The inhibition of mercury absorption by dietary ethanol in humans: cross-sectional and case-control studies.

BACKGROUND: Since the inhibition of mercury absorption by ethanol was serendipitously discovered in 1965,(1) a limited number of small number studies with both animal and human subjects have reported results consistent with this finding. AIMS: To investigate this phenomenon in a large scale human study with low level Hg exposed dentists. METHODS: Data were collected for a sample of 1171 dentists, and both cross sectional and case-control methods were utilised to examine the data. RESULTS: Abstainers (n = 345) had significantly higher urinary mercury concentrations (HgU) than drinkers (n = 826): 5.4 microg/l v 4.8 microg/l. Multiple linear regression showed a significant effect of ethanol dose on HgU after adjusting for potential confounders. A case-control analysis in which cases were defined as those individuals with urinary Hg concentrations of > or =15 microg/l (approximately top 5%), and controls as those with concentrations of <1.0 microg/l ( approximately bottom 5%), showed a clear protective dose-response relation; there was a decreasing risk of being a "case" (having an HgU > or =15 microg/l) with increasing ethanol consumption. The significance of the adjusted model is p<0.001, and the chi2 test for trend across ethanol consumption categories in the adjusted model is p<0.05, confirming the dose-response relation. CONCLUSION: We believe that this straightforward investigation provides the first specific confirmation in a large scale human study of the inhibitory effect of ethanol on urinary mercury concentration, and by inference, on mercury absorption.

Behavioral effects of low-level exposure to Hg0 among dental professionals: a cross-study evaluation of psychomotor effects.

A Across-study design was used to evaluate the sensitivities of five psychomotor tasks previously used to assess preclinical effects of low-level Hg0 (urinary < or =55 microg/l). Pooling dental professional subject populations from six studies conducted over the last 6 years, a larger study population was obtained with a high degree of uniformity (N = 230). The five psychomotor tests were: Intentional Hand Steadiness Test (IHST); Finger Tapping: The One-Hole Test: NES Simple Reaction Time (SRT); and Hand Tremor. Multivariate analyses were conducted following the hierarchical analysis of multiple responses (HAMR) approach. First, multiple scores of each test were combined into a single-factor (or related summary) variable and its reliability was estimated. Second. multiple regression analyses were conducted including log-transformed [Hg0]U levels, age, gender, and alcohol consumption in each model. Computed were both B and bu, the magnitudes of the log-Hg0 standardized coefficient. respectively uncorrected and corrected for dependent variable attenuation due to unreliability. Results indicated remarkable differences in the effects of relative level of Hg0 on psychomotor performance. Significant associations were found for the IHST factor (B = 0.415, p < 10(-6)), followed by finger tapping, which was relatively meager and insignificant (B 0.141, p = 0.17). The IHST results hold the greatest occupational relevance for dental professionals who rely on manual dexterity in restorative dentistry. Further, this statistical approach is recommended in future studies for condensation of multiple scores into summary scores with enhanced reliabilities useful in correcting for attenuation relationships (B(u)s) with exposure levels.

Short-chain carboxylic acid concentration in human gingival crevicular fluid.

Short-chain carboxylic acids (e.g., lactic acid, propionic acid, butyric acid) are metabolic by-products of bacterial metabolism which can accumulate in the gingival crevice. It is of no small consequence, therefore, that 1- to 5-mM concentrations of these acids exhibit significant biological activity, including the ability to alter cell proliferation and gene expression in cells of importance to the periodontium. This communication reports on the in vivo concentrations of propionic and butyric acid in the gingival crevices of periodontal subjects with severe and mild disease. The results indicated that severely diseased subjects exhibited a > 10-fold increase in the mM concentration of these acids when compared with mildly diseased subjects (mean propionic acid-severe = 9.5 +/- 1.8 mM, and mild = 0.8 +/- 0.3 mM; mean butyric acid-severe = 2.6 +/- 0.4 mM, and mild = 0.2 +/- 0.04 mM). These differences (mean +/- SE) were significant (p < 0.0001). The propionic and butyric acid concentrations were below detection limits in healthy sites of mildly diseased subjects. The propionic and butyric acid concentrations also associated significantly with clinical measures of disease severity (e.g., pocket depth, attachment level) and inflammation (e.g., subgingival temperature, % of sites bleeding when probed), and with the total microbial load (all p < 0.05). Taken together, these data suggest that short-chain carboxylic acids play a mediating role in periodontal disease pathogenesis.

