Once decay has penetrated the thick enamel it works very fast at attacking the dentin and next the pulp, which is the blood supply to the tooth, or nerve. There is no definite time frame on this. It's really a matter of how well you maintain your teeth with regular brushing, flossing and check ups.
Once the decay has gotten thru the dentin and into the pulp or nerve chamber, there is a great deal of pain, and an abscess will eventually form at the root of the tooth. An abscess is a pus pocket at the end of the tooth which destroys the surrounding tissue and bone as well as cut off the blood supply required to keep the tooth vital. It's the decay or rotted tooth that is getting into the blood supply that causes the tooth to abscess. As the infection gets worse the abscess will get larger thus making the tooth feel taller in your mouth than the teeth next to it, so when you bite together you hit it first. This makes the tooth even more painful by rocking it around in its socket!
After the decay has gotten this far, you have two choices and two choices only. First choice is root canal therapy, which evolves removing the diseased nerve inside the tooth and replacing it with a special filling material. This will involve getting a crown with a build up material after the completion of the root canal therapy. The second choice is having the tooth extracted. Depending on which tooth it is (and if there is another that occludes with it), your present dental health, financial ability, and how old you are all will be deciding factors. These will be things that you will need to take into consideration prior to your visit. It will help you to be able to make a sound educated decision rather than a snap decision and regret it later.
Hope I've been of some help. Good luck!
If your Orthothodontist said wait, it will be ok. It's only in the enamel, which is the thick outer covering of the tooth and the hardest part, very similar to bone. Now if you had to wait 3-4 months, I would say call and reschedule for an earlier date. It's better to catch them when they are small, rather than take a chance of getting closer to the pulp. The smaller restorations are less expensive too! Since you'll be having it taken care of within the month, you're fine. With it still being in the enamel, you have nothing to worry about, it's very small right now.
It would take more than a few weeks, and lots of neglect, to travel into the pulp, so you can relax. We sometimes let small cavities wait on what we call a "watch" inbetween a patients cleaning visit (after letting the patient know) to see if by keeping it clean it will stop the decay and recalcify. In those cases the patient doesn't require a restoration, but has to keep a close eye on the tooth and take extra care in keeping it clean and palque free. Most patients it does good with, but others wind up eventually having a restoration placed. Usually it's because it's in such an area that it's difficult or impossible to reach. So, that leads me to my next remarks....
Although my guess is that the decay is at the gum line, or somewhere under the band, which is an area you can't get to with a tooth brush. So give yourself a pat on the back if it's under the band, it's due to cement failure, or poor placement, that caused your cavity. It happens sometimes working in a wet area such as a mouth. But ask yourself if there is a chance it's your fault because of gum chewing, peanut butter eating or candy bar induldging. We've all done it, so don't sweat it. Just pay closer attention to your bands on those back teeth making sure they don't become loose inbetween your scheduled ortho appointment. Every once in awhile they get loose due no fault of your own. But when that happens, it allows slavia, along with bacteria normally found in the mouth to seep under the band, giving it the perfect enviroment to form decay. Makes sence doesn't it? Just one of the reasons the ortho say's no gum, nuts, or sticky stuff. Hope I've been of as much help this time around as the first. Good luck!
work in the dental field