A root amputation is the surgical removal of a root from a multi-root tooth. This procedure is necessary when a single root is damaged/infected and cannot be healed, but the rest of that tooth (and roots) can be saved.
After a root amputation, the remainder of the tooth is reinforced, and brought back to full functionality, with a crown or filling. The teeth best-suited to this procedure are molars, the multi-rooted teeth at the back of the mouth.
If the problem root is not removed, the infection will spread to the rest of the roots/tooth, necessitating a complete tooth removal. And while in the past, diseased or injured teeth were always pulled, thanks to technology, today your tooth can be saved through root amputation.