Dentist says for root canaled tooth difference between emax and zirconia negligible, is he right?

[waterpikker]

I didn't completely understand what the dentist was saying, when he said that crown strength is only important on un-root-canaled teeth. He says that since there are some cavities that he'd have to drill away from the outside, tooth structure wise, it's about the same. He also said 1.) something about since it's a root canal tooth, in terms of strength emax and zirconia are pretty much the same and 2.) zirconia will wear away teeth.

The tooth in question is an upper molar. Is there something about adding a post, the physics of this somehow, that explains this? Can anyone point me to some studies? I don't even know what terms to google.He says he rarely has cracking cases with emax. Is what he's saying in the most updated research or is this a hard sell since he has a Cerec machine? I read somewhere that emax is 300 while zirconia is 1000. That's not an insignificant difference...

Thanks in advance for any advice.