Biomedical subjects

B G Leroux

Publications and source records attributed to B G Leroux.

At least 19 recordsLinked to original sources

PubMed2002

Persistence of oral Candida albicans carriage in healthy Portuguese schoolchildren followed for 3 years.

Little is known about carriage of Candida albicans, the predominant pathogenic yeast in oral infection, in children. We cultured buccal mucosal and gingival swabs from 150 Portuguese children to investigate the prevalence of C. albicans at baseline (before dental treatment), post-treatment, and 12, 24, and 36 months post-baseline. The children, aged 8 to 11 years at baseline, had no systemic disease or clinical symptoms of oral candidiasis. At each successive visit, respectively, 47, 32, 21, 27, and 28% of children were C. albicans positive, resulting in an almost 50% reduction in prevalence from baseline to post-treatment (P < 0.0005). Children who carried C. albicans at one visit had 3 to 20 times greater odds of carrying C. albicans at another visit. C. albicans was cultured from 12 children at all time-points and from 10 children at four time-points. Children with oral C. albicans frequently maintained carriage over time, even with regular dental care.

Age Factors↗

PubMed2001

Reliability of individual differences in initial sensitivity and acute tolerance to nitrous oxide hypothermia.

On average, the hypothermia exhibited by rats receiving 60% nitrous oxide (N2O) eventually abates despite the continued inhalation of the drug (i.e., acute tolerance develops). However, large individual differences occur in both the magnitude of hypothermia achieved and the degree of acute tolerance that develops. To determine whether the degree of temperature loss and subsequent recovery during N2O administration are reliable characteristics of an individual, we measured intraperitoneal temperature via telemetry in 77 Long-Evans rats that each received 60% N2O for 5 h during two sessions separated by 14 days. Good intersession reliability (Pearson's r) was observed for simple change and adjusted change scores for both initial N2O temperature sensitivity (.61 < or = r < or = .62), and acute tolerance development (.46 < or = r < or = .52). In a separate experiment, three groups of rats were selected based on their individual body temperature patterns during an initial N2O administration: (1) insensitive to N2O hypothermia (n = 8); (2) marked hypothermia followed by acute tolerance development (n = 6); and (3) marked hypothermia followed by little acute tolerance development (n = 6). When retested 10 days later, each group exhibited a body temperature profile similar to that observed during the initial N2O exposure. Thus, the temperature profile observed during a rat's initial exposure to 60% N2O reflects a reproducible response for that animal.

Anesthetics, Inhalation↗

PubMed2000

Identification of adult populations at high risk for dental caries using a computerized database and patient records: a pilot project.

OBJECTIVES: The purpose of this study is to test the usefulness of dental insurance claims history, supplemented with radiographic caries diagnoses, as a means of identifying caries-active and caries-inactive working adults, as determined by bacterial levels. Computerized identification of at-risk groups may facilitate subject selection for clinical trials designed to test caries-preventive strategies. METHODS: Two groups of subjects were initially selected from an insurance database based upon their dental service utilization during a one-year period: a "low restorative" group of individuals defined as persons who had received no restorative treatment, and a "high restorative" group comprised of individuals who had received at least three multisurfaced restorations. A chart review confirmed a diagnosis of caries in the high restorative group and an absence of caries in the low restorative group. Subjects were then approached for saliva collection. The low and high restorative groups were compared for salivary mutans streptococci and lactobacilli levels, stimulated flow rate, and buffer capacity (n = 48). RESULTS: The high and low restorative groups differed in mutans streptococci levels, but not on other measures. CONCLUSIONS: A group of subjects who had recently received multisurfaced restorations that were placed for reasons of caries had significantly higher levels of mutans streptococci and potential for continued caries activity when compared to a group of subjects who had received no restorations and were caries free.

Adult↗

PubMed2000

Between-subject and within-subject statistical information in dental research.

The evaluation of risk factors in dental research frequently uses observations at multiple sites in the same patient. For this reason, statistical methods that accommodate correlated data are generally used to assess the significance of the risk factors (e.g., generalized estimating equations, generalized linear mixed models). In applications of these methods, it is typically assumed (implicitly, if not explicitly) that between-subject and within-subject comparisons will produce the same estimated effect of the risk factor. When between- and within-subject comparisons conflict, the statistical methods can give biased estimates or results that are difficult to interpret. For illustration, we present two examples from periodontal disease studies in which different statistical methods give different estimates and significance levels for a risk factor. Statistical analyses in dental research should assess whether different sources of information give similar conclusions about risk factors or treatments.

