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Biomedical subjects

U Helfenstein

Publications and source records attributed to U Helfenstein.

At least 37 records · Page 2Linked to original sources
PubMed1994

[The caries occurrence in 7- to 12-year-old schoolchildren in Switzerland. The results of a country-wide survey 1987-89].

Between 1987 and 1989, a random sample of school children aged 7 and 12 years in Switzerland was drawn. In the first stage, districts were chosen. Within the districts, 12 children in the two specified age groups were selected. In addition, Switzerland was subdivided into two strata. The children of stratum 2 had consumed fluoridated salt since birth while those of stratum 1 had only done so during the preceding 4 to 5 years but had benefitted since the age of 5 to 7 from dental health education programs using fluorides at school. The oral examinations were carried out according to the methodology of the World Health Organization. Attendance was 94% (1115 children). 47% of the seven-year-old children were caries-free, and the average dmft was 2.20 (95% confidence limits at 1.87 and 2.52). The average dt was 1.06. These children had an average DMFT of 0.40, with 77% having DMFT = 0. At the age of 12, the average DMFT was 2.03, with confidence limits at 1.73 and 2.33. On average, they had 0.45 DT and 38% of them were caries-free (DMFT = 0). There were only minor differences between the 2 strata. These results agreed well with the data from 6 local surveys carried out during 1987 to 1989. When compared with the majority of European countries, caries experience of Swiss children was fairly low.

Age Distribution↗
PubMed1994

[An empirical report on fissure sealing in private practice with a duration of up to 10 years].

This study reports a follow-up on 2415 occlusal sealings performed in a dental office. After nine to ten years service time, the survival rate of all sealed surfaces dropped to 69.5% because of either occlusal or interproximal carious activities. Retention of the sealings was intact in 91.5% after one year, but dropped to 58.2% after nine years. In the control group 49.3% of the grooves showed either caries or fillings during the last check-up whereas this occurred in only 7.3% of the sealed teeth (ratio 7:1). The difference among those two groups was even bigger (45.7% vs. 5%, ratio 9:1) when excluding all two-sided fillings. The costs of restoring one tooth surface in the control group was on average two to three times higher than for the sealings group. There is no doubt about the beneficial prophylactic effect of the use of sealants, even in the context of the private dental office, and no inconvenient side-effects have been found. The results concerning the retention rate of sealing in this study from a private dental office are comparable with the average of those reported in many papers from U.S. Dental Schools, they are even slightly better for the caries incidence.

Adolescent↗
PubMed1992

Dental predictors of high caries increment in children.

A comprehensive set of dental variables was investigated to find the "best" combination of predictors for high caries increment in 7/8-year-old and 10/11-year-old children. Four populations with widely different caries prevalence were studied. Logistic regression analysis supplied multiple-input models by stepwise selection of predictors. A "low number of sound primary molars" was the best and most consistent predictor of high caries increment. The second best predictors were "high numbers of pre-cavity lesions on permanent first molars" (discolored pits and fissures in the younger age group and white spots on the smooth parts of buccolingual surfaces in the older age group). Inclusion of radiological variables did not substantially increase the quality of prediction. For practical application, models with various multiple inputs selected by stepwise procedures were compared with "fixed" three-input models. These three-input models resulted in predictive quality nearly equal to those of the multiple models. Traditional one-input models, containing DMFT or dmft, were inferior to the three-input models, particularly in the older age class. The lower the caries prevalence of the source data, the better was the prediction. As a summary measure characterizing the predictive performance of a model, we used the index "area under the receiver operating characteristic curve" A. For the 1984 data and the three-input models, the area was approximately 80%, and for the 1972 data, the area was 65-70%.

Age Factors↗
PubMed1991

The environmental accident at 'Schweizerhalle' and respiratory diseases in children: a time series analysis.

