We ask patients about false/loose teeth and caps/crowns 1) so we're aware of them and 2) we let then know that we'll do our best to take good care of them but their life is more important than their teeth. This is an accepted risk, spelled out in our anesthesia consent, and on the rare occasions something happens, we generally don't pay for it.
The only tooth I've ever lost came out because it was embedded in a rubber oral airway. I've never (knock on wood) knocked one out with intubation in 33 years. Front teeth should never be touched and IMHO tooth guards are unnecessary and do next to nothing to actually protect the teeth, given the force that can be exerted by poor laryngoscopic technique. Nowadays, if we're that concerned, the GlideScope is a great option.