The purpose of this study was to evaluate the effect of application of various surface treatment materials on the bond strength of resin luting agent to PEEK (Polyetheretherketone). As the test specimen, a 10 × 10 × 3 mm adherend was cut out from a PEEK disk (Isomet TM LS, Buehler, USA) and was embedded in an auto-polymerizing resin (Palapress, Kulzer, Germany). After sandblasting the surface of PEEK, various surface treatment materials and MMA solution were coated. A stainless steel cylinder (diameter 6 mm, height 10 mm) was glued with resin luting agent, and all samples were immersed in distilled water at 37°C for 24 hours. Then, a compression shear test was conducted to measure the bond strength (n = 15). Compared to no primer treatment (CO), the bond strength of dental resin adhesive material (CAD/CAM resin adhesive, Shofu, Kyoto) (RA) and dental dentin adhesive (Beauty Bond Xtreme, Shofu, Kyoto) (BX) were significantly increased (p < 0.01). On the other hand, there was no significant difference between CO and a silane-treated adhesive material for dental ceramics (Shofu Porcelain Primer, Shofu, Kyoto) (SP), and MMA solution of a general-purpose dental acrylic resin (Provenice, Shofu, Kyoto) (PE) (p > 0.05). The result indicated that the bond strength of resin luting agent to PEEK was improved by applying RA and BX.

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This study investigated the effect of a 4-META/MMA-TBB resin-based luting agent (Super-Bond, Sun Medical, Shiga, Japan, SB) and various primers on the shear bond strength to PEEK. CAD-CAM PEEK (Shofu PEEK, Shofu, Kyoto, Japan) was used as the substrate. After alumina sandblasting, one of six primers was applied: Super-Bond Catalyst V (TBB), Super-Bond Monomer (MMA), a 1:4 mixture of Catalyst V and Monomer (MIX), PZ Primer for porcelain-zirconia (PZP), Metafast Bonding Liner for non-precious metals (META), and M&C Primer (MC). Cylindrical stainless steel rods were bonded to the treated PEEK surfaces using SB, and shear bond strength was measured. The greatest shear bond strength was obtained with META. This result is attributed to the chemical interaction between 4-META and titanium oxide in the PEEK surface, along with the formation of a resin coating layer by MMA infiltration, which may have promoted copolymerization with SB. These findings suggest that 4-META is essential for effective chemical bonding. Furthermore, the composition of the primer, the surface condition of PEEK, and the presence of additives were found to significantly influence bonding performance. This study highlights the importance of appropriate primer selection and surface treatment for improving adhesion between resin cements and PEEK in dental applications.

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After endodontic treatment in clinical practice, when reconstructing the anterior crown shape for a non-vital tooth without enough remaining tooth structure, the application of direct composite resin restoration is gradually expanding. To ensure the reliability of the bonding and filling material of direct composite resin restorations, a new procedure has been developed for reconstructing anterior teeth instead of using a traditional indirect prosthesis with an adhesive composite resin post and core system. Applying a direct crown restoration to endodontically treated teeth is expected to be the last resort for restorative treatment, even in cases with loss of ferrule effect where the amount of residual tooth structure is severely reduced and the tooth is considered to be hopeless and difficult to preserve.

In this report, we outline the procedures and materials used in direct composite resin crown restorations for severely destroyed endodontically treated teeth, and illustrate the results of clinical evaluation of direct resin composite crown restorations.

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