Cyst: pathological cavity lined with epithelium and surrounded by fibrous connective tissue wall containing fluid or semi fluid and was not created by the accumulation of puss

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Oral pathology 8
Cyst: pathological cavity lined with epithelium and surrounded by fibrous connective tissue wall containing fluid or semi fluid and was not created by the accumulation of puss "the difference between it and abscess" .
*Sometimes you can find puss inside it due to infection but its formation doesn't depend on the accumulation of puss.

Cysts of the jaw appear in maxilla or mandible.*

If the cyst is not lined with epithelium it's called pseudocyst or false cyst.
Epithelial cysts
Classification of jaw cysts
Cysts Without epithelial linning

Classification of epithelial jaw cysts



Paradental cyst

Radicular cyst

Dentigerous (15%)

Keratocyst (5%)


Lateral Periodontal
according to aetiology

apical (75%)

Glandular Odontogenic
Lateral (5%)

Residual (20%)

If the epithelial lining of the cyst inside the jaw is odontogenic;the epithelium from the remnants of teeth or from epithelial forming teeth Those are said to be odontogenic cysts and are the majority of the cysts (90%)

odontogenic cysts are further subdivided according on their etiology into:
1)inflammatory cysts the cause is inflammation

2)developmental cysts the cause is unknown.
The most common cyst is the radicular cyst which accounts for more than 50% of the jaw cysts around (70%).
The most common developmental cyst is dentigerous then keratocyst.

The non odontogenic cyst epithelium source is not from the remnants of tooth forming epithelium.

The non odontogenic cyst types:
Nasopalatine Duct Cyst "more common than nasolabial"*

* Nasolabial Cyst

Cysts Without epithelial lining:

Solitary Bone Cyst other names: (simple; traumatic, hemorrhagic) 1-

2- urysmal Bone Cyst

3- stafne’s idiopathic Bone cavity

Those are rare cysts

Cysts of the soft tissue: within the oral cavity or around oral cavity.

1) Salivary Mucoceles (Extravasation & Retention) their source is salivary glands

2) Dermoid & Epidermoid Cysts

Lymphoepithelial Cyst 3)

4) Thyroglossal Cyst

Radicular cyst :-

The most common cyst that the pathologist or surgeon can find .

Clinically :♦
-It's found under non vital tooth so it's easy to diagnose whenever you find caries that have reached the periapical region and there is a cyst under the tooth or near the root then it's a radicular cyst .
If the tooth is not vital then there is no diagnosis for radicular cyst. -
It can occur at any age but mostly at 4th or 3rd decade.*
*seldom seen in primary dentition mostly in permanent the reason is maybe because the cyst needs time to occur and primary teeth will shed early giving no time for the cyst to form.
*it can occur at any tooth but it occur more in teeth that are susceptible to caries more : ant max teeth and post mand teeth.
*most common teeth to hv radicular cyst are ant maxilla ( centrals laterals )because :
they are susceptible to trauma and to turn non vital -

-they have lingual pits especially the lat incisors that have deep lingual pits and will turn non vital easily

-they are susceptible to caries, restoration, irritations so they'll turn non vital.


the chronic periapical granuloma will turn into radicular cyst so the symptoms are alike ( asymptomatic ,no pain) or mild pain until it starts to swell and appear clinically


*There is pain only in the case of infection but normally no pain."here the bacteria have reached the area and there is abscess inside the tooth"

There is a gradual slow balloon like expansion "in all directions" of the cyst.

In the case of maxilla the roots are near the labial surface so the expansion will appear the mandible rarely to find a cyst toward the lingual surface but teeth which are near the palate like max laterals swelling will be palately

The expansion:

There is bone resorption from inside and bone formation from outside and in the case of cyst the resorption will predominate on the formation and the bone will become very thin and upon any pressure it'll break like egg shell crack if the crack occurred in the soft tissue then it'll become bluish translucent fluctuant swelling because it contains fluids.

Apical :-
*the most common type is apical . on radiograph it'll appear as unilecular "one hole" well defined radiolucency surrounded by radio opaque lines located apical to non vital tooth .

*in the radiograph you can't determine if it's radicular cyst or periapical granuloma but sometimes from the size of the radiolucency you might know .if it was small(<.5-1cm) it's granuloma but if large it's cyst. histological sections can determine the difference more precisely

In apical cyst the inflammation came from the apex and formed chronic periapical granuloma then the rest cells of malassez proliferated to form a cyst
Well defined unilecular radiolucency surrounded by radio opaque lines located near the root.

It occurad due to inflammation coming out from lateral canals and did the same process.

The residual cyst will have the same features but it's found in the place of an extracted tooth because the extracted tooth was non vital.
Pathogenesis of radicular cyst:

It's chronic inflammatory cell infiltrate (CICI) that comes from irritation of necrotic pulp .

CICI will release the growth factors and cytokines that will stimulate rest cells of malassez to proliferate and form cystic lesion.


