Smokeless tobacco use: how it affects the performance of major league baseball players

The authors examined the effect of smokeless tobacco use on the athletic performance of major league baseball players during the 1988 season. They evaluated performance records of 158 players on seven major league teams who played or pitched at least 10 games or innings during the 1988 season. ST use, they concluded, is not related to player performance in major league baseball but does place players at significantly increased risk for mucosal lesions and other oral pathology.

A survey of endpoint characteristics in periodontal clinical trials published 1988-1992, and implications for future studies

Endpoints are conditions or events that are associated with individual study subjects and that are used to assess treatment efficacy. 2 types of endpoints can be distinguished: "true" endpoints (reflect unequivocal evidence of tangible benefit to the patient) and "surrogate" endpoints (usually a measure of disease process). The purpose of this study was to survey four aspects of endpoint usage in randomized controlled trials (RCT's) on the treatment of periodontitis: (1) the typical number of endpoints per RCT, (2) the proportion of RCTs using the same endpoint, (3) the proportion of RCTs using true endpoints, and (4) whether treatment choice influenced endpoint choice. 92 publications (1988-1992) reporting on 82 RCT's were identified. The typical number of endpoints per RCT was 6 (range: 1-28). The 3 most frequently used endpoints were mean probing depth (78% of the trials), mean probing attachment level (66%), and the plaque index (37%). In total, 153 distinct surrogate endpoints were defined. Most of these were used infrequently; over 80% of the 153 endpoints were used in fewer than 5 of the 82 trials. No trials used tooth loss as a true endpoint. In the design of an RCT, treatment choice influenced surrogate endpoint choice. Surrogate endpoints based on re-entry surgery were exclusively used for regenerative procedures and microbiological surrogate endpoints were mostly used for RCT's on anti-microbials. The conclusion is that the typical RCT used multiple surrogate endpoints, some of which were used infrequently by other trials. Such endpoint usage characteristics are suitable for exploratory RCTs (designed to identify active treatments or to elucidate treatment mechanisms). The question is raised as to whether periodontal research has reached the point of needing properly designed definitive studies, whose purpose it would be to provide unequivocal evidence of tangible benefits to the patient by the various treatments. If a need for definitive randomized controlled trials is perceived, then the use of (multiple) surrogate endpoints as primary outcomes should be questioned. Surrogate endpoint usage has led to both false positive and false negative conclusions in other chronic disease studies. Endpoint selection and validation in RCTs may be an important element in resolving controversies about periodontal treatments.

Do caries explorers transmit infections with persons? An evaluation of second molar caries onsets

Dental caries explorers may become contaminated during routine caries examinations with pathogenic organisms and thereby potentially transmit infections from one tooth to another within a patient. The purpose of this study was to test the hypothesis that the contamination status of explorers influenced the caries risk of second molars. Two explorer contamination statuses were defined: (1) contamination status 1--explorers which had probed a carious molar just prior to examining the second molar, and (2) contamination status 2--sterile explorers versus explorers which had probed several teeth. Caries examinations were performed by 4 dentists on a cohort of 4th grade students in Belize City. The examination dates and sample sizes (n) were: September-October 1989 (n = 1,277), January 1991 (n = 1,111), and January 1992 (n = 961), and January-February 1993 (n = 861). Within this cohort, there were 221 subjects who (1) had at least one pit and fissure carious onset on a caries-free second molar, (2) had no evidence of dental treatments, and (3) were examined by the same examiner during the entire study. After adjusting for confounding variables, the examination of a second molar with a dental caries explorer in either contamination status 1 or 2 had no substantial effect on the caries risk (rate ratio 0.95, 95% confidence interval: 0.77-1.18, and rate ratio 1.18, 95% confidence interval: 0.89-1.56, respectively). If a true rate ratio of 1.7 or greater was associated with the contamination status 1 and 2, these analyses had more than 99 and 80% probability of detecting it, respectively.

