Influence of PEEK surface modification with titanium for improving osseointegration: an in vitro study

Abstract

This study aimed to examine the impact of PEEK surface modification with titanium to enhance osseointegration. The assessment included the bond strength of the TiO₂ surface coating, as well as an analysis of the hydrophilicity and cell adhesion properties of TiO₂-coated PEEK. The study also explored whether aging affected TiO₂-coated PEEK. The study used 51 disk specimens of ceramic-reinforced PEEK, prepared by wet milling. The disk surfaces were polished and divided into three groups based on surface modification or treatment. The control group (CG) included seven specimens without TiO₂ coating. The nascent group included 22 TiO₂-surface-coated specimens, subdivided equally into the untreated nascent group (NG) and the photo-functionalized, UV-treated nascent group (NGP). The remaining specimens were aged for four weeks and similarly divided into the untreated aged group (AG) and the photo-functionalized, UV-treated aged group (AGP). In the CG, three specimens were evaluated for hydrophilicity, and the remaining four for stem cell culture. For the NG, NGP, AG, and AGP groups, three specimens were evaluated for hydrophilicity, while four specimens were assessed for cell growth and TiO₂ coating bond strength. Bond strength was evaluated using a scratch test, showing an average strength of 24.56 ± 2.28 MPa, with no significant difference between groups. Hydrophilicity was measured via contact angle, revealing that untreated ceramic-reinforced PEEK exhibited hydrophobic properties (99.11 ± 1.07 degrees). The NGP group had the lowest contact angle, indicating the highest wettability. The cell adhesion test showed that NGP had the highest number of adhered cells, followed by NG, AGP, AG, and CG. The study suggests that TiO₂-coated PEEK can serve as a biocompatible, hydrophilic material with improved wettability and osteoblastic cell adhesion.

Fig. 1

Flow Chart: Control and test group specimen.

Fig. 2

Comparison of Bond Strength.

Fig. 3

Bond strength analysis using the scratch test. (A) NG specimen. (B) NGP specimen. (C) AG specimen. (D) AGP specimens.

Fig. 4

Comparison of hydrophilicity.

Fig. 5

Contact angle measurement to the surface of PEEK disks. (A) CG specimen. (B) NG specimen. (C) NGP specimen. (D) AG specimen. (E) AGP specimens.

Fig. 6

Comparison of cell growth.

Fig. 7

Number of cells per cm² counted on the surface of PEEK disks of all groups. (A) SEM image of CG specimen. (B) SEM image of NG specimen. (C) SEM image of NGP specimen. (D) SEM image of AG specimen. (E) SEM image of AGP specimen.