Some oral cysts are caused during development, such as thyroglossal duct cysts and gill slit cysts. If the thyroglossal duct does not disappear during development, congenital thyroglossal cysts can form due to the accumulation of residual epithelial secretions. The parotid gland is also of developmental origin, mostly due to the remaining tissue of the parotid gland during embryonic development. Oral cysts also include odontogenic jaw cysts, mainly seen as apical cysts and tooth-containing cysts. In patients with apical cysts, carious, residual roots or dead pulp teeth can be found in the mouth, resulting in apical cysts due to chronic infection in the root canal that stimulates the apical area, leading to long-term inflammation of the root tip. Oral cysts also include cysts of soft tissues, mainly sebaceous cysts, also known as powdery tumors, which are cysts formed due to obstruction of the excretory ducts of sebaceous glands.