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Introduction Cysts of the Jaws and Oral Region

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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 A cyst is a pathological fluid /semifluid filled material enclosed /semifluid filled material enclosed cavity (Space) within bone or in soft cavity (Space) within bone or in soft tissues, generally formed by a tissues, generally formed by a connective tissue wall and lined connective tissue wall and lined wholly or in part by epithelium wholly or in part by epithelium (mostly non-keratinized).(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 squamousepithelial 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 The cyst wall may or may not be infiltrated by chronic inflammatory cells infiltrated by chronic inflammatory cells (Inflamed).(Inflamed).

If inflamed can change the morphology If inflamed can change the morphology of the cyst with obscuring their of the cyst with obscuring their identifying features.identifying features.

In rare instances intense inflammation In rare instances intense inflammation can destroy the entire epithelial lining can destroy the entire epithelial lining allowing the cyst to resolve completely allowing the cyst to resolve completely without any treatment.without any treatment.

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Some cyst-like lesions, without Some cyst-like lesions, without epithelial lining, also can be seen in epithelial lining, also can be seen in the maxillo-facial regions. the maxillo-facial regions.

Epithelial lined spaces are sometimes Epithelial lined spaces are sometimes known as “True cysts" while those known as “True cysts" while those not lined with epithelium are “False not lined with epithelium are “False cysts or Pseudocyst". cysts or Pseudocyst".

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Where does the Where does the Epithelium lining the Epithelium lining the

Jaw Cysts come Jaw Cysts come from?????from?????

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Two Sources:Two Sources:

““True Cysts”True Cysts”

1.1. Epithelium left behind from Epithelium left behind from developing teeth (Odontogenesis). developing teeth (Odontogenesis).

2.2. Epithelium left behind from face Epithelium left behind from face and mouth development.and mouth development.

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Typical Features

of Jaw Cysts

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1.1. Cysts are common lesions and cause of swellings of Cysts are common lesions and cause of swellings of the jaws.the jaws.

2.2. More common in jaws than in any other bone. More common in jaws than in any other bone.

3.3. Clinically important because they are destructive.Clinically important because they are destructive.

4.4. Mostly behave similarly—they grow slowly and Mostly behave similarly—they grow slowly and expansively (Displacing rather than resorbing the expansively (Displacing rather than resorbing the teeth). teeth).

5.5. Usually painless when small but can cause Usually painless when small but can cause significant bone loss before presenting clinically. significant bone loss before presenting clinically.

6.6. Produce significant signs and symptoms Produce significant signs and symptoms particularly when they become large or infected.particularly when they become large or infected.

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7.7. Pain due to secondary infection.Pain due to secondary infection.

8.8. Noticeable swelling: initally smooth bony Noticeable swelling: initally smooth bony hard lump with normal overlying mucosa, hard lump with normal overlying mucosa, but as bone thins through resorption and but as bone thins through resorption and extends into soft tissues, cyst may show extends into soft tissues, cyst may show through as through as BLUISH FLUCTUANT BLUISH FLUCTUANT SWELLING (COMPRESSIBLE).SWELLING (COMPRESSIBLE).

9.9. If a cyst becomes very large it may expand If a cyst becomes very large it may expand the jaw's outer limits making intraoral the jaw's outer limits making intraoral detection possible.detection possible.

10.10. Rarely large enough to cause pathological Rarely large enough to cause pathological fracture.fracture.

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11.11. Frequently a chance radiographic finding for Frequently a chance radiographic finding for most of the oral-facial cysts as they are most of the oral-facial cysts as they are located within the jaws.located within the jaws.

12.12. Being composed of soft tissues, jaw cysts Being composed of soft tissues, jaw cysts appear as sharply-defined radiolucencies appear as sharply-defined radiolucencies with smooth radioopaque borders. with smooth radioopaque borders.

13.13. These single well-demarcated radiolucencies These single well-demarcated radiolucencies are "unilocular" lesions.are "unilocular" lesions.

14.14. Most unilocular lesions are small, measuring Most unilocular lesions are small, measuring less than one centimeter in diameter. less than one centimeter in diameter.

