As one of the developmental disturbances in shape of teeth, an accessory root may involve any teeth, but has very rare frequency in the deciduous teeth. Because it is possible to diagnose the accessory root only by use of the radiographs, it is important to detect this root early by carefully examining the radiographs. The accessory root produces several problems such as abnormal exfoliation of deciduous teeth, eruption abnormality of successive permanent teeth, infection due to residual root during tooth extraction, and incomplete pulp treatment, and therefore it is necessary to have a continuous follow check-up to prevent these problems.