With a pair of pliers and a sharp pull.

Basically the same thing we do today, but without any anaesthetic.

https://www.wayneoralsurgery.com/blog/what-was-dental-health-like-in-the-middle-ages/

Root canal therapy wasn't invented until the mid-18th century, so the only real treatment for severely decayed or abscessed teeth was to pull them.

In Europe, this was most often performed by a barber-surgeon and painkiller was limited to a swig of alcohol, if that. This is a quote from a popular history book about Catherine the Great's experience with dentists of her time:

>One day as a teenager, after suffering weeks from a decayed tooth, the future Catherine the Great agreed to have it pulled. A “surgeon” came to her room armed with a pair of pliers and yanked out the offending tooth—and a chunk of jawbone as well. Blood gushed all over her gown. The swelling and pain were so shocking that Catherine did not leave her room for a month, and even when the swelling went down, the dentist’s five fingers were imprinted in blue and yellow bruises at the bottom of her cheek.

>How was decayed or abscessed teeth treated back then? Before antibiotics?

In ancient times, people used various natural remedies to treat dental problems. According to a study published in the Journal of the American Dental Association, ancient Egyptian texts suggest the use of various plants, including myrrh, cinnamon, and frankincense, to treat dental pain and infections (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2627095/).

In the Middle Ages, barbers often performed dental procedures, including tooth extractions and bloodletting. The use of silver as a filling material was also recorded during this time (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2627095/).

In the 18th century, extraction was the most common treatment for decayed or abscessed teeth. Some people even resorted to tying a string around the affected tooth and pulling it out themselves (https://www.ada.org/en/about-the-ada/ada-history-and-presidents-of-the-ada/ada-history-of-dentistry-timeline).

In the mid-19th century, arsenic was sometimes used to kill the nerve in the affected tooth, allowing for its removal without causing pain. This was known as "devitalization," but it was a dangerous practice that could lead to serious health complications (https://www.ada.org/en/about-the-ada/ada-history-and-presidents-of-the-ada/ada-history-of-dentistry-timeline).

Overall, the treatment of dental problems before the discovery of antibiotics was often crude and sometimes even dangerous.

There's a good paper on the NIH's site about this. Abscessed teeth was an incredibly deadly condition. The paper cites evidence from the 1500s that put it as the 5th or 6th leading cause of death. Basically if you didn't get the tooth removed and cleaned early, it was a serious life threatening condition.

https://pubmed.ncbi.nlm.nih.gov/10686905/

Prior to sugar becoming commonplace in the Renaissance, tooth decay was uncommon.