Confounding Factors, Epidemiologic↗

PubMed2000

Non-surgical periodontal therapy and tooth loss. A cohort study.

BACKGROUND: No reliable evidence is available regarding the effect of periodontal therapy on major disease endpoints such as tooth loss, edentulism, or quality of life. The primary objective of this study was to assess the association between tooth loss and the non-surgical periodontal treatment history of 1,021 members of the Kaiser Permanente Dental Care Program. METHODS: Tooth loss rates were estimated using Poisson regression models, adjusting for some of the potentially confounding variables such as initial disease severity and extent. RESULTS: Continuous non-surgical therapy (one or more non-surgical procedures performed during 3 successive years), as opposed to no therapy during such a 3-year period, reduced the subsequent tooth mortality rate by 58% (relative rate, 0.42; 95% confidence interval, 0.29-0.61). Intermittent non-surgical therapy reduced the tooth mortality rate by 48% (RR = 0.52; 95% confidence interval, 0.34-0.80). As the number of non-surgical procedures increased, tooth loss rates decreased. CONCLUSIONS: These findings suggest that non-surgical periodontal therapy may be associated with a substantial reduction in tooth mortality. Different study designs and populations are needed to confirm these findings.

Adult↗

PubMed1999

Generalized linear mixed models for meta-analysis.

We examine two strategies for meta-analysis of a series of 2 x 2 tables with the odds ratio modelled as a linear combination of study level covariates and random effects representing between-study variation. Penalized quasi-likelihood (PQL), an approximate inference technique for generalized linear mixed models, and a linear model fitted by weighted least squares to the observed log-odds ratios are used to estimate regression coefficients and dispersion parameters. Simulation results demonstrate that both methods perform adequate approximate inference under many conditions, but that neither method works well in the presence of highly sparse data. Under certain conditions with small cell frequencies the PQL method provides better inference.

Humans↗

PubMed1999

Nitrous oxide-induced hypothermia in the rat: acute and chronic tolerance.

Although inhalation of nitrous oxide (N2O) causes hypothermia in rats, there is a paucity of information as to whether tolerance develops to this effect. The purpose of this study was to determine whether tolerance to N2O hypothermia develops within a single administration as well as over repeated administrations. Temperature was measured telemetrically by implanting intraperitoneal thermal sensors/transmitters in male Long-Evans rats. Experimental rats received an initial 2-h exposure to 60% N2O and became hypothermic relative to controls breathing placebo gas. Only a few rats demonstrated evidence of acute tolerance over the 120 min. Over the next 10 days, the experimental rats received five additional 30-min exposures to 60% N2O and five 30-min exposures to placebo while the control rats received only placebo gas exposures. Chronic tolerance developed to N2O hypothermia over these repeated administrations. A test for Pavlovian drug conditioning found no evidence that conditioned temperature effects contributed to chronic tolerance development. In a second experiment, naive rats were given a 380-min exposure to 60% N2O and a 380-min exposure to placebo gas in a counterbalanced order. Acute tolerance did develop to N2O hypothermia, with the recovery of temperature beginning after a mean of 141 min of gas administration. Hence, both acute and chronic tolerance develop to N2O's hypothermic effects in rats.

Administration, Inhalation↗

PubMed1999

Craniofacial morphology and tooth wear: a longitudinal study of orthodontic patients.

Previous research has suggested that a relationship exists between craniofacial morphology and tooth wear. The primary objective of this study was to determine whether an individual's craniofacial morphology during childhood is related to the degree of tooth wear that occurs in that same individual's adult dentition. Pretreatment orthodontic records taken during the mixed dentition (T1) and follow-up records taken an average of 20 years later (T2) were available for 165 orthodontic patients. Incisal/occlusal tooth wear was measured on a tooth-by-tooth basis from T1 and T2 casts using a four-category scoring system. Measures of craniofacial morphology were made from the T1 lateral cephalometric radiograph. Multiple regression analysis indicated that adult wear was associated with the T1 cephalometric measures of ANB (p = 0.017) and the interaction between ramal height and sex (p = 0.039). These results suggest that the craniofacial morphology observed during childhood has a small but significant relationship to adult tooth wear.

Adult↗

PubMed1999

The informativeness of attachment loss on tooth mortality.

