Why do you get decay under fillings?

When I went to the dentist recently he did some x-rays because I hadn't been for a while and found a few cavities that I need to get fillings in, but he says there is decay under 2 of my old fillings and I will need to get them replaced, and I might even need root canal and a crown on one because the decay looks quite deep.





How do you get decay underneath fillings? Is it something I could have avoided if I'd done something differently? And how common is it? Because after I get these new fillings I'll have about 10 fillings all together and I'm worried that this will happen in the future and I'll need to get root canals on them all. What can I do to make sure it doesn't happen again?

Why do you get decay under fillings?
Fillings break down over time. That is why it is recommended you see the dentist regularly because they can catch things before they get to that point.





Your previous dentist probably didn't do anything wrong, how long have you had the fillings? They really are only meant to last maybe 10 years at the most and I know most people have amalgam fillings that are close to 30 years old.





What happened is the margins where the tooth meets the filling got microscopic breaks in it and that allowed bacteria to seep in and cause decay to form. Just the nature of the beast. Of course not everyone gets decay under fillings, it comes down to your susceptibility to the bacteria that causes decay. Obviously you are a bit more prone.





If the decay has gotten to the nerve of the tooth then it will need a root canal and a crown. This wont necessarily happen every time, especially if you catch it early.





Best thing is prevention, brush, floss, rinse, and I recommend chewing sugarless gum sweetened with Xylitol because this natural sweetener actually inhibits the ability of bacteria to attach to the tooth. It has been proven to decrease decay. You need to chew Xylitol gum (like Trident) for at least 5 minutes at least 3 times a day, preferably after every meal. It will help, but it cant do anything with the cavities you already have. Unfortunately you have to have the dentist fix them!
Reply:one big con mate
Reply:trapped bacteria or food particles getting in afyer the filling has been done
Reply:You got decay because your dentist didn't completely get rid of the earlier decay.
Reply:not your fault,bacteria can get in any crevice, and maybe the dentist didnt clean your cavity well enough before he filled it.
Reply:They're most likely the poisonous amalgam fillings, which can crack or separate from the tooth, allowing decay. If you get new fillings, be sure they're anything but amalgam, which contain mercury. Composite or gold are better.
Reply:Sounds like either the dentist that did the two older fillings didn't do a good job in the first place or if the fillings have been in there for years, that a gap might have formed and decay started between the filling and the tooth ( http://en.wikipedia.org/wiki/Dental_fill... ).
Reply:if you get decay there that means that you did not brush/floss like you were supposed to and eventually (the decay) happened
Reply:Decay under fillings is called "secondary decay". The decay is caused by bacteria being trapped there. It could be original bacteria that has not been flushed out properly or even fresh bacteria leaking under the fillings. Good oral hygiene is the key.

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