Effect of different surface treatments on PEEK-enamel bonds: Bonding durability and mechanism.

Statement of problem: Polyetheretherketone (PEEK) has been used in clinical dentistry because of its excellent physical and biological properties. However, achieving an effective and durable bond with enamel is challenging because of its chemical inertness and low surface energy, and data on the effects of different surface treatments on the durability of PEEK-enamel bonds are scarce.

Purpose: The purpose of this in vitro study was to investigate airborne-particle abrasion, sulfuric acid etching, and the combined use of these treatments on the bonding durability of PEEK-enamel bonds and to gain a deeper understanding of their bonding mechanism.

Material and methods: Sixty specimens were divided into 6 groups based on different surface treatments: untreated, sulfonation for 30 seconds, sulfonation for 60 seconds, airborne-particle abrasion, airborne-particle abrasion and sulfonation for 30 seconds, and sulfonation for 30 seconds and airborne-particle abrasion. Comprehensive evaluations were carried out on the surface morphology and physicochemical properties of the pretreated PEEK. After screening out the preferred surface treatment strategy of PEEK, the durability of PEEK-enamel bonds after thermal cycling (10 000 cycles at 5 to 55 °C) and the bonding mechanism were investigated by bond strength testing, cross-sectional topography, molecular dynamics,and Fourier transform infrared spectroscopy. Data were analyzed by 1-way analysis of variance, Weibull analysis, and the Fisher exact test (α=.05).

Results: The shear bond strength of the 98% sulfuric acid etching group for either 30 seconds or 60 seconds was significantly higher than that of the other groups (P<.05). Intermolecular hydrogen bonding was found between PEEK and the methyl methacrylate- (MMA-) containing adhesive resin. Cross-sectional topography showed that the adhesive resin infiltrated into the pores of the sulfonated PEEK, thereby forming micromechanical locking at the bonded interface. The bond strength between the enamel and PEEK treated with 98% sulfuric acid for 60 seconds was found to be more reliable than that observed in the group treated with 98% sulfuric acid for 30 seconds after aging (P<.05).

Conclusions: PEEK pretreated by 98% sulfuric acid etching for 60 seconds presented the best physicochemical properties. This was better than combined etching and airborne-particle abrasion or airborne-particle abrasion alone and showed durable PEEK-enamel bonds with the application of an MMA-containing adhesive.