• Periapical radiolucencies are most commonly odontogenic. Nonodontogenic radiolucencies tend to be not localized and span across the mandible or maxilla within the alveolus and sometimes extend inter-radicularly.
• The most common PA pathologies can be diagnosed based on the vitality responses from the teeth. Ruling out the tooth associated pathologies is an important step in securing a diagnosis from differential diagnosis panel of PA radiolucencies.
• Inter-relationship of possible results of periapical inflammation:

When formulating radiological differential diagnosis, features should be evaluated carefully, such as

1. location
2. locularity
3. relation to dentition
4. density of lesion
5. margin
6. type of radiological change (radiolucent/radiopaque/mixed)
7. periosteal reaction
8. cortical integrity, and
9. clinical presentation.

🌫 General Radiographic features:

• Location: With periapical inflammatory lesions, which are pathological conditions of the pulp, the epicenter typically is located at the apex of a tooth.

• Periphery: Ill defined

• Effects on surrounding structures: Periapical lesions cause widening of PDL space at apical region of the root.

PA Radiolucencies: (Classification)

PERIAPICAL RADIOLUCENCIES

Developmental

Lateral periodontal cyst

• Definition: lateral periodontal cysts are cystic lesions that tend to occur on the lateral aspect of vital teeth. Epidemiology: lateral periodontal cysts account for fewer than 1% of the reported cases of odontogenic cysts.
• Clinical findings: most lateral periodontal cysts area located in the mandibular incisor-canine-premolar area.
• Radiographic findings: radiographically, lateral periodontal cysts present as a unilocular radiolucent lesion between the roots of teeth or associated with the lateral aspect of a tooth.

• Management: surgical enucleation with preservation of involved teeth is an appropriate treatment of lateral periodontal cysts. Recurrence is rare. The multiloculated variant called botryoid odontogenic cysts has been reported to demonstrate a higher recurrence rate than its unilocular counterpart.

Inflammatory Lesions

Apical periodontitis, periapical abscess

• Definition: spectrum of inflammation involving the PA area of teeth that results from pulpal infection by microorganisms.
• Epidemiology: apical periodontitis is the most frequent inflammatory lesion related to teeth in the jaws.
• Clinical findings: apical periodontitis can be classified as either asymptomatic or symptomatic; clinical examination of percussion and palpation of the tooth yields negative results in the former and usually positive results in the latter. The results of pulp sensitivity tests for both conditions, however, are negative. In the early stage of PA inflammation, the PA PDL can exhibit acute inflammation without abscess formation. This localized alteration may or may not proceed to abscess formation.
• Radiographic findings: in apical periodontitis, radiographs may show a thickened PDL space. If an abscess develops after a long-standing apical periodontitis, radiographs reveal a radiolucent area around the root apex.
• Management: apical periodontitis is an inflammatory disease caused by a persistent infection of the root canal system. The recommended treatment is the removal of the dead nerve and bacteria either through extraction of the tooth or root canal treatment. Antibiotics are recommended only when there is severe infection that has spread from the tooth into the surrounding tissues.

Cystic Lesions

Periapical (radicular) cyst

• Definition: radicular cyst is a cyst of inflammatory origin associated with a nonvital tooth.
• Epidemiology: radicular cysts represent the most common odontogenic cyst. Radicular cysts are most commonly associated with at the tooth apex, but a lateral radicular cyst can be associated with a lateral root canal.
• Clinical findings: radicular cysts are always associated with a nonvital tooth, and this is an important criterion for diagnosis.
• Radiographic findings: radiographs often show a well-defined radiolucent lesion at the apex of a tooth. Radicular cysts can displace or resorb the roots of adjacent teeth.

• Management: the treatment of radicular cysts can include nonsurgical root canal therapy to surgical treatment, such as apicoectomy.

Odontogenic keratocyst

• Definition: an odontogenic cystic lesion with distinctive histologic features. Recently reclassified back into a cystic category in the recent 2017 WHO Classification of Head and Neck Tumours. Current evidence seemed lacking to justify the continuation of classifying it as a tumor.
• Epidemiology: odontogenic keratocysts are the third most common cyst of the jaws.
• Clinical findings: most common location of odontogenic keratocysts is the mandibular molar region.
• Radiographic findings: odontogenic keratocyst size can be variable, ranging from a unilocular radiolucent lesion surrounding the crown of an unerupted tooth, resembling a dentigerous cyst, to a large size that results in facial deformity and destruction of surrounding structures. Lesions tend to grow in a posteroanterior direction, however, that results in a lack of cortical expansion.
• Management: odontogenic keratocysts tend to be more aggressive in its growth pattern with a higher recurrence rate than other odontogenic cysts. Recurrence may be due, however, to incomplete removal or the presence of satellite (daughter) cysts. Treatment includes enucleation (with or without peripheral ostectomy, treatment with Carnoy solution), marsupialization, or resection.

