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Biomedical subjects

J Arends

Publications and source records attributed to J Arends.

At least 145 records · Page 8Linked to original sources
PubMed1988

Microradiographic study of demineralization of shark enamel in a human caries model.

The aim of the present study was to compare the resistance of fluoroapatite (shark enamel) and hydroxyapatite (human enamel) against a high caries challenge in a human in vivo model. Two samples of shark enamel and human enamel were each placed in removable appliances in six children and carried for 1 month and a plaque retentive device was placed over each enamel sample. The results showed that the mean total mineral loss (delta Z) was 1680 vol% micron in human enamel and 965 vol% micron in shark enamel. The corresponding mean values for lesion depth were 90 micron and 36 micron, respectively. It is concluded that even shark enamel containing 30,000 ppm F has a limited resistance against caries attacks.

Adolescent↗
PubMed1988

Influence of extraoral xylitol and sucrose dippings on enamel demineralization in vivo.

This paper describes the effect of xylitol on demineralized enamel in plaque-free and plaque-covered conditions in vivo. Fissure-like plaque retention grooves were created in 66 human enamel blocks and demineralized in vitro. The blocks were mounted in a prosthesis of 11 participants, who used a 2.5% xylitol, a 2.5% sucrose solution or water extraorally in a randomized cross-over design, for three periods of 16 days. The participants submerged the prosthesis twice a day in the solution during 5 min. Mineral loss and lesion depth were measured before and after the in vivo experiment, using quantitative microradiography and polarized light microscopy. Lesion depth at the surface enamel was +/- 45 microns, at the wall of the grooves +/- 30 microns and at the bottom of the grooves +/- 50 microns before the experiment. After 16 days the lesion depth at the wall of the grooves was +/- 40 microns and at the bottom of the grooves +/- 75 microns. In the grooves no differences were found between the xylitol, the sucrose and the water treatment. At the surface enamel a significant reduction of enamel demineralization was found after the xylitol dippings. The lesion depth at the surface enamel increased 17 microns after the sucrose treatment and 7 microns after the xylitol treatment. The mineral loss after the sucrose and the water treatment were both approximately three times higher than the mineral loss after the xylitol treatment.

Adult↗
PubMed1988

In vivo progress of enamel and root surface lesions under plaque as a function of time.

This paper deals with enamel and root surface demineralization under plaque in vivo as a function of time. The enamel was demineralized using the Ogaard method in which preformed orthodontic bands are attached to the premolars in situ for 4, 6, and 8 weeks; a niche in the bands is responsible for plaque accumulation. In a second experiment cement-covered root surfaces (and enamel) were mounted on a removable appliance (Hawley retainer). Also in this case an orthodontic band was placed over the samples to create a space for plaque accumulation of about 0.8 mm between sample and band. All samples were analyzed by means of microradiography. The results show that (1) demineralization of enamel with the Ogaard method and using the Hawley retainer gives values for lesion depth and mineral loss that are statistically not significantly different; (2) lesion progress and mineral loss in vivo is about 2.5 times faster in roots than in enamel; (3) the demineralization in enamel is roughly linear with time, and (4) roots demineralize in vivo very fast during the 1st week and much more slowly there after.

Dental Caries↗
PubMed1988

An in vivo study of microhardness and fluoride uptake in partially demineralized human enamel covered by plaque.

In this investigation, microhardness changes in partially demineralized human enamel were studied after in vivo use of fluoridated toothpaste systems. Flattened enamel specimens were demineralized in vitro and subsequently positioned in approximal positions in the prostheses of 27 participants for three weeks; the samples were plaque-covered in vivo. After brushing for one week with a non-fluoridated paste to achieve an in vivo equilibrium, participants brushed with an assigned product for a two-week period. This test was a six-way cross-over design which used randomization of subjects. Five fluoridated and one non-fluoridated paste were tested. Knoop hardness measurements were carried out on sound and on in vitro demineralized enamel, and after in vivo exposure of the enamel to the dentifrice treatments. The results showed that during the two weeks of in vivo exposure to the fluoride products, net rehardening of the demineralized enamel did not occur, and no correlation was observed between fluoride uptake into the demineralized enamel and changes in microhardness. That we failed to observe rehardening may be due to the fact that the duration of this study was too short for any net remineralization to have occurred, especially because the samples were constantly covered with plaque. Other possibilities, such as the type and/or severity of the lesions used in this study, may account for the lack of rehardening.

