Radicular cysts, or periapical cysts, are the most common type of inflammatory cyst to affect the jawbone.
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Radicular cysts may account for up to as many as 70% of all cystic jawbone lesions. These cysts are thought to be the end results of epithelial cell rests proliferating during inflammation of teeth with infected and necrotic pulp, and apical periodontitis (inflammation of the gums).
Unless the cysts become infected, they are usually asymptomatic. Typically, they present as osteolytic periapical lesions detected with radiographic imaging. Radicular cysts, when seen on radiographic imaging, tend to appear pear-shaped or round. Lesions are typically less than 1 cm in size and are situated in the periapical region of teeth with unilocular and lucent characteristics.
These lesions are most commonly seen in the middle to older ages. The most common areas of the jawbone that are affected are the premolar mandibular and anterior maxillary regions.
Radicular cysts are formed by resorption of the periapical portions of alveolar bone by immune-inflammatory mechanisms. These mechanisms include activities carried out by cells that are pivotal in bone formation and resorption, such as osteoblasts, osteocytes and osteoclasts. The formation of radicular cysts is further augmented by the release of inflammatory cytokines and growth factors.
Radicular cysts are lined with stratified squamous and non-keratinized epithelium, which is irregular, thick and has an abundance of inflammatory cells during an active infection. In contrast, in the absence of an active infection, these cysts have a regular and thin epithelial lining with little infiltration of inflammatory cells.
Cholesterol crystals may be found in the lumen of radicular cysts and the cysts may be classified histologically as true cysts or pocket cysts. In the former category, the cysts are entirely encased with epithelial lining, whereas in the latter, their lumens open into the teeth’s apical root canals.
Histological examination is necessary in order to confirm the diagnosis of periapical cysts. However, the use of computed tomography (CT) and conventional radiography are great tools for ascertaining pathological changes at the organ/ tissue level. Moreover, while CT may help to distinguish between periapical granulomas and cysts, it is still near impossible to make the diagnosis without a histological confirmation.
Once confirmed, radicular cysts can be treated non-surgically, as is most often the approach, with therapy of the root canal, or they can be managed surgically. Cysts that are large and in close proximity to craniofacial structures, such as the mental foramen or maxillary sinus are generally treated with decompression and root canal therapy.
The prognosis following treatment is favorable for the vast majority of people. In the few cases where there is no response to therapy, non-surgical and/ or surgical, the infection may persist in the root canal.