Here is a very good example of a tooth that should have had a crown placed on it. Delaying that protective step allowed the crack to proceed into the core chamber(pulp) of the tooth. Overwhelming stress caused the tissue inside to die leading to bacteria formation. Ultimately overflowing to the tip of the root and coming out on the tongue side. The abcess can form on either the tongue side or cheek side.
The gum boil is typically small. About half the size of a pencil eraser. It can come and go and may be associated with pain on biting. Sometimes it can have a yellow center where the abcess is draining. It can flair up and cause extreme swelling and discomfort.
Here are some tell tale signs of trouble. These can be seen often on exam of teeth that are without symptoms. The question is how long do you wait? Earlier intervention allows for a better long term solution and the avoidance of pain.
Here is another visual, a crack line up close on the cheek side. Your treatment options are either tooth removal or root canal treatment. However, sometimes the crack extends below the gum line. This can be checked. If it hasn’t progressed that far and isn’t causing gum and bone support problems then the tooth is a candidate for root canal therapy. Unfortunately due to financial pressure the patient had to have the tooth removed. A crown placed earlier would have saved half the cost and allowed this patient to continue with a complete complement of teeth.