Root canal treatment, animation. A root canal is needed when the pulp (red) at the centre of a tooth, which contains the nerve and blood supply, becomes infected. The bacteria kill and replace the pulp and eventually spread into the surrounding tissue, causing inflammation. Treatment involves drilling into the tooth to remove the infected area, cleaning the interior of the tooth and then filling the hollow. A crown is also usually fitted over the tooth for added protection.HD master is flattened onto a black background, as seen in this preview. The original file has a transparent alpha channel and is available as the HD master of clip K003 3753.