Objectives: This study aimed to determine the brushing forces applied during in vivo
toothbrushing with manual and sonic toothbrushes and to analyse the effect of these
brushing forces on abrasion of sound and eroded enamel and dentin in vitro.
Material and Methods: Brushing forces of a manual and two sonic toothbrushes (low and
high frequency mode) were measured in 27 adults before and after instruction of the
respective brushing technique and statistically analysed by repeated measures ANOVA. In
the in vitro experiment, sound and eroded enamel and dentin specimens (each subgroup
n=12) were brushed in an automatic brushing machine with the respective brushing forces
using a fluoridated toothpaste slurry. Abrasion was determined by profilometry and
statistically analysed by one-way ANOVA.
Results: Average brushing force of the manual toothbrush (1.6±0.3 N) was significantly
higher than for the sonic toothbrushes (0.9±0.2 N), which were not significantly different from
each other. Brushing force prior and after instruction of the brushing technique was not
significantly different. The manual toothbrush caused highest abrasion of sound and eroded
dentin, but lowest on sound enamel. No significant differences were detected on eroded
enamel.
Conclusion: Brushing forces of manual and sonic toothbrushes are different and affect their
abrasive capacity.
Clinical Significance: Patients with severe tooth wear and exposed and/or eroded dentin
surfaces should use sonic toothbrushes to reduce abrasion, while patients without tooth wear
or with erosive lesions confining only to enamel do not benefit from sonic toothbrushes with
regard to abrasion.