Haben variierende Adhäsivtechnik und Inkrementstärken Auswirkungen auf den Haftverbund zwischen Kompositen und Dentin?
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Zusammenfassung
7.2.1 Aim of the study
This study aimed to assess how varying increment thicknesses of the nanohybrid composite G-ænial® A’CHORD and the bulk-fill composite everX Flow Bulk Shade influence resin–dentin bond strength. Bonding was performed using the four-step etch-and-rinse system Syntac® and the universal adhesive Prime&Bond Active.
7.2.2 Materials and methods
Sixty caries-free human third molars were prepared with standardized Class-I cavities (4 × 4 × 4 mm) and subsequently randomized into 12 groups (n = 5), each treated with different adhesive protocols, increment thicknesses, and composite materials. Application of the adhesive systems was carried out as specified by the manufacturers, cavities were consequently filled with two restoratives, everX Flow Bulk Shade and G-ænial® A'CHORD in varying layer thicknesses. Syntac® was used in six groups, Prime&Bond Active was used in the other six groups. Specimens were etched using the etch-and-rinse technique. Subsequently, the sample teeth were cut into disks and then further into beams with dimensions of 1 × 1 × 1 mm for microtensile bond strength testing. The fractured surfaces of the dentin rods were subsequently analyzed by scanning electron microscopy (SEM) at magnifications of up to 1000×.
7.2.3 Results
The combination of a universal adhesive and a bulk-fill composite achieved the highest bond strength values in this test series (p<0.05). Overall, the universal adhesive exhibited significantly higher bond strength than Syntac® (p<0.05), provided that the recommended maximum layer thickness was not exceeded. Additionally, the universal adhesive demonstrated advantages during conditioning, including reduced technique sensitivity and time savings. In contrast, the bond strength values in the Syntac® groups, particularly in combination with the bulk-fill composite, were statistically significantly lower (p<0.05) and did not meet the required thresholds for clinical use. Furthermore, in the groups where Syntac® was applied, a higher number of pre-test specimen failures occurred during cutting, leading to numerous 0 MPa values.
7.2.4 Practical conclusion
Universal adhesives can be effectively combined with bulk-fill composites to achieve an efficient and reliable filling process. In this study, the highest bond strength values were obtained with a flowable bulk-fill composite, suggesting that an initial lining layer should be applied to ensure optimal adhesion and a secure marginal seal. This should be followed by a covering layer using a packable composite with a higher filler content to enhance abrasion resistance. Due to limited esthetics, their application should be restricted to the posterior region. Only bulk-fill composites can be used in thicker layers, as they are specifically designed for this purpose. In contrast, conventional composites exhibit insufficient dentin adhesion when applied in larger increments, contrary to the manufacturer's recommendations.
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