Assessment of the effect of dentifrices on the growth of dental plaque

A new technique for assessing the effects of dentifrices on the growth of human dental plaque is described. Laboratory personnel brushed their teeth with the dentifrices and a new plaque index, the Gingival margin Plaque Index, was used to measure plaque growth over the next 16 hours. The index estimates the proportion of the length of the buccal gingival margin in contact with disclosed plaque on the surface of each tooth. Dentifrices containing 0.4, 0.8 and 1.2% chlorhexidine digluconate caused a lower plaque growth than a placebo paste. The differences were highly significant ( P < 0.001). The size of the reduction depended on the concentration of chlorhexidine in the dentifrices. The disclosing reagent had no major effect on plaque growth. The coefficient of linear correlation between results from two examiners was 0.89 for the measurement of plaque growth. Dentifrices containing a quaternary ammonium salt also reduced plaque growth.