Biomedical subjects

D Coomans

Publications and source records attributed to D Coomans.

At least 37 records · Page 2Linked to original sources

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

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

Measurement of pulp temperature increase to externally applied heat (argon laser, hot water, drilling).

In order to weld cracks in tooth enamel, it is necessary to bring the surface of the tooth to the fusion temperature of the enamel (greater than 1,000 degrees C). The study investigated whether this increase in surface temperature can cause damage to the vitality of the tooth by recording, using a thermocouple, the temperature in the pulp chamber of teeth exposed to argon laser irradiation (power density after focusing: 4000 W/cm2; duration of continuous irradiation: 1-5 seconds). These pulp temperature increases were compared with those considered safe for the tooth, i.e., contact with a hot drink, drilling of cavities with air + water cooling. It was shown that punctual irradiations with an argon laser for periods of 2 or 4 seconds generated temperature increases in the pulp chamber which were less than inferior to those caused by contact with water at 54-55 degrees C for 1 or 2 seconds, and were of the same order as those caused by the drilling of class III or V cavities of 1 mm in depth and 1 mm in diameter. These results suggest that it is worth continuing research into applying the technique in the mouth.

Body Temperature↗

PubMed1988

Ultrastructural localization of osteocalcin in rat tooth germs by immunogold staining.

Osteocalcin was localized by indirect immunogold staining of thin frozen sections of rat tooth germs which had been fixed by different methods. Acrolein fixation proved to be satisfactory considering the preservation of fine structure and antigenicity. In odontoblasts, osteocalcin was found to be localized in the cisternae of the rough endoplasmic reticulum and Golgi apparatus. Few positive transport vesicles were found. Staining for osteocalcin in odontoblastic processes was only observed after strong fixation and was intense in odontoblasts engaged in early dentine formation. Predentine was slightly positive in the neighbourhood of positive processes. Matrix vesicles were negative and strong osteocalcin labeling of dentine seemed to appear after the onset of mineralization.

Animals↗

PubMed1988

Immunocytochemical localization of osteocalcin in human and bovine teeth.

Antisera against bovine and rat osteocalcin were characterized and used for the immunocytochemical visualization of this protein in human and bovine teeth. Osteocalcin immunoreactivity was localized at the dentino-enamel junctions, whereas the major part of the dentin was unstained. These results suggest some involvement of ameloblasts in the deposition of osteocalcin. The low concentration of the protein suggests that it has no direct function in dentin formation.

Animals↗

PubMed1987

Effect of different combinations of calcium, magnesium and phosphate on the inorganic composition of rat molars in vitro.

Second upper molars from 3-day-old rats were cultured by the Trowell method for 14 days. One of each pair of molars was kept as an uncultured control; the other was cultured. Explants were exposed to eight different combinations of Ca, Mg and P additions to BGJb medium. This resulted in eight groups of explants (control, Ca, Mg, P, CaMg, CaP, PMg and CaMgP) and their eight uncultured contralateral groups. The additions were calculated to double the original measured media concentration. Cultured and uncultured germs were analysed for dry weight (D), ash weight (A), Ca, Mg and P content. The organic fraction (D-A) was calculated. The analysis of covariance by means of multiple regression revealed that Ca-addition to the culture medium stimulated D, A, Ca and P in the explants; P-addition was stimulatory for D, A, D-A and P whereas Mg addition was inhibitory for A, D-A and Ca. A positive interaction for all the tooth-germ variables was demonstrated after CaMg addition; an antagonistic effect was found for the tooth-germ variables D, A, Ca and P after CaP addition. The value of the tooth-germ variables at the time of explantation (covariate) had no significant effect on the value for the variables of the explants (except on their P content). The highest absolute values for all the variables were obtained after CaMg and CaMgP additions. Furthermore, taking into consideration morphological results, the addition of CaMgP can be recommended as medium supplement in the organ culture of rat tooth germs.