During an investigation concerned with the relationship between air pollution and respiratory diseases in children, the 'Schweizerhalle' accident occurred when unknown amounts of pollutants were discharged into the environment. In that investigation, two series of medical data were collected during one year: (a) The daily relative number of preschool children, exhibiting diseases of the respiratory tract, who either came to the outpatients' clinic of the Children's Hospital or were reported by paediatricians in Basle; (b) The daily number of respiratory symptoms per child, observed in a group of randomly selected preschool children. The purpose of the present time series analysis is the assessment of possible change in these series after the environmental accident. The nature of the change is studied by complementary approaches. First, a forecast arising from models identified in the preaccident period is compared with the actual data. Thereafter, intervention models which adequately and parsimoniously represent the change are identified. Finally, an identification of a change-point is performed.

Accidents↗
PubMed1991

The use of transfer function models, intervention analysis and related time series methods in epidemiology.

In epidemiology, data often arise in the form of time series e.g. notifications of diseases, entries to a hospital, mortality rates etc. are frequently collected at weekly or monthly intervals. Usual statistical methods assume that the observed data are realizations of independent random variables. However, if data which arise in a time sequence have to be analysed, it is possible that consecutive observations are dependent. In environmental epidemiology, where series such as daily concentrations of pollutants were collected and analysed, it became clear that stochastic dependence of consecutive measurements may be important. A high concentration of a pollutant today e.g. has a certain inertia i.e. a tendency to be high tomorrow as well. Since the early 1970s, time series methods, in particular ARIMA models (autoregressive integrated moving average models) which have the ability to cope with stochastic dependence of consecutive data, have become well established in such fields as industry and economics. Recently, time series methods are of increasing interest in epidemiology. Since these methods are not generally familiar to epidemiologists this article presents their basic concepts in a condensed form. This may encourage readers to consider the methods described and enable them to avoid pitfalls inherent in time series data. In particular, the following topics are discussed: Assessment of relations between time series (transfer function models). Assessment of changes of time series (intervention analysis), forecasting and some related time series methods.

Epidemiologic Methods↗
PubMed1991

Caries prediction on the basis of past caries including precavity lesions.

The purpose of the present work was the construction of statistical models which allow the prediction of future high caries increments on the basis of the state of primary teeth and first molars taking into account both precavity lesions and DF experience. A child was considered to be experiencing 'high caries increment' when it had at least four new lesions (new DFS) 4 years after the first examination. Two data sets of children aged 7-10 years were analysed: (1) 803 children examined in 1980 and in 1984. The proportion of children with 'high caries increment' was 25.0%. (2) 477 children examined in 1984 and in 1988. In this group, the proportion of children with high caries increment was 16.6%. In the first group with higher prevalence of caries, sensitivity and specificity were found to be on average at 70%. In the second group, sensitivity and specificity were 77% on average. This results shows that caries prediction may be at least as successful when a 'refined' set of clinical data is used instead of a less extensive set of caries data complemented by salivary buffering capacity and microbiological data.

Child↗
PubMed1990

When did a reduced speed limit show an effect? Exploratory identification of an intervention time.

In a statistical analysis of accident data before and after a speed limit reduction, the time of the countermeasure is, of course, well known. Our understanding of the accident process may, however, be increased if we assume in a thought experiment that this time is unknown. We ask if the data themselves can tell us something about such a possible time. By means of time series of traffic accidents in Zurich before and after a speed limit reduction, different exploratory methods are presented to identify the "unknown" time of this measure. For most of the investigated series, the most likely time was found to lie in the three months before the true introduction. A possible explanation of this result may be that the media already informed the public before the countermeasure was actually introduced. This finding leads to an improved parsimonious intervention model which distinguishes between a possible "preintervention effect" and the usual "intervention effect."

Accidents, Traffic↗
PubMed1990

The use of measures of influence in epidemiology.

In epidemiological studies the units of observation often consist of political entities such as countries, each of which has its own specific inner structure. When a multiple regression is performed it is therefore of particular interest to analyse not only the overall behaviour of the dataset, but in addition, to investigate how each individual country contributes to, and deviates from, this overall behaviour. By means of the example 'relation between infant mortality and structural data of countries' several ways are discussed of how each individual country can influence the regression model. Firstly the potential influence which each country might exhibit due to the explanatory variables alone is analysed. Then the actual influence of each country is analysed by taking the explanatory variables and the target variable into account simultaneously. This is done by means of statistical measures not generally familiar to epidemiologists, which have been developed in recent years (leverage values, Cook's distances). These measures also point to deviations of countries from the model, and suggest directions in which to search for explanation. Finally the influence of the 'size' of the countries is investigated.

