Ask to see a portfolio before having any work done of course. Transdermal or percutaneous implants are implants that pass through the skin, with one end being under the skin, and the other end being outside the skin. A pocket very similar to the kind made for 3D Art implants is made. Into this a labret-esque piece of jewelry with a larger than normal base is inserted. A small core of skin is removed to expose it and the entry incision is closed via sutures.
Rejection is a major risk, as is infection.
In the medical industry, much difficulty has been had with successfully healing percutaneous energy transmission systems, which are virtually identical in concept. While several of these procedures have been done successfully, it is not overall considered a viable procedure. Ask around, especially with artists doing implants. Over repeated sessions the tissue is bulked up. It is not as easy as simply injecting silicone using a normal syringe.