Comparative investigation of the surface properties of contemporary bulk fill composites and conventional resin composites after erosive-abrasive applications

The aim of this thesis is to investigate comparatively the changes in surface roughness and surface microhardness of composites applied with traditional incremental layering technique and bulk fill composites after erosive/abrasive applications. In this in vitro study, three conventional composite resins with different contents (FiltekTM Z250, 3M ESPE, St Paul, MN, USA; FiltekTM Ultimate, 3M ESPE, St Paul, MN, USA; Clearfil MajestyTM Esthetic, Kuraray Noritake Dental, Sakazu, Kurashiki, Okayama Japan) and four bulk fill composite resin (X-tra fil, VOCO, Cuxhaven, Germany; FiltekTM One Bulk Fill, 3M ESPE, St Paul, MN, USA; QuiXfilTM, Dentsply DeTrey GmbH, Konstanz, Germany; Tetric N-Ceram Bulk Fill, Ivoclar Vivadent, Schann, Liechtenstein) were used. While preparing the test specimens, composite resins were applied to 8 mm diameter and 2 mm height round plexiglass molds (n:15) and polymerized with a LED curing unit. Each specimen was polished with coarse, medium, fine, and superfine grain discs (Sof-LexTM XT, 3M ESPE, St Paul, MN, USA) respectively. Then, the initial surface roughness and microhardness values of the specimen were measured. Each group had been exposed erosive/abrasive cycle for ten days. After the cycle, by measuring the roughness and microhardness values of the specimen, the alteration of the surface properties was examined. After the initial and erosive/abrasive cycles of the specimens, the surface analyzes 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. According to the findings of this study, there was no statistically significant difference between the initial microhardness values of the FU, VXF, QXF, and FZ groups, and the microhardness 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 microhardness values of only the FZ and VXF groups. (p>0.05). When the initial surface roughness values were examined, there was no significant difference between the FOB, FU, FZ, and TNC groups, and the roughness values were statistically lower than the other groups. A statistically significant increase was observed in the surface roughness 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. In the limitations of this study, the erosive/abrasive cycle induced an increase in roughness values, decrease in microhardness values and a deterioration in the surface appearance of all composite resins. It could be recommended to pay attention to erosive food intake in daily life and timing of daily routine oral hygiene procedures after composite resin applications. Keywords: Abrasion, erosion, bulk-fill composite, surface microhardness, surface roughness