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Biomedical subjects

G H Johnson

Publications and source records attributed to G H Johnson.

At least 55 records · Page 3Linked to original sources

Clinical evaluation of a nystatin pastille for treatment of denture-related oral candidiasis.

Nystatin has been formulated in the form of a flavored pastille (troche) as an alternative to the oral suspension. This parallel, double-blind, randomized, placebo-controlled study evaluated the acceptance and effectiveness of the nystatin pastille at two different dosages. Twenty-four subjects were selected on the basis of clinical signs of denture stomatitis and culture isolation of Candida spp. Each subject was randomly assigned to one of three treatment groups (A, 200,000 units; B, 400,000 units; and C, placebo). At entry, 7 days, 14 days, and at 10 days after cessation of treatment, the clinical condition was evaluated and Gram stain smears and imprint cultures were made and analyzed. The flavored pastille was well accepted by the subjects and both dosages were shown to be effective in significantly reducing or eliminating the Candida organism during active therapy. Data from the 10-day follow-up, however, demonstrated reinfection with the organism. Thus to resolve the condition, effective therapy must include treatment of the etiologic factors of denture stomatitis along with antimicrobial therapy.

Candidiasis, Oral↗

A geriatric program in practice.

The geriatric patient represents an underutilized resource for the small animal practitioner. Thorough examination of the pet annually in detail allows detecting problems before they are too advanced. By using the systems approach to patient evaluation, one is better able to detect diseases and proceed with techniques to diagnose them. The use of in-house hematology and serum chemistry equipment benefits the pet and owner through rapid return of information and provides an added source of revenue for the practitioner. Developing and maintaining a system to reevaluate the geriatric patient is one of the most important aspects of a geriatric practice. Reminding clients that you care about their pet through routine scheduled evaluations develops loyal clients, which in turn generates additional hospital income.

Aging↗

Effect of admixed indium on mercury vapor release from dental amalgam.

The purpose of this study was to evaluate the effect of admixed indium on the amount of mercury vapor released from dental amalgam. We made amalgam specimens according to ADA Specification Number 1. We added various amounts (0-14% by weight) of indium to the alloy powder. We also tested the commercial amalgams Dispersalloy, Valiant, and Indiloy. Specimens were held at 37 degrees C and 100% humidity. We used a Jerome Mercury Vapor Analyzer (model 411) to measure the mercury vapor released. We analyzed the data by means of ANOVA and Student-Newman-Keuls procedures. Admixed indium significantly decreased the amount of mercury vapor released from dental amalgams; the period of the greatest effect on mercury vapor released was during the setting phase of amalgam; and dental amalgams with greater than or equal to 8% admixed indium released the least amount of mercury vapor.

Air Pollutants↗

Peroxisomal disorders. Biochemical and clinical diagnostic considerations.

The peroxisomal disorders are a group of inherited metabolic diseases with serious clinical sequelae. The number of recognized peroxisomal disorders has increased substantially since 1973, when an absence of peroxisomes was observed in patients with the cerebro-hepato-renal (Zellweger's) syndrome. More subtle peroxisomal dysfunction is now recognized, including that deriving from single peroxisomal enzymes. Peroxisomal disorders are relatively rare. However, these disorders assume importance because of our growing ability to relate clinical sequelae to specific enzymatic and biochemical deficits, because some of these disorders can now be identified prenatally and their recurrence can be prevented, and because therapies are rapidly evolving. We reviewed these disorders in light of increasing understanding of the biochemistry of the peroxisome.

Humans↗

An evaluation of finishing instruments for an anterior and a posterior composite.

The same finishing instruments and techniques revealed no significant differences in the surface roughness of the anterior and posterior composites. The smoothest surface was achieved with Mylar strips; the smoothest instrumented surface was achieved with a series of abrasive disks, but a fine diamond bur with 25 micron particles produced the roughest surface. However, an x-fine diamond with 15 micron particles produced a surface smoothness superior to that produced with a white stone and similar to the smoothness produced with a carbide bur and rubber point. Diamond finishing with slow speed produced a somewhat smoother finish than with high speed. SEM analysis revealed qualitative differences in surface texture even though the average roughness was not shown to differ.

