The document discusses cysts of the jaws and oral region. It defines a cyst as a fluid or semi-fluid filled cavity lined by epithelium. Cysts are classified as true cysts, which are epithelial lined, or false/pseudocysts without an epithelial lining. Odontogenic cysts are associated with teeth and develop from epithelial cell rests involved in tooth development. Non-odontogenic cysts occur in areas unrelated to teeth. Theories of cyst pathogenesis include proliferation of dormant epithelial cells due to growth factors, central cell death creating a cavity, and growth through osmotic pressure differences.

1. 1
Introduction
Cysts of the Jaws and Oral Region

2. 2
Aims;
• The student should have
knowledge of cysts which affect
the jaws and their etiology and
pathogenesis.

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Objectives;
The student should be able to;
• Classify cysts of the jaws.
• Discuss in detail their etiology and pathogenesis.
• Know the steps that lead to a jaw cyst diagnosis and
to identify these lesions in their earliest stages.

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 A cyst is a pathological fluid
/semifluid filled material enclosed
cavity (Space) within bone or in soft
tissues, generally formed by a
connective tissue wall and lined
wholly or in part by epithelium
(mostly non-keratinized).

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Cyst lumen

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The cyst's lumen usually contains fluids or semisolid material such as keratin, cellular debris, mucus or
even gaseous contents - which is not created by accumulation of pus.
Cyst lumen
Non-keratinized squamous
epithelial cyst lining

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Connective tissue wall that forms the cyst is composed of blood vessels and fibroblasts, and
various types of lining epithelium which may be stratified squamous nonkeratinizing
(Keratinized) epithelium, pseudostratified, columnar or cuboidal.

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 The cyst wall may or may not be
infiltrated by chronic inflammatory cells
(Inflamed).
 If inflamed can change the morphology
of the cyst with obscuring their
identifying features.
 In rare instances intense inflammation
can destroy the entire epithelial lining
allowing the cyst to resolve completely
without any treatment.

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 Some cyst-like lesions, without
epithelial lining, also can be seen in
the maxillo-facial regions.
 Epithelial lined spaces are sometimes
known as “True cysts" while those
not lined with epithelium are “False
cysts or Pseudocyst".

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Where does the
Epithelium lining the
Jaw Cysts come
from?????

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Two Sources:
“True Cysts”
1. Epithelium left behind from
developing teeth (Odontogenesis).
2. Epithelium left behind from face
and mouth development.

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Typical Features
of Jaw Cysts

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1. Cysts are common lesions and cause of swellings of
the jaws.
2. More common in jaws than in any other bone.
3. Clinically important because they are destructive.
4. Mostly behave similarly—they grow slowly and
expansively (Displacing rather than resorbing the
teeth).
5. Usually painless when small but can cause
significant bone loss before presenting clinically.
6. Produce significant signs and symptoms
particularly when they become large or infected.

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7. Pain due to secondary infection.
8. Noticeable swelling: initally smooth bony
hard lump with normal overlying mucosa,
but as bone thins through resorption and
extends into soft tissues, cyst may show
through as BLUISH FLUCTUANT
SWELLING (COMPRESSIBLE).
9. If a cyst becomes very large it may expand
the jaw's outer limits making intraoral
detection possible.
10. Rarely large enough to cause pathological
fracture.

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11. Frequently a chance radiographic finding for
most of the oral-facial cysts as they are
located within the jaws.
12. Being composed of soft tissues, jaw cysts
appear as sharply-defined radiolucencies
with smooth radioopaque borders.
13. These single well-demarcated radiolucencies
are "unilocular" lesions.
14. Most unilocular lesions are small, measuring
less than one centimeter in diameter.

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15. If, however, a cyst is undetected for some
years, it may increase up to ten-fold (> 10
cm.).
16. These large cysts may be unilocular;
however, some may be partitioned --
"multilocular radiolucencies."
17. Cysts arising in soft tissues are more likely to
be discovered on intraoral examination
where they produce a surface swelling.
18. Small jaw cysts are removed easily & rarely
recur; removal of large ones is more difficult,
may recur.

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19. They differ mainly in relationship to teeth
and radiographic features;
 But it is often difficult to distinguish cystic
appearing mandible/maxillary lesions from
one another with radiography.
20. Careful consideration of the patient history
and the location of the lesion within the jaws,
its borders, its internal architecture, and its
effects on adjacent structures generally
makes it possible to narrow the differential
diagnosis.