Analysis of Variance↗
PubMed1988

Cholinergic muscarinic receptor blockade suppresses arginine- and exercise-induced growth hormone secretion in type I diabetic subjects.

Stimulatory cholinergic pathways participate in the regulation of GH release, and cholinergic receptor antagonists inhibit GH secretion in normal man. Whether similar mechanisms are active in subjects with insulin-dependent diabetes is not known, yet this is of potential importance since GH hypersecretion has been implicated in both the acute and chronic complications of diabetes mellitus. To address this question we studied the effects of cholinergic receptor blockade on stimulated GH release in 18 type I diabetic men. Paired tests were performed using 1 of 2 different stimuli (30 g arginine, iv, or physical exercise for 30 min) with or without prior administration of the selective cholinergic muscarinic receptor antagonist pirenzepine (30 mg, iv). Arginine elicited a mean peak serum GH level of 9.0 +/- 1.9 (+/- SEM) micrograms/L, which was completely suppressed by pirenzepine (1.5 +/- 0.4 micrograms/L; n = 8; P less than 0.01). Blood glucose rose after arginine infusion and was not affected by pirenzepine. Serum GH levels rose during physical exercise to a mean peak of 7.3 +/- 1.6 micrograms/L, which was abolished by pirenzepine (1.2 +/- 0.3 micrograms/L; n = 10; P less than 0.01). Blood glucose was not influenced by pirenzepine. Two subjects had no serum GH response to exercise. We conclude that GH secretion in subjects with insulin-dependent diabetes, as in normal subjects, is modulated by cholinergic pathways and is responsive to pharmacological suppression by muscarinic receptor blockade. This may have implications for therapeutic trials designed to lower elevated GH levels in subjects with diabetes mellitus.

Adult↗
PubMed1988

'Calcium fluoride-like' material formed in partially demineralized human enamel in vivo owing to the action of fluoridated toothpastes.

In this paper are presented the results of a chemical analysis of partially demineralized enamel lesions positioned under plaque in vivo for 3 weeks. During the experimental period the samples were brushed with fluoridated or non-fluoridated toothpaste systems. After the experiment the fluoride and protein uptake was determined. Furthermore, KOH extractions of the lesions were carried out and the solutions analyzed for calcium, fluoride, and phosphate. The results show that 'CaF2-like' material is most likely formed inside lesions during the in vivo period. This in indicated from chemical analysis, Raman spectroscopy, and SEM observations. The amount of CaF2-like material is on the order of 0.1 wt% if we consider its formation all over the enamel lesions, or 1 wt% if we assume its formation in interprismatic regions of the enamel only. About 40% of the fluoride taken up from toothpaste systems is in the form of CaF2-like material. In vivo there is a substantial influx of proteins (approximately 0.3%) and also a very large influx of phosphate ions. The effect of CaF2-like material is most likely strongly dependent on conditions in the lesion, such as pH change.

Calcium↗
PubMed1988

The role of 'CaF2-like' material in topical fluoridation of enamel in situ.

In this paper the role and importance of 'CaF2-like' material deposited on enamel (Fon) by means of an APF gel and the varnishes Duraphat and Fluor Protector are described and discussed. The amount of Fon, determined by KOH extraction, is a measure of the amount of CaF2-like material on the enamel surface. Fluoride in the enamel (Fin), determined by etching, is the amount of F- bound in the solid enamel. Fon and Fin data are presented after various F- treatments and after wearing enamel slabs in dentures for a period of 1 week. The results of this work show that if we compare the three fluoridating agents, APF gel, Duraphat varnish, and Fluor Protector varnish in situ, only Fluor Protector shows a measurable amount of Fon after 1 week. The amounts of Fon acquired by the enamel surface (one application) rank as APF gel approximately Duraphat much less than Fluor Protector. Most likely, Fon in situ leaches away through the pellicle, with an apparent diffusion coefficient of about 10(-6) cm2.sec-1. The Fin data show that after APF gel or Duraphat treatment a substantial amount of Fin leaches away during 1 week in situ; the Fin values of Fluor Protector do not change. The efficiency of the fluoridating agents is most likely determined by the application period and fluoride availability. For APF gel, Duraphat, and Fluor Protector about 5%, 1%, and 44% of the available fluoride participates in the fluoridation process. CaF2-like globules are known to precipitate after gel or varnish treatment on the enamel surfaces and can be dissolved in KOH solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Etching, Dental↗
PubMed1988

Simultaneous quantification by double rocket immunoelectrophoresis of apolipoproteins A-I and B in blood spotted on filter paper.

