Reports & Studies

Should dental floss be used before or after tooth brushing?

PD Dr. Kristina Bertl, PhD MSc MBA

It is often very hard to persuade our patients to clean between their teeth. Patients are often still advised to use dental floss, despite the fact we know that in many cases floss is not their method of choice and, above all, is often rather unpopular.

Irrespective of which method we recommend for interdental cleaning, our patients very often ask us the following question: should I clean between my teeth before or after brushing?

An Iranian research group tackled this very question in a randomized controlled cross-over study (Mazhari et al. 2018). In total, 25 dentistry students were enrolled in the study. After a 2-week familiarization phase, the participants were instructed to forgo all home oral hygiene for 48 hours, to enable the accumulation of an appropriate amount of plaque. They were then randomly allocated to either the ‘floss before brushing’ treatment group or to the ‘floss after brushing’ treatment group. Both groups’ plaque accumulation and fluoride concentration were recorded before and after cleaning with dental floss and a toothbrush. The experiment was repeated two weeks later with the same participants, but participants were crossed over to the other treatment group.

At the end of the study, comparison of the two groups revealed the following results:

  • The ‘floss before brushing’ group achieved a statistically significant higher reduction in plaque in the oral cavity as a whole and in the interdental space in particular. No difference was found for marginal plaque scores.
  • The interdental fluoride concentration was statistically significantly higher in the ‘floss before brushing’ group.

The authors thus also confirmed the results of a previous similar study (Torkzaban et al. 2015). It is suspected that an initial interdental loosening of plaque and food residues with dental floss makes tooth brushing itself more effective, because the loosened layer of plaque can be better removed.

It remains to be seen whether this sequence should also be followed and recommended for interdental brushes.


  1. Mazhari F, Boskabady M, Moeintaghavi A, Habibi A. The effect of toothbrushing and flossing sequence on interdental plaque reduction and fluoride retention: A randomized controlled clinical trial. J Periodontol. 2018;89:824–832. https://doi. org/10.1002/JPER.17-0149 Torkzaban P, Arabi SR, Sabounchi SS, Roshanaei G. The Efficacy of Brushing and Flossing Sequence on Control of Plaque and Gingival Inflammation. Oral Health Prev Dent. 2015;13(3):267-73. doi: 10.3290/j.ohpd.a32678.