Shear-Bond-Strength-Evaluation of One Bulk-Fill and One Build-Up-Composite in Different Curing-Modes

Objectives: One bulk-fill and one build-up composites in combination with one adhesive system were tested for shear bond strength evaluation. The adhesive as well as the composites have dual curing setting modes. We mixed and matched the curing modes with the materials and wanted to test the null hypothesis that there are no differences among the tested groups.
Methods: 40 freshly extracted third molars were cross sectioned and embedded in resin to fabricate specimens with a dimension of 2cm in height and 2.5cm in diameter exposing dentin surface before they were divided into 4 groups of 10. Group1A: shear bond strength measurement (SBSM) with the adhesive PRELUDE (PR)/Zest Dental under chemically cured mode(cc) and the bulk-fill composite BulkEZPlus(EZ+)/Zest Dental cc. Group2A: SBSM with PR under light curing (lc) mode with EZ+ cc. Group3A: SBSM with PR lc and EZ+ lc. Group4A: SBSM with PR cc and EZ+ lc. After SBSM testing, all 40 specimens were re-surfaced with 320 grit carbide paper and used for a second set of tests. Group1B: SBSM with PR cc and build-up composite AnchorBuild-Up (AN)/VistaApex cc. Group2B: PR lc and AN cc. Group3B: PR lc and AN lc. Group4B: PR cc and AN lc. SBSM was done using the Ultratester (Ultradent) at a crosshead speed of 1mm/min. Paired T-tests were performed with a 95% confidence interval.
Results: Statistically significant differences were found in the EZ+ group between Group 1A and 3A(p=-0.0011),Group 1A and 4A(p=-0.02) and Group 2A and 3A(p=0.026). Furthermore, statistical differences were found in the Anchor group between 1B and 2B(p=0.008), Group 1B and 4B(p=0.0004), group 2B and 3B(p=0.0004), Group 2B and 4B(p=0.00007) and between group 2B and 4B(p=0.011). The null hypothesis was rejected.
Conclusions: All EZ+ materials performed better when lc was involved. The Anchor material performs best in cc followed by lc EZ+composite.