The Effect of Thermocycling on the Shear Bond Strength of Polyether Ether Ketone (PEEK) to Resin Cements: A Comparative Study

Abstract

Background: Polyether ether ketone (PEEK) is a promising polymer for dental restorations due to its excellent mechanical properties. Its wide clinical application ranges from prosthetic frameworks to orthodontic appliances. However, understanding the effect of thermocycling on the bond strength between PEEK and resin cements is crucial for its broader clinical utilization. Thermocycling tests offer insights into the durability and reliability of PEEK-based restorations, advancing dental materials and techniques. This study aimed to evaluate and compare the thermocycling effect on the shear bond strength of RelyX Unicem and G-CEM Linkace to PEEK surfaces.

Methods: Forty disk-shaped PEEK specimens (10 × 3 mm) were fabricated and randomly assigned to two groups: Group A, cemented with RelyX Unicem, and Group B, cemented with G-CEM Linkace. Specimens from both groups underwent 500 thermocycles at 5°C and 55°C. Shear bond strengths were determined using a universal testing machine at 1 mm/min. Scanning electron microscopy (SEM) was employed to ascertain failure types, observing fractured interfaces at 5.00 kV x 500 SE at 100 m and 5.00 kV x 150 SE at 300 m magnification.

Results: The mean shear bond strength for RelyX Unicem cement in the control group was significantly higher than in the test group. For G-CEM Linkace cement, the mean shear bond strength was 5.07 ±0.95 MPa in the control group and 4.01±0.68 MPa in the test group, showing a 20.9% reduction. RelyX test group exhibited maximum loss of shear bond strength, while the G-CEM test group showed minimum loss. After thermocycling, G-CEM Linkace demonstrated maximum shear bond strength, and RelyX Unicem showed minimum. An adhesive type of failure was consistently observed for both cementing materials.

Conclusion: Thermocycling, which simulates oral stimuli, can alter certain properties of PEEK. Post-thermocycling, G-CEM LinkAce exhibited the highest shear bond strength among the studied cementing materials. SEM observations confirmed an adhesive failure mode on PEEK surfaces in both groups.