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Biomedical subjects

H M Proskin

Publications and source records attributed to H M Proskin.

At least 91 records · Page 5Linked to original sources
PubMed1992

Statistical considerations related to intra-oral studies.

Intra-oral studies use caries models from which conclusions are drawn concerning the caries process in the clinical environment. Recently, attention has been drawn to the issue of proper analysis and interpretation of the data from such studies, with particular emphasis placed on a consideration of the role such studies can and should play as a component of product claim submissions to the American Dental Association (ADA). This presentation discusses a number of issues relevant to this consideration, including the validity and reliability of the intra-oral modeling process, the relationship between these concepts and the requirements imposed by the ADA Guidelines for superiority and equivalence claims, and a brief enumeration of several other statistical issues which ought to be considered in the handling of data from such studies.

American Dental Association↗
PubMed1992

Interim report of the ad hoc committee for the consideration of statistical concerns related to the use of intra-oral models in submissions for product claims approval to the American Dental Association.

Subsequent to the American Dental Association Symposium on Intra-oral Studies, held in Chicago in September, 1990, the Council on Dental Therapeutics decided that further consideration should be given to statistical issues relating to intra-oral models. The authors accepted the request of Council staff to assist in the development of Guidelines concerning the validity, reliability, and combinability of data obtained from these models. The ensuing work in this area, which began in the fall of 1990 and has continued to date, has thus far focused on the tissue of validity. The purpose of the present paper is to provide the interested community at large with an update on the progress made thus far, and to provide some perspective as to where all of the work in this area may eventually be leading. It is anticipated that a more comprehensive and definitive report will be produced at the completion of this process.

American Dental Association↗
PubMed1992

Microbial contamination of hydrophilic contact lenses. Part II: Quantitation of microbes after patient handling and after aseptic removal from the eye.

We cultured Soflens (polymacon) contact lenses to determine the number of microorganisms present after patient handling and the number present after patient handling and 5 hours of lens wear. Twenty adapted contact lens patients were each dispensed two pairs of new sterile Soflens contact lenses. Both pairs of lenses were handled by the patients during a single experimental session. Prior to handling lenses, patients were instructed to wash their hands with soap and water, rinse with tap water, and dry with a paper towel. One pair (handled-only) was cultured immediately after handling. The second pair (handled-and-worn) was placed on the eyes by the patient, removed aseptically following 5 hours of wear, and then cultured. All 40 handled-only lenses had viable microorganisms associated with them (mean: 653 colony forming units (CFU) per lens). Bacteria were isolated on all of these lenses and fungi were detected on six. The mean bacterial count for the handled-and-worn lenses was 30 CFU/lens; fewer than half exhibited handled-and-worn lenses was 30 CFU/lens; fewer than half exhibited bacteria and no fungi were isolated. These data suggest that patient handling is a highly significant source of microbial contamination of hydrophilic contact lenses. Also, the number of microorganisms on lenses is significantly reduced (P < 0.0001) after the lens has been worn on the eye.

Asepsis↗
PubMed1992

A critical evaluation of the Multi-item Microbial Challenge Test in ophthalmic disinfectant testing.

The Multi-item Microbial Challenge Test (MIMCT) is a stringent, carrier assay of the disinfecting efficacy of a contact lens care regimen. The test involves four steps: 1) in vitro contamination of contact lenses in the presence of organic load; 2) cleansing the contact lens by mechanical rubbing and subsequent rinsing; 3) disinfection of the cleansed lens; and 4) assaying the contact lens and the disinfecting solution for viable microorganisms. The variability of the individual steps was evaluated in this study by the Contributions of Elements protocol. The efficacy of the cleansing step, while reputed to be highly variable, was found to be reproducible and dependent upon the formulation under test. A contact lens disinfecting regimen must reduce the level of contaminants to approximately 10(-4) CFU/lens to enjoy a 95% chance of passing the MIMCT. This reflects a 10-log unit reduction from the initial inoculum of approximately 10(6) CFU/lens. The stringency of the MIMCT depends on the ability of the recovery system to allow the growth of low numbers of residual challenge microorganisms in the presence of the disinfecting solution. Neutralizers included in the recovery system to inhibit the disinfectant are therefore critically important to the stringency of the assay. The design of experiments to evaluate neutralizers specifically for the MIMCT is discussed with suggestions for an improved procedure.

