To verify the effect of surface penetrating sealant on the roughness of posterior resin-based composites before and after mechanical toothbrushing.10 specimens of four different composites (Alert, Definite, Z100 and Prodigy Condensable) were made using a metal matrix (height 2 mm and diameter 4 mm). After 24 hours, the specimens were polished using Sof-Lex discs in sequence: coarse, medium, fine and superfine, each for 40 seconds and, immediately, one of the surfaces was covered with Protect-It surface sealant. All the specimens were examined with a profilometer to measure the initial surface roughness before mechanical toothbrushing at a constant speed of 250 strokes/minute with a total of 30,000 cycles, using a toothbrush and dentifrice containing calcium carbonate as abrasive, under a load of 200 g. After toothbrushing the surface roughness was measured once again. The data were analyzed with ANOVA and the Tukey test at a 95% confidence level.Mechanical toothbrushing increased the surface roughness of all the composites studied (Alert: 0.7303 +/- 0.0942 microm; Definite: 0.4961 +/- 0.1255 microm; Z100: 0.3428 +/- 0.0841 microm), with the exception of Prodigy Condensable (0.2782 +/- 0.0678 microm) (P > 0.05). The surface penetrating sealant effectively decreased the surface roughness for Alert (0.5435 +/- 0.2182 microm) and Definite (0.2956 +/- 0.0368 microm) (P 0.05).