Investigation of the effect of different surface treatments on the bonding between polyetheretherketone (PEEK) and soft lining materials

The aim of this study to investigate the effect of various surface treatments applied on the PEEK surface on the surface roughness and bond strength between soft lining material. With the help of CAD/CAM and a precision cutting device, 7x7x2mm PEEK samples were prepared and randomly divided into 8 groups according to the surface treatment to be applied (n=12): Group 1; control (no surface treatment applied), Group 2; 98% sulfuric acid application, Group 3; Sandblasting with 50µm Al2O3, Group 4; Sandblasting with 110µm Al2O3, Group 5; Er, Cr: YSGG laser (2W), Group 6; Er, Cr: YSGG laser (3W), Group 7; ultrafast fiber laser (5W), Group 8; ultrafast fiber laser (10W). After the applied surface treatments, the roughness values of all samples were measured with a profilometer, and the surface examination of one sample selected from each group was performed under a Scanning Electron Microscope (TEM). Afterward, soft lining material was bonded to PEEK samples. 5000 cycles of thermal aging were applied to all samples, and the tensile bond strength values were determined by connecting the samples to a universal test device. The failure surfaces of the samples were examined with a stereomicroscope and the failure types were determined. TEM and Energy Dispersive Spectrometer (EDS) analyses were performed on a representative sample from all groups according to each failure type. The obtained surface roughness and bond strength data were statistically analyzed using one-way ANOVA and Tukey's post hoc test. While the highest surface roughness values were obtained in the 3W Er, Cr: YSGG laser group samples, the highest bond strength value was found in the samples sandblasting with 110µ Al2O3 particles. The lowest surface roughness and bond strength values were observed in the control group. Sandblasting group with 110µm Al2O3 showed statistically higher bond strength values than all groups (p<0.05). Except for the 5W ultrafast fiber laser application, all-laser groups showed higher bond strength values than the control group (p<0.001). The bond strength values of the samples treated with sulfuric acid were found to be similar to the control group. As a result, laser applications can be used as an alternative to sandblasting to increase the bond strength between PEEK and soft lining material, provided that the parameters are chosen correctly.