Animals↗

PubMed1987

Light and transmission electron microscopy of the effects of calcium, magnesium and phosphate on dentine and enamel formed by rat molars in vitro.

The effect of addition of eight different combinations of Ca, Mg and P supplements (control, Ca, Mg, P, CaMg, CaP, PMg and CaMgP) on three-day-old rat maxillary second molars, explanted at the premineralizing stage and cultured for two weeks, was studied. Light-microscopy sections, cut parallel to the occlusal plane, were divided into four sectors and given a score according to an ordinal scale for dentine and enamel depending on the regularity of these matrices. An analysis of variance on these scores revealed a significant favourable effect of Mg, CaMg and CaMgP and an adverse effect of Ca on enamel. A favourable effect on dentine regularity was obtained after addition of Ca or Mg. Ultrastructurally, enamel changes such as amorphous enamel matrix, voids and disturbance in rod-interrod pattern were seen after addition of Ca, P, CaP. Thin enamel with less tight packing of crystals was observed after CaMg addition. A thick layer of enamel with highly-organized rod-interrod pattern was seen with Mg, PMg and CaMgP addition. It is suggested that Mg plays an important role in the interaction with Ca and P for the harmonious development of enamel and dentine in vitro.

Animals↗

PubMed1987

Immunocytochemical localization of osteocalcin in developing rat teeth.

Osteocalcin was purified by gel chromatography from a crude extract obtained after decalcification of rat incisors. The apparent molecular weight, as determined by 5-15% SDS-polyacrylamide gel electrophoresis, was 18,000, and amino acid analysis revealed 60 gamma-carboxyglutamic acid residues per 1000. Antisera against osteocalcin, raised in rabbits, reacted specifically with osteocalcin when investigated by immuno-electroblotting of dentin crude extract. 4-micron cryosections of formaldehyde-fixed tooth germs showed positive immunocytochemical staining for osteocalcin in dentin and odontoblasts. The staining of the mantle dentin at the coronal sides of the tooth germs was more intense than that of the adjacent circumpulpal dentin, while the odontoblasts involved in the formation of mantle dentin showed stronger immunoreactivity than did odontoblasts involved in circumpulpal dentin formation. This marked difference was not observed on the root sides of the tooth germs. In 1-micron cryosections, osteocalcin immunoreactivity was found evenly distributed throughout the entire cell body, with the exception of the Golgi region, which was less intensely stained, while the nucleus and the cell process were negative. The positive staining reaction with anti-osteocalcin antiserum was found in dentin from the very onset of its formation in the fetus. In conclusion, our results demonstrate the presence of osteocalcin in odontoblasts and dentin. Its immunocytochemical localization may be compatible with a distinct role in early dentinogenesis.

Animals↗

PubMed1986

An ultrastructural study of dentinogenesis and amelogenesis in rat molar tooth germs cultured in vitro.

Molar tooth germs from three-day-old rats were cultured successfully for fourteen days, permitting the study of the development in vitro of both extracellular matrix and cellular elements such as odontoblasts and ameloblasts. The ultrastructure of the cultured tooth germs was compared with the ultrastructure of tooth germs in vivo at a comparable developmental stage. Progenitor cells of odontoblasts and ameloblasts were found to differentiate in vitro. Odontoblasts seemed to contain more lysosome-like bodies and fewer secretory granules than in vivo. They formed normally mineralizing dentine or a thick layer of dense, unmineralized predentine with incidentally some amorphous, extracellular material. Enamel was exclusively present opposite well developed dentine. It was often hyper- or hypomineralized and enamel rods were not as regularly shaped as in vivo. In places where no enamel formation had taken place, large amounts of amorphous extracellular material were sometimes seen. From these observations it can be concluded that cellular development in cultured tooth germs appeared more or less normal, but extracellular matrix formation and mineralization were sometimes disturbed.

Ameloblasts↗

PubMed1986

Scanning electron microscopy of the extracellular matrices of rat molar tooth germs in organ culture in vitro.

