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Biomedical subjects

S D Meryon

Publications and source records attributed to S D Meryon.

At least 19 recordsLinked to original sources
PubMed1990

Penetration of dentine by three oral bacteria in vitro and their associated cytotoxicity.

Three common oral bacteria, namely Streptococcus sanguis, Actinomyces viscosus and Corynebacterium spp. were studied with regard to their ability to penetrate etched and unetched dentine and for their effect on underlying cell cultures. The test organisms were grown in cylinders above dentine slices 100 and 500 microns thick for 72 hours. The slices were in contact with tissue culture medium covering a layer of fibroblasts. Penetration of 100 microns slices was most rapid with S. sanguis, followed by A. viscosus and Corynebacterium. The pattern was similar but slightly delayed when 500 microns slices were used, but in most cases penetration had occurred by 72 hours. The presence of a smear layer had no effect on the results obtained. Following penetration, cell destruction was most extensive with S. sanguis, the most cytotoxic organism, followed by Corynebacterium and A. viscosus. In the limited number of dishes where no penetration occurred there was little effect on cell numbers.

Acid Etching, Dental↗
PubMed1990

In vitro comparison of the cytotoxicity of twelve endodontic materials using a new technique.

An in vitro method for the cytotoxicity testing of endodontic materials is described which aims to simulate the clinical situation. Materials can be tested in the presence or absence of a compacted layer of dentine chips mimicking the periapical dentine plug. A total of twelve materials were tested. In the absence of dentine, Kloroperka, Biocalex, Diaket and Endomethasone were slightly cytotoxic; AH26 with and without silver, Sealapex, Tubliseal and Kerr's pulp canal sealer were moderately cytotoxic, while Forfenan, Spad and Kri paste were strongly cytotoxic. In the presence of dentine the cytotoxicity of these materials was considerably reduced, with the exception of Endomethasone, Forfenan, Spad and Kri paste. The method provides a satisfactory alternative to implantation testing and is an inexpensive and reproducible test system in which dentine can be incorporated.

Administration, Topical↗
PubMed1990

Stimulation of the growth of Streptococcus sanguis (NCTC 7864) by zinc in vitro.

Zinc, which is present in many materials used in dentistry, including restorative and endodontic materials and mouthwashes, is reputedly bactericidal. However, the addition of this element at concentrations in the range 10-50 ppm to cultures of Streptococcus sanguis (NCTC 7864) stimulated the growth of the micro-organism relative to that of controls. A second antibacterial element, namely fluoride, reduced growth. Similar results were obtained whether the organism was grown aerobically or anaerobically. In view of the susceptibility of some organisms to zinc, the results of this study may help to explain conflicting reports in the literature; the results will vary depending on which organism is predominant.

Streptococcus mutans↗
PubMed1989

In vitro cytotoxicity of three dentine bonding agents.

While several studies have been reported on the physical testing of dentine bonding agents, very few studies have been involved with their biological evaluation. This report describes a new in vitro method for assessing the cytotoxicity of these materials through dentine simulating their clinical use. An experimental bonding agent, now marketed as Tripton by ICI Dental, Scotchbond 2 and GLUMA were exposed to BHK-fibroblasts through 100 and 500 microns slices. All materials were significantly cytotoxic compared with controls through both thicknesses of slice. The ICI Dental experimental material was the least toxic through 100 microns slices (68.8 per cent of controls) followed by Scotchbond 2 (54.2 per cent) with GLUMA the most cytotoxic (26.9 per cent). However, with 500 microns slices values for the ICI Dental experimental material and GLUMA were similar (70.8 and 66.6 per cent respectively), with Scotchbond 2 exhibiting greatest toxicity (52.6 per cent). The results indicate that these materials are considerably more cytotoxic than most restorative materials which have been tested using a similar system. It is anticipated that all materials, in particular Scotchbond 2, could cause severe reactions in deep cavities in vivo in the absence of an adequate lining.

Aldehydes↗
PubMed1989

The antibacterial properties of four elements released from dental restorative materials.

