A.A. Grant

The Use of Additives to Improve the Mechanical Properties of Gypsum Products

The effects of adding a combination of calcium oxide and gum arabic additives to calcium sulfate hemihydrate have been determined. It has been found possible to produce gypsum products with properties superior for dental applications. In particular, formulations are suggested for die, model, and flasking materials.

The use of magnetic forces in prosthetic dentistry

Abstract Recently there has been developed a raze earth/cobalt magnet which possesses exceptional magnetic properties and can be produced in a size suitable for intra-oral use. Preliminary studies have been directed to determine the most effective form of magnet design which could be used to improve denture retention. Breakaway loads of over 200 g have been recorded together with attractive forces of up to 50 g at air-gap separations of 2 mm.

Hardening of model and die materials by an epoxy resin

By use of epoxy resin impregnation, it has been found possible to improve the mechanical properties of gypsum-based model and die materials.

Chewing side preference and muscle quality in complete denture-wearing subjects

Abstract Complete denture wearers commonly report that they are more able to chew on one side of their mouth than on the other. Where a marked chewing side preference exists, the muscles on the preferred side may be more efficient, but this assumption has remained unproven as bite force is an insensitive and unreliable index of muscle quality. de Vries (1968) has shown that the quality of a muscle can be measured by relating the electromyogram (EMG) and isometric force properties. Using this definition we have shown that in complete denture wearers, the masseter muscle in the preferred chewing side is superior in quality to that of the non-preferred chewing side. Whether this difference in muscle quality is the cause or the result of the chewing side preference is unknown

Studies on polycarboxylates and related cements 4. Properties of cements

Abstract The mechanical properties, setting times, apparent pH of setting cements, solubility, film thickness and adhesion to enamel and dentine have been determined for a range of zinc polycarboxylate cements. The properties are discussed in relation to the suitability of the cements as linings and luting agents. The effect of composition on properties is also discussed.

The effect of complete dentures on the development of speech articulation in children

Abstract The development of articulation in the speech of children aged 3–9 years and wearing full upper dentures was compared with that of children having natural teeth. Each group contained 20 children matched by sex, age and social class. Articulation testing using the Edinburgh Articulation Test was carried out at three stages: when the experimental group was edentulous, on insertion of the denture and 2–3 months after insertion. Tests of auditory discrimination, vocabulary and intelligence were also carried out. The average raw scores of the experimental group for the first and third tests were lower than those of the control group. Ninety per cent of the experimental group had their lowest score in the second articulation test. Variation from the adult form of phonetic features for the experimental group occurred in both immature phonetic realizations and atypical phonetic realizations. No such variations occurred in the control group other than the normal immature features spoken by the younger patients.

A technique for screening implant materials i n the rat

Abstract Cobalt-chromium implants were placed in a trough formed in the vertex of the skull of albino Wistar rats and the tissue reactions observed at 4, 7, 14, 30 and 180 days postoperatively. The implants did not interfere with the mechanisms of healing. Active bone deposition followed the reflection and replacement of the periosteum and dura mater. After 30 days the implants were surrounded by fibrous tissue. Mononuclear cells resembling macrophages intervened between the fibrous tissue and the implant and almost completely enveloped the implant 6 months postoperatively. The mononuclear cells become flattened and are not distinguishable from fibrous tissue in haematoxylin and eosin sections, but can be distinguished by other staining techniques.