Bond strength of a resin composite to PEEK or glass fiber-reinforced polymer: Effect of surface treatments and thermocycling

This in vitro study evaluated the effects of different surface treatments and thermocycling on the shear bond strength (SBS) of nanoparticulate light-cured resin composite (Filtek Z350 XT, 3M ESPE) to polyether ether ketone (PEEK, Tecapeek, Ensinger) and glass fiber-reinforced polymer (GFRP) (Zantex, Biofunctional). The 168 specimens (10 mm diameter x 10 mm high) were divided into 6 groups based on material and surface treatment: control (PEEK with 98 % sulfuric acid and untreated GFRP), roughening with diamond bur (DB) or with aluminum oxide (AlO). Resin composite cylinders (2 mm diameter x 4 mm high) were constructed and divided into groups (n = 14): with or without thermocycling (5000 cycles) for SBS testing. Failure modes were examined via stereomicroscope (40x) and scanning electron microscopy (SEM). Results showed no significant SBS differences between PEEK and GFRP in the control group. AlO roughening significantly increased SBS compared with DB, but not with the control. GFRP with DB and AlO had higher SBS than the PEEK control group. Thermocycling did not significantly impact SBS. Regarding PEEK, mixed failures predominated in the control and AlO groups, while adhesive failures were common with DB. Thermocycling increased adhesive failures without significant differences. GFRP showed mostly mixed failures, except for adhesive failures in the control group with thermocycling. SEM revealed microporosities in PEEK control and grooves in PEEK DB; PEEK AlO showed rougher topography. GFRP DB and AlO created rougher surfaces than the control (no treatment). In conclusion, regardless of thermocycling, DB and AlO roughening improved bond strength for the GFRP. For PEEK, DB showed the weakest performance, while AlO sandblasting provided bond strength similar to sulfuric acid treatment.