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Classification;

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 Most cysts of the oral and facial
regions are located within the
jaws, they are either Intraosseous
or Intrabony lesions.
 Given the sources of epithelium;

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 Some jaw cysts will be associated
with teeth found in tooth-bearing
areas; these are Odontogenic
Cysts, develop during or after the
formation of teeth.
 The others will be found in places
where oral-facial processes fused;
these are Fissural cysts (Non-
odontogenic).

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A. Odontogenic Cysts based on
Typical Clinical & Radiographic Features;
1. Inflammatory
2. Developmental

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Odontogenic; Inflammatory;
Result of inflammation;
1. Radicular (Periodontal) cyst
2. Residual cyst
3. Paradental (Inflammatory buccal, or
Mandibular infected buccal) cyst

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Odontogenic; Developmental;
Unknown origin but are not the
result of an inflammatory reaction;
1. Dentigerous cyst
2. Eruption cyst
3. Odontogenic keratocyst
4. Gingival cyst of the new born
5. Gingival cyst of the adult
6. Lateral periodontal cyst
7. Calcifying odontogenic cyst
8. Glandular odontogenic cyst.

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B. Histogenetic Classification;
“Based on Tissue of Origin”

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Derived from Rests of Malassez;
 Comprised of small groups of epithelial
cells found close to the root surface and
are remnants of Hertwig’s epithelial root
sheath.
1. Periapical cyst (Radicular)
2. Residual cyst

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Remnants of the disintegrated root sheath called epithelial rests can remain for long periods of
time following eruption of the tooth. The first dentin that is formed is called mantle dentin,
while the remaining dentin is called circumpulpal dentin. There is also a small layer interposed
between these two dentin layers of less mineralized dentin called globular dentin.

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Derived from Reduced Enamel Epithelium;
 The reduced dental/Enamel epithelium
covers the crown of the tooth until it erupts.
 The histology of the REE varies from the
occlusal surface towards the cervical region.
1. Dentigerous cyst (Eruption cyst)
2. Paradental cyst ???

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Following the formation of the crown , the enamel organ collapses to form the reduced enamel
epithelium which covers the tooth through eruption. The reduced enamel epithelium consists
of the mature/protective ameloblasts and remnants of the outer layers of the enamel organ.
Numerous capillaries, which had formed to supply oxygen and nutrients to the ameloblasts
following dentin formation, surround the reduced enamel epithelium.

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Derived from Dental Lamina (Rests of Serres);
1. Odontogenic Keratocyst
2. Lateral periodontal cyst
3. Glandular odontogenic cyst.
4. Gingival cyst of the new born
5. Gingival cyst of the adult.

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During the fifth week of embryonic development, the oral epithelium thickens along the future
dental arches to form the dental lamina. The dental lamina appears as an epithelial thickening
of the oral epithelium adjacent to a condensation of ectomesenchyme.

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Unclassified;
1. Paradental cyst → The cystic epithelium
may be derived from the cell rests of
Serres, the cell rests of Malassez, apical
migration of cells of the dental lamina
or reduced enamel epithelium.
2. Calcifying odontogenic cyst….??

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Non- Odontogenic;
1. Fissure
2. Bone
3. Soft tissue

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A. Fissural;
1. Nasopalatine
2. Nasolabial
3. Median palatine
4. Globulomaxillary

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B. Bone;
1. Simple bone cyst;
a. Solitary,
b. Haemorrhagic,
c. Traumatic
2. Aneurysmal bone cyst.

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C. Soft Tissue;
1. Mucous Extravasation and Retention cyst.
2. Dermoid/Epidermoid
3. Lymphoepithelial (Branchial)
4. Thyroglassal duct cyst

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Incidence of Jaw Cysts;

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Odontogenic; → 90%
1. Radicular  65 – 70 %
2. Dentigerous  15 – 20 %
3. OKC  5 – 10 %
4. Paradental  3 – 5 %
5. Gingival  < 1 %
6. Lateral periodontal  < 1 %

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Non- Odontogenic;  10%
1. Nasopalatine  5 – 10 %
2. Nasolabial  0.5 %
3. Others (Combined)  5 %

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Etiology & Pathogenesis;

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 The etiology and pathogenesis of jaw
cysts simply is not known.
 There is very little experimental
evidence that sheds light on their
origin.
 This lack of hard evidence doesn't
prevent speculation,
however………..

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 There are two long-standing theories
regarding the formation of the cyst
cavity;
1. The nutritional deficiency theory.
2. The abscess theory → postulates that
the proliferating epithelium surrounds
an abscess formed by tissue necrosis
and lysis, because of the innate nature
of epithelial cells to cover exposed
connective tissue surfaces.