BACKGROUND: In periodontal clinical trials, clinical attachment level measurements are commonly used as surrogates for tooth loss. Conclusions regarding treatment efficacy in these trials are valid if: 1) the surrogate is informative on tooth loss, and 2) the surrogate captures the effect of treatment on tooth loss. The goal of this study was to evaluate the first criterion: Are serial clinical attachment loss measurements informative on overall tooth mortality? METHODS: Young Norwegian men (aged 17 to 35) were first examined in 1969 (n=565) and followed for 26 years with examinations in 1971 (n=381), 1973 (n=292), 1975 (n=245), 1981 (n=228), 1988 (n=202), and 1995 (n=223). Several aspects of the serial attachment loss measurements were related to tooth mortality risk using statistical models that take into account the time-dependent changes of the clinical attachment loss measurements. RESULTS: The results provided evidence that moderate attachment losses were informative on tooth mortality. Both the lifetime cumulative attachment loss, as well as attachment loss since young adulthood, of > or = 2 mm or > or = 3 mm was informative on tooth mortality. Tooth mortality risk increased as the attachment loss increased; loss > or = 3 mm at the buccal or mesial site increased tooth mortality risk, by 91% (relative risk, 1.91; 95% confidence interval, 1.01-3.60) and 270% (RR, 3.70; 95% CI, 1.83-7.49), respectively. CONCLUSIONS: We concluded that clinical attachment loss was moderately informative on overall tooth mortality in this Norwegian population. Since this finding has now been demonstrated in 3 different populations, the focus of further research should be on evaluating whether the second criterion for a valid surrogate is satisfied: Does clinical attachment loss capture the effect of periodontal treatments on tooth loss?

Adolescent↗

PubMed1998

Treatment outcomes with mandibular removable partial dentures: a population-based study of patient satisfaction.

STATEMENT OF PROBLEM: Little is known about the outcomes of treatment with mandibular removable partial dentures provided by dentists in private dental practice. PURPOSE: This study examined 15 aspects of patient satisfaction and explored the factors found to be associated with dissatisfaction. MATERIAL AND METHODS: A questionnaire was mailed to people whose dental insurance claims included CPT Code 5214 within the last 5 years. A composite measure of treatment outcome was created by combining the responses to the 15 satisfaction items, and 10 factors were then tested statistically to determine their relationship to dissatisfaction. RESULTS: A majority of the respondents were satisfied with the prosthesis, but a substantial amount of dissatisfaction existed. Dissatisfaction was greater when there was no previous wearing experience or when there was an opposing maxillary removable partial denture. Respondents under the age of 60 expressed more dissatisfaction than did those over the age of 60, and subjects with lower levels of general health also reported less satisfaction. One third of the respondents believed their prosthesis required adjustment or replacement, and one fourth said the removable partial denture had caused a problem with the natural teeth. CONCLUSION: A majority of survey respondents treated with a mandibular removable partial denture in private dental practice were satisfied with the prosthesis, but a substantial amount of dissatisfaction existed. Dissatisfaction was related to age, health, prior experience with a prosthesis, and the type of opposing dentition.

Denture, Partial, Removable↗

PubMed1998

Validity of spot urine samples as a surrogate measure of 24-hour porphyrin excretion rates. Evaluation of diurnal variations in porphyrin, mercury, and creatinine concentrations among subjects with very low occupational mercury exposure.

Porphyrin, mercury, and creatinine levels in single-void urine specimens ("spot samples") were compared with calculated 24-hour urine concentrations among 146 (77 male and 69 female) practicing dentists who are participating in an ongoing study of urinary porphyrin changes as a biomarker of mercury body burden. All subjects had urinary mercury concentrations < or = 5 micrograms/L, a level comparable to that of the general US population and which is below that determined to be associated with mercury-induced changes in urinary porphyrin excretion rates. The results confirmed previous findings of no significant diurnal variation in any of the porphyrin levels normally found in urine or in total porphyrin levels combined among males but describe significant diurnal variations in most porphyrin levels as well as concentrations of total porphyrins combined among females. Similarly, no evidence of large diurnal variation in mercury excretion among males was apparent, whereas significant diurnal variation in the mercury excretion rate among females was found. Creatinine adjustment of porphyrin or mercury concentrations had no significant effect on these findings. Moreover, no evidence of diurnal variation in urinary creatinine excretion among either male or female subjects was obtained, despite substantial between-subject variability in this parameter. These results support the view that spot urine samples may be utilized to derive reasonably accurate estimates of 24-hour porphyrin and mercury excretion rates in male subjects. In contrast, time of day appears to be of considerably greater importance when spot samples are utilized as 24-hour estimates of either porphyrin or mercury excretion rates among females. Additionally, time of day may be an important consideration in studies involving serial (repeated) porphyrin or mercury measurements using spot urine samples, irrespective of gender distribution of study subjects.

