Root canal dental X-ray. X-ray of a tooth filled during root canal dentistry. The root canal shows up as white on the X-ray. This specialist root canal dentistry, which takes 2 hours, has two stages. The first is the drilling, cleaning and disinfecting of the tooth's root canal. The second is to fill the hole with hot gutta percha gum (over 200 degrees Celsius). The temperature and the use of an injection gun ensures the gum fills all of the hole. This technique helps avoid later infection, which can result in an infected tooth that needs to be extracted, and can also cause damage to the jaw bone. The X-ray shows how successful the operation has been.