Second upper molars from 3-day postnatal rats were cultured for 2 weeks and compared with in-vivo specimens from 7-day postnatal rats. Several preparatory techniques were applied to expose the extracellular matrices, the three-dimensional structure of which were examined by SEM. The combination of phosphate-buffered saline and ultrasonics as preparation for the observation of the enamel, hypochlorite treatment to study the predentine, the freeze-fracture technique for the dentinal tubules and oxygen-plasma-ashing for the mineralization front of dentine gave best results. Enamel formed in vitro was prismatic similar to in vivo. The fissures were devoid of enamel and the enamel-free areas at the cusp tips were larger than in vivo. In the cervical area in vitro, the enamel stopped abruptly instead of gradually decreasing. The predentine and the dentine were normal in structure.

Animals↗

PubMed1986

Characterization and immunocytochemical localization of dentine phosphoprotein in rat and bovine teeth.

Dentine phosphoprotein (DPP) was isolated from unerupted bovine molars and from rat incisors. The proteins were characterized biochemically and used to immunize rabbits and guinea pigs. Antibody activity was investigated by enzyme-linked immunosorbent assay (ELISA). Guinea-pig anti-rat DPP did not cross-react with bovine DPP, but rabbit anti-bovine DPP did cross-react with rat DPP. Anti-rat DPP antiserum was applied to cryotome sections of rat molar tooth germs and DPP immunoreactivity was seen in dentine, odontoblasts, odontoblast processes and pre-ameloblasts. Anti-bovine DPP antiserum reacted positively in bovine dentine and dentinal tubules. When this antiserum was applied to rat tissue, predentine was positive but dentine was negative. Adsorption experiments with DPP, purified by methods including and excluding precipitation with calcium, suggested that non-calcium precipitable DPP is present in rat predentine. Rat and bovine DPP are thus species-specific and DPP is synthesized by the odontoblasts, transported through their processes and secreted into the dentine.

Amino Acids↗

PubMed1986

Characteristics of mineralization of rat molar tooth germs in organ culture.

The behaviour of first (M1) and second (M2) upper molars of 3-day-old rats was compared histologically and by measuring several variables (dry and ash weight, Ca, P and Mg content) on cultured teeth and contralateral control teeth (not cultured). New information was gained by additional computations and calculating correlation coefficients between the variables of the control and cultured molars separately and combined. The M2 seems to perform better in culture than the M1. The M2 model revealed possibilities for further standardization.

Animals↗

PubMed1985

The classification of subjects with joint complaints on incomplete biochemical and haematological datasets.

We performed a retrospective study on 163 subjects suffering from rheumatic fever (16), rheumatoid arthritis (36), lupus erythematosus (17), gout (21), arthrosis (50) and osteomyelitis (23). The number of variables evaluated was 39. These were all of a general biochemical and haematological nature. A feature reduction resulted in sixteen variables that matched well with those known from the literature. Linear discriminant analysis yielded poor results in classifying the six disease categories (with 18 variables 61.8%). A reduction to three disease categories improved the classification results remarkably. This, and the excellent discriminating power between patients and the reference group, shows that the selected variables are illustrative only for general clinical pictures, such as infection, and not for the desired differential diagnosis.

Arthritis, Rheumatoid↗

PubMed1984

Use of a microcomputer for the definition of multivariate confidence regions in medical diagnosis based on clinical laboratory profiles.

The use of multivariate confidence regions is proposed for the classification of clinical laboratory profiles into diagnostic classes. For this purpose, a multivariate confidence region is developed for each diagnostic class. Three methods (UNEQ, EQ, and SIMCA) are evaluated and compared with classical linear discriminant analysis. As an example, a small data set concerning the differentiation of the thyroid functional states on the basis of five laboratory tests is used. It is shown that related procedures can produce results of very different quality and that the multivariate region approach is attractive for the clinician's daily practice since the methods are easily implemented on a microcomputer.

Computers↗