<qa>  What is the name of the study that was used to measure early plaque formation?This is a double blind, cross over, randomized clinical trial. 35 volunteers will stop mechanical supragingival biofilm removal measures for 96h following a complete scaling and polishing of the tooth surfaces. During this period they will be asked to rinse for a minute a Solution containing chlorhexidine and alcohol or a solution with chlorhexidine alcohol-free or placebo. Every 24h the presence of deposits will be registered with special attention to the presence of a plaque free zone between the apical border of the deposits and the gingival margin. Absence of deposits is scored 0, presence of deposits and plaque free zone 1 and presence of deposits and absence of plaque free zone 2 MALISKA, A. N. et al. Measuring early plaque formation clinically. Oral health preventive dentistry, v. 4, p. 273-278, 2006. The prevalence of scores and the rate of changes from scores 0 and 1 into 2 will be evaluated for significance. Sample size was calculated taking the results from the study o MALISKA, AN 2006 as reference. 