Antibiotics for toothache: what they can and cannot do

Ask most people what an infected tooth needs and they will say antibiotics. It is an understandable answer — infection, antibiotics — but for the great majority of tooth infections it is the wrong one, and understanding why can save weeks of recurring pain.

Where the bacteria are

A dental abscess begins inside the tooth. Once the pulp has died, the empty canals become a sealed space full of bacteria, with no blood supply and therefore no way for the body's immune system or a drug in the bloodstream to reach them. The bacteria and their by-products leak out of the root tip into the bone, and that is where the swelling, the pain and the shadow on the X-ray come from.

What antibiotics can do

Antibiotics act on the infection that has spread into the tissues outside the tooth. They can reduce a swelling, bring down a temperature and make you feel better within a day or two. That is genuinely useful when an infection is spreading, when you are unwell, or when definitive treatment has to be delayed for a short time. In those circumstances a dentist may prescribe them.

What they cannot do

They cannot reach the bacteria inside the canals, so they cannot remove the source. When the course ends, the bacteria that were never touched continue to leak out, and the infection returns — in days, weeks or months. They also do not treat pain, which comes from pressure and inflammation rather than from the bacteria directly. A pattern of "antibiotics, better for a while, back again" is the signature of a tooth that needs treatment rather than medication.

Why repeat courses matter

Every unnecessary course of antibiotics contributes to resistance, which is a growing problem in dentistry as elsewhere, and exposes you to side effects for no lasting benefit. Current UK guidance is clear that antibiotics should not be used as a substitute for treating the tooth.

What does cure the infection

Removing its source. For a tooth that has not been root-treated before, that means root canal treatment: the dead tissue is removed, the canals are disinfected and sealed, and the body clears the remaining infection in the bone over the following months. For a tooth with an old root filling, retreatment or an apicectomy does the same job. Where the tooth cannot be saved, extraction removes the source too. See tooth abscess and root infection.

What to do if you have an infected tooth now

Book an assessment and say your symptoms are urgent if you are in pain or have a swelling. Take ordinary painkillers regularly in the meantime, and avoid heat on the face. If a swelling is spreading rapidly, you have difficulty swallowing or breathing, or you feel very unwell, get medical help straight away through NHS 111 or A&E — that is the one situation where antibiotics, given promptly, really are the first step.