The reason the abscesses in your mouth won't heal on their own is due to:
- The fact that the mouth is one of the areas of the body with the most bacteria
- Therefore, the immune system cannot get ride of all bacteria, especially when they reside in or around teeth, which are relatively poorly vascularised and doesn't regenerate after being damaged, since the enamel doesn't contain cells that are remain alive after eruption.
If a chronic abscess (one that stays for a long time) is present in your mouth, it means that there is an underlying cause that is not being addressed, as was said in the comments bellow your question. It is not necessarily painful, since there is no build up of puss, which leaves through the opening. An acute abscess could happen if the wound in the gum closes completely and traps the pus in the gums and bone.
One could look at it like bones that are permanently sticking out of the body, a situation which would be unacceptable anywhere else in the body.
As far as dental abscesses are concerned, There are generally two possible causes:
- The pulp (nerf) inside the tooth has died (necrotic) and the bacteria have reached the apex (bottom of the tooth).
- Clinically Performing hot&cold, percussion and electrical test in the mouth
- Taking radiographs (X-rays) Looking for radio-transparent space around the root of the suspect tooth
- Generally a root canal therapy (RCT) is sufficient to prevent entry of further bacteria and enable the body to repair the bone and allow the abscess to heal.
- Another possibility is to extract the tooth, if it is not possible to perform a root canal or to restore it afterward (with a crown for example).
- The gums around the tooth have detached from the roots, allowing bacteria to thrive in so-called periodontal pockets between supporting tissues and the root of the tooth. if the top of the pocket closes, it can force the pus to leave via a fistule instead of the gum
- Clinically Performing the same test as for the first type of abscess, as well as using a probe (like in my profile picture) to measure and detect any "deep" pockets
- Taking radiographs (X-rays) Looking for bone loss and space around the root of the suspect tooth
- Depending on the state of the tooth, if it is salvageable, it will require scaling and root planing to clean the area of bacterial debris and to allow the gums to reattach to the root.
- Another possibility is again to extract the tooth, if there is not sufficient bone and gums to support the tooth
As always, only an exam by a dental professional will allow you to find and treat the cause of your abscess(es).