Effect of chemical and mechanical degradation on surface roughness of three glass ionomers and a nanofilled resin composite.

Nanofillers have been incorporated into glass ionomer (GI) restorative materials to improve their mechanical and surface properties. The aim of this present laboratory study was to compare the superficial roughness (Ra) of nanofilled GI (Ketac N100) with that of conventional GI (Fuji IX GP), resin-modified GI (Vitremer), and a nanofilled resin composite (Filtek Supreme) after pH cycling and toothbrush abrasion. Ten specimens of each material were made using Teflon molds, which were polished using aluminum-oxide abrasive disks. Three measurements of Ra were made of each specimen to serve as baseline values. The specimens were submitted to pH cycling for 10 days in a demineralization solution for six hours (pH 4.3) and were then stored in remineralization solution for 18 hours (pH 7.0). Ra measurements were recorded after the pH cycling. Specimens were then submitted to toothbrush abrasion in a brushing machine with a 200g load for 30,000 cycles at 250 cycles/min. The Ra values were then recorded. The surface morphology of specimens from each group was analyzed using a scanning electron microscope. Data were analyzed by analysis of variance, Tukey, and t-tests. After toothbrushing, only Fuji IX GP (1.10 ± 0.80) showed Ra values that were statistically different from those of the other materials evaluated. Ketac N100 (0.68 ± 0.16) showed intermediate Ra values, but it did not differ statistically from the results associated with Vitremer (1.04 ± 0.46) and Filtek (0.30 ± 0.15). Ketac N100 showed intermediate values of superficial roughness among the conventional glass ionomer cement, resin-modified glass ionomer cements, and the nanofilled resin after chemical and mechanical degradation.