The Influence of Different Polishing Systems on the Surface Roughness and Microhardness of Nanocomposites after Exposure to Acid Drink

Abstract

Aims: This in vitro study evaluated the surface roughness and microhardness of nanocomposites, after storage in acid solution for three months, with different techniques polishing systems. Study Design: In vitro study. Place and Duration of Study: Department of Restorative Dentistry, School of Dentistry, State University of Western Parana (UNIOESTE), Cascavel, Parana, Brazil, between June, and October, 2014. Methodology: A total of 280 specimens (4-mm in diameter, 2 mm thick) were fabricated for both tests (n=140 each test) in a plexiglass mold covered with a Mylar strip. After polymerization, specimens were divided into seven groups (n=20) according to the technique polishing systems: G1 – control group (no polishing treatment); G2 - Soft-Lex Discs; G3 - Diamont Master Discs; G4 - Po Go; G5 – Flexi discs; G6 – Enhance; G7 – Felt disks associated with diamond paste. All polishing systems were applied according to the manufacturers’ instructions. The specimens were randomly divided into two groups according to the storage solution: a) distilled water and b) Coca-Cola classic, for a period of three months at 37°C. The surface roughness values were determined using a roughness test (initially and after three months). The microhardness measurements were performed using a digital microhardness tester (initially and after three months). The mean Ra and microhardness values were submitted to the LS means analysis and Tukey-Kramer test of 5%. Results: There were no statistically significant differences between polishing systems in the roughness and microhardness of nanocomposites (p<0,05). The solution of Coca-Cola led to higher values of reduced surface roughness and microhardness values after 3 months of storage. Conclusion: All polishing systems may be successfully used for polishing nanocomposites.