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Biomedical subjects

F C Gillespie

Publications and source records attributed to F C Gillespie.

At least 37 records · Page 2Linked to original sources
PubMed1979

Theoretical of the measurement of choroidal blood flow using a radioactive inert gas clearance technique.

A mathematical model for the diffusion of krypton in ocular tissues and its removal by blood flow has been developed to explain the complex clearance pattern found experimentally in the rabbit--an animal which has predominantly a choroidal circulation. Comparison of theoretical and experimental results has shown that the initial slope of the clearance curve is a measure of choroidal blood flow for values of blood flow over 500 ml/100 g/min. The shape of the curve at later times has been shown to be attributable predominantly to the diffusion of krypton into other ocular tissues.

Animals↗
PubMed1978

Microhardness studies on the setting characteristics of fissure sealants.

The hardness of five fissure sealants was measured using a Wallace Microhardness Tester and found to continue to increase long after the initial setting. The effect of the intensity of radiation and exposure time on the setting of two u.v. activated sealants (Nuva-seal and Alphaseal) was also investigated, with higher intensities producing both a more rapid set and greater final hardness. Alphaseal required longer exposure at a given intensity of u.v. radiation to achieve the same hardness as Nuva-seal, and displayed relatively slow setting in depth, which could give rise to incomplete polymerization during clinical use, resulting in early sealant loss. Thus special care must be taken to ensure that Alphaseal receives an adequate exposure to u.v. radiation, and sources which are suitable for setting Nuva-seal may not be sufficiently powerful when applying Alphaseal.

Acrylates↗
PubMed1978

Ultra-violet absorption by two ultra-violet activated sealants.

Since the ability of u.v. setting pit and fissure sealants to set in depth is dependent on the penetration of the u.v. radiation, the absorption coefficients of Nuva-seal and Alphaseal were determined at 365 nm, the wavelength of radiation used to polymerise both materials. Nuva-seal and Alphaseal had absorption coefficients of 0.165 mm-1 and 6.25 mm-1, respectively. The u.v. fluorescent dye present in Alphaseal contributed 2.5 mm-1 to its absorption coefficient and the remaining absorption was due to the 5% w/w catalyst concentration present, since the basic resin had no significant absorption. Therefore Nuva-seal may set adequately to the depths required of fissure sealants, but Alphaseal may not, unless a very high intensity u.v. source is used. A reduction in the catalyst concentration and the removal of the u.v. fluorescent dye might improve the setting characteristics of Alphaseal.

Adsorption↗
PubMed1977

The performance of ultraviolet lights used to polymerize fissure sealants.

The performances of ultraviolet (uv) lights used to initiate polymerization in fissure sealant systems were studied with a view to establishing recommendations for improving clinical results. The relationship between the setting time of an uv polymerized sealant (Nuva-seal) and the intensity of radiation applied was first established. This was compared with the intensity and distribution of radiation from seven Nuva-lites and one Quartzlite. It was found that some of the Nuva-lites did not produce an average intensity of uv radiation sufficient to completely polymerize Nuva-seal within the manufacturer's recommended exposure times. It is suggested that this may be a factor contributing to the large variation in sealant retention found in the different clinical trials with Nuva-seal. Finally, a number of recommendations are made to ensure that sufficient uv radiation is applied to all sealant surfaces when the Nuva-seal system is used.

Dental Equipment↗