The relationship of gingival crevicular fluid short chain carboxylic acid concentration to gingival inflammation.

Short-chain carboxylic acids (SCCA; C < or = 5; e.g., lactic acid, propionic acid, butyric acid) are metabolic by-products of bacterial metabolism which accumulate in the gingival crevice, and exhibit significant biological activity, including the ability to alter gene expression. It has been hypothesized that among the activities of SCCAs are their ability to contribute to gingival inflammation. This concept complements the notion that specific periodontal pathogens are the causative agents of gingival inflammation. To begin testing these 2 hypotheses, we examined the relationship between SCCA concentrations, specific putative periodontal pathogens, and gingival inflammation in medically healthy periodontally diseased subjects. We reasoned that if SCCAs and/or specific periodontal pathogens were causative gingival inflammatory agents, gingival inflammation should increase with increasing concentration of the inflammatory mediator. We also recognized that other clinical variables needed to be controlled for, and an objective quantitative assessment of gingival inflammation used. To accomplish these tasks, sites within subjects were stratified by location and pocket depth, and the following quantified: bacterial presence; SCCA concentration; and gingival inflammation. The results indicated that gingival inflammation directly and significantly correlated with SCCA concentrations in the maxillary and mandibular molars, incisors and canines (all r > or = 0.47; all p < or = 0.015; too few bicuspids were available for complete analysis). The relationship between gingival inflammation and SCCA concentration was best described by a natural log relationship. Gingival inflammation did not, however, correlate positively with either the total number of specific putative periodontal pathogens, or the sum of subsets of these pathogens (-0.31 < or = r < or = 0.39; 0.08 < or = p < or = 0.75) for any of the locations. Finally, the SCCA concentration did not correlate with the level of individual or groups of pathogens. These data, together with historical work and other preliminary data, support the hypothesis that SCCA, rather than specific putative periodontal pathogens, may be a causative agent in gingival inflammation. This work may, in part, begin to explain the apparent lack of a direct relationship between current gingival inflammation and the prediction of bacterially mediated periodontal attachment loss.

The validity of spot urine samples for low-level occupational mercury exposure assessment and relationship to porphyrin and creatinine excretion rates.

Hg and porphyrin levels in single void urine specimens (spot samples) were compared with calculated 24-hr urine levels in 35 (20 [correction of 25] male and 15 female) practicing dentists who had been occupationally exposed to low levels of elemental Hg. The study aimed to: 1) determine the individual variability for Hg and porphyrin concentrations in spot samples over a 24-hr period; 2) test for the presence of diurnal variation in urinary Hg and porphyrin concentrations; and 3) determine the time of day at which a spot sample would give a Hg concentration closest to the 24-hr average concentration. Results confirmed previous reports of a first-order diurnal pattern with a mid-morning peak for Hg concentration (P < .001). A second-order model best described creatinine excretion (P = .0089), with peaks at about 5:00 and 19:00. The use of creatinine adjustment for Hg concentration significantly reduced the intraindividual variation around the diurnal curve. No diurnal patterns were found for any of the porphyrins examined. We recommend that, for small clinical studies using urinary Hg concentration, 24-hr sampling would be ideal, but that for mass screenings and cross-sectional studies, spot samples may be useful because they correlate fairly well with 24-hr averages (creatinine adjusted, r = 0.61; unadjusted, r = 0.74). Because of the existence of diurnal variation, for all cases using serial sampling attention should be paid to time of day.