Adult↗

PubMed1998

Factors associated with caries incidence in an elderly population.

The purpose of this paper was to identify baseline factors associated with future caries development in older adults (age 60+) during a 3-year study period. Poisson regression analysis was used to determine the association between potential risk factors and disease incidence. The significant factors associated with high coronal caries incidence rates were high baseline root DMFS (P<0.001), high counts of mutans streptococci and lactobacilli (P=0.036), male gender (P=0.007), and Asian ethnicity (P=0.002). These factors had small to moderate effects on incidence rates, with relative risk values of approximately 1.2 to 2. The significant factors associated with higher disease incidence on root surfaces were baseline coronal DMFS (marginally significant, P=0.078), high bacterial counts (P=0.002), and Asian ethnicity (P=0.009). The predictive value of the models was low for both coronal and root caries. This result may be because this population had a higher than usual caries incidence rate, making discrimination among these caries-active individuals difficult. The current study affirmed the value of baseline DMFS and salivary variables to modeling caries incidence and introduced ethnicity as a variable useful for the study of dental caries in older adults.

Aged↗

PubMed1998

Forty-five-year tooth survival probabilities among men in Oslo, Norway.

Changes in tooth survival probabilities over a person's lifetime have remained largely unexplored. The goal of this study was to evaluate changes in the 45-year tooth survival probabilities in a cohort of 565 Norwegian males who were examined in 1969 as young adults, and followed up into mid-life (examination years and sample sizes (n): 1971 (n = 381), 1973 (n = 292), 1975 (n = 245), 1981 (n = 228), 1988 (n = 202), and 1995 (n = 223). The results indicated that the tooth survival probabilities varied considerably both (i) among teeth within individuals, and (ii) over time. The 45-year survival probabilities for the 28 teeth fell into the following ranges: larger than 95% for incisors and cuspids; between 84% and 92% for premolars; and between 59% and 96% for molars. Over the first 4 post-eruptive decades, the tooth mortality risks (excluding orthodontic extractions) were: 1st decade, 2.0% (from 1.7 to 2.4%); 2nd decade, 0.2% (from 0.1 to 0.4%); 3rd decade, 0.6% (from 0.4 to 0.8%); and 4th decade, 1.1% (from 0.8 to 1.5%). The tooth mortality risks in the 2nd, 3rd, and 4th decades were probably somewhat underestimated (due to dropout bias), suggesting that the true underlying tooth mortality hazard function may have been V-shaped. The conclusions were that the tooth mortality hazard during the first 4 post-eruptive decades was bathtub-shaped and that it varied considerably among teeth within individuals.

Adolescent↗

PubMed1998

Evaluating the burst hypothesis at a site-specific level using the lack-of-fit test.

It has been hypothesized that periodontal disease progresses by means of sudden losses of periodontal attachment surface area. Obtaining reliable tests of this burst hypothesis has proven to be difficult; the signal (true model of disease progression) often gets lost in the noise. The purpose of this study was to determine how reliably we could distinguish sudden changes from linear disease progression at a site using a time series of clinical attachment levels. Specifically, the following question was investigated: If, in reality, disease progresses by means of sudden changes in clinical attachment level (bursts), and a linear model is fitted to these data, what is the likelihood of rejecting the linear model using the lack-of-fit test? This likelihood was determined as a function of the probing measurement error (range: 0.2 to 1.0 mm) and the number of clinical examinations over time. The results suggested that bursts of 2 mm or smaller cannot be reliably distinguished from linear disease progression using the lack-of-fit test, except under unusual clinical circumstances. Under typical clinical circumstances, burst sizes needed to be 3 to 5 mm in order to be reliably distinguished from linear disease progression. These results are probably overly optimistic. The ability to verify the burst hypothesis at the site level is likely to be even less than our results indicate because of various assumptions that were required. We conclude that the lack-of-fit test will reliably reject the linear model at a site-specific level only if true disease progresses in such a fashion that a handful of sudden changes leads to a tooth mortality event.

Algorithms↗

PubMed1997

A longitudinal study of tooth wear in orthodontically treated patients.

