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Biomedical subjects

J Arends

Publications and source records attributed to J Arends.

At least 109 records · Page 6Linked to original sources
PubMed1991

Chlorhexidine and thymol release from a varnish system.

The release of chlorhexidine and/or thymol from an antimicrobial containing varnish in an in vitro model was investigated. Four varnishes with the same polymer base were studied; one with chlorhexidine only, one with thymol only, one with both agents and a placebo varnish without the active agents. Microscope glass slides were covered with the varnishes and stored in water. During the following three months liquid samples were regularly withdrawn and analysed for chlorhexidine and thymol content. The released amounts of chlorhexidine and/or thymol were determined by means of U.V. spectrophotometry. The results showed that chlorhexidine was released slowly from the chlorhexidine-only varnish compared with the thymol release from the thymol-only varnish. In the case of the clinically tested varnish (containing both active ingredients chlorhexidine and thymol) the amounts of thymol and chlorhexidine released were comparable. Most important, however, was the observation that in the last mentioned case both agents continued to be released after 3 months.

Chlorhexidine↗
PubMed1991

The effect of an antimicrobial releasing varnish on root demineralisation in situ. The influence of the demineralisation period.

Caries in exposed root surfaces is becoming a significant problem in dentistry. Varnish applications have interesting preventive possibilities against root caries. The effect of such a varnish, containing two antimicrobials, was studied on the demineralisation of roots with a twofold aim. Firstly, the efficacy of the varnish was investigated in situ as a function of the demineralisation period. Ten participants wore sound intact roots treated with the varnish in an intra oral appliance for 2, 4 and 6 weeks. Secondly, the effect of the varnish on root demineralisation after removal of the varnish was measured. The results showed that the reduction, in demineralization of about 80% after 2 weeks, decreased in magnitude with the length of the in situ demineralisation period. After 4 weeks there was no longer statistically significant difference compared with untreated roots. The acid attack by plaque was, however, substantial in this model; after 6 weeks in situ untreated roots were so strongly demineralised that microradiography was no longer possible anymore. In the second experiment in which the varnish was removed 2 days after application there was a trend toward a reduction of about 30% in root demineralisation after 2 weeks. This was not statistically significant when compared with no application.

Adult↗
PubMed1991

A new profilometric method for determination of enamel and dentinal abrasion in vivo using computer comparisons: a pilot study.

A technique, sensitive enough to determine both dentinal and enamel abrasion in vivo, is presented. Computer-aided profilometry was used to measure the surface of dentinal and enamel samples before the experiment. Samples were subsequently placed in the buccal flanges of the mandibular dentures of two test subjects, who then brushed these pieces with a soft, multitufted brush, and two different toothpastes. Results of these pilot studies showed that the samples brushed with Colgate BiFluor had markedly less enamel and dentinal abrasion than did those brushed with Smokers. In addition, surface roughness was greater in the specimens brushed with Smokers. However, person-to-person variation can have a great influence on the abrasion process; moreover, only two persons were involved in this pilot study, and no definitive statement can be made about the effect of the toothpastes.

Dental Enamel↗
PubMed1990

Analysis of plasma hippurate in humans using gas chromatography-mass spectrometry: concentration and incorporation of infused [15N]glycine.

To allow in vivo determination of synthetic rates for individual proteins, physiological incorporation of infused [15N]glycine into urinary hippuric acid has been used as an indicator of intrahepatic tracer dilution. Although the kidneys might contribute to hippurate production, the relationship between hepatic, plasma, and urinary hippurate has not yet been established in humans. To further investigate these issues we developed a fast, sensitive, and reliable method for measuring simultaneously hippurate concentrations and in vivo tracer incorporation into hippurate in plasma and urine using stable isotopes and gas chromatography-mass spectrometry. We then tested this assay under several experimental conditions. Reference compounds [( 15N]- and [ring-2H5]hippurate) were synthesized and gave linear standard curves. Postabsorptive hippurate plasma levels in healthy subjects ranged from 1.2 to 10.5 microM and protein binding was 79 +/- 6% (mean +/- SD). Following a bolus dose of [15N]glycine tracer appeared in plasma hippurate; enrichment in hippurate was indistinguishable from that in glycine after an equilibration period of 20 min, indicating a close relationship between intracellular glycine and plasma hippurate. A 16-h infusion of [15N]glycine resulted in identical enrichment levels in urinary and plasma hippurate; glycine enrichment in a hepatic export protein (VLDL-ApoB) was approaching plasma hippurate but not plasma free glycine enrichment. The ability to monitor plasma hippurate is of practical advantage compared to the sampling of urine. Furthermore it allows the monitoring of rapid events in the intrahepatic dilution of an infused glycine tracer. This assay may, therefore, become an important tool in the study of hepatic protein metabolism.

Administration, Oral↗
PubMed1990

Maternal serum markers in screening for Down syndrome.

