Over 235,000 Americans undergo craniomaxillofacial (CMF) surgery annually, withimplant failure rates averaging 5.5% in general and up to 37% and 52% in the orbital and temporal regions,respectively. Failures are attributed to prosthetic infections, poor osseointegration, corrosion, and fracture. Mostcan be linked to implant materials that underperform in terms of bioactivity, infection control, osseous integration,or mechanical stability. Thus, there continues to be a critical clinical need for medical imaging compatible3DP biomaterials for craniomaxillofacial osteoplasty that can be personalized, promote integration, andprevent infection. SINTX Technologies, Inc. pioneered the use of silicon nitride (Si3N4) as a high-performancealternative to metal and polymer-based biomaterials for bone and joint repair. Si3N4 is a promising biomaterialfor CMF defects because of its antibacterial activity, osseointegration, radiographic imaging, and durability, butthe stiffness of Si3N4 engenders stress shielding and may be susceptible to subsidence and brittle fracture. Incontrast, PEEK and PEKK are more flexible, radiotransparent biomaterials, but these polymers lack antimicrobialand osseointegrative properties. To overcome these limitations, SINTX proposes to combine its bioactive Si3N4with PEKK to form a 3D-printable composite that will be radiolucent, possess an elastic modulus similar to corticalbone, and simultaneously provide improved antimicrobial and osteointegration properties. The purpose of thisapplication is to design, build, and test 3DP PEKK/Si3N4 composite for non-load-bearing CMF implants thatsatisfy material requirements and enhance infection resistance and osseous integration. Aim 1. Design,produce, and characterize porous 3DP PEKK/Si3N4 implants for non-load-bearing CMF applications.Milestones: 1) Prepare PEKK/Si3N4 composite filaments based on a range of PEKK/Si3N4 volume ratios; 2)Design an appropriate CMF implant based on the amount and type of included porosity; 3) Validate the 3Dprintability of the various PEKK/Si3N4 composites; and 4) Assess the physical and mechanical properties of the3DP CMF composite designs. Aim 2. Complete in vitro antibacterial and osteoconductivity testing of thepreferred 3DP PEKK/Si3N4 implant from Aim 1. Milestones: Demonstrate that test components from thepreferred 3DP PEKK/Si3N4 implant 1) Achieve a ⥠1.5-log10 reduction in Staphylococcus epidermidis (S.epidermidis) and Escherichia coli (E. coli); and 2) demonstrate an ability to significantly upregulate osteoblasticactivity. Aim 3. Test the in vivo antimicrobial effectiveness and overall healing of the 3DP PEKK/Si3N4implant compared to PEEK. Milestones: 1) Prepare and characterize identical 3DP partially porous PEKK/Si3N4and PEEK implants; and 2) Complete a 28-day in vivo time-course study of these implants under aseptic andseptic conditions in Wistar rats. Impact - This proof-of-concept project is expected to provide strong rationaleand preliminary data to support further study and commercialization of a 3D-printable PEKK/Si3N4 composite forCMF implants, which could substantially reduce implant failures due to infection and/or poor bone integration.
Public Health Relevance Statement: PROJECT NARRATIVE
Materials used to reconstruct facial bones after disease or injury fail about 5.5% of the time, resulting in
substantial pain and suffering for patients as well as increased healthcare costs. This project is designed to
develop and test a new composite material for implants that combines the flexibility and durability of PEKK with
the antibacterial and bone-integrating properties of silicon nitride. If successful, this new material could be used
in place of other implant materials with high failure rates, which could greatly improve patient outcomes and
reduce healthcare costs.
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