Periapical lesions of pulpal origin
They are caused by irritating inflammatory products that escape from a non-vital pulp and initiate a local reaction in the periapical area.
Multiple radiolucencies
They are multiple unilocular radiolucencies which are distinctly separated by normal bone. They should be distinguished from the multilocular type of radiolucency that produces a single lesion formed of contiguous and coalescent cystic spaces.
Pericoronal radiolucencies
This type of lesions is related to an impacted or semi-impacted tooth. The radiolucency may surround only the crown or the whole tooth causing the displacement of the associated tooth.
Periapical radiolucencies of non pulpal origin
They are caused by:
– anatomical structures that are projected in contact with the apex of the tooth
– cysts or bony lesions of non-pulpal origin
– localized manifestations in the periapex of a systemic disease
Interradicular radiolucencies
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.
Circumscribed radiolucencies
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.
Multilocular radiolucencies
They are produced by multiple, adjacent, frequently coalescing and overlapping lesions in the bone. They contain two or more pathologic chambers that are separated by septa of bone. They often described as “soap bubble”, “honeycomb” and “tennis racket.
Ill defined radiolucencies
They are divided into central and peripheral lesions:
– The central type of lesion originates in the bone.
– The peripheral type originates in the soft tissues and in a later stage they may infiltrate the underlying bone.
Generalized rarefactions
This category includes a number of general diseases (such as metabolic bone diseases or diseases of the hematopoietic tissue) that cause a disruption of bone homeostasis.