The addition of two new markers in maternal serum, estriol and HCG, to those already known, namely the level of maternal serum alfa-fetoprotein and maternal age, considerably improves the expected results of a screening strategy for Down syndrome. The detection rate is slightly increased from 53.0% to 57.6%, but, more importantly, the false-positive rate decreases from 9.4% to 7.3%. It is our belief that, at least in women aged less than 35 years, a screening strategy based on a combination of maternal age and biochemical markers should be incorporated into antenatal care. For older women, the results of such a maternal serum test may refine counseling for genetic amniocentesis, as a much more explicit risk calculation can be performed than that based on age alone.

Amniocentesis↗
PubMed1990

Effect of an antimicrobial-containing varnish on root demineralisation in situ.

The effect of an antimicrobial-containing varnish on root demineralisation was investigated. The in situ demineralisation effect on the varnish, with or without the active ingredients chlorhexidine and thymol, was measured by means of microradiography in comparison with no application after a 2-week period in vivo. Furthermore, the effect of one or two applications was investigated by the 10 participants who carried sound intact roots in an appliance for four consecutive 2-week periods. In each period, different roots were mounted in the buccal flanges of a lower prosthesis, the experiment being of a randomized cross-over design. The results show that: (1) A single varnish treatment with active ingredients reduced lesion depth and mineral loss by about 77 and 82%, respectively. (2) The control varnish had no effect, and it can be concluded that antimicrobial-releasing varnishes are promising materials for root caries prevention.

Administration, Topical↗
PubMed1990

Mineral density and mineral loss after demineralization at various locations in human root dentine. A longitudinal microradiographic study.

From intact roots of human cuspids 83 dentine specimens were cut. The specimens with known location and thickness were embedded in a holder of polymethyl methacrylate and microradiographic images were made. From the longitudinal microradiography (LMR) measurements the average mineral density (kg/m3) of the sound human dentine specimens was calculated. All specimens were subsequently demineralized using a constant composition method in a solution containing 3 mM CaCl2.2H2O, 3 mM KH2PO4, 50 mM CH3COOH and 0.2 ppm fluoride as NaF at pH = 5 for 24 h. After demineralization the LMR measurements were repeated to calculate the amount of mineral lost. The data show that there is no correlation between: (1) the location of a dentine specimen in the root and the mineral density of sound human dentine, (2) the location of a dentine specimen in the root and the degree of demineralization after 24 h and (3) the mineral density of sound human dentine and the demineralization degree. This information is useful for future in vitro and in vivo studies on human roots.

Analysis of Variance↗
PubMed1990

Remineralization of human enamel in situ after 3 months: the effect of not brushing versus the effect of an F dentifrice and an F-free dentifrice.

The in situ remineralization of 100-microns-deep enamel lesions positioned in a full prosthesis just under the first molar was determined in 13 participants after 3 months. The outer surface of the samples was always flush with the acrylic surface: there was no measurable plaque accumulation on the samples. The effect of not brushing of the samples (A) is compared with the effect of brushing with a nonfluoridated dentifrice (B) or with a fluoridated paste (C) containing 1,250 ppm F. The results show that lesion depth (and mineral loss) data increase by about 50% (case A), do not change statistically in case B and decrease by about 40% in case C. The increase of lesion depth in case A is most likely due to acidic food and/or beverage intake by the participants. With respect to nonbrushing, the remineralization effect of brushing with an F-free paste is about 50% and with the fluoridated paste about 90% in 3 months. It is suggested that the remineralization efficacy of fluoridated pastes is due to the cleaning effect of the brushing by the dentifrice (presumably on the pellicle) as well as due to the fluoride effect on mineral nucleation and growth.

Adult↗
PubMed1990

Remineralization of human dentine in vitro.

In this paper the in vitro remineralization of human dentine with 0, 0.5, 2 and 10 ppm F in the remineralization solution is presented and analyzed by microradiography. Furthermore, the remineralization data of human and bovine dentine are quantitatively compared. The main results of this paper are: (1) the efficacy of human (and bovine) remineralization is about proportional to the square root of the F level in the remineralizing solution, and (2) the amount of mineral effectively deposited in the dentine is most likely controlled by the diffusion of fluoride into the tissue. This study shows furthermore that although numerical differences exist in the remineralization of human and bovine dentine, the general remineralization behaviour is quite similar. The presence of F- in the parts per million range is essential for the remineralization efficacy in vitro and also for the 'overremineralization' of the outer dentine surface.

Adolescent↗
PubMed1990

CA 125, placental alkaline phosphatase, and tissue polypeptide antigen in the monitoring of ovarian carcinoma. A comparative study of three different tumor markers.