Candida albicans↗
PubMed1992

Microbial contamination of hydrophilic contact lenses. Part I: Quantitation of microbes on patient worn-and-handled lenses.

We cultured Soflens (polymacon) contact lenses to determine the number of microorganisms present following normal patient wear and handling just prior to disinfection. Total protein deposited was determined for the companion lens from each patient. A random population of 109 adapted soft contact lens patients participated in the study. Some patients participated more than once, resulting in a total of 196 lenses being cultured and 195 lenses analyzed for total protein. The left lens was cultured immediately. The right lens was extracted at 70 degrees C in sodium hydroxide, and the total protein in the extract determined using a modified Lowry protein assay. The mean protein deposition per lens was 3.4 micrograms (median 2 micrograms per lens; range less than 1 to 78 micrograms/lens). Microorganisms were cultured from 95% of the lenses. The mean bacterial count (in colony forming units per lens) was 2,482 (median: 123; range less than 3 to 150,000). Fungal contamination was found on 11% of the lenses at very low levels (3-9 yeast/lens and 3-18 mold/lens). Statistical analysis found no significant relationship between bacterial bioburden and any of the study parameters, including total protein, lens age, or subjective evaluation of lens cleanliness.

Bacteria↗
PubMed1991

Dimensional accuracy of denture resin cured by microwave energy.

Microwave processing has several time-saving advantages over conventional processing of denture base resins. Little is known about the adaptation of bases processed by microwave radiation to the cast and the mouth. Comparisons were made in five regions of the palate and ridge. The microwave-processed denture bases had equal or better dimensional accuracy than conventionally processed bases.

Acrylic Resins↗
PubMed1991

Associations of microbiological factors and plaque index with caries prevalence and water fluoridation status.

Plaque indices, numbers of mutans streptococci, lactobacilli and total viable flora in plaque and saliva were assessed as part of a large-scale cross-sectional study designed to determine the factors that are associated with high caries activity in children. Subjects, 12 to 15 years old, residing in areas where the water supplies were either fluoridated (n = 140) or fluoride-deficient (n = 173) were studied. Mutans streptococci and lactobacilli numbers in saliva were positively correlated with plaque index. Plaque indices were significantly higher in the high-caries group than in the zero-caries group of the fluoride-deficient community. In the fluoridated community, there was no difference in the plaque index between the zero- or high-caries groups. In each community, pooled dental plaque and saliva harbored fewer mutans streptococci and lactobacilli in the zero-caries than the high-caries group. Greater numbers of mutans streptococci were found in the dental plaque and saliva of the zero-caries subjects in the fluoridated community than in the fluoride-deficient community, suggesting that a greater caries challenge can coexist with zero-caries status in the fluoridated community.

Adolescent↗
PubMed1990

Ioxilan, a third generation low osmolality nonionic contrast medium. Systemic and renal hemodynamic effects.

The choice between high cost, low toxicity nonionic contrast media (CM) and low cost ionic CM poses a dilemma for radiologists. Ioxilan, a third generation nonionic CM, is obtained by simple conversion from an ionic CM. To examine how this economically promising, low osmolality CM (570 mOsm at 300 mgI/ml) affects canine systemic and renal hemodynamics, IV bolus injections of 350 mgI/ml at 2 ml/kg of Iohexol and Ioxilan were compared. Satisfactory nephrograms and pyelograms were produced by both agents, without significant differences. The effects on systemic and renal hemodynamics were minimal and statistically equal for both CM. The acute systemic and renal responses and radiographic image quality of Ioxilan and Iohexol confirm that the two compounds are biologically equivalent, and that the novel molecular design employed in Ioxilan to achieve very low osmolality also provides good biological tolerance.

Animals↗
PubMed1990

Comparison of the iodide permeability test, the surface microhardness test, and mineral dissolution of bovine enamel following acid challenge.

