Figure 5.

Bonding and debonding schematic diagram and FE-SEM images (the magnification was 500× and the scale bar was 50 μm) of (poly)aryl–ether–ketone (PAEK) materials. Firstly, the sandblasted surfaces of PAEKs retained their scratch characteristics (A). After the priming process, swelling bubbles were found on the surfaces of PAEKs (B). (C) The cavities shown in the figure are an enlarged schematic diagram of the irregular holes created by sandblasting. The volume shrinkage that occurred during the photopolymerization process was accompanied by the generation of bubbles (①). During the photopolymerization process, the bubbles would gradually move to the primer surface (②→③). After the photopolymerization was completed, if bubbles moved onto the primer surface (④), these would become swelling bubbles; if the bubbles adhered to the substrate wall (③), the contact area between the priming agent and PAEK would reduce. Schematic diagram of denture acrylic bonded to PAEKs is shown in (D). After the SBS test, the denture acrylic was debonded from the PAEK surface. According to the FE-SEM image (E), the appearance of the PAEK side (base material; left FE-SEM images) was the same as the sandblasting surface (A), while the denture’s acrylic side (adhesion; right FE-SEM images) was rough and uneven.