FLUORIDE VARNISHES (DURAPHAT) - A METAANALYSIS

In the present article we analyze a series of studies designed to dete ct the caries preventive effect of Duraphat by means of meta-analysis. Meta-analysis is a collection of statistical methods designed to inve stigate and to summarize a series of investigations. It may be a valua ble tool to complement traditional narrative reviews. During the last years meta-analysis has attracted increasing interest in sociology, ps ychology and medicine. In order to find previous studies concerned wit h the clinical effects of Duraphat we applied a systematic literature search. Papers were included independent of results when they fulfille d a checklist of well defined methodological selection criteria. In or der to aggregate the results of the Duraphat-studies we used different complementary statistical approaches: Firstly, the so-called file dra wer problem is considered. This may help to get a better insight into the problem of underreporting non-significant results or publication b ias. It was found to be very unlikely that underreporting of non-signi ficant results could reverse the conclusion into an overall null-resul t. After that, the inhomogeneity between studies is investigated. The overall variation of caries reduction R is separated into two componen ts: A between study component of variance and a variance pertaining to the individual studies (random effects model). It was found that the overall variation is dominated by the between studies variation and no t by the sampling variation. Due to the pronounced variation between s tudies the confidence interval of the overall effect size (R=0.38) is quite large (95%)-Cl: 0.19-0.57). The heterogeneity of our studies nat urally suggested exploring possible sources thereof by investigating t he dependence of caries reduction on variables characterizing the stud ies. It was found that caries reduction is negatively correlated with study duration. This finding provided a study-duration-adjusted effect of caries reduction.