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Biomedical subjects

K W Stephen

Publications and source records attributed to K W Stephen.

At least 91 records · Page 5Linked to original sources
PubMed1984

Five-year double-blind fluoridated milk study in Scotland.

A 5-yr double-blind fluoridated milk study has been completed and, following baseline stratification, 94 children aged 4 1/2/5 1/2 yr were allocated to the test group and 93 to the control. Each subject received 200 ml school milk daily, identification between the test and control plastic packs being by colour-coding alone with the former containing 1.5 mgF- giving a potential topical benefit of approximately 7 ppmF- per school day. After 5 yr, 50 of the test children remained and 56 of the controls. While the mean DMFT incremental data relating to permanent teeth was always in favour of the test group, it was not until the fourth year that a significant difference was obtained (P less than 0.01) between the fluoridated group (mean, 1.65) and the non-fluoridated group (mean, 2.56). For permanent teeth which were unerupted at baseline, the mean DMFS differences increased to 39.6% at the same time and to 48.0% by the fifth year. No benefit was noted for previously erupted primary teeth. Cavitation was less in the test group throughout the study. When the third, fourth and fifth year DMFT reductions obtained were compared with previously published artificial water fluoridated data where children were of comparable age at the onset of water adjustment, similar caries inhibition data were noted.

Animals↗
PubMed1983

An assessment of new dental ultraviolet sources and u.v.-polymerized fissure sealants.

The performance of six dental ultraviolet (u.v.) sources was assessed to establish minimum output requirements and possible u.v. hazards. Exposure criteria for u.v.-cured materials (Nuva-seal P.A., Nuva-cote P.A., Nuva-fil P.A., Lee-seal, u.v.-Dentoseal, Uviobond, Visiobond) were assessed by determining setting time-intensity characteristics, u.v. transmission and microhardness as a function of u.v. intensity and depth. A minimum intensity of 10 mW cm-2 was required for adequate curing and both Nuva-seal P.A. and Nuva-cote P.A. set well in depth with realistic exposures. Total u.v. outputs, average intensities and spatial distributions were assessed for the u.v. sources, most of which were well above minimum requirements. Ultraviolet spectra and maximum permissible exposure measurements indicated that all of the sources were safe in normal use.

Chemical Phenomena↗
PubMed1983

Surface treatment studies aimed at streamlining fissure sealant application.

Three laboratory studies were carried out with the aim of improving or streamlining enamel surface treatment procedures in fissure sealing. In Study 1, the effect of reducing acid etch time from 60 s to 10 s was assessed by SEM and tensile bond strength measurements. Reduction in etch time produced a finer etch pattern, gave a reduced but still high, bond-strength, albeit with slightly poorer long-term adhesion. Study 2 showed that a conventional acid etch treatment could completely remove acquired pellicle, without prior prophylaxis. SEM studies and bond-strength measurements corroborated this view. In Study 3, compressed air and chemical drying agents were compared for drying speed and efficiency. Compressed air gave more rapid, thorough drying, and greater resultant bond strengths.

Acid Etching, Dental↗
PubMed1981

The effect of salivary contamination on fissure sealant--enamel bond strength.

The effect of accidental salivary contamination on the retention of fissure sealants is investigated via in vitro bond tests and scanning electron microscopy. The strength of the bond between sealant and saliva contaminated and washed enamel (168 +/- 14 kg cm-2) is not found to be significantly different from the bond strength to uncontaminated enamel (174 +/- kg cm-2). Unwashed contaminated enamel gives significantly reduced bond strength (68 +/- 11 kg cm-2).

Dental Bonding↗