An artificial crown may be better, but not the roots. Natural teeth are fixed in the jaw in a very ingenious way that is durable and somewhat flexible at the same time. Not so with implants; the metal fuses with the bone in a hard way and transmits all the shocks fully into the jaw.
I don't know what you mean by "core", but using it as a material in the center of an implanted post, such that another material faces the bone, seems like cost for no benefit.
And gold is not a good bone-facing material, because bone doesn't fuse with it.
Titanium is favored for implants because it supports osseointegration.
Depending on the location, state of the bone and other parameters, anything from mild discomfort to catastrophic failure of the implant and a jaw fracture.
I have four implants, two in my lower jaw, two in my upper jaw. My lower jaw is basically stone, an extremely hard bone even by usual lower jaw standards; the dentists (plural, as one was unable to finish the job) drilling into it destroyed a few drilling bits doing so. I have never had any problems with the lower jaw implants. That bone can take almost anything in stride.
My upper jaw, on the other hand ... very delicate, just enough bone left for the implants to work, and I learnt to be careful about biting into anything harder with them.
