Effect of nanofillers on surface properties after toothbrush abrasion

Objectives: To investigate the effect of filler particle size of model and commercial resin-composites on three surface properties: surface roughness (SR), surface gloss (G) and colour stability (CS) using toothbrush abrasion. Methods: Four model (Ivoclar/Vivadent, Liechtenstein) and two commercial resin-composites: Filtek Supreme (3M-Espe St. Paul, USA) and Estelite Sigma (Tokuyama, Osaka, Japan) with filler size varying from 20 to 1000 nm were examined. Six discs (10 mm x 2 mm) from each product were mechanically polished. The samples were then submitted to 20,000 brushing strokes in a toothbrush abrasion machine. SR parameters (Ra, Rt) (Taylor Hobson profilometer), G (NovoCurve glossmeter) and CS (Minolta-CIE-L*a*b* method) were measured before and after toothbrush abrasion. Changes in SR and G were analyzed by 2-way ANOVA, with Bonferroni post-hoc test. CS values were submitted to one-way ANOVA and Bonferroni post-hoc test (p=0.05). Results: There was no statistically significant difference in colour (ÄE* ranging from 0.88 to 0.38) for all groups tested (p=0.11). Bonferroni post-hoc ascertained that toothbrush abrasion resulted in rougher and matte surfaces for all materials tested. Larger filler sizes resulted in higher surface roughness values (Ra and Rt) after abrasion (r2=0.97). Initial G values ranged between 73 and 93 gloss units (GU) and were reduced after toothbrush abrasion to a range of 8.5 to 67 GU. Conclusion: Toothbrush abrasion revealed significant modifications in surface roughness and gloss amongst the materials tested, that related to filler sizes. There was strong correlation between gloss and roughness (Ra) (r2 = 0.93). Filler size did not affect colour stability.