Hi ok i can throw a little light on this as my wife was a dental nurse , we have found a couple of great products over the years mainly due to my blackouts and knocking teeth out and just general not being fit to go to a dentist the wife does a repair to keep it going and get me out of pain .
I would put links to the products on amazon not sure thats allowed ,so here are the names of 2 great products
Prevest denpro CRYSTA glass ionmer "it takes a little getting use to working with but is the best for repairing a crack break or chipped tooth is it far better than the rubbish you get in the chemist that with one bite falls out or off .
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Prevest denpro COPAL F now this stuff is like a brush on rub on with a cotton bud varnish to seal sensitive teeth , now long story short our teeth suffer because of the huge amount of meds we have to take and well wear as well , dry your tooth or teeth with a little kitchen roll as it does not stick to the tooth get it as dry and possible then open the stuff dip in a cotton bud rub it on you might get a little zing from it as it goes on but in a minute i mean just a few seconds you will notice the pain easy and if it is sensitive in a few hours you will be eating hot and cold with out a care lol ,it is true we have been doing it for years and i mean on broken teeth smashed and just nervs showing she sealed them until i could get to a dentist 18 months later so as i say we love the stuff and keep 2 extras in stock at all time , great to easy a kids tooth ache to if it is a crack or break .
For nerv damage there is not mush you can do other than cover it and get to a dentist when you can .