Shear bond strength of intraoral porcelain repair systems to various CAD/CAM restorative materials

The aim of this research was to evaluate and compare the shear bond strength (SBS) of two intraoral porcelain repair systems to various restorative materials with and without thermocycling.

The study employed an in vitro design with a disc-shaped samples (7 mm × 3 mm) bonded to repair systems, including thermocycling and SBS test with a universal testing machine.

Two hundred polyetheretherketone (PEEK), cobalt-chromium, zirconia, titanium, and glass ceramic samples were prepared with the computer-aided design/computer-aided manufacture system according to the ISO 6872:2024 (n = 40). After all samples were polished with silicon carbide sandpaper, the bonding surface was roughened with 50 µm Al2O3. Then, all materials were divided into two subgroups (n = 20) according to the repair system used: Bredent and Clearfil repair systems. After sample preparation, each group was divided into two subgroups (n = 10) and subjected to different storage conditions, short- and long-term storage (with 5000 thermocycles). SBS tests were performed on all samples, and fracture types were examined.

The data were analyzed using two-way analysis of variance and Tukey's honestly significant difference test. Significance was determined as P < 0.05.

In short-term storage, when Clearfil repair system was evaluated, the lowest SBS values were recorded for glass ceramic (7.88 ± 1.63 MPa), and the highest SBS values were recorded for titanium (14.92 ± 3.65 MPa) (P < 0.05). When Bredent repair system was evaluated in short-term storage, the lowest SBS values were recorded for zirconia (8.33 ± 1.84 MPa), and the highest SBS values were recorded for titanium (15.77 ± 5.79 MPa) (P < 0.05). Long-term storage decreased the bonding between the materials and the repair systems.

The Clearfil system, used on metal, titanium, and zirconia, and the Bredent system used on PEEK, metal, and titanium materials, demonstrated a minimum SBS of 10 MPa in the short term, suggesting their appropriateness for clinical use. Long-term storage decreased the bonding between the materials and the repair systems.