For custom facial implants, the most useful way to think about silicone versus PEEK is that both can be manufactured as dense, nonporous implants, so the comparison becomes much cleaner than silicone versus Medpor. Once porosity is removed, surface finish and biologic conditioning probably matter at least as much as the polymer’s nominal surface energy.
The key point is that an implant does not remain a pristine polymer surface after implantation. Within a short time it becomes coated with host proteins. Bacteria then interact with this protein-conditioned surface, not simply with bare silicone or bare PEEK. That is why low surface energy alone is a poor predictor of infection. In experimental work on PEEK and related polymers, surface-energy measurements have sometimes shown little or no correlation with bacterial adhesion, whereas polishing and roughness had measurable effects.
Why smooth silicone may perform surprisingly well
Silicone has three relevant characteristics:
1. It is extremely smooth when molded properly.
A smooth surface offers relatively few crevices that mechanically shelter bacteria.
2. It is nonporous.
A bacterium can adhere to the surface, but it cannot migrate into an interconnected internal pore network as it could with porous polyethylene.
3. It does not substantially integrate into surrounding tissue.
The body tends to form a fibrous capsule around it instead.
That third feature is usually discussed as a disadvantage because the implant is less biologically incorporated. From an infection-management standpoint, however, it has an advantage: if a silicone implant develops a mature biofilm and needs removal, it is often comparatively straightforward to remove the foreign material completely.
So silicone is not bactericidal, but its physical architecture can be relatively unfavorable for bacterial retention.
Why PEEK isn’t automatically better despite being a “high-tech” material
PEEK is also dense and nonporous when conventionally milled, which is favorable. But untreated PEEK is biologically inert and relatively hydrophobic. It can adsorb proteins and support S. aureus and other bacterial biofilms.
More importantly, the actual PEEK surface produced by manufacturing can differ dramatically from the idealized polymer surface.
A polished laboratory PEEK coupon might look like this conceptually:
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A milled custom implant can have microscopic cutter marks more like:
An additively manufactured implant may have still more complex texture.
Those microscopic irregularities increase true surface area and can create regions protected from shear and irrigation. Studies of dental polymers, including PEEK, have found that stronger polishing generally reduces bacterial adhesion and that manufacturing technique substantially influences colonization.
So saying “this implant is PEEK” does not tell you enough. You really need to know:
What PEEK? How was it manufactured? What is its final Ra/Rz roughness? Was it polished? Are there machining grooves at the margins?
Silicone versus PEEK in a contamination event
Imagine that 100 S. aureus organisms are introduced into the pocket during insertion.
With a very smooth silicone implant, many organisms may be removed by irrigation, immune activity, antibiotics, and fluid movement. The organisms that remain can certainly adhere and eventually make biofilm, but there are relatively few microscopic protected recesses.
With a rougher milled PEEK implant, you might have exactly the same initial inoculum, but more bacteria could become mechanically retained in machining features.
That does not prove the patient will develop an infection. Host immunity, vascularity, antibiotic exposure, bacterial species, inoculum size, dead space, hematoma, and operative contamination all influence whether those few bacteria progress to a clinically meaningful biofilm.
But it explains why I would care enormously about surface finish when comparing custom silicone and custom PEEK.
There is also a major mechanical difference
Silicone and PEEK interact with the surrounding anatomy very differently.
Silicone is relatively compliant. It can conform somewhat to the underlying skeleton and soft tissues.
PEEK is much more rigid and behaves structurally more like a hard engineering plastic. This can be advantageous for large, precisely designed craniofacial reconstructions and areas where maintaining an exact contour matters.
That rigidity means PEEK is usually designed to achieve precise bone contact and fixation. Silicone can often tolerate somewhat different mechanical relationships with the underlying bone.
Thus, material selection shouldn’t really be reduced to infection resistance alone.
Tissue integration produces an interesting tradeoff
There is a continuum:
Smooth silicone ? little tissue integration
PEEK ? little integration unless its surface is modified
ePTFE ? moderate incorporation
porous polyethylene ? extensive fibrovascular ingrowth
Increasing tissue integration offers mechanical stability and potentially vascular access around or within the implant.
But increasing porosity also gives bacteria:
- greater surface area,
- more protected niches,
- more difficult-to-access surfaces,
- and potentially a much harder foreign body to completely remove.
PEEK researchers are actively trying to solve this tradeoff. For example, porous or chemically modified PEEK surfaces can increase mechanical interlocking and bone integration, but the effects on bacterial behavior aren’t automatically beneficial. A 2025 study found that a porous surface treatment improved PEEK’s mechanical interlocking while bacterial attachment remained similar to smooth PEEK.
That illustrates an important principle:
A surface modification that improves tissue integration doesn’t necessarily improve infection resistance.
What about actual infection rates?
This is where we need to be cautious.
There isn’t good evidence showing that custom silicone facial implants have a definitively lower infection rate than custom PEEK implants in equivalent patients and equivalent anatomical sites.
A very recent 2026 systematic review of patient-specific craniofacial implants found a pooled infection rate of approximately 1.5% for PEEK, although those studies mostly compared PEEK with titanium rather than silicone. Importantly, the authors found no statistically significant material advantage after accounting for study variability.
That is one reason I wouldn’t tell a patient silicone has a lower infection rate.”The evidence doesn’t justify that statement.
I would say instead:
For a custom facial implant, smooth nonporous silicone has several physical characteristics that may reduce bacterial retention, but PEEK can also perform very well when it is dense and highly finished. The material label by itself probably matters less than surface topology, surgical contamination, pocket environment, and implant handling.
The part I think is especially relevant clinically
If I were trying to optimize a custom implant specifically for infection resistance, I would be interested in four specifications that manufacturers don’t always emphasize:
Surface roughness (Ra/Rz)
Not merely “smooth.”
Manufacturing method
Molded silicone versus CNC-milled PEEK versus printed PEEK.
Final finishing process
Especially whether machining marks are polished away.
Edge and screw-hole geometry
Sharp transitions, screw holes, recessed areas, and machining grooves may create much more relevant bacterial-retention sites than the broad flat surface.
That means there is a potentially important distinction between material science and implant design science.
A beautifully polished PEEK implant could plausibly have a better bacterial-retention profile than a rough/textured silicone implant, while an extremely smooth molded silicone implant could plausibly outperform poorly finished PEEK. The nominal surface-energy numbers alone would not predict that.
So icould custom silicone actually be intrinsically advantageous over PEEK from an infection standpoint?”, I think the defensible answer is possibly, particularly because of its extremely smooth, nonporous molded surface and easy removability—but we do not currently have strong enough head-to-head clinical evidence to claim that silicone itself is more infection resistant.
Dr. Barry Eppley
Pkastic Surgeon