They occur either between the roots of a single tooth or between the roots of adjacent teeth. Usually they are projections of anatomical structures such as: the maxillary sinus, the incisive foramen and canal, the mental foramen and canal and the nutrient canals. True lesions in this location are usually related to odontogenic cysts and tumors.
They also called cystlike lesions. They are solitary, round or oval, unilocular, well- defined radiolucencies. They can have a thin surrounding radiopaque cortex caused by a hyperostotic layer of bone. They may not teeth related and they can be located anywhere in the jaws. They are usually related to cysts, odontogenic tumors or other benign tumors. Rarely they are related to a malignant tumor.