Factors contributing to mercury exposure in dentists.

Although mercury exposure levels among dentists have been steadily decreasing, occupational mercury exposure among dental professionals continues to be a matter of interest. This study examined personal professional and office characteristics of dentists to determine which factors contribute most to exposure. The resulting information will help dental professionals change their practices to minimize unnecessary exposure to elemental mercury.

Subgingival temperature as a gingival inflammatory indicator.

Elevated temperature is one of 4 cardinal inflammatory signs. Previous work indicates that subgingival temperature assessments are accurate and re- liable, and provide objective, quantitative information over a broad 10 degrees C range, in small 0.1 degrees C increments with a direct, immediate report on the inflammatory status at the pocket base. However, complicating the use and interpretation of subgingival temperature assessments are its 3 forms: actual subgingival temperature, sublingual temperature minus subgingival temperature (temperature differential), and a temperature indicator light. We reasoned that if one could determine which of the temperature assessments reflected the periodontal condition, and which were independent variables, they would provide new and unique information about the inflammatory status of the periodontium. We also reasoned that by providing objective, quantitative data over a broad range, subgingival temperature should reduce the sample size required to obtain significance in clinical trials. Therefore, the purpose of this study was 2-fold: (1) to determine whether the 3 subgingival temperature assessments could differentiate between clinically defined periodontal health and disease; (2) to determine whether the 3 assessments were dependent or independent clinical variables. The data indicated that all 3 subgingival temperature assessment methods differentiated between clinically-defined periodontal health and disease (all p<0.02). All 3 assessments also correlated significantly (all p<0.03), but modestly (all r>0.49), with bleeding on probing. Based on scatter-plot matrices and common factor analysis, the data indicated that only actual subgingival temperature and temperature differential were independent variables. Taken together, this data indicates that subgingival temperature and temperature differential provide unique information about the periodontal inflammatory state. Power calculations indicated that the temperature differential may significantly reduce the subject number required to achieve significance in clinical trials examining gingival inflammation. Because of the body's rapid temperature response, these assessments may also significantly reduce the time required for gingival inflammation trials.

Behavioral effects of low-level exposure to elemental Hg among dentists.

Exposure thresholds for health effects associated with elemental mercury (Hg degree) exposure were examined by comparing behavioral test scores of 19 exposed (mean urinary Hg = 36 micrograms/l) with those of 20 unexposed dentists. Thirty-six micrograms Hg/l is 7 times greater than the 5 micrograms Hg/l mean level measured in a national sample of dentists. To improve the distinction between recent and cumulative effects, the study also evaluated porphyrin concentrations in urine, which are correlated with renal Hg content (a measure of cumulative body burden). Subjects provided an on-site spot urine sample, were administered a 1-h assessment consisting of a consent form, the Profile of Mood Scales, a symptom and medical questionnaire, and 6 behavioral tests: digit-span, symbol-digit substitution, simple reaction time, the ability to switch between tasks, vocabulary, and the One Hole Test. Multivariate regression techniques were used to evaluate dose-effects controlling for the effects of age, race, gender and alcohol consumption. A dose-effect was considered statistically significant below a p value of 0.05. Significant urinary Hg dose-effects were found for poor mental concentration, emotional lability, somatosensory irritation, and mood scores. Individual tests evaluating cognitive and motor function changed in the expected directions but were not significantly associated with urinary Hg. However, the pooled sum of rank scores for combinations of tests within domains were significantly associated with urinary Hg, providing evidence of subtle preclinical changes in behavior associated with Hg exposure. Coproporphyrin, one of three urinary porphyrins altered by mercury exposure, was significantly associated with deficits in digit span and simple reaction time.(ABSTRACT TRUNCATED AT 250 WORDS)

Fractional mercury levels in Brazilian gold refiners and miners.

