PEEK plastic is not weak and is fairly tough to cut with simple steel tools. most PEEK is Tan colour so i wouldnt use it anywhere that was close to a margin. perhaps for an implant placed very subgingival, with a lot of taper where porcelain will be used.
doesnt stick to glue very well though so i have doubts about its use as abutments/cores/posts. as far as the biocompatibility of it, well the only advantage i can see it having over titanium inserts is that it is less affected by extreme cold and won't make the patient uncomfortable in the Arctic.
