I thought crowns were made of a substance that could not become decayed. When a dentist says you have decay under a crown what exactly does he mean? Decay in the root? In the stub of the real tooth the crown is affixed to?
The material in crowns is metal, or porcelain fused to metal. They dont decay. The tooth (or what's left) beneath is another story. I have had LOTS of crown and bridge work, and all but one has eventually decayed, requiring root canals with post and core buildups. I have a pretty bad night grinding problem, and I think that loosens them, allowing decay beneath. I associate it with my grinding because my husband has crowns (including a molar that all the porcelain broke off of years ago, leaving only the metal base) that have remained secure for 10+ years, while mine are loose within 2-3 years. It's hard sometimes to tell it's a little loose, but the tooth underneath has been reshaped and is prone to decay if it is exposed at all. These are just my own experiences, but I hope this answers your question
Decay can easily happen under a crown. Assuming the crown fit properly to your tooth, decay can begin at the margin of the crown. The margin is where the crown meets the tooth. Sometimes there is a slight ridge there that catches plaque. When you have a crown you have to be sure that you are properly brushing around the crown and removing the plaque from that margin thouroughly. Also you need to floss between your teeth to clean the plaque from between the teeth, again because plaque can get caught at the margins of the crown between your teeth. And last, sometimes we recomend using a toothpick around the margins of a crown to help keep it clean. Plaque is what causes the decay, the better you are at removing plaque daily, the less decay you will have. I hope this helped you, Good Luck!
That seems to be a case by case situation. Also, different dentists seem to have different aproaches. If the crown is already loose, it can sometimes be worked off intact. I've had Dr's drill, or cut them off, thus sacrificing the crown. They have also used a slide type of hammer, and a hammer and chisel type set up. My current Dr's prefer not to use those measures for fear of causing more damage. I've also had them use a sticky ball that you bite on (sorta the constitancy of a Jolly Rancher candy), then open the mouth, but the only thing one of those ever took out on me was the filling above. I won't let them use those on me anymore. If there's decay beneath extensive enough to require some rebuilding of the tooth, the old crown can't be reused, so cutting it off is generally best in that case. I was always numbed anyway, so there wasn't any pain involved. I've also had a root canal done through the crown where they just drill through the top of the crown, then they fill it as if it were any other tooth surface. Hope this helps.