Interdental Biofilm Reduction and Composition after Use of an Activated and Inactivated Side-to-side Toothbrush — a Proof-of-principle Clinical Study

To evaluate interdental biofilm reduction and composition after powered toothbrushing with a side-to-side (sonic) toothbrush compared to manual toothbrushing following single brushing exercises in periodontally healthy young adults. All participants brushed with a side-to-side toothbrush without toothpaste in four different modes: toothbrush (a) inactivated without instruction (OFF-NI), (b) activated without instruction (ON-NI), (c) inactivated with instruction (OFF-I), and (d) activated with instruction (ON-I) at consecutive visits (single brushing exercises). Before and after brushing, the Approximal Plaque Index (API) was assessed at three interdental spaces and plaque samples were taken from two interdental sites. Biofilm reduction and composition were analyzed microbiologically by total bacterial load and 16S rRNA sequencing. Thirty participants (age: 22.9 ± 2.5 years) completed the study. Most participants showed no or incomplete plaque removal assessed by API following single brushing exercises, while the frequency of API reduction was higher after ON-NI compared to OFF-I (p = 0.023). Irrespective of the brushing mode, a significant reduction of total bacterial load was detected with lower bacterial counts after OFF-NI compared to ON-NI (p = 0.008) and ON-I (p = 0.007). Biofilm composition showed slight changes in the relative abundances of bacterial taxa, regardless of the brushing mode. Manual and powered toothbrushing with a side-to-side toothbrush, with and without instruction, showed incomplete interdental biofilm removal in periodontally healthy young adults following single brushing exercises. Data has to be validated in further studies on other groups, however, in periodontally healthy young adults, additional devices seem to be necessary for sufficient interdental cleaning.