Adhesion: A Challenge For New Materials

Objectives: The universal adhesive’s total etch and rinse (2-steps) and self-etch (1-step) systems promote versatile bonding. Given the lack of studies on the use of adhesives with Biodentine®, this study aimed to evaluate the shear bond strength (SBS) between Biodentine® and a composite resin, using the two universal adhesive strategies.
Methods: Sixty acrylic blocks were each prepared with a hole measuring 2 mm depth x 5 mm diameter. The holes were filled with Biodentine®, following the manufacturer’s instructions, and then divided in two time groups: 12 minutes (n=30) and 24 hours (n=30). Each group was then subdivided in two groups according to the adhesion strategy: 2-step (n=15) or 1-step (n=15). After application of the adhesive, composite resin (Grandio®) was applied over the Biodentine® and stored at 100 % humidity, at 37 °C, for 24 hours, before SBS test. Data were analyzed with one-way ANOVA and Fisher post-hoc test.
Results: No statistically significant differences were observed between adhesive systems (p=0.871) regardless of adhesion time (12 minutes or 24 hours). However, adhesion time showed statistically significant differences (p=0.021), with the highest values of adhesion observed at 24 hours. At 12 minutes, the 2-step system had a higher adhesion than the 1-step. However, at 24 hours the results were reversed.
Conclusions: The universal adhesive obtained good SBS results over Biodentine® at both 12 minutes and 24 hours adhesion, but superior adhesion was observed at 24 hours post- Biodentine® placement. Hence, before a restorative treatment, it is essential to consider the longest possible setting time for Biodentine®.