Mayo Clinic explains that a tooth abscess is a bacterial infection caused by unfinished dental work or an untreated cavity and, if left untreated, can lead to life-threatening complications. OnHealth.com notes that the biggest danger of an abscess is that the infection will spread from the tooth to the surrounding areas, resulting in cellulitis.
According to OnHealth.com, cellulitis is a severe infection that spreads from the abscess of a broken or rotten tooth into the surrounding tissues. Cellulitis is life-threatening on its own and often leads to Ludwig's angina. Ludwig's angina is also life-threatening and involves severe swelling on both sides of the mandible.
OnHealth.com also notes that the signs of simple cellulitis include fever, a feeling of lethargy and exhaustion, swollen lymph nodes on the neck and sinus drainage due to the pressure caused by the infection. Once signs of these conditions are present, immediate IV treatment at the hospital is necessary.
MedicineNet.com explains that it is not uncommon for an abscessed tooth to fail to present symptoms. In fact, many abscesses are diagnosed through routine X-ray exams. Even without obvious symptoms, an abscessed tooth's infection can still spread, leading to serious and even life-threatening complications without proper treatment.