The effect of dental floss sequence on plaque removal efficacy and periodontal health: a randomized controlled trial

Manual toothbrushing with interdental flossing is the gold-standard for plaque removal in preventive dentistry. This trial examines how flossing sequence (pre-, mid-, or post-brushing) impacts plaque removal efficacy and periodontal health. In a single-blind randomized controlled trial (RCT), 54 university students were randomized to three groups: pre-brushing flossing (A), post-brushing flossing (B), or mid-brushing flossing (C). Participants followed protocols for 21 days under supervision. Rustogi Modified Navy Plaque Index (RMNPI), bleeding index (BI) and probing depth (PD) were measured at baseline, day 7, and day 21. Analyses used ANOVA (α = 0.05). Based on the results at day 7, the RMNPI decreased most significantly in the mid-brushing flossing group (p = 0.0388). However, at day 21, no significant difference in plaque removal was observed among the three groups (p = 0.9330). Notably, mid-brushing flossing significantly reduced BI at both day 7 and day 21 (p = 0.0275, p = 0.0151). Additionally, no statistically significant differences were observed among the three groups in terms reducing PD (p = 0.7420, p = 0.4220). These results suggested that mid-brushing flossing may be more effective in daily dental plaque removal and improving gingival bleeding. The trial was retrospectively registered with Chinese Clinical Trial Registry (ChiCTR) with identifier no. ChiCTR2500108845, registered on 09/08/2025. ( https://www.chictr.org.cn/showproj.html?proj=285669 ).