Rest cells of malassez : are inactive cells found in the periodontal ligament they come from the remnants root forming epithelium .

there are two theories upon the formation of cyst :

1)degeneration of central epithelial cells the proliferation of rest cells of malassez resulted in a ball of epithelium and the center part of the ball is away from blood supply so necrosis will occur in the center giving rise to a cavity filled with fluid.

2)the proliferating cells will encircle connective tissue and this CT will get necrotic.

the majority agree with the first theory.

Q: The expansion is balloon like why?

The cystic cavity contains: A:

a)Degenerated epith, inflammatory cells & C.T

b) high Serum proteins 5-11g/dl most are immunoglobulins and antibodies due to inflammation

c) Cholesterol crystals
These contents will make a dense fluid allowing fluids to move from outside to the inside (hydrostatic pressure)and the epithelium as well will allow the water to enter and preventing proteins from exiting the cavity
If there was no bone resorption around it then no expansion would occur.

As we said before there is bone resorption and cystic expansion at the same time .

Release CICI & epithelium release Ink 1& 6 will stimulate Fibroblasts
PGE2,F2,I & collagenaze will stimulate osteoclasts in the bone

Become activated

bone resorption

In general true cyst is made of cavity lined with non- keratnized stratified squamous epithelium surrounded by fibrous CT to support epithelium.
newly formed cyst:



irregular of variable thickness and hyperplastic with elongated rete ridges and there are areas with loss of continuity of the epithelium.


the source of this CT is from the periapical granuloma so the histopathology is the same ( immature fibrous tissue , cholesterol crystals, giant cells, CICI…etc) with high vascularity.

late (mature) cyst:-

thin, flattened regular with well organized layers, sometimes there is metaplasia to keratinized epithelium and sometimes inside the epithelium there is eosinophilic structurless materials that are called “Rushton bodies ”

* they say that Rushton bodies are released from the epithelium but it's not known and they don't know what their function is .


-increase in fibrous tissue

-decrease in vascularity

- decrease in inflammation

The reason why there is a change in the wall is due to the mature epithelium that prevents the irritation to reach the surrounding tissue so the inflammation and vascularity will decrease.

Dentigerous cyst:
- It's found around the impacted teeth.
The unerupted tooth is surrounded by dental follicle which is remnants of ameloblast that bind the crown the form of reduced enamel epithelium (REE)and are surrounded by thin CT so the enamel of unerupted teeth is not directly attached with bone, it's surrounded by this protective soft tissue.
If the follicle is absent then there is a bone formation on the enamel preventing the tooth from erupting. So the role of the follicle is protection and forming a path for the tooth to erupt.
In impacted teeth there is a separation of dental follicle forming a cystic cavity filled of fluid

*it's of unknown cause>>>developmental cyst.

* but they think that the cause might be due to the impacted tooth tries to erupt compressing on the lymphatic vessels in that area and so accumulation of fluids would occur and separates REE from the crown and forming a cyst.
* There is another theory of the aeitology of dentigerous cyst :

the proliferation of REE and the source of REE is inflammation but this is NOT TRUE because it's not an inflammatory cyst.

To differentiate it: it's attached to CEJ & covers part or all of the crown not attached to the root.

- Wide age range but on avg 2nd and 3rd decades , M>F, Max>Mand

-affects L8>U3>U8>L5 "most common impacted teeth"

-the patient will have a missing tooth

-if the diagnosis is late jaw expansion "swelling" would occur.

-it could be a chance radiographic finding (upon taking radiograph for sth else you find this cyst by chance)

-pain in the case of infection.

Well defined, corticated "white line", unilocular radiolucency either: surrounding the whole crown (central type)

surrounding part of the crown (lateral type)

it covers the crown and expanded toward the root so in the radiograph it looks like it's surrounding the whole tooth (Circumferential type v.rare)


- Uniform thin 2 - 4 layers of non- keratnized stratified squamous epithelium or low cuboidal epithelium

-it's the same as REE.

-fibrous CT wall with no inflammation.

Mucous cells "not always"-


* yellowish fluid:

Water & electrolytes-

Protein 5-7 g/dl -

Cholesterol crystals -

Eruption Cyst:
variant of Dentigerous Cyst (DC)
The tooth will try to erupt but for some reason or another it stays within the soft tissue so it's a dentigerous cyst within the gingiva\soft tissue.

It'll appear clinically

On radiograph you can't see it because it's within the soft tissue.
It'll appear mostly in children with primary molar or primary incisor or permanent molar so the complaint would be that there is an erupted tooth but the other is not and there is a bluish swelling instead.
-the swelling can spontaneously rupture or the dentist can make an incision and open it and the tooth will erupt.
Differences between eruption cyst and DC:

1) Clinically visible

2) it can undergo trauma so the content will have blood that's why it looks bluish

3) due to trauma there is inflammation in the wall.

Paradental cyst:
-buccal bifurcational cyst
Cyst occurs around a partially erupted tooth especially lower 3rd molars.
The part that is impacted is normally on distal side which is covered by operculum .
This tooth will undergo pericoronitis so this inflammation in the operculum it might cause proliferation of REE that is covering the unerupted part so histologically the same as radicular cyst but the same principle as dentigerous cyst.
The location of the swelling\ well defined radiolucency is distal or disto-buccal.
If it was buccal then it'll not appear on the radiograph.