Three different tumor markers, placental alkaline phosphatase (PLAP), tissue polypeptide antigen (TPA), and cancer antigen 125 (CA 125), were measured in serum samples obtained during chemotherapy in 57 ovarian carcinoma patients. At the start of chemotherapy, 37, 63, and 77% had elevated serum values of PLAP, TPA, and CA 125, respectively. During chemotherapy, changing PLAP serum levels reflected disease regression and, later, progression in only 2 patients. TPA serum levels reflected the disease course in 15 patients and CA 125 in 28 patients. Rising CA 125 values predicted disease progression in 12 patients for a median of 2 months. At second-look laparotomy, all 11 patients with pathological complete response were marker negative. In the remaining 46 patients with residual or progressive disease, 27, 50, and 61% had elevated serum levels of PLAP, TPA, and CA 125, respectively. None of the markers reflected microscopic disease or pure carcinomatosis. For management decisions, CA 125 was clearly the most useful of the markers. In this study no further information was gained from the other two markers.

Alkaline Phosphatase↗
PubMed1990

Relative cariostatic effects of KOH-soluble and KOH-insoluble fluoride in situ.

The relative cariostatic effects of fluoride as fluorapatite, CaF2, loosely-bound fluoride, or KOH-soluble fluoride are debated. The present study was carried out to investigate this further in an intra-oral caries model. Pairs of premolars extracted for orthodontic reasons were used. Enamel from one tooth of each pair was used as control (untreated). Two slabs were cut from the enamel of the other contralateral premolar. These slabs were treated with 2% NaF for 24 h. One slab was then treated with 1 mol/L KOH twice for 24 h for removal of all loosely-bound fluoride. The slabs treated with 2% NaF and then with 1 mol/L KOH would contain the KOH-insoluble fluoride. Those treated with only 2% NaF would, in addition, contain KOH-soluble fluoride. Each slab, control, KOH-insoluble F, and KOH-soluble and insoluble F was mounted on different upper removable appliances. The slabs were covered with orthodontic banding material, thus allowing space for plaque accumulation. Five individuals wore the appliance in three separate four-week periods. The slabs were analyzed by quantitative microradiography. The average mineral loss (delta Z) was 1680 +/- 1000 vol% x microns in the control teeth, 620 +/- 76 vol% x microns in the KOH-soluble and -insoluble F teeth, and 2167 +/- 1278 vol% x microns in the KOH-insoluble F teeth. The average lesion depths were 90 +/- 41 microns in the control teeth, 35.3 +/- 5.5 microns in the KOH-soluble F teeth, and 88 +/- 35 microns in the KOH-insoluble F teeth. It was concluded that only KOH-soluble fluoride reduced mineral loss and lesion depths significantly, compared with the untreated teeth.

Calcium Fluoride↗
PubMed1990

Nature and role of loosely bound fluoride in dental caries.

This paper discusses loosely bound fluoride and its role in dental caries and prevention. Loosely bound fluoride (abbr. by Fa) is fluoride adsorbed onto enamel mineral crystallites. Several recent studies indicate that a high total level of fluoride in enamel does not guarantee protection against caries. This leads to the conclusion that a major part of fluoride present in the solid enamel is not active in prevention. The adsorption of Fa to the mineral under acidic conditions is described. Most likely there is a dynamic equilibrium between fluoride in solution and adsorbed Fa at the crystal surface interface. When the crystallite is completely covered by adsorbed Fa, there is a maximum inhibition of dissolution. The rate of dissolution of mineral depends on pH, the actual concentrations of calcium and phosphate in the liquid in contact with the crystallites, and on the fraction of the surface covered by adsorbed fluoride. The fluoride, Fs, localized in the inner part of the crystallites is relatively unimportant. "CaF2-like" material can be formed on and in enamel depending on conditions. The in vivo-formed globular "CaF2-like" material is not pure CaF2 and releases F- ions when dissolving; these ions will also be partly adsorbed as Fa in and on enamel. Presently, the amount and importance of Fa originating from in vivo-formed "CaF2-like" material are not known. The level of fluoride, Fa, necessary for strong inhibition of enamel demineralization in vitro is estimated to correspond to a fluoride concentration, FL, in the liquid phase of 1 ppm or 50 mumol/L fluoride ions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMed1990

Fluoride uptake in bovine enamel and dentin from a fluoride-releasing composite resin.

To determine the fluoride uptake in enamel and dentin, a fluoridating composite resin was fixed at a 100-microns distance from bovine enamel and dentin for 2 weeks. The results revealed a substantial increase in the level of fluoride in both enamel and dentin. This model investigation showed that the fluoride released by the composite resin was effectively taken up by the surrounding tissues. The fluoride released from the composite resin and the subsequent uptake by the tissues would be expected to protect against secondary caries.

Animals↗
PubMed1990

Effect of fluoride release from a fluoride-containing composite resin on secondary caries: an in vitro study.

The effect of fluoride, released from a fluoride-containing composite resin, on secondary caries was investigated by quantitative microradiography. In all teeth investigated, less demineralization was found near the composite resin than was found at a distance of a few millimeters from the material after an acid attack. The presence of the fluoride-releasing composite resin reduced the lesion depth measured after an acid attack by about 35%. Therefore, in vivo, a reduction of recurrent caries may be expected around fluoride-containing composite resins.

Adult↗