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Biomedical subjects

M Tyas

Publications and source records attributed to M Tyas.

7 recordsLinked to original sources
PubMed2004

Influence of food-simulating solutions and surface finish on susceptibility to staining of aesthetic restorative materials.

OBJECTIVES: To determine the degree of surface staining of resin-based composites (RBCs) and glass-ionomer cements (GICs) after immersion in various stains and food-simulating solutions (FSS). METHODS: Six tooth-coloured restorative materials were used: a light-cured microfilled RBC (Durafil, Kulzer), a light-cured microglass RBC (Charisma, Kulzer), a polyacid-modified RBC (F2000, 3M/ESPE), a conventional GIC (Fuji IX, GC) and two resin-modified GICs (Fuji II LC, GC; Photac Fil, 3M/ESPE). Disk-shaped specimens were prepared and tested with either a matrix finish or polished using wet silicon carbide papers up to 2000 grit. All specimens were immersed in 37 degrees C distilled water for 1 week, followed by three different FSS (water, 10% ethanol, Crodamol GTCC) and five stains (red wine, coffee, tea, soy sauce and cola) for a further 2 weeks. Three specimens of each material for each stain were tested. Colour coefficients (CIE L* a* b*) were measured by a spectrophotometer after each treatment. The change in colour (DeltaEn) was calculated using the formula: DeltaEn=[(DeltaLn+(Deltaa(n))2+(Deltab(n))2]1/2. RESULTS: Distilled water caused no perceptible colour change as tested by ANOVA and Tukey's tests. The effect of surface finish on staining was not statistically significant (P>0.05). There was no strong interaction between FSS and stains or between FSS and materials. There was a strong interaction between surface and material, and stain and material (P<0.001). CONCLUSIONS: All materials were susceptible to staining by all stains especially coffee, red wine and tea; Fuji IX showed the least susceptibility and F2000 the greatest.

Analysis of Variance↗
PubMed2001

Bonding to previously bleached teeth.

Some authors have reported a decrease in the bond strength of restorative composite resin to previously bleached enamel. Since there has been an increase in the number of adult patients seeking orthodontic treatment, this study was undertaken to determine whether the act of bleaching would somehow affect the bonding of orthodontic brackets to enamel surfaces. Sixty extracted premolar teeth were divided into 6 groups of 10, for comparison of the shear/peel bond strength of orthodontic brackets to enamel using light-cured composite resin cement and a resin-modified glass-ionomer cement. For each material, one group of teeth was used for bonding to unbleached enamel, and the other two for bonding to enamel at 24 hours and 14 days after bleaching. The experimental method simulated clinical procedures as closely as possible. No significant difference in the shear/peel bond strength was found between the bleached and the unbleached groups. t was concluded, therefore, that at-home bleaching with Nite Lite does not affect the shear/peel bond strength of light-cured composite resin and resin-modified glass-ionomer cements used for bracket bonding.

Adult↗
PubMed1999

[New direct restorative materials].

People worldwide have become increasingly aware of the potential adverse effects on the environment, of pollution control and of toxic effects of food, drugs and biomaterials. Amalgam and its potential toxic side effects (still scientifically unproven) continue to be discussed with increasing controversy by the media in some countries. Consequently, new direct restorative materials are now being explored by dentists, materials scientists and patients who are searching for the so-called 'amalgam substitute' or 'amalgam alternative'. From a critical point of view some of the new direct restorative materials are good with respect in aesthetics, but all material characteristics must be considered, such as mechanical properties, biological effects, and longterm clinical behaviour.

Biocompatible Materials↗
PubMed1998

New direct restorative materials. FDI Commission Project.

People worldwide have become increasingly aware of the potential adverse effects on the environment, of pollution control and of toxic effects of food, drugs and biomaterials. Amalgam and its potential toxic side effects (still scientifically unproven) continue to be discussed with increasing controversy by the media in some countries. Consequently, new direct restorative materials are now being explored by dentists, materials scientists and patients who are searching for the so-called 'amalgam substitute' or 'amalgam alternative'. From a critical point of view some of the new direct restorative materials are good with respect to aesthetics, but all material characteristics must be considered, such as mechanical properties, biological effects, and longterm clinical behaviour.

Biocompatible Materials↗
PubMed1978

Microdensitometric quantification of the lead capture method for the histochemical demonstration of acid phosphatase in cultured cells.

A fibroblast-like BHK-21 (C-13) line, grown as monolayer on glass cover-slips, was incubated for the demonstration of acid phosphatase by the lead capture method. The density of final reaction product was measured with a scanning microdensitometer. A peak absorption was found at 510 nm. The extinction of discrete areas of stain was within the range of linear response of the instrument. The frequency distribution of the density of reaction product in 100 cells was normal (Gaussian), and the density increased linearly with incubation time. It is concluded that this method is valid for the measurement of the density of lead sulphide reaction product in cultured cells.

Acid Phosphatase↗