CONCLUSIONS

Examining a sound second molar with a contaminated dental explorer either does not affect the caries risk, or results in such a small increase in caries risk that it can only be reliably identified in studies where the exposure of sound teeth to contaminated dental explorers is randomized.

Within-subject coronal caries distribution patterns: an evaluation of randomness with respect to the midline

The distribution of caries among homologous surfaces can exhibit three possible patterns: random, aggregated, or regular. In a random caries pattern, caries lesions are randomly distributed among homologous surfaces. An aggregated caries pattern is distinguished by the aggregation of lesions on one side of the mouth or the other to a greater extent than would be expected by chance alone. For a regular caries pattern, the left-right distribution of lesions is more homogenous than would be expected by chance alone. A test statistic based on the left-right distribution of caries lesions among discordant homologous pairs was developed to investigate which of these three caries patterns is present in a representative sample of the adult United States population. The data originated from the National Survey of Oral Health in the US (Employed Adults), 1985-1986. Of the 15,132 subjects studied, 12,776 subjects had 2 or more decayed or filled teeth. (At least 2 carious or filled teeth are required for detection of patterns.) Approximately 50% of these subjects (n = 6,439) had two or more discordant homologous tooth pairs. With these tooth pairs, the hypothesis of a random caries pattern was rejected in favor of an aggregated caries pattern (p < 0.0001). Similar findings were obtained with discordant homologous surface pairs. This aggregation of caries on one side of the mouth or the other may be due to genetic, infectious, and/or environmental factors.

A re-analysis of caries rates in a preventive trial using Poisson regression models

The analysis of caries incidence in clinical trials has several challenging features: (1) The distribution of the number of caries onsets per patient is skewed, with the majority of patients having few or no cavities; (2) the number of surfaces at risk varies (i) over time and (ii) between patients, due to eruption and exfoliation patterns, dental diseases, and treatments; (3) surfaces within a patient differ in their caries susceptibility, and (4) caries onsets within a patient are correlated due to shared host factors. Recent statistical developments in the area of correlated data analyses permit incorporation of some of these characteristics into the analyses. With Poisson regression models, the expected number of caries onsets can be related to the number of surfaces at risk, the time they have been at risk, and surface- and subject-specific explanatory variables. The parameter estimated in these models is an epidemiological measure of disease occurrence: the disease incidence rate (caries rate) or the rate of change from healthy (sound) to diseased (carious). Differences and ratios of these rates provide standard epidemiological measures of excess risk. To illustrate, Poisson regression models were used for exploratory analyses of the Ylivieska xylitol study.

Evaluation and control of post-cementation pulpal sensitivity: zinc phosphate and glass ionomer luting cements

Many studies have documented pulpal sensitivity after crown cementation, but none have determined its cause. By controlling technique variables in a large-scale clinical trial, the authors evaluated the contribution of zinc phosphate and glass ionomer luting cements in causing pulpal sensitivity or necrosis.

Measures of treatment efficacy

Measures of treatment efficacy are those numbers we think about when we decide whether one treatment is "better" than another. Such measures quantify the differences between treatments and help patients and clinicians make informed choices. The usual measure of treatment efficacy in periodontal research has been the mean difference between treatments in probing level measures. This measure has frustrated clinicians and researchers alike for its failure to communicate the size of the association between treatment and clinical outcome. How does one interpret the clinical relevance of a small mean difference between treatments, such as 0.4 mm? This report compares the advantages and disadvantages of the different measures of treatment efficacy: the mean difference, the relative risk, significance levels (P-values), the risk difference, and, the preventable fraction.

