The term abscess refers to a closed-off deposit of pus (remains of blood, cells and bacteria).

Untreated abscesses in the jaw area may cause life-threatening conditions. Besides fever, pain and mouth opening troubles, painless processes may happen.
You notice a dense swelling which hurts when pressed.
Abscesses in the mouth, jaw or face area are usually caused by badly performed root canal treatment, retained wisdom teeth, parodontitis which has gone untreated and/or by necrotic teeth without root canal treatment.
Here you see a patient, who had his teeth capped 3 years previously, and reports feeling a dragging pain every now and then. He noticed a dense swelling in his gums. It may be that while the caps were being sanded not enough was done to cool down the teeth and a nerve may have been damaged due to overheating. The tissue died and caused imflammation in the bone – which became acute and resulted in an abscess.
The method used to treat this is called an inner incision, which means the abscess is being cut open, which allows the pus to flow out. A drain is used to allow the pus to keep flowing out as long as necessary – in this case an iodine strip, as otherwise the incision would close up again immediately. This pus can now flow out , and the strip is removed after 1 to 2 days.

The incision treats the abscess but not the cause. In this case root treatment should be performed to eliminate the responsible tooth, as soon as the worst symptoms are over. Otherwise a new abcsess is built.