Comparative study regarding the surface roughness of highly viscous flowable composites after immersion in acidic drinks

Abstract

The aim of the present study was to assess, by profilometry, the effect of different immersion regimes in Coca-Cola drink on the surface roughness of two highly viscous flowable composite resins. The studied materials were Gradia Direct LoFlo (GC Corporation,Tokyo, Japan) and Micro Esthetic flow-viscous (Bisico, Germany). Fifteen cylindrical samples having the of 5 mm and the thickness of 2 mm were made from each material using plastic molds placed on glass plates. The samples were light-cured for 40s on both sides through the glass plates, to ensure complete polymerization of the material. They were divided into two groups as follows: Group I. Gradia Direct LoFlo and Group II. Micro Esthetic flow-viscous. Specimens of each group were then randomly divided into 5 subgroups. In subgroup A (control group) 4 samples were kept only in artificial saliva. In subgroups B-E (each having 4 samples) the samples were immersed in Coca- Cola drink according to 4 different protocols. The mean values of roughness parameters, Ra, were calculated. The Kolmogorov-Smirnov normality test was used to determine the distribution of data in groups. ANOVA and Tukey post hoc statistical tests were used to compare the results from the groups. For both materials, the highest surface roughness was determined for the samples that were submerged 7 times/day in Coca Cola. The assessment of surface microstructure of the samples, after immersion, revealed for both materials a statistically significant increase of Ra values.