Biomedical subjects
Publications and source records attributed to J S Brudvik.
This study compared heat-cured acrylic resin denture baseplate distortions following a second heat cure used to add the denture teeth. The second heat cure was done with three different water-bath curing temperatures. The distortions were evaluated in three planes by use of a measuring microscope. Recorded distortions were not clinically significant.
During the metal finishing phase of removable partial denture construction, metal is removed from all aspects of the casting. The amount removed from areas designed to contact prepared surfaces of abutments is critical to the resulting fit of the partial. Castings were evaluated before and during finishing procedures to measure metal loss at the tooth-removable partial denture interface. Finishing and fitting techniques for controlling the loss of metal are presented.
Inlay-onlay composite resin restorations have been introduced to the profession as alternatives to amalgam and direct composite resins. Two-body wear testing was performed on three inlay-onlay resins and one direct composite resins using a machine designed to produce sliding wear. The composite resins were opposed by human enamel, type III gold alloy, and porcelain. Of the investigated materials, the homogeneously microfilled inlay-onlay material showed significantly less wear. The direct composite resin showed significantly the greatest wear. The hybrid inlay-onlay resins showed intermediate wear. The hybrid inlay-onlay resins and the direct composite (small particle, heavily filled) resin created wear tracks in the opposing surfaces while the homogeneous microfill inlay-onlay resin did not. The depth of the observed wear tracks in the opposing surface was sufficiently substantial to warrant further investigation into the wear of materials that oppose composite resin restorations.
The Triad light-cured resin system appears to have potential for making processed record bases for special patients. The close adaptation of this material to the dental cast often results in internal voids and defects. These defects are greatly reduced when a dry cast is used instead of one with a high moisture content. Vacuum-assisted adaptation using a sheet of rubber dam in connection with a vacuum adaptor also results in an improved internal surface. Finger pressure alone is not a dependable method of adaptation.
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Peak curing temperatures of hard, direct, autopolymerizing reline resin materials tested were all within ADA specification guidelines. A temperature range of 10 degrees C was demonstrated among materials, with the highest polymerization temperatures recorded for Perm and Lang's Self-Curing Rebase Acrylic, and the lowest for KOOLiner, Flexacryl, and COE-Rect. This temperature difference is probably clinically detectable. However, intraoral testing of polymerization temperatures yielded lower peak values than those observed with specification testing, and the temperature peaks occurred earlier with intraoral conditions. There were significant color changes with simulated aging for three of the products tested: Flexacryl, COE-Rect, and Lang's Self-Curing Rebase Acrylic. The color changes occurred after only 24 hours of accelerated aging. Although there was only a small change in color with aging for Perm and KOOLiner, there was a moderate shift in the color of KOOLiner (delta E = 2.2) before aging. Thus only Perm demonstrated little color change with simulated aging. Of the reline products, one material, KOOLiner, demonstrated lower bond tensile strengths to denture base materials. However, the clinical significance of this was not known. One denture base material (Astron) recorded significantly higher bond strength values for all reline products and failure always took place within the denture base.
During the polishing of clasps, two possible changes that could affect their properties are thinning of the clasp and work hardening of the alloy. Two distinctly different clasp pattern forms were selected and 20 samples of each were cast. They were then divided into two groups, polished and unpolished, in an effort to determine the total influence of the polishing procedure on clasp behavior. The results indicate that polishing produces a slightly more flexible clasp. Any influence resulting from possible work hardening is offset by the reduction of clasp thickness. Effects of width/thickness ratios and magnitude of deflections on finishing and polishing techniques may also alter clasp flexibility in the polished clasp.
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The clinical relationship between the removable partial denture cast occlusal rest and the corresponding rest seat was examined. Under the conditions of the study, it was found that rests of mandibular Class I and II removable partial dentures fit significantly better than those of mandibular Class III and IV prostheses. No significant difference was noted between similar types of maxillary removable partial dentures in this regard. In evaluating the fit of specific portions of the occlusal rest, it was found that the marginal ridge zone was more closely adapted to the rest seat than other zones for all types of removable partial dentures. However, contact, as defined in this analysis, was found to exist on a random basis in all four quadrants of the occlusal rests evaluated. In spite of this fact, one fifth of the occlusal rests did not contact the opposing rest seat at any point. Improved fit with length of service was not substantiated by a cross-sectional analysis. Suggestions were made to assist the clinician in achieving a better fit between the framework and dentition in removable partial dentures.
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This article has described a technique to achieve maxillary orthopedics for the infant with a bilateral cleft lip, protruded premaxilla, and intact palate. Both maxillary expansion and retraction of the premaxilla can be accomplished with the same prosthesis.
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This preliminary report has shown the following interesting points: (1) Measurements of tissue pressures beneath dentures are possible using the Sanborn 350 recorder. (2) Stable dentures produce high pressures on the supporting tissues and transmit these pressures from region to region, varying with how the patient uses the dentures. (3) Most often, an opposite large or negative pressure immediately followed the production of positive pressure at the same site beneath the denture. Thus, each movement actually traumatizes the tissue twice. (4) Nonmasticatory pressures produced under dentures are as great as or greater than masticatory pressures. (5) Wave forms for each biting maneuver or sound produced can be charted and are typical for each patient, probably representing denture movement. (6) Swallowing unassociated with eating or drinking produced very high positive and very low negative pressures, giving the greatest ranges of pressures recorded in this experiment. (7) Smoking (recorded in only one patient) also produced a great range of pressures. (8) Sticky foods such as cheddar cheese produced greater negative pressures than the other foods tested. (9) The one patient with natural teeth opposing his denture gave much more uniform and lower pressures than did the patients with complete dentures. (10) This method allows visualization of pressure movement under dentures. The effect of these continually occurring, nonmasticatory, induced pressure changes and pressure waves beneath the dentures may well be of greater significance than that of mastication.
A method for using the functionally generated-path technique to fabricate full occlusal porcelain-fused-to-metal fixed partial dentures and crowns has been described. Proper use of this technique in carefully selected patients should eliminate occlusal adjustments and the concomitant polishing and glazing that are often necessary before the restoration can be permanently cemented.
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