Development and clinical symptoms
The radicular cyst enlarges slowly, its formation taking several years. Over time, the lesion reaches a diameter of 3–5 cm, causing resorption and remodeling of the surrounding bone tissue. This leads to a noticeable increase in the volume of the alveolar process or the jaw body.
When localized on the hard palate, a spherical protrusion is identified that is easily compressible. As it grows, the bone thins, and upon palpation, it begins to spring and crepitate — the "parchment" crunch sign (Dupuytren's sign) is revealed. A similar sign occurs when the formation invades the nasal cavity (cavitas nasi) or the maxillary sinus (sinus maxillaris). If the anterior wall of the bone is completely destroyed, fluctuation appears upon palpation.
On the mandible (mandibula), in the area of the ramus and angle, the deformation is visually noticeable only at giant sizes. The growing cyst critically thins the jaw body, creating a direct threat of a pathological fracture. At the same time, the neurovascular bundle is displaced but not involved in the pathological process itself. Growth from the 2nd and 3rd lower molars is often directed lingually, since a thick layer of spongy and compact bone is located on the vestibular surface.
Effect on teeth and local status
The pressure of the cystic sac on adjacent intact teeth leads to a change in their axis: the roots diverge in a fan-like manner, and the crowns tilt toward each other. The electrical excitability of such teeth caught in the growth zone decreases.
Upon examination, the mucous membrane over the site of bone perforation retains its normal color. A carious cavity is found in the causal tooth that served as the source of infection.
The clinical picture during dental manipulations is telling:
- During endodontic treatment, if the pulp extractor goes beyond the root apex, a characteristic exudate begins to discharge from the canal — a transparent straw-yellow fluid, opalescent due to the presence of cholesterol crystals.
- When extracting the causal tooth, the cystic exudate flows directly from the socket, and a bulbous probe freely enters the cystic cavity during revision.
Radiological diagnostics
Radiography plays a key role, determining the exact dimensions and topography of the lesion, including its connections with the mandibular canal (canalis mandibulae), the maxillary sinus, the nasal cavity, and tooth roots.
On the radiograph, a radicular cyst appears as a round or oval-shaped area of bone destruction with smooth and clear margins. The root of the tooth acting as the primary source of infection is visualized inside the cavity.
To assess the involvement of adjacent teeth, the periodontal ligament space is studied in detail:
- True immersion of roots into the cyst: the periodontal ligament space is absent on the radiograph due to resorption of the socket's compact lamina. As a rule, the roots themselves do not undergo resorption.
- Projection superposition: the periodontal ligament space is preserved — this means the teeth are intact and merely project onto the destruction lesion.
When growing into the sinus maxillaris, the radiograph of the sinuses shows a dome-shaped bulging and displacement of the bony floor, which requires diagnosis clarification using a contrast radiograph or computed tomography (CT).
Differential diagnosis
The radicular cyst must be differentiated from other jaw lesions:
- Follicular cysts: detected more often in children and young adults, not associated with gangrenous teeth. On the radiograph, the crown of an impacted permanent tooth is located inside the cavity (the tooth is missing in the arch or replaced by a deciduous one). The capsule attaches strictly at the neck of the unerupted tooth.
- Ameloblastoma: more frequently affects the body and angle of the mandible. On the X-ray, it may look like a polycystic or unilocular lesion; an unerupted wisdom tooth may lie within the cavity. The punctate is usually whitish, turbid, and viscous. The definitive diagnosis is made exclusively pathohistologically.
- Osteoblastoclastoma: clinically differs by a bumpy surface and abundant bleeding. On the X-ray, the boundaries are less clear, the focus is trabecular (in the form of "honeycombs" or "soap bubbles"), and the tooth roots in the tumor zone often undergo resorption. Puncture yields a brownish-bloody fluid without cholesterol crystals.
Briefly: answers to topical questions
What surgical treatment methods are used for a radicular jaw cyst?
Two main surgical treatment methods are used for a radicular jaw cyst: cystectomy and cystotomy. The choice of method depends on the size of the lesion.
- Cystectomy is the complete (radical) removal of the cyst lining with placement of tight sutures. It is used for small-sized cysts (up to 3 cm). In this procedure, root-end resection is performed on the causal tooth after root canal filling.
- Cystotomy is a surgery in which the cystic cavity is communicated with the oral vestibule, turning it into an accessory cavity. Indicated for large-sized cysts.
- Oroantral cystectomy is used when removing cysts that have grown into the maxillary sinus.
What is the histological composition of the radicular cyst lining?
The radicular cyst lining has a two-layered morphological structure.
- Outer layer is represented by connective tissue that directly adjoins the surrounding bone.
- Inner layer is represented by an epithelial lining. Most commonly, this is non-keratinized stratified squamous epithelium of the oral cavity; cylindrical epithelium is rarer.
With inflammatory changes, erosion of the epithelium occurs, followed by necrosis of part or all of the cyst lining. Due to necrosis, the epithelial lining may be detected only in isolated focal areas during morphological examination. A characteristic feature of a radicular cyst is the presence of cholesterol in the contents and walls of the cyst.
Dupuytren's sign is easy to remember as a "parchment crackle" — imagine that the bone thinned by the growing cyst depresses and springs under your fingers, making a sound similar to crushing dry parchment.
Class and exam questions
Is the neurovascular bundle involved in the pathological process in the mandible?
No, the growing cyst merely displaces the neurovascular bundle, but the bundle itself is not involved in the pathological process.
How to determine from a radiograph whether the root of an adjacent tooth has grown into the cyst?
If the root is indeed located within the cystic cavity, the periodontal ligament space is not detected on the radiograph due to resorption of the socket. If the space is preserved, it is merely a projection superposition.
Do the roots of teeth immersed in a radicular cyst undergo resorption?
As a rule, resorption of the roots themselves in the area of a radicular cyst is not observed. This is how it differs from osteoblastoclastoma, in which the roots frequently undergo resorption.
What else to study on this topic
- Etiopathogenesis and stages of development of follicular jaw cysts
- Differential diagnosis with non-odontogenic cysts (nasopalatine, globulomaxillary, and nasolabial)
- Surgical picture and operative approaches during cyst penetration into the maxillary sinus
- Features of pathohistological examination in suspected ameloblastoma
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