The power of tests to detect differences between periodontal treatments in published studies

10 studies comparing periodontal treatment modalities were re-examined to see if they had adequate power to detect true differences. Attachment level (AL) and pocket depth (PD) were the 2 variables assessed. A statistical test's power refers to its probability of detecting a significant sample difference in treatment means, given a predetermined value for alpha (level of significance), delta (a clinically meaningful underlying difference), and the sample size. Studies were included that stratified their data by initial pocket depths, reported sample size, and lasted at least 6 months. Power calculations were done for 173 treatment comparisons, using delta = 0.5 mm and alpha = 0.05. For shallow pockets (1-3 mm), most studies had a strong chance of detecting true differences (median power = 83%). For moderate pockets (4-6 mm), median power dropped to 38%. However, median power dropped to 14% for deep pockets (> 6 mm), with 75% of the tests having less than a 20% chance of detecting a 0.5 mm difference. Many of the modalities reported as "not significantly different" from each other have not had a fair trial, especially for deep pockets. In order to improve a study's power, 4 factors are discussed: the number of compared treatments, the expected noise or random error, the patient sample size, and the average number of sites per patient for each pocket depth category.

A cohort study of the risk of cervical intraepithelial neoplasia grade 2 or 3 in relation to papillomavirus infection

BACKGROUND

Human papillomavirus (HPV) has been associated with cervical intraepithelial neoplasia, but the temporal relation between the infection and the neoplasia remains unclear, as does the relative importance of the specific type of HPV, other sexually transmitted diseases, and other risk factors.

METHODS

We studied prospectively a cohort of 241 women who presented for evaluation of sexually transmitted disease and had negative cervical cytologic tests. The women were followed every four months with cytologic and colposcopic examinations of the uterine cervix and tests for HPV DNA and other sexually transmitted diseases.

RESULTS

Cervical intraepithelial neoplasia grade 2 or 3 was confirmed by biopsy in 28 women. On the basis of survival analysis, the cumulative incidence of cervical intraepithelial neoplasia at two years was 28 percent among women with a positive test for HPV and 3 percent among those without detectable HPV DNA: The risk was highest among those with HPV type 16 or 18 infection (adjusted relative risk as compared with that in women without HPV infection, 11; 95 percent confidence interval, 4.6 to 26; attributable risk, 52 percent). All 24 cases of cervical intraepithelial neoplasia grade 2 or 3 among HPV-positive women were detected within 24 months after the first positive test for HPV. After adjustment for the presence of HPV infection, the development of cervical intraepithelial neoplasia was also associated with younger age at first intercourse, the presence of serum antibodies to Chlamydia trachomatis, the presence of serum antibodies to cytomegalovirus, and cervical infection with Neisseria gonorrhoeae.

CONCLUSIONS

Cervical intraepithelial neoplasia is a common and apparently early manifestation of cervical infection by HPV, particularly types 16 and 18.

Validity issues in split-mouth trials

The main purpose of the split-mouth design is to remove all components related to differences between subjects from the treatment comparisons. By making within-patient comparisons, rather than between-patient comparisons, the error variance (noise) of the experiment can be reduced, thereby obtaining a more powerful statistical test. Unfortunately, comparisons made on a within-patient basis have potential disadvantages. Treatments may have effects on experimental units other than those which they were assigned to (carry-across effects). Such effects cannot be estimated from split-mouth data. Neither can treatment effects be estimated. The estimable parameter in a split-mouth design is the treatment effect plus the sum of all carry-across effects. Unless a priori knowledge indicates that no carry-across effects exist, reported estimates of treatment efficacy are potentially biased. In the design of split-mouth clinical trials, potential gain in precision should be carefully weighed against a potential decrease in validity.

Determination and selection of the optimum number of sites and patients for clinical studies

Calculating required sample sizes is a critical step in the design of any study. For dental studies, the sample size needs to be specified at two levels: (1) the number of patients (n) enrolled in the study, and (2) the average number of sites (m) examined per patient. In general, m and n should be selected in such a way that the precision of the research findings is maximized, while the cost of the study is minimized. This objective can be realized by taking stock of the components of variation and the costs involved with enrolling patients and examining sites. The research cost for n patients ($C1/patient), at an average of m sites per patient ($C2/site), can usually be approximated by nC1 + nmC2. The precision varies as a function of the variance components, m, and n. To optimize precision for a fixed cost, the average number of sites examined per patient (m(opt)) should be approximately equal to [formula: see text] where rho is the within-patient correlation coefficient of the site-specific variable measured. When m(opt) is approximately equal to or in excess of the average number of sites available per patient, whole-mouth examinations are indicated. When m(opt) is considerably smaller than the average number of sites available, the sample of optimum size should be obtained by some random mechanism. Examination of a number of sites considerably different from m(opt) results in a waste of resources, regardless of the number of patients studied. Standard statistical analyses for determination of the patient sample size required to obtain a pre-specified precision or power are discussed.