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15.15. If, however, a cyst is undetected for some If, however, a cyst is undetected for some years, it may increase up to ten-fold (> 10 years, it may increase up to ten-fold (> 10 cm.). cm.).

16.16. These large cysts may be unilocular; These large cysts may be unilocular; however, some may be partitioned -- however, some may be partitioned -- "multilocular radiolucencies.""multilocular radiolucencies."

17.17. Cysts arising in soft tissues are more likely to Cysts arising in soft tissues are more likely to be discovered on intraoral examination where be discovered on intraoral examination where they produce a surface swelling.they produce a surface swelling.

18.18. Small jaw cysts are removed easily & rarely Small jaw cysts are removed easily & rarely recur; removal of large ones is more difficult, recur; removal of large ones is more difficult, may recur.may recur.

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19.19. They differ mainly in relationship to teeth They differ mainly in relationship to teeth and radiographic features; and radiographic features;

But it is often difficult to distinguish cystic But it is often difficult to distinguish cystic appearing mandible/maxillary lesions from appearing mandible/maxillary lesions from one another with radiography. one another with radiography.

20.20. Careful consideration of the patient history Careful consideration of the patient history and the location of the lesion within the jaws, and the location of the lesion within the jaws, its borders, its internal architecture, and its its borders, its internal architecture, and its effects on adjacent structures generally effects on adjacent structures generally makes it possible to narrow the differential makes it possible to narrow the differential diagnosis. diagnosis.

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Classification;

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Most cysts of the oral and facialMost cysts of the oral and facial

regions are located within the regions are located within the jaws, they are either Intraosseous jaws, they are either Intraosseous or Intrabony lesions. or Intrabony lesions.

Given the sources of epithelium;Given the sources of epithelium;

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Some jaw cysts will be associated Some jaw cysts will be associated with teeth found in tooth-bearing with teeth found in tooth-bearing areas; these are areas; these are Odontogenic Cysts, Odontogenic Cysts, develop during or after the develop during or after the formation of teeth.formation of teeth.

The others will be found in places The others will be found in places where oral-facial processes fused; where oral-facial processes fused; these are these are Fissural cysts (Non-Fissural cysts (Non-odontogenic).odontogenic).

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A. Odontogenic Cysts based on Typical Clinical & Radiographic Features;

1. Inflammatory

2. Developmental

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Odontogenic; Inflammatory;Odontogenic; Inflammatory;

Result of inflammation;Result of inflammation;

1.1. Radicular (Periodontal) cystRadicular (Periodontal) cyst

2.2. Residual cystResidual cyst

3.3. Paradental (Inflammatory buccal, or Paradental (Inflammatory buccal, or Mandibular infected buccal) cystMandibular infected buccal) cyst

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Odontogenic; Developmental;Odontogenic; Developmental;

Unknown origin but are not theUnknown origin but are not theresult of an inflammatory reaction;result of an inflammatory reaction;

1.1. Dentigerous cystDentigerous cyst2.2. Eruption cystEruption cyst3.3. Odontogenic keratocystOdontogenic keratocyst4.4. Gingival cyst of the new bornGingival cyst of the new born5.5. Gingival cyst of the adultGingival cyst of the adult6.6. Lateral periodontal cystLateral periodontal cyst7.7. Calcifying odontogenic cystCalcifying odontogenic cyst8.8. Glandular odontogenic cyst.Glandular odontogenic cyst.

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B. Histogenetic Classification;

“Based on Tissue of Origin”

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Derived from Rests of Malassez;Derived from Rests of Malassez;

Comprised of small groups of epithelial Comprised of small groups of epithelial cells found close to the root surface and cells found close to the root surface and are remnants of Hertwig’s epithelial are remnants of Hertwig’s epithelial root sheath.root sheath.

1.1. Periapical cyst (Radicular)Periapical cyst (Radicular)

2.2. Residual cystResidual 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;Derived from Reduced Enamel Epithelium;

The reduced dental/Enamel epithelium The reduced dental/Enamel epithelium covers the crown of the tooth until it erupts. covers the crown of the tooth until it erupts.

