Cysts of the jaws


A cyst is a pathological epithelial lined cavity that fills with fluid or soft material and usually grows from internal pressure generated by fluid being drawn into the cavity from osmosis. The bones of the jaws, the mandible and maxilla, are the bones with the highest prevalence of cysts in the human body. This is due to the abundant amount of epithelial remnants that can be left in the bones of the jaws. The enamel of teeth is formed from ectoderm, and so remnants of epithelium can be left in the bone during odontogenesis. The bones of the jaws develop from embryologic processes which fuse together, and ectodermal tissue may be trapped along the lines of this fusion. This "resting" epithelium is usually dormant or undergoes atrophy, but, when stimulated, may form a cyst. The reasons why resting epithelium may proliferate and undergo cystic transformation are generally unknown, but inflammation is thought to be a major factor. The high prevalence of tooth impactions and dental infections that occur in the bones of the jaws is also significant to explain why cysts are more common at these sites.
Cysts that arise from tissue that would normally develop into teeth are referred to as odontogenic cysts. Other cysts of the jaws are termed non-odontogenic cysts. Non-odontogenic cysts form from tissues other than those involved in tooth development, and consequently may contain structures such as epithelium from the nose. As the cyst grows from hydraulic pressure it causes the bone around it to resorb, and may cause movement of teeth or other vital structures such as nerves and blood vessels, or resorb the roots of teeth. Most cysts do not cause any symptoms, and are discovered on routine dental radiographs.
Some cysts may not require any treatment, but if treatment is required, it usually involves some minor surgery to partially or completely remove the cyst in a one or two-stage procedure.

Classification

Odontogenic cysts

Odontogenic cysts have histologic origins in the cells of the dental structures. Some are inflammatory while others are developmental.
There are several development cysts of the head and neck most of which form in the soft tissues rather than the bone. There are also several cysts, previously thought to arise from epithelial remanents trapped in embryonic lines of fusion, most of which are now believed to be odontogenic in origin or have an unknown cause. Their names are included for the sake of completeness.

Developmental cysts of the jaws

Cysts rarely cause any symptoms, unless they become secondarily infected. The signs depend mostly upon the size and location of the cyst.
If the cyst has not expanded beyond the normal anatomical boundaries of the bone, then there will be no palpable lump outside or inside the mouth. The vast majority of cysts expand slowly, and the surrounding bone has time to increase its density around the lesion, which is the body's attempt to isolate the lesion.
Cysts that have expanded beyond the normal anatomic boundaries of a bone are still often covered with a thin layer of new bone. At this stage, there may be a sign termed "eggshell cracking", where the thinned cortical plate cracks when pressure is applied.
A lump may be felt, which may feel hard if there is still bone covering the cyst, or fluctuant if the cyst has eroded through the bone surrounding it. A cyst may become acutely infected, and discharge into the oral cavity via a sinus. Adjacent teeth may be loosened, tilted or even moved bodily. Rarely, roots of teeth are resorbed, depending upon the type of cyst.
The inferior alveolar nerve runs through the mandible and supplies sensation to the lower lip and chin. As most cysts expand slowly, there will be no altered sensation, since the inferior alveolar canal is harmlessly enveloped or displaced over time. More aggressive cysts, or acute infection of any cyst may cause altered sensation. Sometimes, they cause higher risk of pathological fracture of lower jaw, especially around angle of mandible.

Diagnosis

Most cysts are discovered as a chance finding on routine dental radiography. They are often asymptomatic unless there has been long-standing with significant enlargement or secondary infection.
On an x-ray, cysts appear as radiolucent areas with radiopaque borders. On an x-ray, cysts appear as radiolucent areas with radiopaque borders in the jaw. However, cysts in maxillary sinus, also known as antrum, can appear radiopaque as the surrounding air absorbs fewer photons than the cystic fluid content.
Cysts are usually unilocular, but may also be multilocular. Sometimes aspiration is used to aid diagnosis of a cystic lesion; e.g., fluid aspirated from a radicular cyst may appear straw-colored and display shimmering due to cholesterol content. Almost always, the cyst lining is sent to a pathologist for histopathologic examination after it has been surgically removed. This means that the exact diagnosis of the type of cyst is often made in retrospect, and definitive treatment can be made for the patient.

Treatment

As many cysts of the jaws have similar presentations and treatment options, it is common to perform one of the following treatment options and send the cyst lining to histopathology to provide a retrospective definitive diagnosis.
Cysts treatment is limited to surgical removal for the majority of cysts. There are two techniques used to manage cysts with the deciding factor being the size of the cyst.
The exception to these treatments; is the management of cysts which have a higher rate of recurrence – for example odontogenic keratocysts. Options to reduce the recurrence rate include: curettage post enucleation, Carnoy’s solution or mandibular resection. These treatments are less conservative than the above options.

Prognosis

The prognosis depends upon the type, size and location of a cyst. Most cysts are entirely benign, and some may require no treatment. Rarely, some cystic lesions represent locally aggressive tumors that may cause destruction of surrounding bone if left untreated. This type of cyst are usually removed with a margin of healthy bone to prevent recurrence of new cysts. If a cyst expands to a very large size, the mandible may be weakened such that a pathologic fracture occurs.
After treatments, the patient should be informed of the risk of recurrence. Some people are more susceptible than others. This can be due to their oral and dental condition or inherited condition. In some cases, there are some cysts remain after the surgery called the residual cysts and most of them arise from a periapical cyst. Glandular odontogenic cysts tend to recur after curettage.
The radicular cyst is the most common type of cyst followed by dentigerous. The most common odontogenic cyst is a follicular cyst. Rarely, the walls of this type of cyst can progress into mucoepidermoid carcinoma, ameloblastoma or squamous carcinoma if the cyst is not properly removed early enough.

Epidemiology

s are by far the most common cyst occurring in the jaws.
Jaw cysts affect around 3.5% of the population.10 They are more common in males than females at a ratio of 1.6:1 and most people get them between their 40s and 60s. The order of the jaw cysts from most common to least common is; radicular cysts, dentigerous cysts, residual cysts and odontogenic keratocysts. Radicular lesions are most commonly found in the anterior region of the maxilla12 – usually around the canines.11 The majority of cysts are of inflammatory origin12. They are most commonly found in the posterior mandible11