How to select study designs and parameters to investigate the effect of mouthrinses? Part II: comparisons between the...

A variety of parameters is available to assess the efficacy of oral antiseptics. Most study protocols select the parameters according to the specific study goal or according to preferences of the researchers. Beside general recommendations for home-use studies, no recommendations exist for other study types. Therefore, pre-selected parameters should be compared within several study designs and the most suitable parameters should be recommended for further application. The following parameters were selected before study start: plaque indices (PlI, Silness & Loe 1964, M-QHI, Turesky et al. 1970), plaque area (PlA), bacterial vitality (BV, Netuschil et al. 1989), gingivitis indices (GI, Loe 1967; M-GI, Lobene et al. 1986; BOP, Ainamo & Bay 1975), gingival crevicular fluid, colony forming units, and the discoloration index (DI, Brecx et al. 1993). The parameters were applied in four study designs: eight-hour substantivity studies, four-day plaque re-growth studies, 21-day experimental gingivitis studies, and six-month home-use studies. Pearson correlation coefficients were computed. The highest correlations were found between PlI and M-QHI and between GI and M-GI (p<0.01) in all corresponding studies and treatment groups. Few middle correlations existed between BOP and the other gingival indices. Neither GI nor M-GI correlated with GCF nor did BV with plaque indices. Inconsistent correlations were obtained between PlA and plaque indices and between PlI and GI. It is concluded, that primary parameters for these designs should be one plaque index and/or one gingivitis index to monitor plaque and gingivitis. The other parameters did not yield additional information about the study outcome.