The relationship among the iodide permeability (Ip) test, the surface microhardness (SMH) test, and enamel demineralization chemically analyzed as mineral loss was investigated using bovine enamel blocks. Demineralization periods of 0 (control) and 5, 15, 30, and 45 min using 0.05 mol/l lactate (pH 4.75) were chosen to approximate the acid challenge occurring during the intraoral enamel demineralization test. Mineral loss (Ca and PO4) was found to be directly proportional to dissolution time (r = 0.95). Changes (delta) in Ip and SMH each increased linearly over time (r = 0.58 and 0.64, respectively) and were similarly related to mineral loss (r = 0.60 and 0.65, respectively). The correlation between delta Ip and delta SMH was 0.55. When longer demineralization periods (60, 120, and 240 min) were included, the correlation between delta Ip and delta SMH was 0.68. We conclude that both the Ip test and the SMH test can be used as measures of the early stages of enamel dissolution.

Animals↗
PubMed1990

Correlations between numbers of microflora in plaque and saliva.

An epidemiologic investigation to reliably identify caries-susceptible subjects by microbiological and chemical assessment of plaque and saliva is currently in progress. As part of that study, the numerical relationships of mutans streptococci, lactobacilli and total viable microflora in plaque and saliva among 12- to 15-year-old children in a fluoridated community were determined. Paraffin-stimulated whole saliva and pooled dental plaque were collected. Each sample was suspended in reduced transport fluid, chilled on ice, and assayed. The bivariate normal distribution was found to be a suitable model for the distribution of the pairs [numbers of bacteria in plaque (log10), numbers of bacteria in saliva (log10)]. Statistically significant positive correlations were found between numbers of mutans streptococci in plaque and saliva, and between lactobacilli in plaque and saliva.

Adolescent↗
PubMed1990

Patient satisfaction in four types of dental practice.

There has been a significant growth in alternative types of dental practice. To determine satisfaction, patients were surveyed in urban private practices, a hospital dental clinic, a neighborhood health center, and a large group practice situated in a shopping center, using a 14-item survey and a 5-point rating scale. Patient satisfaction was related to the following factors in descending order: dentist, staff, efficiency, time-cost, and accessibility. Patients rated private practice most favorably for all factors with the exception of accessibility, which was rated highest for the shopping center practice. Patients rated the hospital least favorably for all factors with the exception of dentist, which was rated least favorably for the shopping center practice. Although private practices were the most favorably perceived, alternative types of practice were also highly rated and met specific patient needs. Satisfaction was greater for older patients, for patients with less education, and for white compared with black patients.

Adult↗
PubMed1989

Inhibitory effect of barium on caries formation in rats.

The aim of this investigation was to study the effect of barium and fluoride in drinking water on caries formation in rats. Sprague-Dawley rats were fed a cariogenic diet (MIT-200) 17 times daily in a König-Hofer programmed feeding machine for 37 days. Drinking water containing barium (0, 50 or 100 ppm) and fluoride (0 or 10 ppm) was available ad libitum. Rats to whose water was added 50 ppm barium had significant reductions in the mean severity of both buccolingual lesions and sulcal lesions compared with those rats whose water contained no barium. As expected, F at 10 ppm in the drinking water significantly reduced caries severity but this F effect was independent of the barium effect. This suggests that the inhibitory effects of barium and fluoride at these levels are additive and operate by separate mechanisms.

Animals↗
PubMed1989

Fluoride uptake into demineralized primary enamel from fluoride-impregnated dental floss in vitro.

Fluoridated mouthrinses are not advised for preschool children who may swallow much of the agent. An alternate method of delivering topical fluoride to the interproximal tooth surfaces in these young patients may be fluoridated dental floss. The purpose of this study was to determine the fluoride levels of demineralized primary enamel both before and after the use of a commercially available dental floss impregnated with commercially available fluoride-containing products. The results showed that demineralized primary tooth surfaces treated with fluoride-impregnated dental floss exhibited significantly higher fluoride levels than those surfaces treated by immersion in a fluoridated mouthrinse or deionized water.