The antibacterial activity of four elements (zinc, copper, fluoride and mercury), previously reported to be released from dental restorative materials, was investigated. This was carried out using two aerobic micro-organisms isolated from dentine beneath cavities in the ferret. These were grown in the presence of the test elements over a concentration range of 10-100 micrograms/ml for 72 hours. Concentration and exposure time were found to have a highly significant effect on the growth and viability of both micro-organism. Zinc, mercury and copper exerted the greatest effect, fluoride the least.

Actinomyces↗
PubMed1989

The modified model cavity method for assessing antibacterial properties of dental restorative materials.

A new in vitro method for assessing the antibacterial properties of dental restorative materials is described with ratios of test material/culture medium volume aiming to simulate conditions around a restoration in vivo. Antibacterial activity is determined by the reduction in optical density of the test culture relative to controls. The method was used for assessment of the antibacterial activity of five dental materials of different composition against five oral bacteria. Release of zinc and fluoride from these materials was also measured and correlated with antibacterial activity. There was a general trend toward greater antibacterial activity with increased zinc release, while fluoride release had a significant effect on only one organism. While all the materials, when freshly mixed, were strongly toxic to three out of the five bacteria studied, much of this activity was lost after the materials had set.

Anti-Infective Agents, Local↗
PubMed1987

Uptake of zinc and fluoride by several dentin components.

The uptake of zinc released from ZOE and Dispersalloy, and fluoride from ChemFil by different components of dentin was studied in vitro. These materials were placed over a 500-micron layer of the dentin fraction in a simulated cavity, and the zinc and fluoride levels in the fraction and underlying solution determined after 7 days. Parallel studies were also carried out in which these components, alone in simulated cavities, were placed over solutions containing different concentrations of zinc and fluoride and the uptake determined after 24 h. Zinc uptake was considerably greater by the inorganic than the organic fractions used in this study. Uptake from ZOE was disproportionately higher than from Dispersalloy presumably reflecting the fact that the zinc in ZOE is more loosely bound. In addition the high zinc levels in collagen beneath this material may be attributed to the binding of the eugenol component. In contrast fluoride uptake was generally highest by the organic fractions with relatively low uptake by the inorganic fractions which is in contrast to previous studies. Uptake of zinc and fluoride from solution by these fractions was consistent with these findings. Thus zinc is more strongly bound by the inorganic and fluoride by the organic fractions of dentin.

Biological Transport↗
PubMed1987

The influence of surface area on the in vitro cytotoxicity of a range of dental materials.

In the toxicity testing of dental materials the quantity of material used may have a profound influence on the biological response obtained. This was investigated in vitro by assessing the cytotoxicity of equal volumes of nine materials in artificial cavities of three different diameters, chosen to cover the range found in vivo. With seven materials there was a significant increase in toxicity with increasing surface area. The pattern of response of different materials within specific groups was fairly uniform. The degree of toxicity of the test materials relative to controls was also investigated. From the data obtained it is apparent that the maximum cavity diameter appropriate for the material under test must be considered when evaluating the toxicity of dental materials.

Animals↗
PubMed1986

Zinc release from dental restorative materials in vitro.

Zinc release from a range of dental restorative materials was measured in the absence and presence of dentin over a 2-week period. The presence of dentin was designed to simulate the residual dentin in vivo. There were considerable differences in both the levels and pattern of zinc release for the different materials. In several cases the concentrations exceeded the level which has been reported cytotoxic to cells in culture. With dentin, little zinc passed into solution, and high concentrations were measured in the dentin. This may explain the discrepancy between in vivo toxicity tests using zinc-containing materials and previous in vitro tests which have not included dentin in the test system.

Dental Caries↗
PubMed1986

An in vitro study of the role of dentine in moderating the cytotoxicity of zinc oxide eugenol cement.

The protective role of different dentine fractions and of dentine slices in moderating the cytotoxicity of zinc oxide eugenol (ZOE) was investigated. The collagen fraction of dentine powder provided increased protection over intact powder. Slices of dentine offered greater protection probably by providing a physical barrier to the diffusion of eugenol which may also bind to the contents of the dentine tubules. With increasing thickness of the dentine slices this protection was increased. ZOE stimulated calcium release from dentine but in view of the low levels attained it is unlikely that this process has any significant effect on the protective role of dentine.

Animals↗