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7/22/2019 radicularcyst-110925110030-phpapp02

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Radicular Cyst

Inflammatory Odontogenic Cyst

Synonyms

Periapical cyst, apical periodontal cyst, or dental cystDone By:

Mahmoud Amir Alagha


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Definition

A radicular cyst is a cyst that most likely results

when rests of epithelial cells (Malassez) in the

periodontal ligament are stimulated to

proliferate and undergo cystic degeneration by

inflammatory products from a non-vital tooth.


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Clinical Feature

Most common type of cyst of the jaws.

Rarely seen before the age of 10.

Most frequent between 20 and 60 years.

More common in males than females 3 to 2.

Maxilla affected more than 3 times the

mandible.


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Clinical Feature

Cause slowly progressive painless swelling.

No symptoms until they become large enough

or infected.

If infection enters, the swelling becomes

painful and may rapidly expand, partly due to

inflammatory edema.


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Clinical Feature

The swelling is rounded and at the first hard

Later, when the bone has been reduced to

egg-shell thickness, a crackling sensation

(crepitant) may be felt on pressure

Finally, part of the wall is resorbed entirely

away, leaving soft fluctuant (rubbery and

fluctuant) swelling, bluish in color, beneath

the mucous membrane.


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Clinical Feature

The dead tooth from which the cyst has

originated is present, and its relationship to the

cyst will be apparent in a radiograph


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7

Radicular cyst / pathogenesis

a Initiation b Cyst formation c Cyst enlargement


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Pathogenesis & Pathology

The main factors in the pathogenesis of cyst

formation are:

Proliferation of epithelial lining and fibrous

capsule

Hydrostatic pressure of cyst fluid

Resorption of Surrounding bone


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Pathogenesis of Cyst Formation

Epithelial Proliferation

Infection from the pulp chamber inducesinflammation and proliferation of the epithelial

rest of Malassez.

If infection can be eliminated from the root

canal, small radicular cysts (up to 1 or 2 cm

diameter) may regress without surgery.


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Hydrostatic pressure

Radicular cyst expand in balloon-like fashion,wherever the local anatomy permits, indicates

that internal pressure is a factor in their

growth.

The hydrostatic pressure within cysts is about

70 cm of water and therefore higher than the

capillary blood pressure.

h f


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Cystic fluid is largely inflammatory exudateand contains high concentration of proteins,

some of high molecular weight which can

exert osmotic pressure.

Consistent with the inflammation usually

present in cyst walls, cyst fluid may contain

cholesterol, breakdown products of bloodcells, exfoliated epithelial cells, and fibrin.

h i f i


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The cyst wall does not seem to act entirely asa simple semi-permeable membrane. Low-

molecular-weight proteins are present in

similar concentrations to those in the plasma

but there are smaller amounts of high-

molecular-weight proteins.

P h i f C F i


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The capillaries in the cyst wall are morepermeable as a result of inflammation and

contribute varying amounts of immuno-

globulins and other proteins.

The net effect is that pressure is created by

osmotic tension within the cyst cavity.

P h i f C F i


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Bone-Resorbing Factors

Experimentally, cyst tissues in culture release bone-resorbing factors. These are predominantly prostaglandins E2 and E3.

Different types of cysts and tumors may producedifferent quantities of prostaglandins but if so, it isunclear whether this affects the mode of growth ofthe cyst.

Collagenases are present in the walls of keratocysts,

but their contribution to cyst growth is also unclear.


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Pathology

All stages can be seen from a periapicalgranuloma containing a few strands ofproliferation epithelium derived from the

epithelial rest of Malassez, to an enlarging cystwith a hyperplastic epithelial lining and denseinflammatory infiltrate.

Epithelial proliferation results from irritantproducts leaking from an infected root canalto cause periapical inflammation.


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Pathology

The epithelial lining

The epithelial lining consists of stratifiedsquamous epithelium of variable thickness.

It lacks a well-defined basal cell layer and issometimes incomplete.

Early, active epithelial proliferation is associatedwith obvious chronic inflammation and may thenbe thick, irregular and hyperplastic or appear net-like, forming rings and arcades.

Hyaline bodies may be seen in the epithelium andmucous cells are often present as a result ofmetaplasia.


