Eruptive cysts

An eruptive cyst is a benign lesion normally associated with tooth eruption. On the basis of the current World Health Organisation classification (WHO) of cysts of the oral cavity, an eruptive cyst is categorised separately from an odontogenous cyst; the former develops around the crown of an unerupted tooth at the level of the bone. Indeed, an eruptive cyst can be considered as such when a tooth is obstructed from erupting by the overlying soft tissue.
Clinically, an eruptive cyst presents as round swellings on the crestal mucosa, it is soft on palpation and it varies in colour from no colour (transparent) to bluish, including a reddish colour. Its dimension can vary on the basis of the association with deciduous or permanent teeth and the number of teeth involved in that particular cyst. An eruptive cyst generally measures 1 cm in diameter.
An eruptive cyst incorporates a part of all of the corona of the erupting tooth, including the lingual aspect.
Radiographically, an eruption cyst has a typical appearance in that both the cyst and the tooth do not involve the bone.  On the other hand, an odontogenous cyst has a well-defined, unilocular radiolucency, which is similar to a half-moon on the corona of the suspect tooth.
Regarding  histo-pathology, an eruptive cyst shares the same features of an odontogenous cyst with fibrous, connective tissue, enveloped by a thin, non-keratinised epithelial layer.
The majority of eruption cysts naturally regress and do not normally require surgical intervention.  When symptomatic, it may be infected and/or haemorraghic, in which case surgery is required to expose and drain the tooth by means of the surgical excision of the upper part of the cyst. Occasionally a cyst ruptures spontaneously, thus obviating the need for surgery.