Epidemiologic Factors↗
PubMed1990

Levels of soluble interleukin-2 receptors correlate with the severity of atopic dermatitis.

Levels of soluble interleukin-2 receptors (sIL-2R) were measured as a marker of lymphocyte activation in serum of 37 patients with atopic dermatitis (AD) and of 16 patients with psoriasis vulgaris (PV), all individuals being hospitalized in the Zurich High Mountain Clinic of Davos-Clavadel (altitude 1,600 m above sea level). Measurements were performed at admission and at discharge. The PV patients served as a control group. As a further control, 20 AD patients from the Department of Dermatology in Zurich (altitude 400 m) were also evaluated. The serum sIL-2R concentration in AD patients at admission was significantly elevated in comparison with PV patients and was highly correlated with the severity of the cutaneous involvement. Comparing the 'extrinsic' and 'intrinsic' types of AD, no significant differences of sIL-2R levels were found. The sIL-2R concentrations dropped at discharge. These results suggest that the measurement of the sIL-2R level could be a marker of disease activity.

Adolescent↗
PubMed1990

Detecting hidden relations between time series of mortality rates.

In the present report a method is described which may help to decide if a disease is influenced by an environmental factor which fluctuates in time: For each of two naturally arising subgroups of a population (such as males and females) an ARIMA model (autoregressive integrated moving average model) is identified. These models are used as filters to remove the autocorrelation in each series. If the resulting crosscorrelation function between the two filtered series shows a marked peak at time lag 0 this may indicate that such an environmental factor is present. The procedure is demonstrated using yearly data of mortality rates among the elderly.

Aged↗
PubMed1989

[Urinary excretion of fluorides in schoolchildren of Lausanne and Geneva in relation to salt fluoridation].

Urinary excretion of fluoride and sodium and urinary flow were studied in 230 schoolchildren (average age: 11.1 years) in the following situation: in 1984 and 1988 in Geneva, 1 year and 5 years after the introduction of fluoridated domestic salt (250 mg/kg), and in 1985 in Lausanne, 15 years after the general introduction of salt fluoridation for this city and its surrounding canton (Vaud). Among consumers of fluoridated salt, the average excretion of F ion during morning and afternoon was 15.4 and 43.7 micrograms F/h, respectively, in Geneva (1988) and 26.4 and 49.9 micrograms F/h, respectively, in Lausanne (1985). Among non-consumers of fluoridated domestic salt, excretion values during morning and afternoon were 9.9 and 20.7 micrograms F/h, respectively, in Geneva (1988), and 18.4 and 26.1 micrograms F/h, respectively, in Lausanne. Between 1984 and 1988, an increase in fluoride excretion was observed in schoolchildren of Geneva. During approximately 10 night hours, 8.8 to 16.4 micrograms F/h were excreted in Geneva, but F-salt consumers in Lausanne excreted 25.8 micrograms F/h. Averages of sodium excretion varied between 80 and 144 mg Na/h at daytime and between and 81 mg Na/h at night.

Adolescent↗
PubMed1987

[Time series analysis of the influence of prevention using the example of the occurrence of accidents in Zurich before and after Tempo 50].

In the evaluation of the effect of preventive measures data often arise at fixed time intervals and it is likely that successive observations are stochastically dependent. By means of the example of the "possible reduction of traffic injuries after the introduction of a speed limitation (50 km/h) in Zurich" it is shown how time series methods can help to assess the efficiency of such measures. For the series before the intervention a statistical model is identified which describes the probability structure of the series. This model is used to forecast the course of the series one would expect when no intervention takes place. The forecast and the actual series are then plotted in the same figure and the difference is analysed with a test. In addition to that the magnitude of the effect and its standard error are estimated (intervention analysis). The series "numbers of accidents with injuries" showed after the intervention a yearly reduction of approximately 250 accidents (14%) with a corresponding standard error of 30. The reduction is markedly less pronounced in the series "number of seriously injured persons" than in the series "number of slightly injured persons".

