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Biomedical subjects

H F Morris

Publications and source records attributed to H F Morris.

At least 73 records · Page 4Linked to original sources
PubMed1990

Veterans Administration Cooperative Studies Project No. 147: association of metallic taste with metal ceramic alloys.

We examined patients to find out whether they noticed the prevalence of metallic taste and set out to determine the association of metallic taste with demographic, medical, and dental factors. Data were collected as part of a Veterans Administration Cooperative Study investigating the suitability of alternative metal ceramic alloys as substitutes for alloys that contain gold. Crowns and fixed partial dentures were made from control and alternative alloys for accepted volunteer patients. A month after placement of the restorations and at regularly scheduled recall appointments, the patients were asked if they tasted a metallic flavor. Of the 2023 times the question was asked, 101 positive responses were given by 68 patients (46 reported metallic flavor once, and 22 reported it more than once). Results indicated that youth, sensitivity to heat and cold, bruxism, grinding, and an increasing number of restorative units were significantly related to metallic taste. For any given visit, about 5% of the patients reported tasting a metallic flavor regardless of the type of alloy that was used in the restoration. Metallic taste does not appear to be a problem with alternative alloys.

Adult↗
PubMed1990

Properties of cobalt-chromium metal ceramic alloys after heat treatment.

A comparison of mechanical properties of seven metal ceramic alloys in as-cast and heat-treated conditions resulted in significant differences. The alloys that were tested included seven cobalt-chromium metal ceramic alloys. Mechanical properties include strength, elongation, modulus of elasticity, and microhardness. Twenty-four tensile bars were cast for each alloy. Twelve of the 24 bars for each alloy were randomly selected for heat treatment with the Ceramco technique. Results indicated that the tested alloys had similar mechanical property values as a group in both the as-cast and the heat-treated conditions. The heat treatment had little effect on the cobalt-chromium alloys, although several did become significantly harder. In either condition, the cobalt-chromium alloys showed a high value of strength, a low percent of elongation, a high modulus of elasticity, and a high value of hardness. The high value of hardness and the low percent of elongation would make these alloys difficult to handle clinically.

Analysis of Variance↗
PubMed1989

Veterans Administration Cooperative Studies Project No. 147. Part VIII: Plaque accumulation on metal ceramic restorations cast from noble and nickel-based alloys. A five-year report.

In 1980, the Veterans Administration Cooperative Studies Program No. 147 initiated a multicentered, multidisciplinary clinical study to evaluate the use of alternative alloys for porcelain-fused-to-metal restorations. This segment of the study compares the accumulation of dental plaque, over time, on restorations made from either Olympia or one of several alternative alloys, including W-1, Ceramalloy II, Micro-Bond N/P2, or Ticon in comparison to: (1) an unrestored tooth, which served as the periodontal control, (2) Olympia, the alloy control, and (3) among the alternative alloys. The restoration of approximately 800 teeth with fixed partial dentures/crowns was not found to contribute to plaque accumulation when measured by using the Löe and Silness plaque index. Statistically, more plaque was exhibited by the unrestored periodontal control tooth than by any of the restored teeth. No differences in plaque accumulation were observed between Olympia and the alternative alloys or among the alternative alloys themselves after 36 months of clinical use.

Clinical Trials as Topic↗
PubMed1989

Veterans Administration Cooperative Studies Project No. 147/242. Part VII: The mechanical properties of metal ceramic alloys as cast and after simulated porcelain firing.

Comparison of mechanical properties of seven metal ceramic alloys in as-cast and heat-treated conditions resulted in significant differences. Tested alloys included one Au-Pd (control), three palladium-based, and three nickel-based alloys. Mechanical properties included strength, elongation, modulus, and microhardness. Twenty-four tensile bars were cast for each alloy. Twelve of the 24 bars for each alloy were randomly selected for heat treatment by the Ceramco technique. After heat treatment the Au-Pd alloy became stronger and harder and showed an increased elongation. The effects of heat treatment on the strength of the palladium-based alloys were variable, showing a decrease in hardness and an increase in elongation. The nickel-based alloys were weakened by the heat treatment and showed a decrease in hardness and an increase in elongation. Heat treatment did not significantly affect the modulus of any of the tested alloys.

Chemical Phenomena↗
PubMed1986

Influence of polishing on cast clasp properties.

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.

Dental Polishing↗
PubMed1986

Veterans Administration Cooperative Studies Project No. 147. Part I: A multidisciplinary, multicenter experimental design for the evaluation of alternative metal-ceramic alloys.

The factors necessary for a comprehensive multidisciplinary, multicenter clinical study have been incorporated into CSP No. 147. The experimental design provides the potential for multiple laboratory and clinical data comparisons of alternative alloys. The study incorporates clinical performance observations with dental and medical histories that permit many unique correlations. This potential demonstrates the comprehensiveness of the CSP No. 147 study design and its contributions to clinical dental research in the evaluation of restorative materials.

Chromium Alloys↗
PubMed1986

Veterans Administration Cooperative Studies Project No. 147. Part II: A new assessment system for rating metal-ceramic crowns.

The rating system developed for this study combined ordinal and numerical scoring. The method involved the following: defining the critical criteria, defining the ordinal rating criteria for the assignment, assigning numerical scores for each individual criterion and totalling the scores for each restoration, adding an adjustment number, and scaling the results to the 0-to-10 range and rounding off to the nearest tenth. When tested on sample data gathered at the 12-month followup appointment, the new system elicited a finer discrimination of differences in the quality of the restorations. Although the system fully meets the needs of the specific project, it should not be considered an answer to the needs of all clinical investigations. It should be viewed as a different approach in the development of an acceptable clinical rating system.

Cementation↗
PubMed1984

Changes in mechanical properties and microstructure following heat treatment of a nickel-chromium base alloy.

Heat treatment of a nickel-chromium base metal alloy produced changes (percent elongation, ultimate tensile strength, modulus of elasticity, yield strength, and hardness) that simulated properties of various types of noble metal alloys. Further research is indicated to determine if the properties of a base metal alloy can be altered by heat treatment or other means to enable its use for a wide variety of fixed dental restorations.

Chemical Phenomena↗