An immediate dual purpose restoration of posterior root-filled teeth (the "amalgam crown").
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Biomedical subjects
Publications and source records attributed to H Judes.
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One of the advantages in using the carbon dioxide laser in medicine is the sterilization of the wound at the site of surgical intervention. In microbial studies, using the Sharplan Model 743 Medical Laser, we found substantial contamination of the area directly below the probe by viable bacteria and fungi. The levels of contamination varied from experiment to experiment, but were always substantial. The contamination is likely due to the stream of nitrogen gas emitted during and following laser irradiation in order to cool the lens. Following the implementation of several simple prophylactic procedures, including insertion of a filter on the end of the tube emitting the nitrogen gas, contamination by the gas stream was reduced to insignificant levels.
The cell surface hydrophobicity of bacteria obtained directly from human tooth surfaces was assayed by measuring their adherence to liquid hydrocarbons. Fresh samples of supragingival dental plaque were washed and dispersed in buffer. Adherence of the plaque microorganisms to hexadecane, octane, and xylene was tested turbidimetrically and by direct microscopic observation. The results clearly show that the vast majority of bacteria comprising dental plaque exhibit pronounced cell surface hydrophobicity. These data support the hypothesis that hydrophobic interactions play a major role in mediating bacterial adherence on tooth surfaces.
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Severe reactions can be caused when elastic impression materials are trapped beneath soft tissues. To develop a rank order of severity of responses, a series of these materials was injected beneath the oral mucosa of a baboon. Alginate and polysulfide rubbers containing lead peroxide produced severe reactions; hydrocolloid, polysulfide without lead, silicone, and polyether produced more mild reactions. The more toxic materials proved to be more radiopaque than the others. Tests for foreign body toxicity should be made a part of future specifications for these materials, and the use of toxic ingredients should be reduced as much as possible. These materials should be made opaque to X rays and of a different color than those of soft or hard tissues.
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Applying a bonding agent and a resinous adhesive layer before amalgam condensation has become a common clinical procedure. However, interactions between the different interfaces formed, and the extent of sealing obtained, have not been extensively studied. This study characterized the interfaces formed in the bonded amalgam restoration. Specifically, the individual contributions of the bonding agent (One-Step) and the adhesive resin (Resinomer) were examined, along with their mode of application on the prevention of microleakage and the formation of a tight, continuous adhesion to amalgam. To this end, a dye penetration assay and scanning electron microscopy (SEM) were used, including high resolution elemental analysis, for the characterization of the sealing properties and the interface structure obtained following various procedures of applying amalgam adhesives. Results indicated that placing bonding material under the amalgam restoration is essential to preventing microleakage. When condensed against uncured or cured adhesive material, the adhesive resinous glass layer creates a thick interface with protrusions and inclusions in the amalgam, though microleakage studies indicate that condensation over the uncured adhesive results in a better seal than that of the cured adhesive. SEM combined with elemental analysis indicates that the adhesion between amalgam and adhesive material is mainly of mechanical character and is formed by interdigitations of the adhesive material protruding into the amalgam. Gaps formed at the various interfaces in the different modalities could be localized. In addition, resinous glass composite alone, without bonding, was found to provide an unacceptable degree of sealing between the tooth and amalgam. The clinical significance of these findings is further discussed.
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