Dentigerous cyst

Developmental cyst:

developmental cysts mean that they are of uncertain origin on the reverse of inflammatory cysts that are associated with inflammation as in radicular cyst in which bacteria from pulp stimulate inflammatory response ,hence inflammatory cells release cytokines as messengers to fibroblasts in cyst wall that release prostaglandins & collagenese so cyst expansion by bone resorption and all this with the aid of Osmosis as we mentioned before, another scenario as in the paradental cyst which is also inflammatory cyst associated with pericoronitis.

1-Dentigerous cyst(Follicular cyst).

-Dentigerous cyst is the most common developmental cyst and the second most common odontogenic cyst after radicular cyst.

Origin, Etiology & pathogenesis,

Pathogenesis of dentigerous cyst is uncertain,it arises from reduced enamel epithelium covering unerupted tooth after complete formation of the crown ,it may by accumulation of fluid between reduced enamel epithelium & tooth crown

BUT, although all dentigerous cysts are to be developmental in origin ,there are some examples that appear to have an inflammatory pathogenesis i.e dentigerous cyst may develops around unerupted permanent tooth as a result of periapical inflammation from an overlying primary tooth. Another similar scenario involved paradental cyst or buccal bifurcation cyst.

So ,know;

1)Dentigerous cyst is adevelopmental cyst but there are some cases that are inflammatory i.e periapical inflammation of decidous tooth may stimulate cystic changes of the underlying permanent one causing inflammatory dentigerous cyst

2)Paradental cyst is an inflammatory dentigerous cyst (or variant) formed on the buccal aspect of the lower wisdom mainly ,but inflammation here associated with pericoronitis overlying vital tooth( lower 3rd molar).

Clinical features,
-Dentigerous cyst may occur around ay unerupted tooth but most often it involves mandibular 3rd molar ,other frequent site include maxillary canine , maxillary 3rd molar ,mandibular premolars respectively.

-Dentigerous cyst is completely asymptmatic unless infection occurs and if it becomes infected ,it will associated with pain ,such infections may be from extension of periapical or periodontal infecions from adjacent tooth or may arise in a dentigerous cyst that is associated wih partially erupted tooth.

-Dentigerous cyst shows male predilection and uncommon on decidous teeth.

-Dentigerous cyst may occur around supernumerary teeth or odontomes.

Radiographic picture,
-Dentigerous cyst appears as well-defined unilocular radiolucent area associated with crown of unerupted tooth. A large dentigerous cyst may give the impression of multilocular appearance because of the persistence of bone trabeculea within the radiolucency ( pseudoloculation of bone trabeculea) however ,dentigerous cyst are grossly and histologicaly unilocular and never are truly multilocular.

-The affected unerupted tooth usually displaced,it may also displace or resorp root of adjacent erupted tooth.
-The cyst to crown relationship shows several radiographic variations :
a) central type : the most common type, the cyst is completely surround the crown
b) lateral type : the cyst projects laterally from the side of the tooth.
c)circumferential type: the cyst durround the crown and extends around the roots so portion of roots appear to lie within the cyst.

-Radigraphic picture is not diagnostic for dentigerous cyst, keratocyst,unilocular ameloblastome and other odontogenic & nonodontogenic tumors have radiographic pictures identical to those of a dentigerous cyst.

Dentigerous cyst associated with premolar

Cyst expansion,

Mechanism of expansion si,ilar to that of radicular cyst by osmosis and bone resorption

Histopathology,
histopathology varies depending on whether the cyst is inflammatory or developmental, in the common non inflammed dentigerous cyst, the lining is thin , regular ,nonkeratinized stratified squamous epithelium, may flattened or low cuboidal,mucous cells may be found in epithelial lining as a result of mucous metaplasia of epithelial cells, the connective tissue capsule of the cyst free from inflammatory cells and there are islands of odontogenic epithelial rests may be seen.

Islands of odontogenic epith. within cyst wall

Lining of ciliated stratified may be seen

Mucous cells within lining due to metaplasia

-In the inflammed one, the epithelial lining is thicker with hyperplastic rete ridges, the fibrous capsule is more collagenized with diffuse infiltration of chronic inflammatory cells.

-Rushton bodies and colestrol clefts may be found within the cyst wall.

Inflammatory dentigeous cyst

Treatment,
the usual treatment is enucleation with removal of unerupted tooth, the cyst may be treated by marsupialization when the tooth is allowed to erupt or if it can be orthodontically guided to its position in the arch.and in case of large dentigerous cyst.

Prognosis,
prognosis of dentigerous cyst is excellent and recurrence is seldom occurs. However ,several complication may be noted, dentigerous cyst may complicate to:

1)Ameloblastoma (lining of the cyst may undergoes neoplastic transformation)
2)Squamous cell carcinoma (due to mucous metaplasia)
3)Intraosseous mucoepidermoid carcinoma (due to mucous metaplasia)
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paradental cyst

4-Paradental cyst(Buccal bifurcation cyst)

• Inflammatory cyst:

1. Radicular cyst.
2. Residual cyst.
3. Lateral cyst.
4. Paradental cyst.

-Paradental cyst or buccal bifurcation cyst is a variant of dentigerous cyst. It's actually a dentigerous cyst which arising from the third molar (or rarely other molars) as dentigerous cyst is mainly developmental in origin but may occur due to inflammation (para dental cyst) -see dentigerous cyst-

Origin,

- The cyst is inflammatory in origin and may arises as a result of extension of inflammation stimulating proliferation and cystic changes in the reduced enamel epithelium covering un erupted tooth.

Radiographically,

-Well-circumscribed unilocular radiolucency along buccal bifurcation and root area, the root apices are tipped towards lingual surface or buccal tipping of the crown so occlusal radiographic view is more helpful.

Root apices are tipped towards lingual surface

Clinically,

-Occurs around partially erupted teeth especially 3rd mandibular molar (lower wisdom)

-Affected tooth is vital.

-Occurs mainly in males between age 20-25 years old

Histologically,

-The tooth resembles radicular cyst histologically but shows more intense inflammatory infiltrates due to pericoronitis.despite the fact that it probably arise from reduced enamel epith.(REE),for this it may resemble dentigerous cyst histologically

SO,Histological picture of paradental cyst is NON SPECIFIC.

Treatment,

-Enucleation.

Lateral inflammatory cyst

3-Lateral inflammatory cyst.

-Lateral inflammatory periodontal cyst forms on the side of non vital tooth as a result of opening of lateral branch of root canal.

-It must be distinguished from lateral developmental cyst, the last is related to a vital tooth.

Residual radicular cyst

2-Residual radicular cyst

-It's a radicular cyst which persists after tooth extraction
-It's a common cause of swelling of edentulous jaw in older age
-Lining of thinner epithelium than that of radicular cyst
-It may slowly regress spontaneously,this is suggested by the progressive thinning of the lining

thinner lining of the cyst

-It's similar to radicular cyst in pathogenesis, clinically ,histologically & treatment
so it's a persistent radicular cyst.