Design issues specific to studies of periodontitis

Guidelines for clinical trials demonstrating equivalence or superiority for treatments for periodontitis are badly needed because of the great variety of drugs, agents, and devices now being developed. This paper focuses on three design issues. These are primary outcome variables and their measurement, disease-active vs disease-inactive sites and patients, and study duration. Determinants for selection of outcome variables include the biologic events to be observed, changes that are specific for periodontitis, and methods chosen to detect those changes. The primary outcome variables specific for periodontitis and appropriate for use in clinical trials are periodontal attachment level and alveolar bone status. Improved methods for measurement of both with excellent accuracy and reproducibility are now becoming available. Studies performed on untreated patients over the past decade demonstrate clearly that disease-active and disease-inactive pockets exist, at any given point in time most are inactive, disease progression is episodic and in most patients infrequent, and a rather small portion of the population--possibly around 5%--are unusually susceptible to rapid disease progression. These observations need to be taken into account in enrolling subjects into periodontitis clinical trials. Conducting a prestudy to identify actively diseased sites and susceptible subjects, or screening to enrich the proportion of active sites, is recommended. Determination of study duration is a very complex issue. It is related to the length of time required for maximal change and stabilization to occur in the biological events to be observed, the outcome variable(s) used to detect change, and the nature of the therapeutic interventions to be studied. No single duration is applicable to all periodontitis clinical trials. Large gaps in our knowledge about the design of periodontitis trials still exist, and additional research is needed.

Quantification of periodontal attachment at multi-rooted teeth

The purpose of the present study was to estimate the lost attachment surface area (LAS) and the remaining attachment surface area (RAS) of molars from a combination of clinical and radiographic measurements. Clinical and radiographic measurements on 32 maxillary and 26 mandibular molars were correlated with the post-extraction measurements of LAS and RAS. The results indicate that linear models may increase the precision of the estimate of LAS by a factor of 1.2 for maxillary molars and 1.4 for mandibular molars when compared to estimates of LAS using only attachment level measurements. A diagnostic model for RAS predicts the square root of the remaining attachment surface area with the information obtained from the remaining radiographic attachment area and a gingivitis index. It is concluded that modeling of periodontal data may provide a method for predicting lost and remaining periodontal attachment area of molar teeth.

Cromolyn versus triamcinolone acetonide for youngsters with moderate asthma

Although both cromolyn (C) and inhaled corticosteroids are anti-inflammatory therapies for childhood asthma, there are few controlled comparisons of these medications for asthma therapy in children. None were conducted in the United States, and none specifically study triamcinolone acetonide (T) versus C. This 12-week evaluation followed 31 youths, aged 8 to 18 years, with moderate asthma who were assigned to receive C or T according to a prerandomized and blinded code. Patients were instructed to take two inhalations from the study metered-dose inhaler (active T or placebo) and to inhale the contents of one study-provided ampule (C, 20 mg, or placebo) from a compressor-driven home nebulizer three times per day. Patients also used albuterol, two inhalations from a metered-dose inhaler, three times a day (before study medication) and, additionally, if needed. Patients maintained a daily diary, recording extra medication use, adverse experiences, peak flow rates morning and night, and asthma symptom scores. Laboratory assessment of pulmonary function was done at 1, 4, 8, and 12 weeks. Cosyntropin challenge and methacholine bronchoprovocation challenge were performed at the beginning and end of the study. C and T provided similar, adequate asthma control. Symptoms of wheezing, cough, and chest tightness decreased, and daily peak expiratory flow rate increased with both regimens compared to during a 2-week baseline when patients received medication only as needed. There was no significant change in methacholine sensitivity and no change in endocrine function, as measured with fasting plasma control before and after administration of cosyntropin.(ABSTRACT TRUNCATED AT 250 WORDS)

