The study aimed to evaluate the shear bond strength (SBS) and to analyse the failure mode at the resin-dentine interface of different dental adhesive systems. A total of 75 sound premolar teeth were selected and randomly assigned into five different adhesive groups (n=15): OptiBond Solo (OBS, total-etch), OptiBond Versa (OBV, two-bottles, self-etch), Adhe SE Ivoclar (ADHE, two-bottles, self-etch), G-Bond (GB, one-bottle, self-etch), and OptiBond All in One (OBO, one-bottle, self-etch). The occlusal surface of each tooth was flattened and composite resin cylinder (4x2 mm) was built up on the flat dentine surface using a custom made mould. The specimens were then subjected to 500 thermal cycles between 5 °C and 55 °C and dwell time of 20s. The SBS test was conducted using a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed using one-way ANOVA and Dunnett T3 Test. Failure mode was determined as adhesive, cohesive or mixed mode using a stereomicroscope and the data were analyzed using Fisher's exact test. The total-etch (OBS) had significantly higher value of SBS than the two self-etch (ADHE and GB) adhesive systems. Within the self-etch systems, OBV showed significantly higher SBS value compared to ADHE and GB. There were no statistically significant differences between types of failure mode (p > 0.05) and adhesive group. It can be concluded that the different compositions in the self-etch adhesive materials may contribute to the different SBS value. The failure modes detected within all tested groups did not show clinically important differences.
This study compared the surface roughness of selected tooth coloured restorative materials that were polished according to manufacturers’ instructions and Sof-Lex. It also assessed the surface roughness of polished materials after thermocycling.Filtek Z350XT, Beautifil-Bulk Restorative and Cention N, were used in this study. A stainless steel mould (10mm diameter x 2mm height) was used to fabricate 75 cylindrical specimens: 15 Filtek Z350XT (FZ), 30 Beautifil-Bulk Restorative (BB) and 30 Cention N (CN). All 15 FZ specimens were polished with Sof-Lex. Fifteen BB and CN specimens were polished according to manufacturers’ instructions. The remaining fifteen BB and CN specimens were polished using Sof-Lex. All the specimens were subjected to thermocycling (1000 cycles). Surface roughness was assessed quantitatively with profilometry after specimen preparation (Mylar stage), polishingand thermocycling. Data were analysed using SPSS version 25.0 at α=0.05. When polished according to manufacturers’ instructions, BB had the lowest mean surface roughness (Ra) values (0.13±0.01μm) followed sequentially by CN (0.14±0.03μm) and FZ (0.15±0.02μm). The differences were not statistically significant. When polished with Sof-Lex, BB exhibited the smoothest surface (0.116±0.03μm) followed sequentially by and FZ (0.150±0.02μm) and CN (0.157±0.02μm). Thermocycling caused an increase in the Ra. The differences were statistically significant. All materials tested had Ra values below the threshold value of 0.2 μm at Mylar stage and after polishing with their recommended polishing system and Sof-Lex. Thermocycling produced rougher surfaces that did not exceed the threshold Ra value. Polishability was material dependent.