This Brazilian study investigated how often toothbrushing and interdental cleaning is needed to prevent the development of gingivitis. 52 university students were divided in four experimental groups and instructed to brush and floss with a frequency of 12, 24, 48 or 72 hours during a test period of 30 days. The examiners were blinded to the brushing frequency.

 

In the 12 and 24 hour groups the mean GI remained statistically unchanged during the test period, but in the 48 and 72 hour groups GI increased significantly. The authors’ conclusion is that mechanical plaque removal is needed at least every 24 hours to prevent an increase of gingival inflammation in otherwise healthy persons.

 

However, these results are not in consistent with the results from Lang et al. (1973) which showed that plaque removal every 48 hours is compatible with gingival health. An explanation to the diverse results could be that in the study conducted by Lang et al., the plaque removal was probably more complete due to use of disclosing solution and supervision by a dental hygienist.