We didn't all drop dead from cracked teeth before there were dentists.

Your body knows what to do. The tooth will die without treatment, and may get infected. But your body will fight it. It will port the rotton root to the outside of the gum line and you will have a foul blister along your gum. When this abscess pops, all the bacteria will drain and the infection will slowly go away as your body will encapsulate the remaining bacteria in a firm cyst like material. Eventually the tooth will begin to fall apart but by this time the body has sealed off the root cavity.

This is not a pleasant process. It will hurt like hell. And it may take years for the dead tooth to break down. It's important to remain healthy and keep your mouth very clean while this is occurring.

Just know it's not a death sentence. I've been through it a few times due to a phobia of dentists.

The best treatment is to just get it pulled.