Research Article: Manual polishing of 3D printed metals produced by laser powder bed fusion reduces biofilm formation

Date Published: February 27, 2019

Publisher: Public Library of Science

Author(s): Marissa McGaffey, Alex zur Linden, Nathanael Bachynski, Michelle Oblak, Fiona James, J. Scott Weese, Antonio Riveiro Rodríguez.


Certain 3D printed metals and surface finishes may be better suited for canine patient specific orthopedic implants on the basis of minimizing potential bacterial biofilm growth. Thirty disks each of titanium alloy, stainless steel, and cobalt chromium alloy were 3D printed via laser powder bed fusion. Fifteen disks of each metal were subsequently polished. After incubation with a robust biofilm-forming methicillin-resistant Staphylococcus pseudintermedius isolate, disks were rinsed and sonicated to collect biofilm bacteria. Serial dilutions were plated on blood agar, and colony forming units were counted log (ln) transformed for analysis of variance. Interference microscopy quantified surface roughness for comparison to biofilm growth. Scanning electron microscopy on both pre- and post-sonicated disks confirmed biofilm presence and subsequent removal, and visualized surface features on cleaned disks. Significantly more bacteria grew on rough versus polished metal preparations (p < 0.0001). Titanium alloy had more bacterial biofilm growth compared to cobalt chromium alloy (p = 0.0001) and stainless steel (p < 0.0001). There were no significant growth differences between cobalt chromium alloy and stainless steel (p = 0.4737). Relationships between biofilm growth and surface roughness varied: positive with the rough preparations and negative with the smooth. Polished preparations had increased variance in surface roughness compared to rough preparations, and within disk variance predominated over between disk variance for all preparations with the exception of rough cobalt chromium alloy and rough stainless steel. Using scanning electron microscopy, bacterial biofilms tended to form in crevices. Overall, manual polishing of 3D printed surfaces significantly reduced biofilm growth, with preparation-specific relationships between surface roughness and biofilm growth. These results suggest that metallic implants produced by laser powder bed fusion should be polished. Further research will elucidate the optimal surface roughness per preparation to reduce potential biofilm formation and implant associated infection.

Partial Text

Postoperative surgical site infections (SSIs) are a common and potentially devastating complication in human and veterinary patients and are estimated to occur in 2–5% of human surgical patients in the United States [1,2]. In veterinary medicine, the incidence of SSIs vary between populations, with reported ranges of 0.8–18.1% [3–7]. SSIs come with a high cost to both patient and client as a result of increased medication and revision surgery requirements, extended hospital stays, financial expenditures, and patient mortality [1,4,6,7,8]. Medical advancements have led to an increase in frequency of surgical procedures that include insertion of implants [4], including those made from metals, plastics and ceramics [9]. Further advances have allowed for pre-operative creation of patient-specific implants, which provide direct patient benefits, including reduced time under general anesthesia, reduced need for analgesics, decreased blood loss, reduced risk of infection, decreased need for antibiotics, and improved surgical outcome [9,10], as well as a reduction in intraoperative fluoroscopic navigation, decreasing radiation exposure [10]. The use of 3D printing techniques such as laser powder bed fusion (LPBF) to manufacture detailed patient specific implants is one reason for the increasing use of 3D printing in the medical field [11].




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