Can an untreated dental abscess be fatal?

Yes: In fact, before the advent of antibiotics an infection of the upper front teeth was one of the leading causes of death because of the ability of the infection to make it to the brain.

Yes: Yes. Dental abscess can spread to other areas of the body and cause encephalitis or cause your throat to swell shut. Both of these scenarios are life threatening.

Yes: It can happen. The infection can dissect into vital structures -- into your chest or into your head/brain. Not common, but possible. Additionally, the infection gets in your blood stream and is carried throughout your body.

Definitely, yes: If not treated, a serious dental abscess can eventually kill. The death from tooth abscess is not rare. Boston study (2008) found that 66 patients died due to dental abscess.