Like HowStuffWorks on Facebook!

Root Canal Procedure

Measuring and Cleaning Root Canals

Over the course of one to three visits, the dentist will diagnose the problem, determine whether or not root canal treatment is the correct form of therapy and, if needed, perform the procedure.

The first step toward diagnosis is an external (face and neck) examination to assess for any swelling, tenderness or enlarged lymph nodes. Next is an internal (inside the mouth) examination to assess the patient's overall oral health and hygiene.

The dentist will also take x-rays of the affected tooth to help analyze its health. While an x-ray offers a good look at the affected tooth's size, shape and surrounding tissue -- information that's necessary while performing a root canal procedure -- the dentist will also use those x-rays to look for two specific things to help with diagnosis: enlargement of the periodontal ligament and the presence of a dark area at the root tip, two determining factors of an infection in the pulp chamber.

Additionally, the dentist will determine how healthy the pulp of the tooth is. Pulp testing may be done in a few different ways. The dentist may gently tap a finger against the tooth to assess for sensitivity and tenderness. Electric pulp testing (EPT) or thermal pulp testing may also be conducted. EPT is a painless way in which to test the health of the pulp, and it works by sending a gentle pulse of electricity into the tooth to test the life of the nerve tissue. Thermal pulp testing involves applying either hot or cold stimulus to the tooth to see if the tissue responds to stimulus.

With diagnosis complete, the first step in a root canal procedure is -- you can relax -- administering local anesthesia. A sheet of latex (also known as a rubber dam) is placed around the affected tooth to isolate it from other teeth and to keep the area clean and saliva-free during the procedure.

With the prep done, it's time to remove some decay. The dentist will drill a small opening in the top or the back of the tooth -- this is the access hole to the pulp chamber -- and will begin to remove decaying tissue. Before they can be cleaned thoroughly, though, the canals inside the tooth need to be measured.

Dentists use a few different methods for measuring canal depth, including diagnostic x-rays, radiographic techniques (x-rays taken during the procedure) and a specialized tool called an apex locator, which uses a gentle electrical current to make canal measurements. Measuring the root canal is the only way to ensure the tooth is clean from tip to top. These measurements will also be used to determine the amount of filling needed to replace the pulp, but let's not get ahead of ourselves -- that comes next.

After taking measurements, the dentist will use a series of small files, endodontic files, each progressively larger in diameter, to clean and shape the inside of the tooth until all unhealthy tissue has been removed and the canal has been enlarged in preparation for the next step of the process, filling.