Measures of dental disease occurrence

The purpose of the paper is to relate standard epidemiologic and statistical methods for measures of disease occurrence to the description of prevalence proportions and incidence rates of dental diseases. No new concepts are introduced, but the choice of the unit of analysis of numerator and denominator is discussed, and the biological interpretation of the within-patient correlation coefficient is discussed.

Clinical study of diffusion hypoxia after nitrous oxide analgesia

In order to estimate the incidence of diffusion hypoxia, arterial oxygen saturation was measured in 104 healthy adult dental patients who were administered nitrous oxide-oxygen analgesia and who did not receive postcessation oxygen. Pretreatment saturation levels as determined by pulse oximetry ranged from 93% to 100%. When the nitrous oxide-oxygen administration ceased, the saturation levels were from 95% to 100%. The mean saturation dropped about 2% over the next 4 min and then stabilized. No patient had a posttreatment oxygen saturation of less than 92%.

Assessment of relationships between site-specific variables

The assessment of relationships between site-specific variables has been a matter of controversy because of the claim that periodontal sites within individuals can be used as independent observations in statistical models. One problem with this approach is the unreliability of the calculated Type I and Type II error rates. Another problem is that such inappropriate analysis may prohibit a correct assessment of causal relationships between site-specific variables. The host-factor can act as an effect modifier and modulate the magnitude of the site-specific effects and/or the host-factor can act as a confounder by superimposing a patient-effect on the studied site-specific effects leading to bias. As a result, site-specific biological mechanisms of disease progression may be misinterpreted. Sites can be used as the experimental unit of analysis, but the sampling design from which the site-specific data originated should not be ignored.

Relationship between gingival crevicular fluid levels of aspartate aminotransferase and active tissue destruction in treated chronic periodontitis patients

Data from several sources demonstrate that disease-active and disease-inactive periodontal pockets exist, and that disease progression occurs in bursts of activity. Currently used diagnostic procedures do not distinguish between disease-active and disease-inactive sites at any given point in time. We report the results of studies aimed at determining whether levels of the enzyme aspartate aminotransferase (AST) in gingival crevicular fluid (GCF) are associated with disease activity as assessed by the level of gingival inflammation and probing attachment loss. 25 previously treated periodontitis patients participating in a quarterly recall maintenance program, who had experienced recurrent periodontal deterioration, served as experimental subjects. Patients were evaluated at 3-month intervals for 2 years. Values for plaque index, gingival index, and probing attachment level were recorded, and 30-second samples of gingival fluid harvested from the mesiobuccal aspect of the 4 first molars and the distal of the 4 lateral incisors. GCF volume was measured using a Periotron 6000, and AST activity was measured by a standard method. Sites were ranked in a hierarchy based on the degree of certainty of attachment loss as well as the severity of gingival inflammation, and the relationship of the values to AST levels was determined. Three models were used to analyze the resulting data, and all led to the same conclusion. Maximum enzyme level was significantly elevated at sites with confirmed disease activity as assessed by attachment loss, with maximum AST levels 725 units higher at these sites, on average, than at other sites (p less than 0.0001). Our data support the idea that an objective diagnostic test, based on levels of AST in GCF, that distinguishes between disease-active and disease-inactive sites may be possible.