Pathogenesis: proliferation of REE; cystic expansion of follicle

They found that those teeth have an enamel extension from the crown toward the root bifurcation. So REE is a bit deep.
Lateral periodontal cyst 1% :
Developmental cyst

Found lateral in the root

Formed from the remnants of dental lamina "Rests of Serres "

Found in50 yrs old patients in Mand premolar; Max between 2 & 3

Radiograph :

Small ~1cm unilocular radiolucency between the roots of vital roots.

Or it might appear as tear drop shape.


1-3 layers of non keratinized squamus cell epithelium. with glycogen-rich clear cells


Focal epithelial thickenings (Plaques)

*so it's thin in general but with some thick areas.

Fibrous CT tissue wall with no inflammation.

It has a variant : polycystic\multilocular:botryoid odontogenic cyst.

Gingival cyst:
Not apparent in the radiograph but clinically is coz it's found inside the gingival.

They think it's a variant from the lat periodontal cyst so it has the same histology and age.

It might get confused with gingival cyst of newborn
The newborn might have whitish swellings on the alveolar ridge they are remnants of dental lamina filled with keratin . they will appear at birth then disappear after 3 months "they will attach to the surface epithelium and rupture their lining will become part of the surface epithelium"
Sometimes newborn might have those cysts in the palate they are the same but here the epithelium comes from remnants of the palate fusion they are called Epstein’s Pearls.
Or the cyst of newborn could appear at palatal surface of alveolar ridge their source is minor salivary glands and are called Bohn’s Nodules.

Ginival cysts of adults will appear :

Firm compressible, fluid-filled swelling

Found in Max or Mand buccal gingival

Premolar; canine; incisor region "more ant located than the other cysts"


Normally it doesn't appear but if it was very large and compressing the underlying tissues leading to resorption of bone so it will appear as a radiolucent area in the place of the cyst.

Odontogenic keratocyst:
It's of a clinical importance it has a high recurrent level.

Orgin of dental lamina.

Wide age range "2nd ,3rd decade mostly"

Found in Mandible, 3rd molar and ramus area

Its expansion in antero-post direction "within the bone without apparent expansion so it'll be diagnosed late "
Symptomless until well advanced
Radiograph: *

Well defined radiolucency with scalloped margins

Multilocular ,polycystic or it could be unilocular
Might occur with unerupted tooth

This case might get confused with dentigerous cyst especially if it was unilocular but what actually happened is that this keratocyst pushed the 3rd molar toward ramus .

The cyst may displace the roots and will not do an apparent root resorption.
Usually single lesion

But it might be multiple either at the same time discovered or each year he discovers a new lesion.

If multiple we have to think Nevoid Basal Cell Carcinoma Syndrome:
Autosomal dominant -

Also called Basal Cell Naevus Syndrome and Gorlin-Goltz Syndrome


-High recurrence rate (whenever you remove it it'll reappear in the same place"

-Those ppl will have multiple basal cell carcinomas that will appear on the skin
This BCC will appear at areas that are mostly exposed to the sun or it could appear on other areas.
-Characteristic faces: ballooning of the skull "temporal,frontal areas" ,wide distance between the eyes hypertelorism
- Skeletal abnormalities

- Increased susceptibility to Tumors: ovarian fibroma, medulloblastoma

-Those ppl might have an extra cervical rib or bifid ribs.

Calcification of falx cerebri-

6-10 layers of stratified squamus epithelium.


Epithjelium layers:

1)Palisaded basal cell layer of columnar epith mostly or cuboidal epith of reversed polarity ;nucleus is away from basement membrane.

2)Stratum spinosum

3) Thin eosinophilic layer on the surface " Parakeratinized epithelium"

No rete ridges so Flat junction
High mitotic activity of basal & parabasal layers and a finger like projections through out the cancellous bone that's why some ppl may classify it as benign odontogenic keratinized tumor.
This High mitotic activity helps it in expansion.
Weak attachment of epithelium to wall ….this helps in increasing recurrence rate.

Thin fibrous wall with decrease tensile & rupture strength .so it'll rupture easily during surgery but because it's thin it might rupture and stay in the cavity.


Thick gray white cheesy material made of keratin-

Serum protein is less than 4 gm/dl-

-Inside the wall there is small cystic lesions "daughter cysts" or "Satellite cysts" found in 7-30% and those will increase recurrence rate.

-In some of the cases especially those with syndromes there is epithelial budding inside the CT this will increase recurrence rate.
-There is no CICI unless there is trauma or infection so no inflammation in the wall

Expansion doesn't depend a lot on hydrostatic pressure but on:-

●Epithelial proliferation

● Bone resorption

●Mural squames the accomilation of connated cells in a finger like

projection that will form a pressure leading into expansion.

Good luck

Lara lahham

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