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Biomedical subjects

A D Wilson

Publications and source records attributed to A D Wilson.

At least 145 records · Page 8Linked to original sources
PubMed1980

Zinc oxide eugenol cements. V. Instrumental studies of the catalysis and acceleration of the setting reaction.

Zinc oxide eugenol (ZOE) cements were prepared by mixing powders of widely differing reactivity with a variety of liquid formulations. The course of the setting reaction was followed by penetrometer, rheological and electrical techniques. Small amounts of water, organic acids, and the reactivity of water, organic acids, and the reactivity of the zinc oxide all have a profound influence on the setting characteristics of cement pastes.

Acids↗
PubMed1979

Clinical manifestations of dynamic left ventricular outflow tract stenosis in infants with d-transposition of the great arteries with intact ventricular septum.

Four infants with d-transposition of the great arteries and intact ventricular septum who manifested early clinical symptoms and deterioration due to dynamic left ventricular outflow stenosis are presented. All four had an anatomically adequate atrial septal defect, made at the initial balloon atrial septostomy, that was later confirmed intraoperatively. Two infants continued to have a low arterial oxygen saturation level because of inadequate interatrial mixing, and one of these had severe persistent cyanosis and was treated with the Mustard operation at age 4 days. The other two infants subsequently presented with hypercyanotic spells at age 3 months. All four infants had features of dynamic left ventricular outflow stenosis on hemodynamic, angiocardiographic and echocardiographic studies. The left ventricular outflow pressure gradient was shown to increase after administration of isoproterenol in one infant, and relief of a cyanotic spell with reduction of left ventricular systolic pressure was achieved in another after intravenous administration of propranolol. The Mustard operation relieved symptoms in all infants. The effect of left ventricular outflow tract stenosis on the mechanisms responsible for interatrial mixing in d-transposition of the great arteries with intact ventricular septum is discussed.

Cardiac Catheterization↗
PubMed1979

The hydration of dental cements.

A study was made of the hydration of dental cements, water being classified as "non-evaporable" and "evaporable". The ratio of these two types of water was found to vary greatly among different cement types, being lesser in zinc oxide and ionic polymer cements and greater in ion-leachable glass and phosphoric acid cements. The cement with the least "non-evaporable" water, i.e., showing least hydration (the zinc polycarboxylate cement), had the lowest strength and modulus and the greatest deformation at failure. A linear relationship was found to exist between strength and the degree of hydration of dental cements. All the cements were found to become more highly hydrated and stronger as they aged.

Absorption↗
PubMed1979

The structure of a glass-ionomer cement and its relationship to the setting process.

The G-200 glass of the glass-ionomer cement has two phases: a continuous calcium aluminosilicate matrix and partly crystalline calcium fluoride-rich droplets, the nature of which depend on the thermal history of the glass. The setting process of the cement takes place when the glass is mixed with poly(acrylic acid). It has two overlapping stages corresponding to the rapid leaching of calcium ions from the uncrystalline part of the droplets, followed by the slower release of aluminum (and some calcium) from the main glass phase. These processes are affected by the microstructure and microcomposition of the glass.

Acrylic Resins↗
PubMed1979

The quantitative measurement of the opacity of aesthetic dental filling materials.

A method is described for measuring the opacity of anesthetic dental filling materials using a goniophotometer. Procedures are given for converting measured opacity values to those referred to a 70% reflectance background (C0.7 values) as required by existing specifications. The conversion is involved, and, since most available white surfaces have reflectance of about 80%, it is recommended that in future specifications opacity be recorded as C0.8 values. Opacity values for 28 materials are reported. It was found that the opacity of dental cement decreases for several days following preparation and that powder/liquid ratio has little effect, while pigmentation has a marked effect on opacity.

Acrylic Resins↗
PubMed1978

A study of temperature changes occurring in setting dental cements.

A study has been made of the rise in temperature associated with the setting of dental cements. Results are discussed in terms of the chemistry of the cement systems and are related to specification testing and clinical usage. Zinc oxide cements evolve more heat than those based on ion-leachable glasses, and phosphate bonded cements evolve more heat than polycarboxylate cements.

Acrylic Resins↗
PubMed1978

Infrared spectroscopic studies on the development of crystallinity in dental zinc phosphate cements.

An infrared spectroscopic study has been made of the development of crystallinity (hopeite) in dental zinc phosphate cements. Crystallization in the bulk of a cement is prevented only by the incorporation, in the liquid, of aluminum which forms complexes with phosphoric acid. The development of surface crystallinity is related to the chemical composition of the cement and the speed of the reaction. No acid phosphates are to be found in the matrix which consists solely of neutral orthophosphates.

Aluminum↗