Magnets used in dentistry (preliminary data on in vitro biocompatibility).)

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  • J. Dent. 1991; 19: 67 67

    International Abstracts

    Section Editor: W. R. E. Laird

    Magneti utilizzati in odontoiatria (dati preliminari di biocompatibilit& in vitro.) (Magnets used in dentistry (preliminary data on in vitro biocompatibility).) Gonella A. M., Amedeo M. R., Cannas M. et al. (1989) Minerva Stomatol. 38, 1053-I 058.

    Magnetic materials used as retentive devices in dentistry normally use a magnet encapsulated with stainless steel, titanium (Ti) or palladium (Pd) caps. The influence of the magnetic field on the tissues surrounding such magnets was studied. Six groups of four cobalt-samarium open field magnets were used (one without a cap, three with stainless steel, Pd and Ti caps) and two closed field sandwich-type magnets. The same elements, but not magnetized, were used as a control. All the materials were sterilized. The growth of fibroblasts (BH K Cl 3/2 1) in Dulbeccos Modified Eagle Medium was studied. After 24 h the cultures were divided in two groups, one fixed with glutaraldehyde and stained with haematoxylin-eosin and the other evaluated with a vital staining technique. LDH activity was determined by spectrophotometer in order to evaluate the possible membrane damage. Closed field magnets showed some adverse effect on cell growth, probably because of the corrosion products. Open field encapsulated magnets show good biological acceptability. (8 references) Mario Pezzoli

    Vloga vodetin oovrsine u retnciji parcialnih proteza. (The role of guide planes in the retention of partial dentures.) StamenkoviC D. and TihaCek L. (1989) Acta Stomato/. Croat. 023, 49-59.

    The theoretical effect of guide planes and of an inclined path of removal was tested quantitatively. Trials were carried out on two cobalt-chromium frameworks of identical design, constructed for a Kennedy Class III case. Guide planes were provided in one framework and omitted in the other. Forces were applied to remove the dentures from their respective casts, which were mounted on a surveyor table fixed in an lnstron testing machine. Fifteen tests were performed on each denture for each of two paths of removal.

    The denture without guide planes required an average mean displacement force of 8.76 N with a vertical path of withdrawal and I I .27 N when the cast was angled at 10. When guide planes were used, forces of 10.96 N and 12.27 N respectively were required. These differences were significant at P = 0.001.

    Quantitative tests confirm that guide planes and an inclined path of insertion increase the resistance to displacement of a cobalt-chromium framework. (20 references) A. J. Shapiro

    @ 1991 Butterworth-Heinemann Ltd. 0300-5712/91/010062-01

    Manipulation of gallium restorative materials; Part 1. Control of wetting action of mixture by mulling with ethanol. Habu H., Uchida H., Kohno H. et al. (1989) Jap. J. Dent Mat. 8, 730-796.

    The wetting action of gallium alloy is a handicap when handling the material. Ethanol mulling after mixing was assayed in an attempt to control the wetting action of such mixtures.

    A mixture of gallium and Ag-Sn-Cu spherical alloy particles was mulled with a small piece of an ethanol- soaked sponge for 10 s following mixing by an amalgamator. The effect of ethanol on the adherence of the mixture to the capsules, the physical properties and microstructures was determined.

    Mulling with ethanol effectively controlled the wetting action of the mixture, and reduced adherence to the capsules without affecting physical properties. A decreased reaction phase around the alloy particles was observed in the microstructure of the ethanol-mulled specimen. (12 references) H. Hisamitsu

    Luso del C.V.I. come sottofondo di cavitk esperienze cliniche. (The use of glass ionomer cement as a liner: clinical study.) Parnalardo G., Cicciu D. and Galioto S. (1989) Sromar. Medit. 9, 141-l 47.

    Patients with Class V cavities were restored with composite resins using as a liner calcium hydroxide on the left side and glass ionomer cement on the right side. The teeth were then submitted to sensitivity tests. The tests were performed immediately before the restorations, then 24 h, 7 days and 30 days after the restorations were placed.

    After 24 h there was a reduction in sensitivity which was more evident in the teeth treated with calcium hydroxide (75 per cent) compared to glass ionomer cement (56 per cent). After 7 days hypersensitivity was present in 15.3 per cent of teeth treated with glass ionomer and 5 per cent of teeth treated with calcium hydroxide. Finally, after 30 days no difference was observed between these methods.

    The use of glass ionomer cements as liners is suitable as they are chemically bonded to the dentine and mechanically, through the etching process, to the composite restorative material. Moreover they present better biomimetic characteristic properties towards the dentine. (14 references) Mario Pezzoli

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