What happens if I stop root canal treatment midway?

If you stop in the middle, bacteria re-enter through the open canals, the inflammation comes back, and the next round of treatment becomes much harder than the first. The temporary filling placed between visits is not designed to last long term, so if it sits for several weeks, it tends to crack or leak and reinfection follows easily. If the inflammation progresses all the way to the bone around the root tip, even a retreatment may not save the tooth and extraction may be needed. Even if the pain has gone away, bacteria can still remain inside, so please complete the scheduled treatment to the end.