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Nutritional Deficiency
Theory

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1. Jaw cysts arise from epithelium (Main
source) associated with formation of the
teeth, oral cavity, and face.
2. If this epithelium is somehow
stimulated (Possible links to genetic
defects in a tumor suppressor gene)
by inflammation, for example, they
proliferate forming an ever-larger mass.

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The genesis of true cysts
has been discussed as
occurring in three
stages;

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During the first phase;
1. Proliferation [hyperplasia] of dormant
epithelial cells, probably under the influence
of growth factors (Epidermal growth factor
& Transforming growth factor) that are
released by various cells residing in the
lesion.
2. As a result the cells in the center of the mass,
being at some distance from their blood
supply, die (their source of nutrition is being
removed).

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 During the second phase;
a) Central cell death (necrosis and
degeneration) produces an epithelium-
lined central cavity surrounded by
viable epithelial cells -- a true cyst is
formed.

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 During the third phase;
a. The cyst grows, but the exact
mechanism has not yet been
adequately clarified……..??

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59

 In the early and intermediate stages
In the early and intermediate stages
of cystic growth, osmotic pressure
of cystic growth, osmotic pressure
differences play an important role;
differences play an important role;
however, for very large cysts, this
however, for very large cysts, this
role becomes negligible and cell birth
role becomes negligible and cell birth
in the lining dominates growth.
in the lining dominates growth.

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Suggested Mechanisms
for continued cyst
growth and
accompanying bone
resorption.

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1. Hydrostatic mechanisms
2. Bone resorption.

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Hydrostatic Mechanisms

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1. All cysts expand in balloon like fashion
indicating that Internal pressure plays a
major role in their growth.
1. The degradation of the central cells in the
cyst results in an increased osmotic pressure
in comparison to the osmotic pressure of the
surrounding stroma.
2. This gradient draws water into the cavity (to
balance the osmotic pressure), resulting in an
increase in hydrostatic pressure inside the
cyst in comparison to the stroma.

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4. The volume expansion stretches the epithelial
layer inducing division of the epithelial cells in
order to maintain the intact epithelial lining.
5. The osmotic pressure difference is therefore
maintained through the constant shedding of cells
into the lumen.
6. The surrounding stroma reacts by producing
varying amounts of collagen fibers and
reorganizing them into the so-called cystic capsule.

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Bone Resorption

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Pro-inflammatory Cytokines;
 Cyst expansion depends upon osteoclastic
resorption of bone
 Osteoclasts recruited by the mediators that
stimulate bone resorption;
 Mediators generated locally by macrophages,
lymphocytes, epithelial cells and fibroblasts
1. IL-1/ IL-6
2. PGE2 (Fibroblasts)

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62

 IL
IL-
-1 & IL
1 & IL-
-6 stimulate epithelial proliferation.
6 stimulate epithelial proliferation.
interleukin 1 may play an important role in
interleukin 1 may play an important role in
cyst expansion by its direct effects on
cyst expansion by its direct effects on
fibroblast proliferation and bone resorption
fibroblast proliferation and bone resorption
and by stimulating prostaglandin synthesis in
and by stimulating prostaglandin synthesis in
stromal fibroblasts of the cyst capsule.
stromal fibroblasts of the cyst capsule.

 PEG2 a potent stimulator of bone resorption
PEG2 a potent stimulator of bone resorption
and its presence in the cyst walls have been
and its presence in the cyst walls have been
demonstrated to have considerable bone
demonstrated to have considerable bone
resorptive activity which facilitates
resorptive activity which facilitates
intraosseous cyst expansion.
intraosseous cyst expansion.

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
 Cyst expansion and bone resorption occur
Cyst expansion and bone resorption occur
together as the lesion enlarges
together as the lesion enlarges

 It is not clear whether cyst growth
It is not clear whether cyst growth
promotes the bone resorption or the bone
promotes the bone resorption or the bone
resorption allows the cyst growth
resorption allows the cyst growth

 Or indeed they are coincidental events
Or indeed they are coincidental events
unrelated to each other
unrelated to each other

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3
Some cysts can become large and affect nearby healthy teeth. A cyst will not go away by itself. If it starts to
cause problems, it is usually best to treat the cyst before symptoms get worse.
3
Some cysts can become large and affect nearby healthy teeth. A cyst will not go away by itself. If it starts to
cause problems, it is usually best to treat the cyst before symptoms get worse.