Does the Sequence of Powered Toothbrushing and Dental Flossing Affect Residual Dental Plaque Scores? A Randomized Crossover Clinical Trial

Effective dental plaque control requires both toothbrushing and interdental cleaning; however, the optimal sequence of these procedures remains unclear, particularly when powered toothbrushes are used. This randomized, examiner-blinded, two-period crossover clinical trial evaluated whether the sequence of powered toothbrushing and dental flossing influences residual plaque scores. Forty-six healthy young adults were randomly assigned to one of two intervention sequences: brush–floss followed by floss–brush or the reverse sequence, with a 15-day washout period between study phases. Following a standardized 48-h plaque accumulation period, participants performed the assigned oral hygiene procedures under supervision. Residual plaque was assessed using the Plaque Index (PI) and the Turesky modification of the Quigley–Hein Plaque Index (TQHPI). Data were analyzed using a linear mixed-effects model including treatment, period, and sequence as fixed effects and participant as a random effect. No significant difference was observed between the brush–floss and floss–brush conditions for PI (p = 0.275). Before correction for multiple comparisons, lower residual buccal (p = 0.041) and lingual (p = 0.008) TQHPI scores were observed following brush–floss compared with floss–brush. After adjustment for multiple comparisons, the brush–floss condition resulted in significantly lower residual lingual TQHPI scores than the floss–brush condition (adjusted p = 0.024), whereas differences in PI and buccal TQHPI were not statistically significant. Significant period effects were detected for TQHPI outcomes, whereas no sequence effects were observed. These findings suggest that performing powered toothbrushing before dental flossing may modestly improve residual plaque control when assessed using a sensitive plaque index. Further randomized clinical trials with longer follow-up are required to determine the long-term clinical relevance of these findings.