What is the likelihood of requiring a root canal procedure after receiving a crown?

My new dentist informed me that there's a 20% chance of requiring root canal treatment after getting a crown, especially since it could potentially irritate the nerve. My risk is heightened because I have a crack (which was filled but didn't resolve the issue, leading to the need for a crown) and I want a porcelain crown, which involves more drilling. I'm seeking a second opinion to verify if this 20% or greater figure is accurate. It's worth noting that this concerns a lower molar, and the dentist in question has approximately six years of practice experience as a general dentist.