Variability of gingival bleeding in experimental gingivitis trials.

Gingival bleeding is a difficult parameter to assess in experimental trials. The Confirmed Bleeding Day was recently developed as a measurement for this purpose. It was observed that considerable variations existed between the measurements made in a pilot study and an experimental trial, and these variations were subjected to a statistical analysis. The reasons for the variations are discussed, and recommendations made for the design of experimental trials involving gingival bleeding.