Accidents, Traffic↗
PubMed1985

[Atopy screening: prick multitest, total IgE or RAST? On the value of allergologic testing of the staff of an industrial bakery].

The predictive value of diagnostic tests for the recognition and differentiation of allergic diseases of the immediate type has been evaluated on the basis of the results of a non-selective allergologic-pneumologic examination of the staff of an industrial bakery. Out of the 314 subjects tested, 22 (7%) had a respiratory allergy against flour (flour rhinitis and/or flour asthma), and 21 (6.7%) a preexistent atopic disease without actual symptoms of flour allergy. Thus the predominance of atopy in the group examined was 13.7%. A prick-multitest was carried out in all 314 subjects on each forearm and allowed simultaneous and easy application of twice eight test substances ("atopy-screening" and "bakery-line"). 50% of the bakers with flour allergy also showed positive skin tests with non-occupational inhalative allergens (housedust, housedust mite, pollen) while only 9.2% of the subjects without respiratory allergy to flour did so. 17.1% of the heavily exposed, asymptomatic bakers showed a positive immediate reaction to the highly sensitive intracutaneous test with wheat flour. Here the problem of latent sensitization arises. With histamine the prick-multitest resulted - compared to the intracutaneous test - in 1.6% "false negative" and 3.2% only questionably positive results. Furthermore, 6.1% of the subjects showed a strong, and 3.2% a very strong, nonspecific reaction to the control solution glycerin. Despite these restrictions the prick-multitest proved far superior to measurement of total serum IgE for screening of atopy. Technical improvements have been made in the meantime by the manufacturer. Specific IgE was detected in RAST screening in 59 of the 306 subjects who underwent blood tests. The geometric mean of total IgE values was only 75 U/ml, and for the RAST-negative subjects 23.3 U/ml, while their 95% confidence level was 225 U/ml. This logarithmic-normal distribution of the measured values, together with the excessive normal-atopic overlap, makes it impossible to lay the test cutoff point in a way which results in an acceptable relation between sensitivity and specificity. For the population examined the sensitivity of the total IgE measurement was already below 50% at a cutoff point of 80 U/ml, while the positive predictive value did not yet reach 50% at 160 U/ml. This diagnostic test is at present certainly used too often and without sufficient awareness of its very limited predictive value. As a screening method the RAST is too expensive. Furthermore, the problem of a latent sensitization also exists for the RAST.

Adolescent↗
PubMed1980

[Radiological findings in teeth and periodontium in a group of Swiss youths].

Bite-wing x-ray films of 1084 Swiss recruits were examined. Approximately 96% of the recruits showed signs of early bone loss around one or more teeth. Only a very small number had recognizable bone changes in furcation areas. Per recruit, 7.3 carious lesions were found; the majority of these were entirely within enamel. Of 6287 restored approximal posterior surfaces, 71.4% were inadequate. A number of these filled surfaces showed secondary caries.

Adolescent↗
PubMed1980

[Clinical periodontal findings in a group of Swiss youths].

A clinical epidemiological examination of the health status of the teeth and supporting structures of 1084 recruits at a summer recruits-school was conducted. With one exception all of the Swiss cantons were represented among the recruits. Only one recruit had a clinically healthy periodontium; all of the others showed inflammatory changes of the gingivae. The average PDI was 3.58. In the majority of the recruits signs of early bone loss around one or more sites was observable. Teeth with markedly abraded chewing surfaces did not show an increased prevalence of bone loss. An examination of existing fillings and crowns revealed a large number of unsatisfactory filling margins. The average DMFT value of 14.5 was mainly the result of the high number of filled teeth.

Adolescent↗
PubMed1979

[Influence of educational level and preventive measures on theperiodontal condition of adolescents].

From their answers to a questionnaire 1063 Swiss army recruits were included in one of 6 occupational groups. The clinical periodontal findings from the group were recorded and compared. The recruits with higher educational levels had a better periodontal status than those with less schooling. Regardless, the recruits from areas with well-organized prophylaxis programs had less gingivitis and smaller DMFT scores than the others.

Adolescent↗