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The thumb rule that we follow, or that we would like to follow, is that the crown should be resting on sound tooth structure. What I mean is, at least the bottom 1/3rd of the tooth should be still present. The rest of it can be built up with silver amalgam or cement. In cases where the tooth has been badly destroyed, all is not lost. What is done then, is placement of a post (think of it as a cylindrical pin) inside the root canals, and then building up the rest of the tooth. This gives the tooth extra strength. So as the botXXXXX XXXXXne is, unless the tooth is shaky, almost any tooth these days can be crowned, with some modifications in the procedure.
Crown lenghtening procedure can also be done on your tooth for the proper placement of the crowns.
I would like to conclude by saying that until and unless your tooth is not mobile i.e. is not shaky it can be filled and crowned with certain modifications.
I would therefore recommend you to consult your dentist as soon as possible and get the tooth looked at soon. A clinical evaluation along with an x-ray will confirm the prognosis of this tooth.
I hope this helps!
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