Dental Devices, Home Care↗
PubMed1988

Role of angiotensin II in renal hemodynamic functions during the initial stages of acute ureteral obstruction.

This investigation examines the role of Angiotensin II in renal hemodynamic functions during acute unilateral ureteral obstruction (UUO) in a dog model. An electro magnetic flow probe was utilized to assess renal blood flow while the arteriovenous extraction technique of technetium 99m DTPA was utilized for the assessment of changes in filtration fraction and glomerular filtration rate. The effects of Angiotensin II receptor blockade on renal hemodynamic functions during acute UUO was evaluated in six dogs and compared to acute ureteral obstruction without receptor blockade in seven dogs. Angiotensin II blockade with (Sar1, Thr8)-Angiotensin II during UUO led to a striking increase in renal blood flow that was significantly different in comparison to normalized values from UUO alone (+delta 63 +/- 17 vs. +delta 22 +/- 6% at 30 min; p less than 0.05). There were, however, no significant differences in the magnitude of the decrease in filtration fraction and glomerular filtration rate in comparison to UUO alone. This investigation demonstrates that Angiotensin II has an inhibitory effect on the initial increase in renal blood flow with acute UUO. The possibility of successful pharmacologic intervention in the setting of UUO can be examined using animal models similar to the one described here. Pharmacologic treatment in the setting of acute UUO in patients might permit better preservation of renal function.

Angiotensin II↗
PubMed1988

Computed tomographic evaluation of the density of the temporomandibular joint meniscus.

Pathologic alteration of the articular disk, including moderate calcification within the meniscus proper, has been reported to occur in many cases of TMJ dysfunction with chronic anterior meniscal displacement. The purpose of this investigation was to measure, by means of direct sagittal computed tomographic scanning technology, the density (x-ray attenuation) of the meniscus. Fifty-two joints, shown to have meniscus displacement with or without reduction (MD/MDR), and 24 symptomatic joints with normal tomograms were evaluated with the use of a GE 8800 CT scanner. Mean attenuation values were extrapolated with the use of a symmetrical (1 to 9 pixels) region-of-interest (ROI) cursor. Density gradients of the masseter muscle, lateral pterygoid fat pad, and lateral pterygoid muscle were also obtained. The results of this study showed that the mean meniscal density values were 116.7 +/- 4.2 Hounsfield units (HU) for MD subjects, 111.3 +/- 4.6 HU for MDR subjects, and 82.4 +/- 2.9 HU for subjects with symptoms. The MD and MDR density group means were significantly different (p less than 0.001) from the normal group means. A relative comparison of the meniscus density with that of the lateral pterygoid muscle, its fat pad, and the masseter muscle showed a consistent mean difference when the paired t test was used. Meniscal displacement was found to be associated with an increase in density gradient, which suggests histologic alteration.

Adult↗
PubMed1988

Retention of topical fluoride in the mouths of xerostomic subjects.

The total fluoride concentration in unstimulated whole saliva was measured before and at selected intervals after a self-applied 1.1% neutral NaF topical fluoride gel or use of a 0.05% neutral NaF fluoride mouthrinse in both normal individuals and patients with radiation-induced xerostomia. As expected, the gel resulted in higher peak fluoride values than the rinse and was retained in the mouth for longer periods of time in both groups. The xerostomic group expressed a mean oral fluoride concentration of 575 micrograms fluoride per gram of saliva within 1 min after the gel application and 150 micrograms/g following use of the mouthrinse, whereas the normal group exhibited peak concentrations of 112 and 71 micrograms/g, respectively, within 1 min after the same two treatments. The initial high levels of fluoride observed in normal subjects following the gel application decreased rapidly to less than 1 microgram/g within 2 h, whereas fluoride levels in the xerostomic subjects remained elevated above 12 micrograms/g for longer than 2 h. Similarly, following use of the mouthrinse, normal subjects' saliva fluoride levels decreased to less than 1 microgram/g within 1 h, whereas xerostomic subjects' saliva fluoride levels remained above 4 micrograms/g for longer than 2 h.

Adult↗