CYSTS OF THE ORAL REGION

DEFINATION

A cyst is a pathological cavity having fluid, semifluid or gaseous contents and which is not created by accumulation of pus. It frequently , but not always, lined by epithelium

CYSTS OF JAW

Diagnosis

Clinical features

Asymptamatic Accidental finding in radiographs Presence of swelling

Swelling

As the cyst grows larger, expansion of buccal/ labial cortical plate occurs.

In some cases lingual cortical plate expansion seen.

Expansion of both cortical plates often indicative of a lesion other than a cyst

Consistency of swelling

distension or bulging of the external bony surface.

As cyst increases in size , the periosteum is stimulated to form a layer of new bone, and it is this subperiosteal deposition which alters the outline of the affected portion of the jaw and produces enlargement

At early stage it is smooth, hard and painless prominence

Later stage, center of convexity becomes thinned and can be indented with pressure – elastic in consistency

Consistency of swelling

Later the fragile outer shell of the bone becomes fragmented, and the sensation imparted and sound produced on palpation – egg shell crackling

Then bone resorbed in area resulting soft in consistency – fluctuant swelling

Clinical features of cyst

Percussion of tooth overlying cyst – dull or

hollow sound Drifting of adjacent tooth Pathological fracture In maxilla, may cause nasal obstruction,

recurrent sinusitis or epiphora. Impairment of sensation in large cysts- rare In edentulous jaw, instability of dentures

due to swelling.

Clinical finding

Clinical features of cyst

Radicular cyst – non vital tooth Periodontal cyst- any vital tooth Dentigerous cyst- unerupted /impacted

tooth Fissural cyst – maxilla Solitary bone cyst – mandible Static bone cyst- below IA canal OKC – Lower 3rd molar extending to ramus

Radiographic features

Well defined round or oval area of radiolucency , circumscribed by a sharp radio opaque margin.

Rule out normal anatomic structure Pathology – gaint cell lesion, myxoma and

ameloblastoma IOPA, occlusal or OPG

Occlusal view

IOPA

OPG

Aspiration

Wide bore needle Straw colour fluid – radicular cyst Air- maxillary sinus Failure to obtain aspirate – solid lesion

CYST ASPIRATION

PATHOGENESIS

Steps in cyst formation1.Intiation 2. Cyst formation3. Enlargement or expansion ofof cyst cavity

Cyst initiation

1.Cyst intiation Chronic low grade infection activate cell

rest of mallassez

Cyst formation 2. Cyst formation

• Cyst lined by stratified squamous epithelium

• Blood supply rich at periphery

• Cells present at centre lack nutrition

• Cells desquamate into the centre of the mass

• Fluid with increased osmolarity in the centre surrounded by

epithelial lining

• Epithelial cells at periphery proliferates adjacent to vascular

connective tissue

Cyst formation

The desquamated cells lie in the centre surrounded by this epithelial layers. The surrounding connective tissue forms the capsule of the cyst

The number of epithelial layers is determined by the viability of the cells . They start at basement membrane , maturation takes place and then they finally desquamate.

Epithelial layer and capsule – protective mechanism – isolate the infective process.

Cyst enlargement

1. Increased volume of the cystic contents2. Increased surface surface area of cystic

contents 3. Displacement of surrounding hard and

soft tissue to accomodate the growth of the lesion

Cyst enlargement

Increased volume of the cystic contents The attraction of fluid into the cyst cavity The retention of the fluid within the

cavity The production of a raised internal

hydrostatic pressure The resorption of surrounding bone with

increase in the size of the bony cavity

Cyst enlargement

Attraction of fluid into the cystic cavityOsmotic theory Fluid formed due to the desquamated and

necrosed epithelial cells in the centre of the mass high osmolarity. . This property of the fluid tends to draw in or attract fluid from the surrounding tissues into the cystic cavity

Osmotic pressure difference draws fluid into the cystic cavity

Cyst enlargement

Retention of fluid within the cystic cavity

Cyst lining is semipermeable membrane preventing fluid from going out.