The histology of the REE varies from the The histology of the REE varies from the occlusal surface towards the cervical region.occlusal surface towards the cervical region.

1.1. Dentigerous cyst (Eruption cyst)Dentigerous cyst (Eruption cyst)

2.2. Paradental cyst ???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 Derived from Dental Lamina (Rests of Serres);(Rests of Serres);

1.1. Odontogenic KeratocystOdontogenic Keratocyst

2.2. Lateral periodontal cystLateral periodontal cyst

3.3. Glandular odontogenic cyst.Glandular odontogenic cyst.

4.4. Gingival cyst of the new bornGingival cyst of the new born

5.5. Gingival cyst of the adult.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;Unclassified;

1.1. Paradental cystParadental cyst → → The cystic epithelium The cystic epithelium may be derived from the cell rests of may be derived from the cell rests of Serres, the cell rests of Malassez, apical Serres, the cell rests of Malassez, apical migration of cells of the dental lamina migration of cells of the dental lamina or reduced enamel epithelium. or reduced enamel epithelium.

2.2. Calcifying odontogenic cyst….??Calcifying odontogenic cyst….??

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Non- Odontogenic;Non- Odontogenic;

1.1. Fissure Fissure

2.2. BoneBone

3.3. Soft tissue Soft tissue

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A. Fissural;A. Fissural;

1.1. Nasopalatine Nasopalatine

2.2. Nasolabial Nasolabial

3.3. Median palatineMedian palatine

4.4. Globulomaxillary Globulomaxillary

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B. Bone;B. Bone;

1.1. Simple bone cyst; Simple bone cyst;

a.a. Solitary,Solitary,

b.b. Haemorrhagic,Haemorrhagic,

c.c. Traumatic Traumatic

2. Aneurysmal bone cyst.2. Aneurysmal bone cyst.

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C. Soft Tissue;C. Soft Tissue;

1.1. Mucous Extravasation and Retention cyst.Mucous Extravasation and Retention cyst.

2.2. Dermoid/EpidermoidDermoid/Epidermoid

3.3. Lymphoepithelial (Branchial)Lymphoepithelial (Branchial)

4.4. Thyroglassal duct cystThyroglassal duct cyst

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Incidence of Jaw Cysts;

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Odontogenic; Odontogenic; → 90%→ 90%

1.1. Radicular Radicular 65 – 70 % 65 – 70 %

2.2. Dentigerous Dentigerous 15 – 20 % 15 – 20 %

3.3. OKC OKC 5 – 10 % 5 – 10 %

4.4. Paradental Paradental 3 – 5 % 3 – 5 %

5.5. Gingival Gingival < 1 < 1 %%

6.6. Lateral periodontal Lateral periodontal < 1 < 1 %%

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Non- Odontogenic; Non- Odontogenic; 10% 10%

1.1. NasopalatineNasopalatine 5 – 10 % 5 – 10 %

2.2. Nasolabial Nasolabial 0.5 % 0.5 %

3.3. Others (Combined) Others (Combined) 5 % 5 %

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Etiology & Pathogenesis;

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The etiology and pathogenesis of jaw The etiology and pathogenesis of jaw cysts simply is not known. cysts simply is not known.

There is very little experimental There is very little experimental evidence that sheds light on their evidence that sheds light on their origin. origin.

This lack of hard evidence doesn't This lack of hard evidence doesn't prevent speculation, prevent speculation, however………..however………..

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There are two long-standing theories There are two long-standing theories regarding the formation of the cyst regarding the formation of the cyst cavity;cavity;

1.1. The nutritional deficiency theory.The nutritional deficiency theory.

2.2. The abscess theoryThe abscess theory → → postulates that postulates that the proliferating epithelium surrounds the proliferating epithelium surrounds an abscess formed by tissue necrosis an abscess formed by tissue necrosis and lysis, because of the innate nature of and lysis, because of the innate nature of epithelial cells to cover exposed epithelial cells to cover exposed connective tissue surfaces.connective tissue surfaces.

