Patient with periapical cyst, forming a chronic periapical abscess, perhaps the drainage, antibiotic therapy and endodontical treatment. At the moment of the cyst enucleation, it appears a latex drain as a foreign body in the deep of the cyst cavity as origin of the persistant infection. Foreign body was extracted, the corresponding apicoectomies were performed and another drain, fixed to the mucosa, was placed for one week. Periodic inspections show no recurrence of suppurative process.