Root canal treatment is the most common treatment in dentistry, and is the basic treatment for dental treatment. Many tooth preservation treatments are done first with root canal treatment before other treatments. As a complex treatment, why is it necessary to take pictures and how many pictures are taken? Root canal treatment is also “filling”, but it is different from the traditional “filling”, because the caries progresses and affects the nerve and even the periapical tissue, root canal treatment needs to prepare, disinfect and fill the root canal that houses the nerve, and then finally fill the crown. It is a complex treatment for preserving teeth. During the root canal procedure, the most important thing that patients do not understand is why the doctor has to take dental films repeatedly and what they have to do with the treatment. In fact, these dental films are for better diagnosis and treatment. Generally speaking, root canal treatment requires 3 dental films to be taken. The first film is to diagnose the extent of the dental disease to determine whether treatment is needed; the second film is used to measure the length of the root canal to determine the length of the treatment filling; and the third film is to detect the effect of the treatment and whether the filling is in place, which is helpful to determine the prognosis. In the treatment, if the root canal varies or if the filling is not in place or is over-impacted during the treatment, the fourth film may be taken. Therefore, root canal treatment may take up to 3 to 4 dental films, which are all for better diagnosis and treatment, and are an important part of standardized root canal treatment.