A Twelve‐Month Observation Analysis of Real‐Time Contact Pressure‐Controlled Powered Tooth Brushing as a Subgroup Analysis of a 36‐Month RCT

OBJECTIVE: Bristle splaying may be associated with reduced cleaning efficacy; however, the relationship between the bristle splaying index (BSI) and contact pressure (CP) during brushing with a powered toothbrush (PT) with real-time CP control for oscillating brush head movement (range: 0.8-2.5 N) remains unknown. METHODS: This subgroup analysis of a randomised controlled trial (RCT), which included 47 subjects with gingival recession (GR), included digitally recorded data from 42 PT users: total brushing time (Btime; in minutes), brush head usage time (BHtime; in days), mean CP (in N), time duration with CP > 2.5 N (CPhigh; in minutes) and CP < 0.8 N (CPlow; in minutes) over 1 year with quarterly brush head replacement (Q1-Q4). The extent of bristle splaying was measured using a standardised set-up to calculate the BSI. In addition to multivariate statistical tests, a linear regression model was employed (p ≤ 0.05). RESULTS: The highest BSI (mean (standard deviation)) occurred in Q1 with 7.9 (4.8) (p ≤ 0.001) (BSI in Q2/Q3/Q4: 5.5 (4.9)/4.4 (4.0)/3.5 (2.8); p > 0.05), with Btime, BHtime, CP, CPlow and CPhigh remaining constant (p > 0.05). The BSI was significantly correlated with the CP (r = 0.252; p = 0.001) and study quarter (r = -0.363; p < 0.001), but not with subject gender (r = 0.088; p = 0.254) and age (r = -0.025; p = 0.745), nor with Btime (r = 0.009; p = 0.905), BHtime (r = 0.109; p = 0.158), CPlow (r = -0.104; p = 0.181) and CPhigh (r = 0.145; p = 0.061). The regression model showed a significant effect on the BSI for the CP (B = 2.912; p < 0.001) and study quarter (B = 1.678; p < 0.001). CONCLUSION: Cleaning periods with a CP > 2.5 N were short and did not result in higher BSI. CLINICAL RELEVANCE: CP with PT may be important for cleaning efficacy, safety of the marginal gingiva and reduced brushing head wear.