Numbness in lower lip and chin.

On October 18th I had I root canal. The procedure went well, no pain or any side effects. On October 24th, I had the temporary filling replaced with a permanent filling on the same tooth and again everything went great, no pain or side effects. On the morning of November 11th, I woke up with numbness on my right lower lip and as the day wore on the right side of my chin became numb and both the chin and lip have been numb ever since. I called the dentist on the same day(Nov. 11th) and he prescribed antibiotics and said to take them until I finished them. I was to call if the numbness continued. I called again this week and told the dentist that the numbness was still there. I was told that I didn\'t need to do anything further as I was having residule effects from the root canal and that the numbness would eventually go away. I guess my concern is that the numbness ocurred a few weeks after the the root canal and not immediately, even though the procedure went well. Is this normal?