Search PubMed⌕ Search

PubMed · 9699446

A polyvinylsiloxane denture soft lining material.

Abstract

A new denture soft lining material based on a polyvinylsiloxane system, similar to that used in addition-curing silicone impression materials, has recently been developed. The purpose of the work reported here was to compare certain key properties of the new material with those of other commercially available materials. Setting characteristics, resistance to penetration, elastic properties, water absorption, peel strength and contact angle with water were determined for five materials including the new product. In addition, the change in properties following water storage were determined. In many respects the properties of the new material were noted to be similar to those of a heat-cured silicone product. It is initially elastic and of "medium" softness as defined by ISO 10139-2. It was the only product which did not lose weight on storage in water and over 90 days of storage it gave only a small change in compliance as measured by surface penetration. Bond strength of the new material to an acrylic denture base appears only moderate. However, failure was cohesive within the soft material with no peeling, suggesting that peeling is unlikely to occur in practice. The affinity between the surface of the material and water, as determined by contact angle, is significantly better than for other silicone products. The properties of the polyvinylsiloxane denture soft lining material are in many respects similar to those of other silicone soft lining materials. However, the efficacy of the adhesive which prevents peeling combined with a convenient packaging, proportioning and mixing system suggests that the material may offer some advantages which warrant its clinical evaluation.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J F McCabe. A polyvinylsiloxane denture soft lining material.. https://doi.org/10.1016/s0300-5712(98)00022-0

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Adsorption, absorption, and biological degradation of ammonia in different biofilter organic media.

A tailor-made apparatus called ammoniometer, which is a batch mode respirometer applied to the study of ammonia biodegradation in biofilter media, has been used to evaluate adsorption, absorption, and biodegradation in five different organic materials (compost, coconut fibre, bark, pruning wastes, and peat) obtained from full-scale biofilters in operation in several waste treatment plants. The results showed that absorption could be represented by a Henry's law linear equation, with values of the Henry coefficient significantly higher (from 1,866 to 15,320) than that of pure water (1,498). Adsorption data were successfully fitted to Langmuir and Freundlich isotherms and maximum adsorption capacity varies from 1.06 to 1.81 mg NH(3)/g dry media. Ammonia biodegradation rates for each organic material were also calculated. Biodegradation rates varied from 0.67 to 7.82 mg NH(3)/kg media/d depending on the material tested. The data obtained showed important differences in the behaviour of the biofilter organic media, which has important implications in the design and modelling of these systems.

Absorption↗

The use of an oil absorber as a strategy to overcome starvation periods in degrading 1,2-dichloroethane in waste gas.

This work investigates the use of an oil absorber as an operational strategy in vapor phase bioreactors exposed to starvation periods, during the treatment of inhibitory pollutants. After being exposed to 1,2-dichloroethane (DCE) starvation periods, the response and stability of a combined oil-absorber-bioscrubber (OAB) system was compared to that of a bioscrubber only (BO) system. In the BO system, after a 5.2 days starvation period, the DCE removal efficiency was reduced to 12%, and 6 days were needed to recover the initial removal efficiency when the DCE feed resumed. The total organic discharged (TOD(DCE)) was 16,500 g(DCE) m(bioscrubber) (-3) after the DCE starvation. Biomass analysis performed using fluorescence in situ hybridisation (FISH) showed that the microbial activity was significantly reduced during the starvation period and that 5 days were needed to recover the initial activity, after the re-introduction of DCE. In contrast, the performance of the OAB system was stable during 5.2 days of DCE starvation. The DCE removal efficiency was not affected when the DCE feed resumed and the TOD(DCE) was significantly reduced to 2,850 g(DCE) m(bioscrubber) (-3). During starvation, the activity of the microbial culture in the OAB system showed a substantially lower decrease than in the BO system and recovered almost immediately the initial activity after the re-introduction of DCE. Additionally, a mathematical model describing the performance of the OAB system was developed. The results of this study show that the OAB system can effectively sustain the biological treatment of waste gas during starvation periods of inhibitory pollutants.

Absorption↗

Pterin pigment granules are responsible for both broadband light scattering and wavelength selective absorption in the wing scales of pierid butterflies.

A small but growing literature indicates that many animal colours are produced by combinations of structural and pigmentary mechanisms. We investigated one such complex colour phenotype: the highly chromatic wing colours of pierid butterflies including oranges, yellows and patterns which appear white to the human eye, but strongly absorb the ultraviolet (UV) wavelengths visible to butterflies. Pierids produce these bright colours using wing scales that contain collections of minute granules. However, to date, no work has directly characterized the molecular composition or optical properties of these granules. We present results that indicate these granules contain pterin pigments. We also find that pterin granules increase light reflection from single wing scales, such that wing scales containing denser granule arrays reflect more light than those with less dense granule collections. As male wing scales contain more pterin granules than those of females, the sexual dichromatism found in many pierid species can be explained by differences in wing scale pterin deposition. Additionally, the colour pattern elements produced by these pterins are known to be important during mating interactions in a number of pierid species. Therefore, we discuss the potential relevance of our results within the framework of sexual selection and colour signal evolution.

Absorption↗