Investigating the influence of infill pattern and layer height on the mechanical and bonding behavior of additively manufactured PEEK for dental applications.

STATEMENT OF PROBLEM: Current knowledge regarding the influence of infill pattern and layer height on the flexural and shear bond strength of polyetheretherketone (PEEK) manufactured via fused filament fabrication technology remains limited. PURPOSE: The purpose of this in vitro study was to investigate the impact of infill pattern and layer height on the shear bond strength (SBS) and the flexural strength (FS) of additively manufactured PEEK bars and disks relevant to dental applications. MATERIAL AND METHODS: The PEEK specimens were prepared in 9 groups (n=10), whereby different layer heights (0.1, 0.2, and 0.3 mm) and different infill patterns (+/-30, +/-45 lines, concentric) were used. The surface roughness (Ra) was recorded with a confocal microscope. For the SBS test, resin composites were applied on the disk surface. All the specimens were subjected to thermal aging. The SBS and FS test was performed through a universal testing device. Two-way ANOVA, 1-way ANOVA, post hoc Tukey, and Tamhane tests were used for statistical analysis. (alpha=.05) RESULTS: The highest SBS values were observed at a layer height of 0.1 mm. The infill pattern had a significant effect on FS at all layer heights (0.1 mm P=.016, 0.2 mm P=.010, 0.3 mm P=.010). While the highest FS values at a 0.1-mm layer height were observed in the concentric pattern, no significant difference was identified between the L45 and L30 groups (P=.186). CONCLUSIONS: Lower layer heights strongly influenced the Ra, SBS and FS, with the highest SBS achieved with a layer height of 0.1 mm. To improve the mechanical properties of PEEK, the process parameters for additive manufacturing should be optimized.