variance. Moreover, a significant higher lead concentration could be demonstrated in the in vitro samples from the region close to the nonferrometal industrial plant.

Dental Enamel↗
PubMed1991

Study of lead and cadmium content of surface enamel of schoolchildren from an industrial area in Belgium.

The amount of lead and cadmium was determined in surface enamel from permanent teeth of schoolchildren by means of an acid etch surface enamel microbiopsy method. Lead and cadmium levels were calculated on the amount of etched enamel. A comparison of the concentrations of these heavy metals was made between children (7 and 11 yr) from a school close to a non-ferrous metal plant and children from the same age group from a school situated nearby the same plant but in a zone polluted to a lesser degree. The lead concentrations in enamel biopsies from the first group were significantly higher than those from the second group. Cadmium shows the same trend but on a much lower level. A significant correlation between lead and cadmium was also found in both groups.

Acid Etching, Dental↗
PubMed1991

Development and testing of bioadhesive, fluoride-containing slow-release tablets for oral use.

The bioadhesive characteristics of tablets for oral use made from modified starch, polyacrylic acid (PAA), polyethylene glycol (PEG) and sodium carboxymethylcellulose (CMC) were investigated. Adhesion force and energy were determined in-vitro and maximal adhesion time was evaluated in-vivo in human subjects. In-vitro, PAA showed the best bioadhesive properties, followed by modified maize starch and PEG with a mol. wt of 300,000-400,000 daltons. The presence of 0.1 mg of fluoride as NaF did not lead to significant differences in adhesion force and energy for the same formulation. The in-vivo bioadhesion was not strongly correlated to the in-vitro data. PAA, despite its excellent adhesion, proved to be irritating to the mucosa. PEG with a mol, wt of 200,000 daltons was subject to erosion. CMC showed good bioadhesive properties but the mechanical strength of the tablets was low. Modified maize starch tablets containing 5% (w/w) PAA and PEG with a mol. wt of 300,000 daltons proved to be the most suitable formulations for a fluoride-slow-release tablet with bioadhesive properties. In-vitro, the tablets released all of the fluoride within the 8 h period, with a high initial release. The release rate was related to the water absorption rate of the tablets. The PAA-containing formulations and the CMC formulations had the fastest release. In-vivo, fluoride levels with a minimum of 150 and a maximum of 1000 micrograms mL-1 were maintained for 8 h in the oral cavity. These fluoride levels were sustained significantly longer than those obtained with the administration of fourfold the amount of fluoride in the form of a fluoride-containing toothpaste. The release characteristics in-vivo exhibited a high variation. The use of bioadhesive polymers in oral pharmacotherapy seems promising.

Acrylates↗
PubMed1991

Relation between lead in surface tooth enamel, blood, and saliva from children residing in the vicinity of a non-ferrous metal plant in Belgium.

Two groups of schoolchildren between seven and 12 years old residing in the vicinity of a non-ferrous industrial plant and exposed to lead (Pb) at a concentration that could cause health problems, were monitored. Concentrations of Pb in blood (blood-Pb), which were determined at regular six monthly intervals, were related to the Pb concentrations in surface tooth enamel (enamel-Pb). Acid etch biopsy samples of surface enamel were taken at the end of the five year study period in the first group (A) and after two years in the second group (B). Salivary Pb (saliva-Pb) concentrations were determined for the first study group on the same day that the enamel biopsies were performed. Calibration of the data was necessary--that is, blood-Pb concentration with respect to age and sex and enamel-Pb concentration with respect to etch depth and age. The blood-Pb concentrations declined with time. Surface enamel Pb concentrations correlated with blood-Pb concentration for the period starting with the pre-eruptive development of the incisors, related to blood-Pb concentration for a long time, and corresponded partly to the exposure at the time of pre-eruptive development and/or eruption. Through the correlation with enamel-Pb concentration, the seasonal behaviour of blood-Pb concentration became apparent. Saliva-Pb concentrations related to blood-Pb concentrations only in the short term.

Biopsy↗
PubMed1991

In vivo use of a dual acid etch biopsy for the evaluation of lead profiles in human surface enamel.

Two successive acid etch biopsies were performed on the permanent maxillary right central incisors of two age-groups of children resident in an urban area in Belgium. Lead was determined in the biopsy solutions and the concentrations were related to etch depths which were calculated from the calcium and phosphorus concentrations in the biopsy solutions. The mean lead concentration of the first enamel biopsy layer was five times higher than in the second biopsy layer. A strong relation was observed between the two biopsies. It was shown that calibration of the lead values with respect to etch depths and Ca/P ratios was desirable and that a robust regression analysis approach was needed instead of classic least-squares regression analysis. However, the second biopsy provided more reliable lead estimates. In this study no increase in lead concentration in surface enamel could be demonstrated with age. Therefore, it was concluded that for these children the presence of lead in surface enamel had to be attributed primarily to preeruptive uptake.

Acid Etching, Dental↗
PubMed1990

A comparison of the influence of lanthanum and fluoride on de- and remineralization of bovine enamel in vitro.

