Evaluation of Shear Bond Strength of Resin-Based CAD/CAM Blocks Repaired with Resin Composite

Abstract

Objectives: Shear bond strength (SBS) of repaired resin-based CAD/CAM blocks with a resin composite were evaluated in this in-vitro study. Materials and Methods: Resin-based CAD/CAM blocks (Hc Block, Shofu; Cerasmart, GC corp.; Lava Ultimate, 3M; Brilliant Crios, Coltene) were used (n=10). Specimens were prepared and aged with thermocycling. Specimens were roughened by using diamond burs and adhesive agent (OptiBond Universal, Kerr) was applied. Resin composite material was placed onto the roughened surface by using silicone molds for the repair procedure. After 24 hours, second thermocycling procedure was applied and loaded in an AGS-X Universal testing machine (Shimadzu; crosshead speed of 1 mm/min) until failure occurred. Leica MZ 75 stereomicroscope (Leica Microsystems; 20x magnification) was used for the determination of failure type. Kruskal Wallis, Kolmogorov-Smirnov and Fisher's Exact tests were used for statistical analysis (p<0.05). Results: Failure type differences were not statistically significant for the tested groups (p<0.05); however, multiple comparisons for the Cerasmart-Lava Ultimate and Cerasmart-Hc Block groups showed statistically significant differences (p<0.05). The highest SBS was measured for the Hc Block group (12.2±7.6 MPa) whereas the lowest was for the Cerasmart group (5.1±4.8 MPa). Conclusions: Within the limitations of this study, the type of resin-based CAD/CAM blocks affected the SBS values of repaired restorative materials and the bond strength of repaired Cerasmart blocks was lower than those obtained in the other three CAD/CAM blocks.