Cyst enlargement

Harris – theories of cyst enlargement 1. Mural growth a. Peripheral cell division b. Accumulation of cellular content 2. Hydrostatic enlargementc. Secretiond. Transudation and exudatione. Dialysis3. Bone resorbing factor

Cyst enlargement

Increased surface area due to mural growth

The thickness and rate of increase of the lining depends on the mitotic activity of the cells forming the lining

The cells of the basal layer of an OKC are considered to have more mitotic activity

Increased growth of the lining contributes to increased surface area of the cyst.

Cyst enlargement

Bone resorption . Growth in the path of least resistance Release of PGI 2 , PGE2 , leukotrienes,

osteoclast activating factor are released which help in bone destruction and enable growth of the cyst

Management

Cysts of the jaws are treated in one of the following four basic methods: (1) enucleation, (2) marsupialization, (3) a staged combination of the two procedures, and (4) enucleation with curettage.

Marsupalisation

Marsupialization refers to creating a surgical window in the wall of the cyst, evacuating the contents of the cyst, and maintaining continuity between the cyst and the oral cavity, maxillary sinus, or nasal cavity.

Marsupalisation

The only portion of the cyst that is removed is the piece removed to produce the window. The remaining cystic lining is left in situ.

This process decreases intracystic pressure and causes shrinkage of the cyst and bone fill.

Marsupialisation can be used either as the sole therapy for a cyst or as a preliminary step in management, with enucleation deferred until later.

Disadvantages

The major disadvantage of marsupalisation is that pathologic tissue is left in situ, without thorough histologic examination.

Although the tissue taken in the window can be submitted for pathologic examination, a more aggressive lesion may be present in the residual tissue.

Another disadvantage is that the patient is inconvenienced in several respects.

The cystic cavity must be kept clean to prevent infection, because the cavity frequently traps food debris. In most instances this means that the patient must irrigate the cavity

Indications

The following factors should be considered before deciding whether a cyst should be removed by marsupialization:

1. Amount of tissue injury. Proximity of a cyst to vital structures can mean unnecessary sacrifice of tissue if enucleation is used. For example, if enucleation of a cyst would create oronasal or oroantral fistulae or cause injury to major neurovascular structures or devitalization of healthy teeth, marsupialization should be considered

2. Surgical access. If access to all portions of the cyst is difficult, portions of the cystic wall may be left behind, which could result in recurrence.

3. Assistance in eruption of teeth. If an unerupted tooth that is needed in the dental arch is involved with the cyst (i.e., a dentigerous cyst), marsupialization may allow its continued eruption into the oral cavity.

4. Extent of surgery. In an unhealthy or debilitate patient, marsupialization is a reasonable alternative to enucleation, because it is simple and may be less stressful for the patient.

5. Size of cyst. In very large cysts, a risk of jaw fracture during enucleation is possible. It may be better to mar- supialize the cyst and defer enucleation until after considerable bone fill has occurred.

Advantages and disadvantages

Advantages. The main advantage of marsupialization is that it is a simple procedure to perform. It may spare vital structures from damage should immediate enucleation be attempted.

Enucleation

Enucleation is the process by which the total removal of a cystic lesion is achieved.

Indications Enucleation is the treatment of choice for removal of cysts of the jaws and should be used with any cyst of the jaw that can be safely removed without unduly sacrificing adjacent structures.

Advantages. The enucleation is that pathologic

examination of the entire cyst can be undertaken.

The patient does not have to care for a marsupial cavity with constant irrigations.

Once the mucoperiosteal access flap has healed, the patient is no longer bothered by the cystic cavity.

Disadvantages normal tissue may be jeopardized,

fracture of the jaw could occur, devitalization of teeth could result, or associated impacted teeth(canine) that

the clinician may wish to save

Technique

After enucleation, watertight primary closure should be obtained with appropriately positioned sutures.

The bony cavity fills with a blood clot, which then organizesover time.

Radiographic evidence of bone fill will take 6

to 12 months. Jaws that have been expanded by cysts

slowly remodel to a more normal contour.