Browsing by Author "Gilmore, H. William (Homer William)"

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    A composite resin versus an amalgam: a study of certain properties and the design and initiation of a clinical investigation
    (1971) Avery, David Roger; Gilmore, H. William (Homer William); Van Huysen, Grant; Garner, La Forrest Dean, 1933-
    Certain properties of a representative composite material were evaluated by in vitro testing and compared to those of other types of restorative materials. A clinical study designed to evaluate the performance of the composite material as compared to amalgam for Class II restorations was initiated and one-year results are reported. Laboratory tests for abrasion resistance, hardness, marginal leakage, strength, color stability, staining characteristics, solubility, and water sorption were conducted. The clinical study is still in progress but the results after one year indicated that the composite resin test restorations, as well as the amalgam control restorations, were generally satisfactory. In overall clinical performance neither material was superior to the other. The amalgam restorations received a superior rating for anatomic form while the composite restorations were superior in terms of marginal adaptation. No clinical evidence of recurrent caries, associated with any of the restorations, was detected. Surface discoloration was a significant finding on the composite restorations, but it was confined to proximal areas and may be related to the difficulty of cleaning these areas with a toothbrush. No conclusions can yet be made regarding the long-term clinical performance of the composite resin used in this investigation as a Class II restorative material.
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    A laboratory study of the adhesion of a restorative acrylic resin and a polycarboxylate cement on bovine enamel etched with fifty per cent phosphoric acid
    (1970) Lee, Brian Dalvin, 1942-; Gilmore, H. William (Homer William); Mercer, Victor H., 1928-; Garner, La Forrest Dean, 1933-
    The purpose of this laboratory study was to determine whether etching of flat bovine enamel surfaces with a 50 per cent aqueous solution of phosphoric acid for 60 seconds increases the bonding of a conventional restorative acrylic resin and a new polycarboxylate cement. The test specimens were subjected to 24 hours, 30 days and six months storage in water and then subjected• to temperature stress cycling and intermittent tensile stress cycling. A tensile test was used to measure the bond strength of both materials. The results of the Newman-Keul's test showed that pretreating the enamel surface with 50 per cent phosphoric acid significantly increased the bonding of the restorative resin, and that the cavity sealer supplied by the manufacturer further improved the resin attachment to enamel surfaces previously etched with phosphoric acid. The bonding of the resin to acid-etched enamel surfaces pretreated with or without the cavity sealer was unaffected by prolonged storage in water, temperature stress cycling, and intermittent tensile stress cycling. However, a significant reduction in the adhesion of the acrylic resin to polished-enamel surfaces pretreated with or without the cavity sealer was observed when the test specimens were subjected to the same testing conditions. The data obtained for the polycarboxylate cement test specimens showed that etching of the enamel surface with phosphoric acid also provided slightly higher adhesive values than the control specimens. Results obtained revealed that prolonged storage in water, and temperature and mechanical stress cycling did not affect the adhesion of the polycarboxylate cement to acid-etched enamel surfaces. However, thermal and mechanical stress cycling after prolonged storage in water appeared to decrease the adhesion of the cement to polished enamel surfaces. When Ca45 was used to assess the marginal seal of resin restorations placed into acid-etched Class V cavity preparations in extracted human teeth, the autoradiographs showed that etching of the cavity preparations with 50 per cent phosphoric acid improved the marginal seal of the restorative resin after one-week storage in water. When both the acid-etched and control restorations were thermal stress cycled 2500 times at a 40°C temperature differential, a slight improvement in the marginal seal of the acid-etched restorations was observed.
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    Retention of resin restorations by means of enamel etching and by pins
    (1971) Ayers, Alvin James, Jr., 1941-; Gilmore, H. William (Homer William); Norman, Richard Daviess, 1927-; Garner, La Forrest Dean, 1933-
    An investigation was conducted into the effect of acid etching of the enamel and the use of pins on the retention of direct filling resins when used for restoration of fractured incisor teeth. The retention secured by these techniques as related to the cavity design also was studied. Four different cavity preparations were used. The retention of the resin in all four was compared when there was no pretreatment of the enamel, when the enamel was etched by 50 per cent phosphoric acid, and when pins were used for retention. Retention was assessed on the basis of resistance of the restoration to displacement by a lingual force. No significant difference was observed in retention as related to cavity design in the control specimens. In all four cavity preparations, acid etching of the enamel and the use of two retentive pins increased the resistance of the restorations to displacement. (However; when only one "L" shaped retentive pin was employed in Conjunction with a flat incisal preparation the force required to accomplish displacement was no greater than for controls.) The acid etch technique when employed with a cavity preparation that extended 1.7 mm. or more onto the lingual surface of the enamel generally offered a higher resistance to lingual force than double pin retained restorations. There was no significant difference between the resistance offered by a circumferential preparation when the resin was retained by either acid etching or by two pins. In the acid etch technique the enamel surface area and its distribution are important factors in retention.