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Nutritional Deficiency Theory

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1.1. Jaw cysts arise from epithelium (Main Jaw cysts arise from epithelium (Main source) associated with formation of the source) associated with formation of the teeth, oral cavity, and face. teeth, oral cavity, and face.

2.2. If this epithelium is somehow If this epithelium is somehow stimulated stimulated (Possible links to genetic (Possible links to genetic defects in a tumor suppressor gene)defects in a tumor suppressor gene) by inflammation, for example, they by inflammation, for example, they proliferate forming an ever-larger mass.proliferate forming an ever-larger mass.

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The genesis of true cysts The genesis of true cysts has been discussed as has been discussed as

occurring in three occurring in three stages;stages;

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During the first phase;During the first phase;

1.1. Proliferation Proliferation [[hyperplasiahyperplasia] ] of dormant of dormant epithelial cells, probably under the influence epithelial cells, probably under the influence of growth factors of growth factors (Epidermal growth factor (Epidermal growth factor & Transforming growth factor)& Transforming growth factor) that are that are released by various cells residing in the released by various cells residing in the lesion.lesion.

2.2. As a result the cells in the center of the mass, As a result the cells in the center of the mass, being at some distance from their blood being at some distance from their blood supply, die (their source of nutrition is being supply, die (their source of nutrition is being removed). removed).

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During the second phase;During the second phase;

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

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During the third phase;During the third phase;

a.a. The cyst grows, but the exact The cyst grows, but the exact mechanism has not yet been mechanism has not yet been adequately clarified……..??adequately clarified……..??

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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 Suggested Mechanisms for continued cyst for continued cyst

growth and growth and accompanying bone accompanying bone

resorption.resorption.

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1.1. Hydrostatic mechanismsHydrostatic mechanisms

2.2. Bone resorption.Bone resorption.

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Hydrostatic Mechanisms

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1.1. All cysts expand in balloon like fashion All cysts expand in balloon like fashion indicating that Internal pressure plays a indicating that Internal pressure plays a major role in their growth.major role in their growth.

1.1. The degradation of the central cells in the The degradation of the central cells in the cyst results in an increased osmotic pressure cyst results in an increased osmotic pressure in comparison to the osmotic pressure of the in comparison to the osmotic pressure of the surrounding stroma. surrounding stroma.

2.2. This gradient draws water into the cavity (to This gradient draws water into the cavity (to balance the osmotic pressure), resulting in an balance the osmotic pressure), resulting in an increase in hydrostatic pressure inside the increase in hydrostatic pressure inside the cyst in comparison to the stroma. cyst in comparison to the stroma.

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4.4. The volume expansion stretches the epithelialThe volume expansion stretches the epithelial

layer inducing division of the epithelial cells in layer inducing division of the epithelial cells in order to maintain the intact epithelial lining. order to maintain the intact epithelial lining.

5.5. The osmotic pressure difference is thereforeThe osmotic pressure difference is therefore

maintained through the constant shedding of cells maintained through the constant shedding of cells into the lumen. into the lumen.

6.6. The surrounding stroma reacts by producingThe surrounding stroma reacts by producing

varying amounts of collagen fibers andvarying amounts of collagen fibers and

reorganizing them into the so-called cystic capsule.reorganizing them into the so-called cystic capsule.

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Bone Resorption

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Pro-inflammatory Cytokines;Pro-inflammatory Cytokines;

Cyst expansion depends upon osteoclastic Cyst expansion depends upon osteoclastic resorption of boneresorption of bone

Osteoclasts recruited by the mediators that Osteoclasts recruited by the mediators that stimulate bone resorption;stimulate bone resorption;

Mediators generated locally by macrophages, Mediators generated locally by macrophages, lymphocytes, epithelial cells and fibroblastslymphocytes, epithelial cells and fibroblasts

1.1. IL-1/ IL-6IL-1/ IL-6

2.2. PGE2 (Fibroblasts)PGE2 (Fibroblasts)

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ILIL--1 & IL1 & 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 enlargestogether 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 growthresorption allows the cyst growth

Or indeed they are coincidental events Or indeed they are coincidental events unrelated to each otherunrelated to each other

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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.

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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.