Bisphenol A-Glycidyl Methacrylate↗

Accuracy of elastomeric impressions disinfected by immersion.

This study evaluates the accuracy and surface quality of stone dies made from impressions that had been placed in disinfectants. Results indicated that selection of the type of impression material is more important than selection of the disinfectant. Addition silicone and polysulfide impressions were disinfected without a loss in accuracy, whereas polyether impressions were adversely affected. The surface quality of dies was acceptable with disinfection and one disinfectant contributed to an improvement in surface quality compared with the control.

Chlorine↗

The malignant lymphoepithelial lesion of the salivary glands.

Malignant lymphoepithelial lesion (MLEL) is a rare neoplasm of the salivary gland which has an exceptionally high incidence in the Eskimo. Eighty-four cases have been previously reported. Seven additional cases in six Eskimos and one Filipino patient are reported in this paper. The etiology, treatment and prognosis of these lesions is then discussed.

Adult↗

Evaluation of hard direct reline resins.

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.

Chemical Phenomena↗

Accuracy and bond strength of combination agar/alginate hydrocolloid impression materials.

The accuracy and bond strength of several combinations of agar and alginate hydrocolloid impression materials were assessed. In general, there was little difference in accuracy among agar hydrocolloids. Of the alginate hydrocolloids, products J and CA produced the most accurate casts in combination with any of the agar hydrocolloids. For all product combinations, however, distortion of the diameter of the improved stone die was evident. The buccal-lingual diameter was 0.32% larger, whereas the mesial-distal diameter was only 0.06% larger. Regarding bond strength, alginate hydrocolloids P, CA, and VA in combination with agar hydrocolloids DB and DG produced the best results of all combinations tested. Thus, considering both bond strength and accuracy, product CA in combination with either DB or DG produced the best overall results.

Agar↗

Accuracy of addition silicones as a function of technique.

Both addition and condensation silicones produced stone dies that were larger in diameter and shorter in height than the tooth preparation. For both materials, there was little change in the distance between stone die preparations compared with the standard. The most significant difference between types of silicone was that condensation silicones produced significantly shorter dies (-0.24% to -0.37%) than addition silicones (-0.08%). Among addition silicones, Cinch produced more than twice as much vertical change (-0.16%) than the other three products (-0.06%). Since castings made from a short die will not seat completely on the prepared tooth, these results support the use of three of the four addition silicones tested. The same accuracy of impressions was achieved for all techniques (that is, putty/wash, single mix, and double mix) when addition silicones were used, whereas the putty/wash technique produced the most accurate dies for the condensation silicones. The custom tray produced dies that were much more accurate in vertical dimensions (-0.03%) than the stock trays (-0.15% to -0.21%). Thus the custom tray is the impression tray of choice, even for addition silicones, which produce relatively little polymerization shrinkage and are dimensionally stable.

Chemical Phenomena↗

Accuracy of four types of rubber impression materials compared with time of pour and a repeat pour of models.

The accuracy of four types of elastomeric impression materials was studied as a function of model location, time of pouring, and repetition of pouring. There was little change in dimension among abutment preparations for all materials, for all times of pour, and with a repeat pouring. It appears that measurements between posts are not sensitive to detecting differences between materials and that other dimensions should be examined to discern where differences might lie. The diameter of the stone post was larger than the standard for the AS and PS materials and was unchanged or smaller than the standard for the CS and the PE. The vertical dimensions of stone posts were, in general, shorter than the standard for all materials, with the AS demonstrating the smallest change. The AS and CS products demonstrated the best recovery from undercuts and the least change in dimensions between an initial and second pour of an impression. The AS and PE were the least affected with delays of 1, 4, and 24 hours in pouring the impression.

Crowns↗

Natural killer cells in in utero diethylstilbesterol-exposed patients.

The observations that limited neonatal diethylstilbesterol (DES) exposure in mice produces persistent natural killing defects and that natural killer (NK) cells have an origin early in gestation suggested the possibility that NK abnormalities may exist in in utero DES-exposed women. However, when compared to controls, these women showed slightly higher NK activity with no evidence of stimulation by accessory mononuclear cells. Altered natural killing cannot be invoked in this population as a contributing factor to increased cancer risk.

Adult↗