1) be sure to tell dentist / oral surgeon that you dive.
2) I had a major root canal that started with an infection. so the infection had to be cleared before the root canal was completed. The endodontist cleared me to dive. Went diving and at 60 feet, my jaw was pretty painful. On the ascent, I thought my face was peeling off! The endodontist told me that he neglected to mention I'd be fine....it was just gonna hurt!
3) after the final root canal work, on advice of a dive medicine friend, I held off diving for 2 days. All was good!