Effect of 1000 ppm relative to 250 ppm fluoride toothpaste. A meta-analysis.

PURPOSE: To estimate the overall effect of 1000 ppm F relative to 250 ppm F toothpaste. METHODS: Experimental caries increment studies from the dental literature, which compared 1000 ppm with 250 ppm fluoride toothpastes, were summarized using meta-analytic methods. RESULTS: The overall caries reduction of 1000 ppm F relative to 250 ppm F paste was estimated to be 0.142 (95%-CL: 0.074-0.210) when applying a fixed effects model and 0.129 (95%-CL: 0.012-0.230) when applying a random effects model. CLINICAL SIGNIFICANCE: The present analysis found slightly lower caries increments (14%, 13%) in children using 1000 ppm F toothpastes compared to children using 250 ppm F pastes. On the other hand, the use of 1000 ppm F pastes is associated with dental fluorosis. Considering these effects it seems justifiable to the authors to keep the use of 250 ppm F pastes for preschool children in Switzerland.

[Caries prevalence among students in 16 Zurich districts in the years 1992 to 2000]. / Kariesprävalenz von Schülern in 16 Zürcher Landgemeinden in den Jahren 1992 bis 2000.

Standardized dental examinations of schoolchildren were regularly carried out since 1964 in 16 rural communities of the Canton of Zurich. In 1964, there were no 14-year-old schoolchildren free from caries; in the Nineties about half of the 14-year-olds had a caries-free permanent dentition (DMFT = 0). From the year 1992 to 2000, the caries prevalence (DMFT) of 14-year-olds decreased once again, by 31%. The pit and fissure caries prevalence (DFS) of 12- and 14-year-olds decreased by 28% and 37%, respectively. In 2000, the mean DMFT-value of the 12- and 14-year-old schoolchildren was 0.90 and 1.27 respectively. In 1964, only few 7-year-old schoolchildren were caries-free; in the Nineties about half of the 7-year-olds had a primary dentition without caries. From the year 1992 to 2000, caries prevalence (dmft) in 7-, 8- and 9-year-olds increased by 64%, 22% and 31%. In 2000, the mean dmft-value of all 7-year-old schoolchildren was 2.45. The Swiss schoolchildren had 1.79 dmft; the schoolchildren from former Yugoslavia and from Albania had 6.89 dmft and those of other nations had 3.37 dmft. Possible reasons for the continuous caries decrease in the permanent dentition and the increase in the primary dentition are discussed. Additional measures in order to improve the situation in the primary dentition are proposed.

An example of complex modelling in dentistry using Markov chain Monte Carlo (MCMC) simulation.

BACKGROUND: In the usual regression setting one regression line is computed for a whole data set. In a more complex situation, each person may be observed for example at several points in time and thus a regression line might be calculated for each person. Additional complexities, such as various forms of errors in covariables may make a straightforward statistical evaluation difficult or even impossible. OBJECTIVE AND METHOD: During recent years methods have been developed allowing convenient analysis of problems where the data and the corresponding models show these and many other forms of complexity. The methodology makes use of a Bayesian approach and Markov chain Monte Carlo (MCMC) simulations. The methods allow the construction of increasingly elaborate models by building them up from local sub-models. The essential structure of the models can be represented visually by directed acyclic graphs (DAG). This attractive property allows communication and discussion of the essential structure and the substantial meaning of a complex model without needing algebra. EXAMPLE: After presentation of the statistical methods an example from dentistry is presented in order to demonstrate their application and use. The dataset of the example had a complex structure; each of a set of children was followed up over several years. The number of new fillings in permanent teeth had been recorded at several ages. The dependent variables were markedly different from the normal distribution and could not be transformed to normality. In addition, explanatory variables were assumed to be measured with different forms of error. Illustration of how the corresponding models can be estimated conveniently via MCMC simulation, in particular, 'Gibbs sampling', using the freely available software BUGS is presented. In addition, how the measurement error may influence the estimates of the corresponding coefficients is explored. It is demonstrated that the effect of the independent variable on the dependent variable may be markedly underestimated if the measurement error is not taken into account ('regression dilution bias'). CONCLUSION: Markov chain Monte Carlo methods may be of great value to dentists in allowing analysis of data sets which exhibit a wide range of different forms of complexity.

[Dental health of adults in the Zurich Canton]. / Zahngesundheit von Erwachsenen im Kanton Zürich.

In 1992 and 1999, dental health in 20- to 79-year-old adults from the canton of Zurich was assessed with a standardized method (WHO). The aim was to establish the current state and changes of dental health. Roughly half of the 852 approached adults selected by chance did take part. In 1992 and 1999, the mean number of unfilled, decayed teeth (DT) was on a low level in all age classes (0.2 to 1.8 depending on age class and examination year). The number of missing teeth (MT) in older adults (60-79) was on a high level (8.8 to 13.4). The number of filled teeth (FT) was highest (14.8 to 16.2) in middle-aged adults (40-59). Total loss of teeth was found only in older adults (60-79). Lack of a "functional" own dentition (5 teeth present in each quadrant) was found in roughly half of the 60- to 69-year-olds and two thirds of the 70- to 79-year-olds. In 1999, the state of the roots and loss of attachment was assessed. Wedge-shaped defects were found in more than half of the middle-aged adults (40-59). Carious roots were found in more than half of the 70- to 79-year-olds. Nearly half of the 70- to 79-year-old participants showed "severe" loss of attachment (> or = 6 mm). In the short period from 1992 to 1999, a significant decrease of 3.7 DMFT was found in 20- to 49-year-old adults. The decrease of 0.9 MT and 2.1 FT means also a decrease in treatment need in this age segment. In contrast, in the 50- to 79-year-olds no change in dental health could be established.