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Pathology

The epithelial lining

Long-standing cysts typically have a thin

flattened epithelial lining, a thick fibrous wall

and minimal inflammatory infiltrate

P th l


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Pathology

The cyst capsule and wall The capsule consists of collagenous fibrous

connective tissue.

During active growth the capsule is vascular

and infiltrated by chronic inflammatory cells

adjacent to the proliferating epithelium.

Plasma cells are often prominent or

predominant, and are a response to antigens

leaking through the tooth apex

P th l


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Pathology

The cyst capsule and wall In a boney wall there is osteoclastic activity and

resorption.

Beyond the zone of resorption these is usuallyactive bone formation.

The net effect is that a cyst expands but retains abony wall, even after it has extended beyond thenormal bony contours.

This bony wall nevertheless becomesprogressively thinner since repair is slower thanresorption, until it forms a mere eggshell, thenultimately disappears altogether.

P th l


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Pathology

The cyst capsule and wall The cyst then starts to distend the soft tissues

and appear as a soft bluish swelling.

P th l


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Pathology

Clefts

Clefts. Within the cyst capsule there are oftenareas split up by fine needle-shaped clefts.

These are left by cholesterol dissolved-out duringpreparation for sectioning.

The cholesterol is derived from breakdown ofblood cells.

Small clefts are enclosed by foreign body giantcells, and extravasated red cells and bloodpigment are associated.

Clefts may also be seen extending into the cystcontents but are formed in the cyst wall.

P th l


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Pathology

Cyst Fluid Cyst Fluid. The fluid is usually watery and

opalescent but sometimes more viscid andyellowish, and sometimes shimmers with

cholesterol crystals. A smear of this fluid may show typical notched

cholesterol crystals microscopically.

Histologically, the protein content of the fluid is

usually seen as amorphous eosinophilic material,often containing broken-down leucocytes andcells distended with fat globules.


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In most cases the epicenter of a radicular cyst

is located approximately at the apex of a

nonvital tooth

Occasionally it appears on the mesial or distal

surface of a tooth root, at the opening of an

accessory canal or infrequently in a deep

periodontal pocket

Radiographic Features

Location


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Note that the epicenter is apical to the lateral incisor

and the presence of a peripheral cortex (arrows).


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R di hi F


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Location

Most radicular cysts (60%) are found in theMaxilla, especially around incisors andcanines.

Because of the distal inclination of the root,cysts that arise from the maxillary lateralincisor may invaginate the antrum.

Radicular cysts may also form in relation to anonvital deciduous molar and be positionedbuccal to the developing bicuspid.

R di hi F


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Periphery and shape

The periphery usually has a well-definedcortical border

A periapical film of a radicular cyst

reveals a lesion with a well-defined

cortical boundary (arrows).Note that the presence of the inferior

cortex of the mandible has influenced

the circular shape of the cyst.



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If the cyst becomes secondarily infected, the

inflammatory reaction of the surrounding bone may

result in loss of this cortex.

or alteration of the cortex into a more scleroticborder.

Note the lack of a well-defined peripheral

cortex as this cyst was secondarily infected

and that the root canal of the lateral incisor is

abnormally wide as it is visible at the root

apex.


Periphery and shape

R di hi F t


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Periphery and shape

The outline of a radicular cyst usually is curvedor circular unless it is influenced by

surrounding structures such as cortical

boundaries.


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Internal structure

In most cases the internal structure of

radicular cysts is radiolucent.

Occasionally, dystrophic calcification may

develop in long-standing cysts, appearing as

sparsely distributed, small particulate

radiopacities.


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Effects on surrounding structures

If a radicular cyst is large, displacement andresorption of the roots of adjacent teeth mayoccur.

The resorption pattern may have a curved

outline. In rare cases the cyst may resorb the roots of the

related non-vital tooth.

The cyst may invaginate the antrum, but thereshould be evidence of a cortical boundarybetween the contents of the cyst and the internalstructure of the antrum.


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Effects on surrounding structures

Cysts may displace the mandibular alveolar

nerve canal in an inferior direction.

The outer cortical plates of the maxilla or

mandible may expand in a curved or circular

shape.


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A and B, Two images of a radicular cyst originating from a non-vital deciduous second

molar show expansion of the buccal cortical plate to a circular or hydraulic shape

(arrows) and displacement of the adjacent permanent teeth.