We describe double rocket immunoelectrophoresis for simultaneous quantification of apolipoprotein A-I (apo A-I) and B (apo B) in blood on filter paper. The apolipoproteins from blood spots on filter paper were eluted with detergents (sodium dodecyl sulfate and Triton X-100). The eluates were subjected to electrophoresis on agarose gel containing antisera against both apolipoproteins. Within- and between-assay CVs for apo B/A-I ratios were less than 5.5% and 7.2%, respectively. The apo B/A-I ratio was influenced by length and temperature of storage. In results for 121 venous blood samples, the apo B/A-I ratios in dried blood spots correlated well with those in serum (r = 0.92) and correlated somewhat with the ratios for low-density lipoprotein/high-density lipoprotein cholesterol in serum (r = 0.87). Of these specimens, 68 were from patients with known familial hypercholesterolemia, all of whom had an apo B/A-I ratio greater than 0.90. We think this method will be of value for detecting familial hypercholesterolemia and possibly familial hyperapobeta- and hypoalphalipoproteinemia.

Adolescent↗
PubMed1988

Fluoride uptake and inhibition of intra-oral demineralization, following the application of varnishes with different concentrations of fluoride.

The relationship between the amount of fluoride acquired by human enamel after varnish application and the resulting inhibition demineralization of is presented and discussed. Intact human enamel was pretreated with Fluor Protector varnishes with differing fluoride contents (0.7; 0.1; 0.05 and 0 wt% F-) for 24 hours. In a first experiment the amount of fluoride acquired after application was determined. In a second experiment the pretreated enamel was stored intra-orally under constant plaque coverage, in order to create a substantial demineralization challenge. The protection against demineralization, induced by the various varnishes was determined four months after varnish application using microradiography. Under the cariogenic conditions created in this study, the fluoride containing varnishes induced a protection of 53-75%. Although the amount of fluoride uptake was strongly related to the fluoride content in the varnishes, no statistically significant difference in demineralization inhibition between the varnishes was observed. SEM investigation of the enamel lesions revealed globular precipitates inside the fluoridated enamel, presumably consisting of calcium fluoride-like material. The present study indicates that the fluoride content in Fluor Protector varnishes can be decreased without reducing its ability to inhibit demineralization.

Dental Caries↗
PubMed1988

The effect of fluoride containing toothpastes on sound human enamel in vivo during 3 weeks.

The F- uptake in vivo in sound human enamel from fluoridated toothpastes is described. Ten participants brushed for about 1 min twice a day, four enamel specimens in a dental appliance over three week periods. The enamel specimens were prepared so that only the right hand side of the enamel was positioned in the appliance; the left hand side being used as a control. The toothpastes all used hydrate silica as the abrasive and contained either 0.1 ppm F- as nicomethanolhydrofluoride, 1100 ppm F- as NaF or 1350 ppm F- as NaF/MFP. After three weeks brushing with the pastes in vivo the F- contents of three thin layers of enamel were determined in all specimens by means of acid etching. The results showed that 1) there were no statistically significant differences between the mean F- contents of the enamel (p less than 0.05), which were comparable, before and after three weeks brushing in vivo. This observation was independent of the toothpaste employed, 2) in the outer approximately 1.5 micron layer of human enamel there was an equilibrium F- level of about 1200 ppm. The microhardness data on polished enamel specimens showed that there was no statistically significant difference between the mean indentation lengths produced in control specimens and these made in specimens after the use of a placebo toothpaste (0.1 ppm F-) in vivo indentation lengths of all specimens brushed with any of the fluoridated toothpastes for three weeks showed, however, a statistically significant decrease of indentation length and thus an increased hardness.

Acid Etching, Dental↗
PubMed1987

Physical factors influencing the blood glucose response to different breads in type II diabetic patients.

