With some amount of bad luck, I can say I have had one bridge and one crown this year. During the time my tooth was pulled I needed to give my mouth time to heal. The oral surgeon recommend I not dive for two weeks longer if possible to let my mouth heal. If you friend's tooth was knocked out, there is an open pocket, under pressure the pocket can be very painfully to deal with. Two you have an opening inside you gum area. Depending where you are diving at and the condition of the water infection to your self can go up a great deal. Although they do tell you to message your gums with saltwater to make they stronger. I guess most of the problem is pressure. I have had two temp's come out after dives. It's mostly just a hassle, and my telling my dentist I told you so.
The last one was this last week in Grand Cayman, there is a temp cement you can use which I found at the local pharmacy. There are solution out there.
Happy diving, and healthy teeth
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