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Radiographic Interpretation

Differential Diagnosis

Differentiation of a small radicular cyst from an apicalgranuloma may be difficult and in some cases impossible.

A round shape, a well-defined cortical border, and a sizegreater than 2 cm in diameter are more characteristic of acyst.

An early radiolucent stage of periapical cemental dysplasia,a radiolucent apical scar, and a periapical surgical defectshould also be considered in the differential diagnosis.

The patient's history helps with the differentiation.

Radicular cysts that originate from the maxillary lateralincisor and are positioned between the roots of the lateralincisor and the cuspid may be difficult to differentiate froman odontogenic keratocyst or a lateral periodontal cyst.


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The vitality of the involved tooth should be

tested.

A non-vital tooth may have a larger pulp

chamber than neighboring teeth because of

the lack of secondary dentin, which normally

forms with time in the pulp chamber and

canal of a vital tooth


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A large radicular cyst that has invaginated the

maxillary antrum may collapse and start filling

in with new bone.


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Axial (A) and coronal (8) CT images using bone algorithm of a collapsing radicular cyst within

the sinus. Note the unusual shape and the fact that new bone (arrows) is being formed from

the periphery (arrows) toward the center. (Courtesy of Drs. S. Ahing and T. Blight, University

of Manitoba.)


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With biopsy, the histological analysis may

result in an erroneous diagnosis of ossifying

fibroma or a benign fibroosseous lesion.

Radiographically, the important feature is thatthe new bone always forms first at the

periphery of the cyst wall as the cyst shrinks

and not in the center of the cyst; this is adifferent pattern of bone formation than is

seen with benign fibroosseous lesions.


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Diagnosis

Is based on the combination of:

Adequate History

Clinical Examination

Selected Investigation:

Pulp vitality testing of associated teeth

Radiographs (intra/extra oral)

Aspiration and analysis of cyst fluids

Histopathology


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Management

Treatment of a tooth with a radicular cyst may

include:

Extraction,

Endodontic therapy,

Apical surgery (Enucleation/Marsupilisation)


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Endodontic therapy

If the involved non-vital tooth is to be retained,conventional intra-canal endodontic treatment will oftenlead to resolution of very small radicular cyst.

The radiographic appearance of the periapical area of anendodontically treated tooth should be checked periodically

to make sure that normal healing is occurring. Characteristically, new bone grows into the defect from the

periphery, sometimes resulting in a radiating patternresembling the spokes of a wheel. However, in a few casesnormal bone may not fill the defect, especially if a

secondary infection or a considerable amount of bonedestruction occurred.


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Endodontic therapy

Recurrence of a radicular cyst is unlikely if ithas been removed completely.

A radicular cyst that is healing after endodontic

treatment. Arrows show the original outline of the cyst;

note that the new bone grows toward the center from

the periphery.


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If the cyst of such a size that is unlikely to

resolve with endodontic treatment alone,

surgery is indicated (enucleation or

marsupialisation)


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Enucleation

Enucleation. Complete removal of the cyst.

All the cyst tissue is available for histological

examination and the cyst cavity will usually

heal uneventfully with minimal aftercare.

It is potentially problematic when the cyst

involves the apices of adjacent vital teeth, as

the surgery may deprive the teeth of theirblood supply and render them non-vital.


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Marsupialisation

Marsupialisation. Is a partial removal of thecyst. It is indicated in large cysts that involvesthe apices of adjacent teeth.

This treatment require considerable aftercareand good patient cooperation in keeping thecavity clean whilst is resolves.

In order to keep the cavity open, a bung oracrylic plug is usually inserted in the opening,often attached to a denture or acrylic splint.


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Marsupialisation

The bung stops food collecting in the cavity,but the cavity must still be syringed by thepatient after each meal.

Marsupialised cyst cavities may take up to 6months to close down to the extent ofbecoming self-cleansing.

Disadvantage. Not all the cyst lining isavailable to histopathological examination, andthis may lead to misdiagnosis.


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Sources

CAWSONS Essentials of Oral Pathology and

Oral Medicine 7thEdition

Oral Radiology Principles and Interpretation

5thEdition (White . Pharoah)

Oral and Maxillofacial Medicine (Crispian

Scully CBE)

Color Atlas of Dental Medicine, Radiology.

(Friedrich A. Pasler)

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