If there is a cavity, clean it out with cotton on the end of a toothpick; then fill it with another small bit of cotton dipped in iodine, oil of cloves, or ammonia, or dusted with baking soda.
"Toothache, scourge of the wilderness, he cured in a novel way. With a thread and a sheet of writing paper he made a cornucopia, the open end of which he placed flat upon a dish; he then set fire to the upper end of the cornucopia, whereupon the burning paper generated a drop of yellow liquid. This liquid—it is extremely bitter—he applied, with a toothpick and cotton, to the cavity, and the toothache perished amid the howls of the possessor of the tooth." (A. W. North).
Probably the yellow liquid is largely creosote. I have seen my partner treat his own tooth this way.
If there is no cavity, but an abscess, it may sometimes be checked by applying to the gum a counter irritant, such as spirits of camphor on a pledget of cotton, or a bit of dough in which red pepper has been mixed, or by painting it with tincture of iodine. A small cloth sack partly rilled with hot salt, rice, or sand, and placed under the patient's face as he lies in bed is effective in many cases.