Surface roughness and surface microhardness of bulk-fill and conventional resin composites after erosive-abrasive...

To investigate comparatively the changes in surface roughness and surface microhardness of resin composites applied with traditional incremental layering technique and bulk-fill resin composites after erosive/abrasive applications.

In this laboratory study, three conventional resin composites with different contents: Filtek Z250 (FZ), Filtek Ultimate (FU), Clearfil Majesty Esthetic (CME), and four bulk-fill resin composites: X-tra fil (VXF), Filtek One Bulk Fill (FOB), QuiXfil (QXF), and Tetric N-Ceram Bulk Fill (TNC) were used. While preparing the test specimens, resin composites were applied to 8 mm diameter and 2 mm height round plexiglass molds (n= 15) and polymerized. Each specimen was polished. Then, the baseline surface roughness (R0) and surface microhardness (H0) values of the specimens were measured. Each group had been exposed to erosive/abrasive cycle for 10 days. After the cycle, by measuring the roughness (R1) and microhardness (H1) values of the specimen, the alterations of the surface properties were investigated. After the baseline and erosive/abrasive cycles of the specimens, the surface analyses were performed with scanning electron microscopy. One-way ANOVA test, Tukey's post hoc test, and t-test were used for statistical analysis. Differences at the P< 0.05 level were considered statistically significant.

There was no statistically significant difference between the H0 values of the FU, VXF, QXF, and FZ groups, and the H0 values of these groups were higher than the other groups (P< 0.05). After the erosive/abrasive cycle, there was no significant difference in the H1 values of only the FZ and VXF groups (P> 0.05). When the R0 values were examined, there was no significant difference between the FOB, FU, FZ, and TNC groups (P> 0.05), and the R0 values of these groups were statistically lower than the other groups (P< 0.05). A statistically significant increase was observed in the R1 values of all composite materials examined after erosive/abrasive applications (P< 0.05). In the SEM findings, erosive/abrasive applications caused degradation of both the organic matrix and surface properties of inorganic fillers.

According to the results of this laboratory study, erosive and abrasive cycles negatively affected the surface microhardness and roughness of conventional and bulk-fill composites at different rates and varied depending on the structural properties. However, the surface roughness of Filtek Ultimate and Filtek One Bulk Fill, both with nanofill structure, was less affected by combined erosive and abrasive cycles.