You can call around to malpractice lawyers and talk it over.
I suspect, however, that a malpractice lawyer is not going to front the money for an expert witness unless the case involves a potentially large award or settlement and liability is pretty clear.
Having had dental implants of my own last year, I don't see big money in a case for implant failure due to negligence. Especially if all you need is to have it redone.
I had also checked on dental colleges and avoided them when I read the disclaimers so there's that issue as well.
Make a few calls and see how it goes.