A field study survey of individuals residing in the region of Para, Brazil, was conducted to determine fractional mercury levels in individuals at risk for exposure in the Brazilian Amazon region. Subjects with a history of exposure to mercury either in the gold mining or refining industry, or exposure to these processes through proximity were included. Three groups were identified as either having recent (less than 2 d since last exposure), intermediate (less than 60 d), or remote (greater than 60 d) exposure to mercury vapors. Fractional blood and urinary mercury levels were assessed for these groups. Group I (recent) had the highest geometric mean blood 24.8 (SD 44.1, range 7.6-158.8) micrograms/L and urine 75.6 (SD 213.4, range 6.5-735.9) micrograms/g-cr (microgram mercury per gram of creatinine) mercury; intermediate (group II) geometric mean blood 7.6 (SD 5.5, range 2.2-19.4) micrograms/L and urine levels 23.8 (SD 84.0, range 7.8-297.0) micrograms/g-cr; the lowest levels in remote exposure (group III): geometric mean blood 5.6 (SD 3.3, range 3.1-14.3) micrograms/L and urine 7.0 (SD 9.8, range 3.1 to 32.9) micrograms/g-cr. The fraction of organic was lowest in group I (32.4%), higher in group II (65.7%), and highest in group III (72.2%). While the frequency of symptoms was comparable in the recent and intermediate groups (2.6 mean, SD 2.3, range 0-8, and 3.1 mean, SD 1.9, range 0-7, symptoms per patient), those with remote exposure demonstrated the highest rate of reporting (6.4 mean, SD 4.1, range 0-11, symptoms per patient). There is significant exposure to mercury for those working in or living near the mining and refining industry. Blood and urine levels are a better marker of recent than remote exposure. The fraction of organic mercury increases with time since exposure. Symptoms may be persistent and low levels of blood and urine mercury do not exclude remote or cumulative toxicity.

Comparative attributes for the description of the relative efficacy of therapeutic agents: general concepts and definitions, and application to the American Dental Association guidelines for the comparison of the clinical anticaries efficacy of fluoride dentifrices.

Comparative attributes are terms or phrases commonly employed in the vernacular of the biomedical literature to convey the results of comparative studies. Examples are such terms as "equivalent" or "superior." Recently, there has developed an increasing tendency in certain areas of application toward the institution of guidelines which provide both a uniform set of criteria for defining such attributes and a set of requirements which must be satisfied in order to demonstrate that such attributes may hold in a particular situation. The present paper provides a general discussion of comparative attributes, from which the application of the underlying concepts to any particular context might better be understood. Second, it provides an explicit and comprehensive discussion regarding the American Dental Associations's guidelines concerning the attributions of "superiority," "equivalence," and "at least as good as," as they are applied to the comparison of the clinical anticaries efficacy of fluoride dentifrices.

Urinary porphyrin profiles as a biomarker of mercury exposure: studies on dentists with occupational exposure to mercury vapor.

Porphyrins are formed as intermediates in the biosynthesis of heme. In humans and other mammals, porphyrins with eight, seven, six, five, and four carboxyl groups are excreted in the urine in a well-established pattern. Mercury selectively alters porphyrin metabolism in kidney proximal tubule cells, leading to an altered urinary porphyrin excretion pattern. Previous studies in rats have shown that changes in the urinary porphyrin profile during exposure to mercury as methylmercury hydroxide are uniquely characterized by highly elevated (20- to 30-fold) levels of four- and five-carboxyl porphyrins and by the excretion of an atypical porphyrin ("precoproporphyrin"), which elutes on high performance liquid chromatography (HPLC) approximately midway between penta- and coproporphyrins. Changes in the urinary porphyrin profile are highly correlated with the dose and duration of mercury exposure and persist for up to 20 wk following cessation of mercury treatment. In the present studies, the utility of urinary porphyrin profile changes as a biomarker of mercury exposure in human subjects was evaluated. Urinary porphyrin concentrations were measured in dentists participating in the Health Screening Programs conducted during the 1991 and 1992 annual meetings of the American Dental Association and compared with urinary mercury levels measured in the same subjects. Among dentists with no detectable urinary mercury, mean concentrations of urinary porphyrins were within the established normal ranges for male human subjects. In contrast, among dentists with urinary mercury in excess of 20 micrograms/L, mean urinary concentrations of four- and five-carboxyl porphyrins as well as of precoproporphyrin were elevated three to four times those of unexposed subjects. Significant differences in urinary porphyrin concentrations remained when porphyrin concentrations in spot urine samples were adjusted for creatinine levels. These findings suggest that urinary porphyrin profiles may serve as a useful biomarker of mercury exposure in clinical or epidemiologic studies of mercury-related human health risks.

