Efeito da degradação biológica seguida da escovação sobre propriedades de superfície de materiais restauradores estéticos

Abstract

Aesthetic restorative materials must withstand the adversities of the oral environment, suffering minimal degradation. This study evaluated the roughness (Ra), Knoop hardness (KHN) and change of color (ΔE) of esthetic restorative materials subjected to contact with biofilm of Streptococcus mutans associated with abrasion generated by brushing. 10 disks (8 mm diameter; 2 mm deep) of each material were prepared (Filtek Z350, composite nanoparticle; Empress Direct, composite nanohybrid and IPS e.Max, ceramic). The ceramic disks received application of glaze. The composites were stored in 100% relative humidity, after 24 h, the composites were polished with sequential abrasive discs. Then, all specimens were stored in 100% relative humidity at 37°C for 24 hours, and so, evaluated the properties of initial surface. The specimens were sterilized with ethylene oxide; and after undergoing biological degradation, by 25 μL Streptococcus mutans inoculum with optical density (OD) standard, maintained by 2 h on discs. The specimens were immersed in brain-heart infusion (BHI) medium with 1% sucrose, which was changed every 48 h. After 7 days, all disks were washed in ultrasound, and evaluated the surface properties again. Finally, the specimens were subjected to a mechanical degradation, being fixed to a device of brushing and worn through for dental bristles, with toothpaste, and after this process, were measured, once again, the surface properties. Data were analyzed by Proc-Mixed and Tukey (α = 0.05). Initially e.Max showed higher Ra and KHN; after biological degradation, the composites showed increased Ra, but KHN has not changed; later the mechanical degradation Empress had its Ra decreased and KHN increased to Z350, and all had lightness increased. The results suggest that when exposed to Streptococcus mutans biofilm and toothbrush abrasion, ceramic undergoes minimal degradation; the nanoparticulate composite promoted increased roughness and composites exhibit variable degradation, depending on the composition of the material.