The influence of fluoride and lanthanum on enamel softening was compared by hardness measurements and by determination of the calcium content in the solution. The addition of lanthanum to an acetate buffer solution (0.05 mol/L, pH = 5.0) had no significant influence on the change of the indentation length and on the calcium release, compared with those of the control group. In the fluoride group, a moderate increase of the indentation length and a reduced calcium loss were observed. In a second experiment, surface-softened bovine enamel was treated with calcifying solutions (Ca/P ratio = 1.67). Differences in treatment were created by the addition of traces (2 ppm) of lanthanum, fluoride, or both. The acid resistance of the treated enamel was evaluated by two successive softening steps (0.1 mol/L acetate buffer, pH = 5.5). Alterations of the enamel surface were longitudinally followed with a hardness tester. The addition of fluoride, lanthanum, or both significantly improved the rehardening of surface-softened enamel, compared with that of the control group. A 2 x 2 factorial analysis of variance showed that lanthanum and fluoride had a highly significant main effect and a significant negative interaction effect on the rehardening of surface-softened enamel. Subsequent acid treatments revealed that only samples treated with a fluoride-containing solution were adequately protected from further dissolution. The enamel surfaces treated with a solution containing both lanthanum and fluoride were covered with an acid-resistant surface coating. SEM observation of this surface layer revealed the presence of globular and spherulite structures.

Analysis of Variance↗
PubMed1990

[Mechanism of retention of a complete prosthesis].

Patients with full dentures often experience some problems with their dentures, one of them is retention. The retention of a full denture is a result of many factors. Some factors are of a physical nature, others of a physiological nature. The dentist has to take these factors into account while modelling the borders, flanks and basis of the prosthesis. In obtaining the best shape of those borders, flanks and basis a special emphasis is put on the border and flank modelling and the individual impression.

Dental Impression Technique↗
PubMed1990

Interaction of magnesium and fluoride in the rehardening and acid resistance of surface-softened bovine enamel in vitro.

Surface-softened bovine enamel was submitted in vitro to a treatment with calcifying solutions containing calcium and phosphate (Ca/P ratio = 1.67). Variation in treatment was created by the addition to the solutions of magnesium, fluoride or both. Subsequently, the enamel samples were submitted to two successive softening steps. Alterations of the enamel surface due to the different treatments were evaluated with a hardness tester. No significant difference in the rehardening was observed between samples treated with a magnesium- or a fluoride-containing solution. A 2 X 2 factorial analysis of variance showed that both additions had a highly significant main effect on the rehardening. A significant interaction effect was obtained between magnesium and fluoride. Subsequent acid treatments revealed that only fluoride adequately protected the enamel surfaces from further dissolution. The presence of magnesium seemed to weaken the acid-protective action of fluoride in vitro.

Animals↗
PubMed1989

Penetration of fluoride-containing self-gelling liquids into human molar occlusal fissures in vitro.

In this in vitro study the ability and speed of self-gelling liquid compositions to penetrate into fissures were evaluated. Two formulations containing either tetraethylsilicate, ammonium fluoride, and sodium lauryl sulfate or tetraethylsilicate, sodium fluoride, and cetylpyridinium chloride at different concentrations were used. It is shown that fissure penetration occurs when a certain minimum content of surface-active agent is present. Fissure penetration is achieved within 3-4 s, according to the fissure morphology.

Fluorides↗
PubMed1989

[Anticalculus dentifrices. A new era in preventive dentistry?].

Anticalculus toothpastes are available on the market. Toothpastes with Zinc compounds interfere mainly with the plaque formation. Dentifrices containing pyrophosphate give the highest reductions in calculus formation. The inclusion of pyrophosphate in a fluoride containing dentifrice did not interfere with the cariostatic action of fluoride on tooth enamel. The influence of anticalculus dentifrices on root caries and root hypersensitivity are, so far, not documented. Fundamentally, a lot of doubt still exists about the precise role of supragingival calculus formation in the onset of periodontal disease.

Dental Calculus↗
PubMed1989

[Changes from aging].

Expectations concerning the future of the oral health of the Dutch elderly and the quantitative results of a computer simulation model are put together. On an individual level no major changes in the oral health of the elderly dentates are to be expected. The ageing of the population and the decrease of the percentage of edentulous patients will result in a strong increase of the number of elderly people who need regular dental care. Due to the increasing age at which people become edentulous, no increase of treatment related to atrophic edentulous jaws is to be expected. On the other hand the introduction of new treatments, like the use of oral implants, might result in an increase of treatments of this kind.

Aged↗
PubMed1987

Surface roughening of human enamel after toothbrushing.

Grooves and scratches on the enamel surface are potential and preferential sites for bacterial adhesion. During toothbrushing groove formation is a potential risk especially in dentin. To obtain information on groove formation in enamel a profilometric experiment has been carried out on polished human enamel. The main result is that no groove formation with a depth more than a few tenths of a micrometer is observable even after 50.000 toothbrush strokes. The fact that material is removed by toothbrushing is indirect proof that enamel is removed by continuous brushing in layers more or less parallel to the original surface.

Adult↗