Statistical analysis of data derived from clinical variables of plaque and gingivitis

Selection of suitable subjects and statistical analysis of data derived from clinical trials presents a number of problems. In this trial, clinical data were analysed separately for pooled whole mouth data and for data including positive scores only for the variables of dental plaque and gingivitis. It was demonstrated that comparable data sets and statistical analyses were obtained using both data sets. Furthermore, it was shown that in order to achieve the best possible results in a clinical trial, the variable of gingivitis should be used in preference to plaque scores, that only individuals of high and/or moderate susceptibility to inflammation should be selected for inclusion in the statistical analysis, and that sites which have positive signs of disease only, should be included in the statistical analysis.