Bond Strength Between CAD/CAM Blocks and Repairing Materials: Effect of Repairing Strategies

Objectives: The aim of this study was to compare the different repairing methods on the shear bond strength between CAD/CAM blocks and different type of composite resins.
Methods: A feldspathic ceramic block and two hybrid- ceramic blocks were selected in this study. The Blocks were sliced with ISOMET 5000 (Buehler) device in 5 × 5 × 5 mm and a total of 300 samples were obtained. After the samples were subjected to 5000 cycles of thermal cycling between 5 and 55 °C, all groups were divided into five subgroups according to repairing strategy: Group CT: Clearfil Repair Kit (Kuraray), Group UT: Ultradent Repair Kit (Ultradent Products), Group DB: Diamond Bur + GC Repair Kit (GC Corporation), Group EL: Er-YAG Laser + GC Repair Kit, Group MC: Micro etcher intra-oral sandblasting device (Danville) + GC Repair Kit. Then plastic molds (2 mm high x 4 mm diameter) were inserted on the samples and filled with two different types of composite resins; G-aenial Hybrid Composite (GC Corporation) or G-aenial Universal Flo Composite (GC Corporation) and polymerized for 20 s. The samples were then subjected to shear bond test and the failure modes were examined in a stereomicroscope. Statistical analyses were performed with three-way ANOVA and Bonferroni tests.
Results: The shear bond strength values of Cerec blocks (17.48 ±5.51) were significantly higher than the other blocks (p<0.05). In terms of repairing methods, Group MC showed significantly higher bond strength values (17.19±5.94) than the other tested groups except Group UT (15.15±5.22). G-aenial Universal Flo exhibited significantly higher bond strength values (16.93±5.40) than G-aenial hybrid composite (12.81±5.33).
Conclusions: The sandblasting system can be recommended for the repair of all type of CAD/CAM blocks tested in this study. The G-aenial Universal Flo seems to be a successful repairing material for the repair of CAD/CAM materials.