On Friday, July 19, 2019 at 9:04:50 PM UTC-5, John B. wrote:

Hey! Just the guy I need :-)

Why a 3 months wait?

Hard to say. If there were radiographic changes around the end of the root(s), the dentist might be waiting for them to resolve before buttoning everything up. I don't usually do this because the temporarily restored tooth is vulnerable to harm (fracture, loss of temporary seal, etc.). I'll generally complete most root canals in a single sitting unless they are symptomatic or heavily infected. Otherwise, usually no more than 2 visits a week or two apart.
Check out the new technology my department just acquired: https://sonendo.com/
I'm still learning how to use it, but it seems promising. Beaucoup bucks to buy, though!
Sorry... didn't mean to hijack the thread!