Relationship between levels of aspartate aminotransferase in gingival crevicular fluid and gingival inflammation

Data from several sources demonstrate that disease-active and disease-inactive periodontal pockets exist, but currently available diagnostic procedures do not permit identification of disease-active sites at any given point in time. Using the experimental gingivitis model, we have performed studies aimed at determining whether levels of the enzyme aspartate aminotransferase (AST) in gingival crevicular fluid correlate with the presence and extent of periodontal inflammation. Gingival inflammation was assessed using the Gingival Index and the Sulcular Bleeding Index, and enzyme activity was measured using a standard procedure. Our data reveal a statistically significant association between AST values and Gingival Index scores for spontaneously occurring lesions (p less than 0.02-0.04) and experimentally induced lesions (p less than 0.0001), as well as the extent of change in these values during developing experimental gingivitis (p less than 0.0001) and resolving experimental gingivitis (p less than 0.0001). The data demonstrate that AST levels can be used to assess the presence and extent of periodontal inflammation.

Enhanced risk assessment for primary coronary heart disease events by maximal exercise testing: 10 years' experience of Seattle Heart Watch

A 10 year prospective community practice study in Seattle of risk of primary morbidity (defined by hospital admission) and mortality due to coronary heart disease in 3,611 men and 547 women initially free of clinical manifestations of this disease revealed a crude incidence of 202 coronary heart disease events, or 4.9% in 6.1 +/- 2.6 years of follow-up. The case fatality rate was 16.8%. Stratification by clinical classification of asymptomatic healthy persons versus patients with atypical chest pain syndrome (not angina pectoris) and hypertension (as classified by physicians) showed an incidence rate of primary events due to coronary heart disease of 2.9, 5.5 (not significant) and 10.0% (p less than 0.001), respectively. Identification of conventional risk factors is known to be important for risk assessment. However, the presence of any conventional risk factor, in conjunction with two or more selected maximal exercise predictors (which vary with the clinical classification) at enrollment, substantially increased the cumulative 6 year incidence rate to 24.3, 15.5 and 33.3% in asymptomatic healthy men, patients with atypical chest pain syndrome and hypertensive patients, respectively. Observation of the exercise predictors in the absence of conventional risk factors increased the risk much less, suggesting that the use of maximal exercise testing for risk assessment in those with no clinical manifestations of disease might be limited to persons with one or more conventional risk factors.

Prognostic and predictive value of exertional hypotension in suspected coronary heart disease

The prognostic and predictive value of exertional hypotension was assessed in 1,241 patients having treadmill maximal exercise testing, coronary arteriography, and follow-up averaging 5.4 years. Medically treated patients with coronary artery disease (CAD) with exertional hypotension had poorer survival than did those without such hypotension; however, maximum systolic pressure during exercise was a more powerful predictor of survival. Patients with exertional hypotension had more extensive CAD and more left ventricular (LV) dysfunction than did patients who had an increase in blood pressure with exertion; these findings probably account for the impaired survival. However, exertional hypotension, was an insensitive indicator of significant left main coronary artery stenosis, 3-vessel disease, or severe resting LV dysfunction.

Effect of coronary artery bypass grafting on subsequent hospitalization

The rates of hospitalization during follow-up for a matched pair cohort of medically and surgically treated patients from the Angiography Registry of Seattle Heart Watch were compared. Medically and surgically treated patients were matched according to extent of disease, left ventricular ejection fraction, age, and 3 other survival rate-related characteristics. There was a 26% reduction in cardiovascular hospitalizations in the surgically treated patients (19%/year) compared with the medically treated patients (26%/year). This was due to a significant reduction in hospitalization rate for myocardial infarction (surgically treated patients 1.1%/year, medically treated patients 2.6%/year), and for other cardiovascular reasons (surgically treated patients 12.5%/year, medically treated patients 15.7%/year). No significant (p = 0.146) reduction occurred in hospitalization rate for chest pain not due to myocardial infarction (surgically treated patients 5.6%/year, medically treated patients 7.7%/year). When the perioperative infarctions are included for the surgical cohort, the overall myocardial infarction rate is not significantly different (p = 0.173) between the 2 treatment groups (surgically treated patients 1.9%/year, medically treated patients 2.6%/year). Acute myocardial infarction was an uncommon reason for hospitalization, accounting for only 8% (55 of 685) of all cardiovascular hospitalizations, and was not related to the number of stenotic vessels in medically treated patients.