Abnormalities of the teeth that have had periapical endodontic treatment generally due to recurrent infections of root canal. Infection of the root canal is caused by leakage due to poor quality of coronal restoration and iatrogenic factors. Root canal treatment of the tooth with periapical cyst generally do conventionally. Medication materials used for healing of periapical lesions is calcium hydroxide, since it has properties not irritating, alkaline pH and antibacterial capabilities, so it is a biological stimulator for the formation of hard tissue in the area of damage and is expected to accelerate the healing process. It was reported the case of a 23-year-old student came to the Dental clinic of Conservation Specialist RSGM Sekeloa with complaints lower right back teeth has restored with amalgam, no pain, but less comfortable when chewing. The results obtained after treatment with calcium hydroxide and medikamen gutta percha filling with resin-based root canal cement. Approximately 4 months later, the periapical radiolucent area had thinned. So it was concluded that conventional endodontic treatment proved to heal periapical lesions including cysts, as long as the treatment is taken adequately.