Effect of Acid-Etching Duration on the Adhesive Performance of Printed Polyetheretherketone to Veneering Resin

Abstract

Three-dimensional printing polyetheretherketone (PEEK) provides a new choice for dental prostheses, while its appropriate bonding procedure and adhesive performance are still unclear. This study aimed to investigate the adhesive performance of printed polyetheretherketone (PEEK) after acid etching to veneering resin. In total, 182 PEEK specimens (including 91 printed and 91 milled specimens) were distributed to 14 subgroups (n = 13/subgroup), according to the manufacturing process and surface treatment. The specimens were polished and etched with sulfuric acid for 0, 5, 30, 60, 90, 120, and 300 s, respectively. Two specimens in each subgroup were observed under a scanning electron microscope (SEM) for surface and cross-section morphology separately. Then, the specimens were treated with a bonding primer, and one specimen in each subgroup was prepared for cross-sectional observation under SEM. The residual 10 specimens of each subgroup bonded with veneering resin were tested with the shear bond strength tests (SBS) and failure modes analysis. Statistical analysis was performed by one-way ANOVA followed by the SNK-q post hoc test (p < 0.05). The etched pores on the PEEK surface were broadened and deepened under SEM over time. Printed PEEK etched for 30 s obtained the best SBS-to-veneering-resin ratio (27.90 ± 3.48 MPa) among the printed subgroups (p < 0.05) and had no statistical differences compared with milled PEEK etched for 30 s. The SBS of the milled subgroups etched from 5 to 120 s were over 29 MPa without significant between-group statistical differences. Hence, printed PEEK can be coarsened effectively by 30 s of sulfuric acid etching. The adhesion efficacy of printed PEEK to veneering resin was qualified for clinical requirements of polymer-based fixed dentures.

PEEK in Fixed Dental Prostheses: Application and Adhesion Improvement

“…In terms of concentration, 98% sulfuric acid has been associated with better surface roughness values (Ra, 0.74 ± 0.25 µm) and SBS (27.36 ± 3.95 MPa) compared to a control group (Ra, 0.04 ± 0.02 µm and SBS, 1.75 ± 0.66 MPa), and was therefore considered an ideal concentration for the surface modification of PEEK [77]. Further study revealed that 98% sulfuric acid etching created porous and permeable surfaces in PEEK, resulting in better adhesion [78][79][80]. The duration of etching with 98% sulfuric acid has a significant effect on the adhesive behavior of PEEK, and the optimal duration varies according to the manufacturing method.…”

“…The duration of etching with 98% sulfuric acid has a significant effect on the adhesive behavior of PEEK, and the optimal duration varies according to the manufacturing method. Zhang et al suggest that the appropriate etching duration for printed PEEK is 30 s because the highest SBS (27.90 ± 3.48 MPa) was achieved at 30 s, while for milled PEEK, the ideal duration was <120 s (SBS, over 29 MPa) [78]. On the other hand, Ma et al have recommended 5 min as an ideal duration for 98% sulfuric acid etching because it results in lower wettability (5 min θ at 115.3 ± 9.9 • ) vs. the untreated surface (5 min θ at 92.9 ± 3.2 • ) while maintaining compatibility, and an intact porous structure under scanning electron microscopy (SEM), with less residual acid [79].…”

“…Evidence confirming the positive effect of Visio.link for PEEK adhesion continues to accumulate. Zhang et al treated PEEK with 98% sulfuric acid and then coated it with Visio.link; subsequent cross-sectional SEM imaging indicated that the primer had penetrated the etched pores, and the pore depth increased over the etching time, contributing to the enhancement of micromechanical bonding to the resin cement and ultimately improving the SBS [78]. Elsewhere, Kurahashi et al reported that when combined with Palapress Vario (an autopolymerizing resin adhesive), ceramic primer treatment (Clearfil Ceramic Primer Plus) initially showed no significant effect on the improvement of SBS (3.55 ± 1.14 MPa) vs. control group (3.19 ± 1.06 MPa); however, when combined with silica-modified sandblasting (Rocatec), the ceramic primer treatment resulted in higher SBS (15.32 ± 1.80 MPa) vs. single application of Rocatec alone (12.31 ± 2.10 MPa) [106].…”

PEEK for Oral Applications: Recent Advances in Mechanical and Adhesive Properties

“…Chaijareenont et al [ 144 ] reported that a good bond strength (27.36 MPa) was obtained after the etching of CAD/CAM-milled PEEK surfaces with 98% concentrated sulfuric acid for 60s, as it met the clinical requirements (ISO bond strength of 5 MPa). However, for 3D-printed PEEK, Zhang et al concluded that the best bond strength (27.90 ± 3.48 MPa) could be obtained only after 30s of acid etching with concentrated sulfuric acid [ 143 ]. Moreover, the bonding properties of 3D-printed PEEK after acid etching with concentrated sulfuric acid were slightly lower than those of milled PEEK (SBS; >29MPa), but both were able to comply with the clinical requirements.…”

Bond Strength of Sandblasted PEEK with Dental Methyl Methacrylate-Based Cement or Composite-Based Resin Cement

“…Acid etching causes surface topographical changes and provides a microinterlocking structure on the surface [6,19,20]. For example, etching with 98% sulfuric acid can create a porous surface structure wherein an adhesive penetrates, leading to significantly improved bond strength [21][22][23]. Overall, there is a consensus that alumina sandblasting and sulfuric acid etching are effective surface pretreatment methods for improving PEEK adhesion [24].…”