Cysts of the jaws

The enamel of teeth is formed from ectoderm (the precursor germ layer to skin and mucosa), and so remnants of epithelium can be left in the bone during odontogenesis (tooth development).

The bones of the jaws develop from embryologic processes which fuse, and ectodermal tissue may be trapped along the lines of this fusion.

The reasons why resting epithelium may proliferate and undergo cystic transformation are generally unknown, but inflammation is thought to be a major factor.

[1] 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.

[2] Non-odontogenic cysts form from tissues other than those involved in tooth development, and consequently may contain structures such as epithelium from the nose.

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.

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.

As most cysts expand slowly, there will be no altered sensation (anesthesia or paraesthesia), since the inferior alveolar canal is harmlessly enveloped or displaced over time.

[7] They are often asymptomatic unless there has been long-standing with significant enlargement (causing bony expansion or egg-shell cracking feeling[7]) or secondary infection.

[7] However, cysts in maxillary sinus, also known as antrum, can appear radiopaque as the surrounding air absorbs fewer photons than the cystic fluid content.

Options to reduce the recurrence rate include: curettage post enucleation, Carnoy's solution (treatment of the cavity with a potent fixative) or mandibular resection.

Rarely, some cystic lesions represent locally aggressive tumors that may cause destruction of surrounding bone if left untreated.