Background: The purpose of this study was to assess treatment responses to dental flossing in twins.

Methods: The study was a two-treatment, examiner-blind, randomized, parallel group, controlled study. Fifty-one twin pairs between 12 and 21 years of age were randomized to a 2-week supervised and unsupervised treatment regimen consisting of 1) tongue brushing and toothbrushing (TB) and 2) TB + flossing (TB+Fl). Clinical endpoints were gingival bleeding (papillary bleeding score [PBS]) and oral malodor (levels of volatile sulfur compounds [VSC]). Analysis of variance and covariance methodologies were employed to analyze the data.

Results: Baseline average PBS values were 1.352 and 1.342 for the TB+Fl and TB groups, respectively (P = 0.937). After 2 weeks of treatment, the TB+Fl group had a statistically significant decrease in PBS values of 0.558 (41.5% versus baseline), whereas the TB group showed no improvement from baseline. The change from baseline for the TB+Fl group was superior to that for the TB group (P <0.001). Similar findings were observed for the number of baseline papillary bleeding sites. Baseline average intraoral halimeter values were 45.91 and 41.75 for the TB+Fl and TB groups, respectively (P = 0.504). Both treatment regimens demonstrated highly statistically significant reductions in intraoral breath values versus baseline (all P <0.001), and the difference between treatment groups was not statistically significant (P = 0.339). Similar findings were found for expired air.

Conclusions: In a well-matched twin cohort, tongue and toothbrushing plus flossing significantly decreased gingival bleeding after 2 weeks.