Brushing protocol

Specimens from each treatment were randomly grouped in a 3×3 orientation and fixed with a condensation cured silicone rubber impression material (Zetaplus – Zermack, Badia Polesine, RO, Italy). They were attached to a brushing machine (MEV 2T – ODEME, Luzerna, SC, Brazil) with the vestibular face exposed to the external environment. Each specimen was submitted to two brushing cycles. The first cycle consisted of 180 toothbrush head movements (first use – TI). The second one, with 16,200 movements, was performed to simulate a continuous use (TCU). All specimens were brushed with a soft bristled toothbrush (Colgate Classic – Colgate, São Paulo, SP, Brazil). Both the pressure (200 g/cm 2 ) and temperature (36±1°C) were controlled. During brushing, samples were immersed in a solution of toothpaste, artificial saliva and distilled water obtained by dilution of equal volumes of each component (1:1:1). After each brushing cycle, specimens were washed in running water and the color was measured immediately after washing.