###### Abstract  
Polyetheretherketone is a high-performance thermoplastic polymer that can be used in 3D printing by fused deposition modeling, and is a promising material for dental applications. Some printing parameters are sensitive and can influence the properties of the printed object. Thus, this work aims to evaluate the influence of the print layer thickness on the surface roughness of polyetheretherketone before and after polishing and to verify the effectiveness of the polishing method used, as well as to compare it with the results obtained using polymethyl methacrylate as the control group. Specimens with different impression layer thicknesses were printed with polyetheretherketone (Group A--0.1 mm and Group B--0.3 mm). Additionally, a control group with polymethyl methacrylate specimens was milled. Roughness evaluation was conducted using a contact profilometer after the specimens had been printed (before polishing). Then, silicon carbide sandpaper was used to polish the surface, and the roughness was reassessed. Differences were observed between specimens regarding the print layer thickness and the roughness, with the 0.3 mm layer thickness showing the lowest roughness values. The results of this pilot study suggest that the surface roughness of fused deposition modeling printed polyetheretherketone is influenced by print layer thickness, with the lowest roughness seen at a thickness of 0.3 mm. type: _applied sciences_ Article  
[PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], M.H. Surface Roughness of Polyetheretherketone Printed by Fused Deposition Modeling: A Pilot Study Investigating the Impact of Print Layer Thickness and Polishing Method  
design/computer-aided manufacturing (CAD/CAM) technology, PEEK disks were used to mill crowns, fixed partial dentures, removable prostheses, partial denture frameworks, obturating prostheses, and dental implants. However, low production rates, the excessive waste of grinding material, and an inability to produce more complicated and controlled architectures are the disadvantages of subtractive technology [15; 16]. Fused deposition modeling (FDM) is a method in which layers of molten material are deposited from a filamentous nozzle and then solidified within 0.1 s [17]. This printing technique has become increasingly important, as it allows the construction of parts with complex geometries and is a more economical and simpler method due to using filament instead of powder [18]. Some authors refer to FDM as an alternative method to manufacture complex PEEK structures due to it being a low-cost, easy, and minimal-waste 3D printing technology. This technique overcomes some CAD/CAM milling problems and generates items more resistant to aging since PEEK filaments absorb less moisture than PEEK milling blocks [16]. Moreover, 3D printing in PEEK is an innovation in dentistry that allows for greater effectiveness and efficiency and is a quick and inexpensive process [9; 19]. Several parameters can modify the outcome of FDM printing, influencing the mechanical behavior and properties of the devices, such as print layer thickness, print wire width, printing speed, extruder temperature and diameter, filament feed rate, viscosity, filament quality, and the printing routine itself. Therefore, initial tests are necessary to understand the ideal parameters for each filament [16; 20; 21; 22]. The influence of FDM printing parameters on the printed PEEK parts' dimensional stability and mechanical properties is attracting increasing interest in research. [PERSON] et al. [16] concluded that the surface roughness of 3D FDM-printed PEEK seems suitable for dental restorations. However, information about the surface characteristics of FDM PEEK remains unclear [16; 20; 21; 22]. Given the direct correlation between surface roughness and biofilm formation, polishing materials designed for use in the oral cavity becomes crucial.