Is it normal to need a crown after a filling?

Question

My sister recently went to the dentist because she had noticed what looked like a small cavity on the biting surface of one of her molars. The dentist did a filling, but apparently the cavity was quite large in the dentine layer even though there was only a small hole in the enamel. He said that although it wasn't that DEEP, it was quite an extensive cavity and that she would probably need a crown on that tooth at some point.

Is that normal? I thought you only needed crowns when you had a root canal done on your tooth. And is it common to only have a tiny hole in the enamel but for the cavity to be quite extensive underneath it?

Answer 1

This happens when much of the tooth material is removed due to decay. The decay can be more extensive than what can be seen on the surface of the tooth. It can be filled, but the structural integrity of the tooth is compromised and eventually it may crack. Then it's root canal / crown time.

Answer 2

Not normal but the dentist was advising it may be needed at some point in the future as the inner cavity is big, and they expect further problems. I'd make sure my medical insurance was up to date and start saving for the costs if I were her. At some point is a bit vague a time frame, its not this year and probably not next, could be never but sounds like it won't be.
As for the bigger inner cavity the outer enamel is extremely durable the inner dentine not so, its a bit like putting a slate with a hole in it on top of a lump of chalk then sloshing vinegar over it every day, the slate will hardly erode the chalk will dissolve out under the slate making a big chamber under what is good solid slate.

Answer 3

a crown isn't only for root canal teeth.. if the decay covers a large area of the tooth then you might need a crown, but as long as the decay isn't into the nerve then you dont need a root canal. but if you had a root canal, you definatly need a crown because that tooth is now dead and weak, so the crown will protect it.

as for the size of the cavity.. it can be a tiny hole on the surface, but very deep underneath, kind of like an iceburg.. in fact, i just had a tiny cavity filled that turned out to be large underneath, there is no way of telling until the dentist starts to drill. sometimes it shows up on the x-ray but not as well for the biting surface cavities.

Answer 4

i remember once i saw a theaory says that caries looks like a triangle with its top on the surface of the enamel and its base on the dentine..i mean sometimes the caries looks like a small pit but when the dentist start drilling it turns out that it's deep inside..
maybe that was the case with your sister ...and if the dentist had to enlarge the cavtiy in order to remove all the caries then the remaining tooth structure gets very weak to resist the forces of mastication and it eventually will breaks down.
so here the crown will be needed to increase the resistance of the tooth.

Answer 5

HELLO,
AS SOMEONE SAID DECAY CAN SEEM LIKE A SMALL DARK SPOT ON THE TOP OF THE TOOTH, BUT BE MUCH BIGGER UNDERNEATH, LIKE A TRIANGLE.
ONCE ALL THE DECAY IS REMOVED THERE MAY NOT BE ENOUGH HEALTHY TOOTH TO HOLD A FILLING AND A CROWN MAY BE NEEDED.

Answer 6

No, only after a root canal.
Not usually a filling.
Get a second opinion.
The dentist may be trying to get some extra money.

Answer 7

In one of your answers you said you were a doctor so you should be smart enough to figure it out.