Abstract
This in vitro study evaluated the effects of approximately duration-normalized toothbrushing protocols and brushing load on volumetric wear and surface roughness changes of anterior tooth-shaped restorative composite specimens. One hundred twelve specimens were prepared from two highly filled flowable and two paste-type composites in a balanced 2 × 2 × 2 × 2 factorial design. After finishing, polishing, and 10,000 thermal cycles, seven specimens were mounted per manual-brushing run and brushed for 60,000 carriage strokes at 165 strokes/min (total run approximately 364 min; nominal exposure approximately 52 min/specimen), whereas electric brushing was applied for 52 min/specimen. Both protocols were intended to approximate one year of tooth-specific brushing duration but were not mechanically equivalent. Specimens were tested under 1.96-2.94 N. Volumetric loss was assessed using Primescan-based three-dimensional superimposition, and arithmetic mean roughness was measured before and after brushing. Factorial multivariate analysis of variance and follow-up univariate analyses were used. Toothbrushing protocol and load significantly affected the combined outcomes (Pillai trace = 0.926 and 0.827, respectively; both p < 0.001). Under the approximately duration-matched but mechanically different protocols, electric brushing produced greater roughness difference and volumetric loss, and higher load increased both outcomes. The protocol × load interaction was significant for volumetric loss (F = 89.33, p < 0.001). Composite category and trademark were not significant. The findings do not isolate an intrinsic manual-versus-electric drive-mechanism effect.