During root canal treatment something like a needle was used. What is it?

It is a thin, long instrument called a file. The nerve canals inside a tooth root are as fine as a hair and curved, so we use files to scrape out infected nerve tissue and bacteria and to widen the canal so the disinfectant reaches every corner. Because we work up through increasing sizes and use them repeatedly, treatment is usually divided over 2 to 4 visits. It is done under anesthesia, so there is almost no pain; if you do feel pain during the procedure, raise your hand and we will add more anesthetic.