The primary objective of this study was to determine whether there is a relationship between incisal/occlusal tooth wear during the mixed dentition and subsequent wear of the adult dentition. Pretreatment orthodontic records taken during the mixed dentition (T1), as well as follow-up records taken an average of 20 years later (T2), were available for 223 orthodontically treated patients. Incisal/occlusal tooth wear was measured on a tooth-by-tooth basis from T1 and T2 stone casts with a four-category scoring system. Multiple regression analysis (R2 = 0.33) indicated that wear could be predicted at a given age during adulthood from wear observed on the deciduous mandibular canines and molars at T1 (p < 0.0001). This predictive relationship was modified by the age at which the T1 wear was observed (p = 0.029) and possibly by the sex of the patient (p = 0.10). These results indicate that adult tooth wear is not independent of the tooth wear that occurred as a child. Bruxism is suggested as a possible common etiologic mechanism that may account for the relationship between childhood and adult tooth wear.

Adolescent↗

PubMed1997

Evaluating the validity of probing attachment loss as a surrogate for tooth mortality in a clinical trial on the elderly.

Most periodontal trials are based on the assumption that the superior treatment, as judged by short-term intangible changes in probing attachment levels (the surrogate), is also the treatment most likely to affect tooth mortality. This assumption is valid if: (1) the surrogate is informative about tooth mortality, and (2) the surrogate captures a substantial proportion of the treatment effect on tooth mortality (e.g., > 50% or 75%). The goal of this study was to evaluate whether both conditions were satisfied in a randomized controlled trial (RCT) of elders at high risk for dental diseases. The results suggested that the first condition for a valid surrogate was satisfied: Both one- and two-year changes in probing attachment level were informative about tooth mortality risk. A 1-mm loss measured over a one-year period was associated with a 56% increased tooth mortality risk (relative risk = 1.56; 95% confidence interval, 1.08 to 2.26; p = 0.017); a 1-mm loss measured over a two-year period was associated with a 102% increased risk for tooth mortality (relative risk = 2.02; 95% confidence interval, 1.26 to 3.25; p = 0.004). The second condition necessary for a valid surrogate could not be confirmed in the present trial. With 95% confidence, it was concluded that one-year changes in probing attachment level measurements did not capture a significant proportion of the treatment effect (point estimate, 6%; 95% confidence interval;-38% to 53%). No useful statements could be made regarding the proportion of treatment effect captured by two-year changes, due to the width of the confidence interval (point estimate, 18%; 95% confidence interval;-151% to 140%). It is concluded that (1) the evidence surrounding the one-year change in probing attachment level indicates that it can be ruled out as being anything more than a weak surrogate marker for tooth mortality, and (2) further research is required to study the validity of two-year change in probing attachment level as a surrogate marker. Due to characteristics of the population and the treatments investigated, the generalizability of these findings to other RCTs is questionable.

Aged↗

PubMed1996

A biologically-based dose-response model for developmental toxicology.

The methods currently used to evaluate the risk of developmental defects in humans from exposure to potential toxic agents do not reflect biological processes in extrapolating estimated risks to low doses and from test species to humans. We develop a mathematical model to describe aspects of the dynamic process of organogenesis, based on branching process models of cell kinetics. The biological information that can be incorporated into the model includes timing and rates of dynamic cell processes such as differentiation, migration, growth, and replication. The dose-response models produced can explain patterns of malformation rates as a function of both dose and time of exposure, resulting in improvements in risk assessment and understanding of the underlying mechanistic processes. To illustrate the use of the model, we apply it to the prediction of the effects of methylmercury on brain development in rats.

Abnormalities, Drug-Induced↗

PubMed1996

The estimation of caries prevalence in small areas.

National surveys have been effective for the estimation of caries prevalence in broad regions of the US. However, it is unclear if data from such surveys can be used to estimate prevalences in small areas such as states or counties because of small sample sizes within individual areas. In this study, we applied specialized statistical methods to the estimation of small-area caries measures using data from an oral health survey conducted in the State of Washington. Dental exams to assess caries and the presence of sealants and fluorosis were performed on 2921 third-grade students in 84 public schools selected by a stratified random sample from all 39 counties in the state. Statistical methods for small-area estimation were used to estimate disease and sealant utilization measures for each of the counties. Adjustment was made for covariates measured at the school level, including ethnicity and the proportion of children in the Federally sponsored school lunch program. Substantial variability in disease and sealant utilization between counties was found. The estimated number of decayed and filled surfaces per child was 4.7 (inter-county range, 2.4 to 7.4). The estimated number of surfaces of untreated decay was 1.2 per child overall (range, 0.5 to 3.1). Thirty percent of the children had restorative treatment needs (range, 15 to 54%). The prevalence of sealants on one or more permanent molars was estimated to be 34% (range, 19 to 46%). Overall, only 8% of children showed evidence of fluorosis. The results demonstrate the usefulness of small-area estimation methods for oral health surveys.

Child↗