Blood glucose responses to test meals containing 75 g of different breads were compared in 103 type II diabetic patients under sulfonyl urea treatment. Nine breads differing in type of cereal, physical structure, and dietary fiber content were studied using pairwise intraindividual comparisons. It could be shown that the type of cereal and the fiber content had no significant influence upon the maximal or mean postprandial blood glucose increase. Coarse-grained breads, however, resulted in significantly lower blood glucose responses than breads that were finer grained or were produced from flour. Physical properties determining the access of intestinal hydrolytic enzymes to ingested carbohydrates seem to be major factors that influence postprandial blood glucose responses.

Adult↗
PubMed1987

Biochemical and scanning electron microscope study of lipids chloroform-methanol extracted from unerupted and erupted human tooth enamel.

Almost twice as much fatty acid was extracted without demineralization from the mature enamel of erupted teeth treated with 2:1 chloroform-methanol as from the enamel of unerupted teeth (32.64 micrograms/g versus 15.60 micrograms/g). Palmitic C16:0, stearic C18:0, oleic C18:1 omega 9 and linoleic acids C18:2 omega 6 were the chief fatty acids detected by gas-liquid chromatography. The percentage of free fatty acids and diglycerides was larger in unerupted than erupted teeth, whereas that of triglycerides, phosphatidylethanolamine and phosphatidylcholine was larger in erupted teeth. These changes may be due to bacteria and other contaminants (saliva and pellicle). The large amounts of free fatty acids, diglycerides, cholesterol and phospholipids as intrinsic components were probably due to the persistence of membrane remnants entombed during enamel formation, as indicated by the visualization of holes and by the increase in the size and number of focal holes after lipid-solvent interaction with the enamel surface. These defects always occurred in rods and never in inter-rod material. Other minute defects, including empty-widened intercrystal spaces, were also observed inside some rods.

Adolescent↗
PubMed1987

Protein and mineral changes in bovine enamel during in-vitro demineralization.

Mineral distributions with and without a softened surface layer were studied. The molar Ca:P ratio of released material was due to preferential Ca-loss significantly higher from surface-softened enamel than from lesions. The molecular weight (less than 1800) distributions of released proteinaceous matter were similar. The protein release during surface softening contained more large peptides, whereas its amino-acid composition was more acidic amino acids compared with lesion formation. The protein content of released material during demineralization, acetic acid-soluble protein (at pH 4.5) and total protein of sound enamel showed that (i) enamel proteins were partially soluble in an acetic acid-buffer under mild acidic conditions and (ii) enamel proteins soluble in acetic acid-solution were partially released during demineralization. It is postulated that during enamel demineralization the dissolution of acid-soluble proteinaceous matter and its partial adsorption on newly-created sites of partially-dissolved crystals may explain the partial release of acid-soluble proteins. In case of lesion formation on the other hand new adsorption sites on new crystal surfaces formed in the surface layer are formed as well, which may account for the differences in mol.wt distribution and amino-acid composition.

Amino Acids↗
PubMed1987

In vivo quantification of cell-polymer interactions.

An in vivo rat model was developed to determine cell-polymer interactions under physiological conditions. Microporous tubular grafts, made of polytetrafluoroethylene, a polyetherurethane, a polyesterurethane and also a modified polyetherurethane were implanted intraperitoneally in rats. The grafts were filled with cultured rat smooth muscle cells prior to implantation. At t = 0, 2 and 48 h, the grafts were evaluated macroscopically and also prepared for light microscopy and for cell count of their contents. At t = 0 no cellular attachment was observed on the lumenal side of the capsules. At t = 2 h a monolayer of smooth muscle cells could be observed on all materials except PTFE, on which only small patches of cells were observed. At t = 48 h a multilayer of cells was seen on all materials except PTFE. Cell counts at 48 h demonstrated no multiplication in the PTFE graft but a 1.4, 2.3 and 2.0-fold multiplication in the polyetherurethane, polyesterurethane and the modified polyurethane grafts respectively. These in vivo results show a clear linear relationship with our in vitro results in which it has been proved that cell spreading increased with increasing substratum surface free energy. This rat model allows the study of cell-polymer interactions in vivo, in a standardized way, under controlled physiological conditions.

Animals↗