Reported rates of infection amongst the four materials used in custom facial implants, silicone, PEEK, porous polyethylene and titanium, is hard to define clinically, There are too few clinical studies and some of the materals have very low use in aesthetic facial augmentations (e.g., titanium)
As a result laboratory evidence of the ability of bacteria to adhere to an implant’s surface is one method to quantify a material’s resistance to infection.
Comparative bacterial surface adhesion
The clearest finding is that porous polyethylene provides the most favorable physical surface for bacterial retention. Among custom-implant materials, polished titanium generally shows less Staphylococcus aureus biofilm than PEEK. Smooth implant-grade silicone can have relatively low adhesion, but there is not enough direct evidence to rank silicone reliably against PEEK or polished titanium.
|
Material |
Relevant surface properties |
Expected bacterial behavior |
|
Polished or machined titanium |
Dense and nonporous; naturally covered by a passive titanium-oxide layer. Wettability and surface energy vary considerably with alloy, processing and storage. |
Low–moderate adhesion. A smooth surface offers few protected niches, but titanium is not intrinsically antibacterial and can support mature biofilm. In a small 2026 cranioplasty study, PEEK developed significantly more S. aureus biofilm than polished and commercially pure titanium; the difference versus Ti-6Al-4V was not statistically significant. |
|
Smooth implant-grade silicone |
Very hydrophobic, low-surface-energy and nonporous. Usually smoother and more compliant than the other materials. |
Low–moderate, strongly species-dependent. Smoothness reduces mechanical retention, but hydrophobic organisms—particularly some staphylococci—can adhere through hydrophobic interactions and form persistent biofilm. Implant silicone had the lowest adhesion for five of eight organisms in one direct oculoplastic comparison. |
|
PEEK |
Dense and nonporous when machined; hydrophobic and biologically inert. Surface finish varies substantially between machined, milled and additively manufactured implants. |
Moderate and often higher than polished titanium. Its hydrophobic surface supports protein adsorption and bacterial attachment, and machining marks, print-layer grooves or fillers can increase colonization. A controlled study found that titanium-dioxide-filled PEEK formed more biofilm than unfilled PEEK despite surfaces being polished below Ra 0.2 µm. |
|
Porous high-density polyethylene, such as Medpor |
Hydrophobic, interconnected open pores and a much greater true surface area than its apparent external area. Pores and recesses are much larger than bacteria and provide protected niches. |
Highest retention tendency, especially before tissue ingrowth. Bacteria can attach within the pore network, resist washing and shear, and become difficult to access after biofilm formation. An eight-strain comparison found significantly greater total bacterial recovery from porous polyethylene than from implant silicone. |
Important material-specific qualifications
Titanium: Roughness is not uniformly beneficial or harmful. Microrough, cut, threaded or creviced regions can retain more bacteria than polished regions, while carefully engineered nanoscale topographies may sometimes reduce attachment. Uneven cut surfaces on titanium spinal components showed concentrated bacterial “hot spots.”
Silicone: The distinction between smooth and textured silicone is crucial. A human study of 391 explanted silicone implants found increasing bacterial burden along a surface-roughness gradient, with rougher surfaces showing greater relative abundance of Staphylococcus. Thus, findings for smooth silicone should not be extrapolated to aggressively textured silicone.
PEEK: “PEEK” is not a microbiologically uniform material. Unfilled, carbon-fiber-reinforced, ceramic-filled and titanium-dioxide-filled formulations can behave differently. Milling grooves and additive-manufacturing layer lines can also have more influence than the underlying polymer chemistry.
Porous polyethylene: Fibrovascular tissue eventually grows into the pore network. That integration can improve stability and access by host tissue after healing, but early contamination occurs before complete ingrowth. Once an established infection occupies the pores, complete debridement can be difficult and implant removal may be more traumatic. Animal evidence found that porous polyethylene tolerated exposure better only after host tissue had invaded the pores.
Practical qualitative ranking
For early bacterial attachment and retention before host-tissue integration, a reasonable evidence-based grouping is:
Lowest group: polished titanium and smooth implant-grade silicone, with their order uncertain
Intermediate: smooth, unfilled PEEK
Highest: porous polyethylene
This is not a universal ranking. The direct evidence establishes titanium versus PEEK and silicone versus porous polyethylene more confidently than it establishes silicone versus PEEK or silicone versus titanium. Bacterial species, surface finish, contamination with saliva or blood, protein adsorption and implant geometry can change the result. For example, fibrinogen and fibronectin adsorbed onto titanium can increase staphylococcal adhesion, illustrating why bare-material experiments do not perfectly predict behavior after implantation.
For a custom facial implant, the surface-design inference is to favor a dense, polished soft-tissue-facing surface, minimize crevices and exposed lattice structures, and reserve deliberate roughness or porosity for bone-contact regions where tissue integration is specifically required.
Dr. Barry Eppley
Plastic Surgeon