Use of an in vitro model to assess the effects of APF gel treatment on the staining potential of dental porcelain.

Porcelains and resin composites exposed to acidulated phosphate fluorides (APF) have been reported to result in increased roughness, loss of weight, and loss of specular reflectance (gloss). Six samples of five commercial porcelains were subjected to five four-minute treatments with APF gels. Samples were then subjected to a nine-day cyclic staining procedure that utilized a tea, coffee, and mucin mixture. Changes in reflectance were then measured by means of a Minolta Chromameter (CR121) and converted to CIE L* a* b* values at illuminant D65 against a white background. delta L*, delta a*, delta b*, and delta E values were calculated. There was a substantial decrease in the L* value (lightness) for all porcelains. The average L* value for APF-treated and then stained porcelains was 43.6, for the stained-untreated samples, 48.2, and for untreated-unstained porcelain, 53.5. For three of the five porcelains, the differences in L* between treated and untreated stained porcelains were statistically significant. Changes in a* and b* values were also found to be consistent with but not as large as the changes in L*.

On-site screening for urinary Hg concentrations and correlation with glomerular and renal tubular function.

At the American Dental Association 1985 and 1986 Annual Sessions, an on-site screening for mercury was conducted as part of the Health Screening Program (HSP) to identify dentists having elevated urinary mercury concentrations. The data generated from this study were used to examine the relationship between elevated urinary mercury exposure and kidney dysfunction. Kidney dysfunction was assessed by measurement of serum and urine beta 2 microglobulin concentrations, serum creatinine, and creatinine clearance. The mean values found for urinary mercury were 5.8 micrograms Hg/L and 7.6 micrograms Hg/L for 1985 and 1986, respectively. Urinary mercury concentrations for this population were found to fall within the range of not detected to 115 micrograms Hg/L. Of the total number of participants assayed in 1985 and 1986, roughly 10 percent of the sample exhibited elevated mercury concentrations above 20 micrograms Hg/L. An analysis of the clinical markers indicated no clear relationship between elevated urinary mercury concentrations and kidney dysfunction. In addition to mercury testing, all dentists who participated in the 1985 and 1986 HSP were issued a questionnaire soliciting information as to their professional exposure. Those participants who were identified as having elevated urinary mercury concentrations in the 1985 HSP were issued a followup questionnaire that addressed psychological and neuropsychological symptoms. From these questionnaires three significant relationships were found. These relationships were associated with mercury/amalgam handling and skin contact, the number of amalgams placed by the dentist, and the number of hours of practice per week. The reported absence of a clear relationship between urinary mercury concentrations and potential kidney dysfunction is in agreement with other findings at the mercury concentrations tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of the effectiveness of glove use as a barrier technique in the dental operatory.

To assess the effectiveness of routine glove use as a barrier technique in the dental operatory, the relationship between frequency of glove use and hepatitis B infection was examined. Hepatitis B screening results and information on infection control practices of 1,109 dentists who attended the 1985 annual session were compiled and statistically analyzed. The results showed that 18% of the dentists wore gloves routinely, 65% wore gloves intermittently, and 17% never wore gloves. Frequency of glove use was related to hepatitis B infection (P less than .01), with dentists who never wore gloves being infected more than twice as often as dentists who wore gloves routinely. Dentists with less frequent glove use and more years in practice had a higher incidence of hepatitis B infection (P less than .0001).