Glandular odontogenic cyst

• Definition: a developmental cyst with features that resemble glandular differentiation.
• Epidemiology: glandular odontogenic cysts represent less than 1% of odontogenic cysts.
• Clinical findings: there is a predilection for the mandible.But in the maxilla, the canine seems commonly involved. Swelling and expansion were the most common presenting complaints.
• Radiographic findings: radiographically, glandular odontogenic cysts present as a well-defined unilocular or multilocular radiolucency associated with the roots of teeth; association with impacted teeth is rare.
• Management: glandular odontogenic cysts have a tendency to recur especially when lesions are removed with simple enucleation.

Benign Tumors

Ameloblastoma

• Definition: benign, slow-growing epithelial odontogenic neoplasm with unmitigated growth potential.
• Epidemiology: ameloblastomas are the most common odontogenic tumors, excluding odontomas.89 In the United States, African Americans seem to have an overall 5-fold increase risk of disease compared with whites.
• Clinical findings: tumor often presents as an asymptomatic swelling of the posterior mandible and can be associated with an unerupted tooth. Buccal and lingual expansion often is observed.
• Radiographic findings: radiographs commonly show corticated multilocular (soap- bubble) radiolucency.
• Management: the unmitigated growth potential and tendency to recur require operative management involving segmental or marginal resection. When treated by enucleation alone, much higher rates of recurrence are reported.

Malignant Tumors

Ameloblastic carcinoma

• Definition: a rare, malignant counterpart for ameloblastoma. Not to be confused with metastasizing ameloblastoma, this is a histologically benign ameloblastoma metastasizing to distant sites. In the recent WHO Classification of Head and Neck Tumours, metastasizing ameloblastoma has been separated from ameloblastic carcinoma and included as a type of conventional ameloblastoma.
• Epidemiology: incidence rate was 1.79 per 10 million person/year with male and black population predominance. The overall survival is 17.6 years.
• Clinical findings: the most common site is the posterior mandible. Often, pain and expansion are the first clinical manifestations. Most cases arise de novo, but some arise in preexisting ameloblastomas.
• Radiographic findings: radiographically, ameloblastic carcinomas can present as poorly defined, irregular radiolucencies consistent with a malignancy, or indistinguish- able from a benign radiolucency.
• Management: generally considered radio-resistant tumor, radical surgical resection is the first line of treatment.

Differential Diagnosis: 🔍

• The 2 type of lesions that most often must be differentiated from periapical inflammatory lesions are Periapical cemental dysplasia & enostosis (dense bone island, osteosclerosis) at the apex of the tooth.

• In the early radiolucent phase of Periapical cemental dysplasia, the D/D rely solely on clinical examination and a test of tooth vitality.
• With long standing periapical inflammatory lesions, the pulp chamber of involved tooth may be wider than adjacent tooth.
• More mature PCD show radio-opaque mass within radiolucent area which helps in D/D.
• Also the common site for PCD is mandibular anterior region. External root resorption is more common with periapical inflammatory lesions than PCD.
• When enostosis is centered on the root apex, it may mimic inflammatory lesion but the PDL space has normal width. Also the periphery of enostosis is well defined and does not blend with surrounding trabaculae.
• Small radiolucent periapical lesions with well-defined periphery may be either granulomas/cysts.
• Differentiation may not be possible unless other characteristics of cyst such as displacement and expansion of surrounding structure is not present.
• Larger lesions >1cm are usually radicular cysts.
• If the patient has had endodontic treatment or apical surgery, a periapical radiolucency may remain that resemble periapical rarefying osteitis.
• Metastatic lesions such as leukemia may grow in periapical segment of PDL space with malignant bone destruction.

• Enostosis are common findings that seldom require treatment; however, caution should be exercised when undertaking orthodontic movement in the area of a DBI due to a potential risk of root resorption. Accurate identification and multidisciplinary management are of utmost importance. Monitoring size changes is recommended until completion of patient’s growth.

Dentowesome|@drmehnaz🖊

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References:

1. https://link.springer.com/article/10.1007/s40368-020-00596-w
2. https://www.researchgate.net/profile/Eugene-Ko-2/publication/
3. SlideShare, Study Notes✍🏻