Can a cracked tooth be caused by mercury fillings?

[SugarFiend]

Can having long term mercury feelings eventually lead to a tooth to crack?

If so why didn't my dentist tell me that or work on a porcelain crown before crack had happened?

 

[MattKW]

No. There are a few reasons behind this myth:

1. Original amalgams contained some Zinc which gave it better working properties, and this did lead to some expansion. Zinc was removed many years ago.
2. Original guidelines for preparing teeth were very mechanistic, and did not understand that sharp line angle would initiate cracks. Again, no longer taught.
3. Amalgams do not glue to teeth; composite fillings are meant to glue to enamel and dentine and therefore restrengthen teeth. Except under ideal conditions, this is not as effective as once thought, but it makes a great selling point.
4. Any large cavity filled with any material is more likely to fracture. Such teeth should be crowned or onlayed before a fracture occurs. It's not necessarily the fault of the filling if your tooth fractures, its the weakness caused by the removal of tooth when cleaning out the decay.
5. Some patients don't want to do crowns and take their chances
6. Some cracks are simply unpredictable. An undamaged tooth or even a small cavity will sometimes develop cracks. Dentistry is not an exact science.

 

[Busybee]

I once cracked an amalgam filled tooth crunching hard-boiled sweets. It was totally my fault. The fillings were done pretty well and that was after years of wear and tear. It was saved with a composite which sealed the crack. It's nothing to do with the material but down to the preparation what you subject the tooth to, the bite and how strong the remaining tooth is. If every dentist crowned decayed teeth patients would complain far more because crowns form a bigger risk of root failure etc. I just looked up zinc and it seems they stopped using it in the early 60s.

 

[MattKW]

1. Composites don't seal cracks, except superficially. The bonding is much too weak to be effective. The solution for a crack is to reduce the weakened part of tooth, then cover over with a filling (any type - amalg or composite), onlay, or crown.
2. Crowns do not create bigger risk of root fracture in most cases (e.g. molars); absolute tosh. They can be a risk in small teeth like lateral incisors or 1st premolars. The added risk from crowns is usually further indirect damage to the pulp, therefore ~8% risk of nerve dying. But the tooth has already been seriously worked on before you get to needing crown, so sometimes must weigh up risks/benefits in decision-making.

 

[Busybee]

I didn't mean that crowns create fractures in roots, but that crowns can put a tooth at greater risk of the nerve dying because of the amount of tooth you have to remove. Crowns are also more likely to need replacing faster when the margin goes etc. whereas some people have the same fillings all their lives. Crowns also need greater attention to hygiene.

I'm just telling it as the dentist explained it to me ref the composite. Whatever he did, it was very successful because another dentist sent me to an endo who was quite happy to do a root canal, but the composite was the result of a second opinion. I have found that every dentist has a different approach, which is why I think everyone should get at least two opinions when considering any major dental work.

 

[SugarFiend]

No. There are a few reasons behind this myth:

1. Any large cavity filled with any material is more likely to fracture. Such teeth should be crowned or onlayed before a fracture occurs. It's not necessarily the fault of the filling if your tooth fractures, its the weakness caused by the removal of tooth when cleaning out the decay.

Just wondering why my dentist never mentioned this to me. Based on what you have said, it's standard practice to do the crown or onlay in large cavity filled teeth at risk of fracturing?

 

[MattKW]

If you didn't mean that "crowns create fractures", then don't write it. Also, don't also take my stats re pulp deaths and pretend that's what you meant; that's misrepresentation. The next 2 sentences are also vague without supporting evidence.
Composites and cracks - just repeating what someone told you (which happens to be incorrect) doesn't mean you have the knowledge or experience to give other people advice on the topic in this sort of forum. Your opinions are largely anecdotal and sometimes misleading. Keep to general advice about dental health and you'll be fine.
I only agree with your final statement that 2nd or 3rd opinions are useful for major work.

 

[MattKW]

Just wondering why my dentist never mentioned this to me. Based on what you have said, it's standard practice to do the crown or onlay in large cavity filled teeth at risk of fracturing?

It's because it is impossible to know when a tooth is likely to fracture, there's just some general "rule of thumbs" that we follow. Last week, I had a fellow with a perfect tooth (never filled) that inexplicably cracked and had to be extracted. He'd been to a dentist, 2 doctors, the hospital (CT scans), started various drugs for "neuralgia", and was finally referred to me for an opinion before heading towards neurologist. Even then I wasn't 100% confident until I called him the following day; I was sweating overnight ( and probably so was he!). Every procedure, including crowns, carries risks that are not easily assessed like measuring a tyre pressure for your car. All health professionals face the same issues e.g.medical treatment and drugs have side-effects. All we can do is watch the research for guidance, and throw in a bit of experience.

 

[Busybee]

Excuse me, but where did I say "crowns create fractures"? When I said root failure I meant a root requiring a root canal not a fracture, otherwise I'd have said "root fracture". No need to respond aggressively or to be patronising. I was just repeating something a dentist told me which happens to have worked. You frequently give the same advice I do after I have given it so it seems you agree with me most of the time!

 

[MattKW]

Excuse me, but where did I say "crowns create fractures"? When I said root failure I meant a root requiring a root canal not a fracture, otherwise I'd have said "root fracture". No need to respond aggressively or to be patronising. I was just repeating something a dentist told me which happens to have worked. You frequently give the same advice I do after I have given it so it seems you agree with me most of the time!

Correction, you didn't say "fracture", so I will apologise and retract that particular criticism. And something that "happens to have worked" is anecdotal, just like an earlier post about lateral incisors and crowns; the literature does not support it. I stand behind the rest of my statements - if you want references I have a vast collection and will look for stuff if you request, and if I have the time. Here's a nice graphic one about fractures I have on file from 2002.