Medpor implants are meant to be carved unless you're talking strictly customs. Dr's like medpor because of the (scar??) tissue ingrowth, less chance of rotation or movement long term, can be shaped during surgery, and (falsely) it doesn't cause bone resorption or have a significantly lower infection rate vs silicone.
Recent reports have shown that the bone resorption observed in the past were caused by surgeons who used the fiberous ingrowth or musculature (i.e masseter muscle) to hold the implant in place (as opposed to screwing them in). As such, micro movements from facial animation over time lead to friction between the surface of the implant and the bone, causing the resorption cited in previous literature.
Surgeons who are prudent nowadays with medpor implants always use titanium screws, and have reported that bone resorption is no longer an issue
ALSO @Lestat that PEEK result is amazing, but the sample size is quite small. i worry that since it hasnt been observed long term on a large scale that we dont really know as much as we do about medpor or silastic which have been used for decades
i could be wrong, ofcorse