Seven RCTs were included in the review. Three of these were split mouth RCTs, three used a parallel design and one trial was a cross-over design. In total, 446 participants completed the trials (range 11 to 152). Follow-up times ranged from four to 12 weeks. Overall, included trials were of reasonable methodological quality. The largest risk of bias was in the area of allocation concealment where only two trials were judged to report adequate methods. A detailed quality assessment could be found in the review.
Six studies assessed bleeding as an outcome. However, two of these were excluded from the analyses due to methodological shortcomings. Across the remaining four included studies, the mean difference was 0.08 (95% CI 0.03 to 0.14) which indicated that interdental brushes were more effective in the reduction of bleeding than dental floss. Heterogeneity was observed in this analysis (Ι²=59.72%).
There was a statistically significant reduction in plaque for use of interdental brushes compared to dental floss (WMD 0.13, 95% CI 0.02 to 0.25; seven studies). The authors assumed the studies in this analysis were homogenous (Ι²=34.26%).
The authors explained that a funnel plot was not used to assess publication bias due to the small number of included studies.