Polishing of samples

The four subgroups of group II, group III, and group IV were polished according to the respective manufacture's instructions as follow:

Subgroup A: (control) Mylar strip was used to provide a surface finish and no polishing was carried out.

Subgroup B: Polishing was carried out using Astrobrush single step polishing system (Ivoclar vivadent, AG, Liechtenstein, lot no-RL3771).

Subgroup C: Polishing was carried out using Astropol three step polishing system (Ivoclar vivadent, AG, Liechtenstein, lot no-ML0797).

Subgroup D: Polishing was carried out using Soflex spiral wheel polishing system. (3M, ESPE, St. Paul, MN, USA, lot no-N493180).

The baseline surface roughness (Ra) values of each sample were measured using a profilometer. The Ra value (μm) reading was also recorded using a profilometer (Kosaka Lab. SE 1700) with 0.25 mm cutoff and 0.1 mm/s speed. Three measurements were made and an average was calculated. To reduce the interoperator variability, all the specimens were finished and polished by the same operator. After polishing, the smoothness of the resin composite of all the groups were again calculated and were compared within the baseline values. Data were analyzed by one-way analysis of variance (ANOVA) and Tukey's test for individual comparisons between the groups.