It is quite possible for a tooth with an old restoration, filling, or crown, to be infected while symptom free. That is, there is no pain or sensitivity to pressure or temperature changes. The only obvious warning is a characteristic mouth odour that is quite unpleasant. The pain of a typical tooth infection is the result of pressure build-up of the gaseous and liquid by-products of the infection. Those by-products, when forced through to the apex of the tooth’s root and into the supporting bone, cause an abscess.
In the painless, infected tooth, pressure develops, but the by-products of the infection establish drainage out through the leaking, decaying filling, and supporting bone does not become involved. No evidence of infection will be present on an x-ray film. The tooth is really a dead one. Left untreated, exudates from the infection tooth drain into the mouth and on into the stomach, contributing to an illness possibly on a senior patient with a less efficient immune system. The only treatment that will save infected roots from extraction is a root canal. Infected tissue is removed, and root canals are filled with a product called gutta-percha that prevents another infection. For strength and permanence, posts may be placed in those canals and a crown may be applied if necessary to protect from decay or future fracture.
Because a toothache patient is often desperate many would go to the pharmacy where pain killers and antibiotics are sold to fight the suspected infection. But this is not the correct thing to do for many reasons. The pain of an infected tooth is difficult to relieve without the proper analgesic, even with a narcotic pain-killing drug. The antibiotic takes days to reach infected tissue and will only delay proper treatment while allowing for a more serious infection that involves supporting bone. Besides, the dentist is the only trained professional who can decide the treatment procedure in accordance with the stage and development of the infection. For example, a dental abscess has three stages with a different treatment for each stage.
A toothache is considered an emergency and all dentists should attend to the patient without delay or appointment. Often, it is necessary to anaesthetise, open and drain an infected tooth. Once pulpal drainage has been established, pressure that creates extreme pain is immediately relieved, pain stops, and the infection drains (pus) and does not spread into supporting bone.
Of course, there are other options. If root canal therapy with a post and crown cannot be afforded, an extraction can be done, which no doubt can be an expensive mistake since the tooth should be replaced failing which multiple problems can result obviously sending up the corrective cost tremendously.
Once the problem of a serious toothache is resolved the next step a patient should take is to request a thorough dental examination to learn where his or her next dental problem is likely to be. An infected tooth is no fun for anyone. Fortunately, it can be prevented. My advice is to check with your dentist at least every three months to ensure your mouth is in good standing. If you cannot afford braces, bridges or dentures, at least do not go through the suffering of a serious toothache.