A cyst has been traditionally defined as a pathologic epithelium-lined cavity usually containing fluid or semisolid material (Killey and Kay – 1966). The presently accepted definition is the one coined by Kramer in 1974 as ‘a pathologic cavity having fluid, semisolid or gaseous content and it is frequently, but not always lined by epithelium’.
Cysts of the jaws are often lined by a layer of epithelium and a layer of subjacent connective tissue and these layers can be dissected easily from bone. The thickness and configuration of this lining varies with the type of the cyst. These cysts develop either by the proliferation of epithelial remnants in the jaw or by cystic transformation of neoplastic tissue.
Numerous classifications have been published of cysts of the jaws. Most of them are perfectly satisfactory in clinical evaluation and practise.
I. Kruger’s classification (1964)
A) Congenital cyst
B) Developmental cyst
I) non-dental origin
a) fissural. type
- Incisive canal cyst (Naso-palatine)
b) retention type
II) dental origin
II. Lucas’ classification (1964)
A) Fissural cysts
- median mandibular
- median palatal
B) Odontogenic cysts
C) Non-epithelial bone cysts
- solitary bone cyst
- aneurysmal bone cyst
III. Gorlin’s classification (1970)
A) Odontogenic cysts
- dentigerous cyst
- eruption cyst
- gingival cyst of the new-born infants
- lateral periodontal and gingival cyst
- keratinising and calcifying odontogenic cysts
(cystic keratinising tumour)
- radicular (periapical cyst)
- odontogenic keratocyst
(a) primordial cyst
(b) Gorlin-Goltz syndrome
B) Non-odontogenic and fissural cysts
- globulomaxillary (premaxilla-maxillary) cyst
- naso-alveolar (naso-labial / Klestadt’s) cyst
- naso-palatine (median anterior maxillary) cyst
- median mandibular cyst
- anterior lingual cyst
- dermoid and epidermoid cyst
- palatal cysts of new-born infants
(C) Cysts of neck, oral floor and salivary glands
- thyroglossal duct cyst
- lymphoepithelial (branchial cleft) cyst
- oral cyst with gastric / epithelial epithelium
- salivary gland cyst – mucocoele and ranula
(D) Pseudocysts of jaws
- aneurysmal bone cyst
- static (developmental / lateral) bone cyst
- traumatic (haemorrhagic / solitary) bone cyst
IV. WHO classification published in ‘Histologic typing of odontogenic tumours’ (Kramer, Pindborg, Shear – 1992)
I) Cysts of the jaws
- (I) developmental
- gingival cysts of infants
- odontogenic keratocyst (primordial cyst)
- dentigerous (follicular) cyst
- eruption cyst
- lateral periodontal cyst
- gingival cyst of the adults
- botryoid odontogenic cysts
- glandular odontogenic (sialo-odontogenic / mucoepidermoid-odontogenic) cyst
- calcifying odontogenic cyst
- naso-palatine duct (incisive canal) cyst
- naso-labial (naso-alveolar) cyst
- midpalatine raphae cyst of infants
- median palatine, median alveolar and median mandibular cysts
- globulomaxillary cyst
- radicular cyst (apical / lateral)
- residual cyst
- paradental (mandibular infected buccal) cyst
- inflammatory collateral cyst
- solitary (traumatic/simple/haemorrhagic) bone cyst
- aneurysmal bone cyst
II ) Cysts associated with the maxillary antrum
- benign mucosal cyst of the maxillary antrum
- post-operative maxillary cyst (surgical ciliated cyst of the maxilla)
III) Cysts of the soft tissues of the mouth, face and neck
- dermoid and epidermoid cyst
- lymphoepithelial (branchial cleft) cyst
- thyroglossal duct cyst
- anterior median lingual cyst (intralingual cyst of fore-gut origin)
- oral cyst with gastric / intestinal epithelium (oral alimentary tract cyst)
- cystic hygroma
- naso-pharyngeal cysts
- thymic cysts
- cysts of the salivary glands
- mucous extravasation cyst
- mucous retention cyst
- polycystic (degenerative) disease of parotid
10. parasitic cysts
- hydatid cyst
- cysticerus cellulosae
Signs and symptoms
The physical sign of a cyst in the jaw depends on the size of the cyst. Small cysts do not produce any clinical signs. They may be discovered only on a routine radiologic examination. As the cyst becomes larger, expansion of alveolar bone occurs, usually on buccal / labial aspect. This expansion takes place as a result of continuous deposition of sub-periosteal bone in response to the bone resorption caused by the expanding cyst. This produces a bulged convex contour.
At an early stage, this lateral expansion produces a smooth, hard, painless prominence. As the cyst grows, the bone at the centre of the convexity becomes soft in consistency. This stage is described as ‘tennis ball’ feeling.
Further thinning of the cortical plate causes the bone to become fragile and outer shell of bone becomes fragmented on pressure producing a sound or feeling of ‘egg-shell crackling’. Later, this bone completely disappears, causing the cyst wall to be attached to the periosteum. At this stage, the cyst appears as a smooth, shining, bluish swelling with a soft, fluctuent consistency.
The way and degree of expansion and clinical signs vary with the type of cyst. Keratocysts and dentigerous cysts commonly cause less expansion and more bone destruction. The enlargement of the cyst is at the expense of cancellous bone.
Mobility of teeth rarely occurs with periapical cyst whereas dentigerous cyst and odontogenic keratocyst may cause mobility of teeth because of their high degree of bone resorption. Absence of teeth generally indicates a dentigerous cyst or a primordial cyst. Displacement of teeth rarely occurs in cases of odontogenic cysts whereas developmental cysts such as globulomaxillary cyst can cause displacement of roots of adjacent teeth.
Large mandibular cysts invariably involve the neurovascular bundle and may even deflect this structure to an abnormal position. It is unusual to find anaesthesia of mental nerve, but it may occur in cases of acute infection and sudden increase in intra-cystic pressure. This may produce nerve compression and paresthesia, which is relieved on decompression by surgical drainage.
Periapical cysts are always associated with one or more non-vital teeth. In other cysts also, an increase in the intra-cystic pressure may cause loss of response of adjacent teeth to vitality tests, even though they have vital pulps.
A large maxillary anterior cyst will expand under nasal floor causing distortion of nostril and nasal congestion. Involvement of antrum by an infected cyst will show features of maxillary sinusitis.
Most of the cysts are asymptomatic till it expands the jaw or gets infected. When infected, it causes severe pain and swelling of the involved region. Sometimes the patient notices a lump, which is painless. If the cyst has discharged in to the mouth or has become infected, the patient may complain of bad taste and pain.
Any cyst may cause displacement of adjacent teeth causing convergence of crowns of teeth. In case of cysts in the anterior region, discoloration, extrusion or malalignment of teeth will be the symptoms.
The classic appearance of a common odontogenic cyst in the jaw is a well-defined round / oval radiolucency, circumscribed by a sharp radio-opaque margin. However, there are variations depending on site and type of cyst. Also there are some other lesion
which may produce radiolucency similar to that of a cyst (e.g. some benign tumours may produce radiolucency similar to that of a cyst).
A small cyst in the marrow space normally round in shape and as it enlarges, become oval in shape. Later, resorption and expansions of cortical plates take place. Generally, buccal cortical plate expands fast. Exceptions are mandibular 3rd molar region where the lingual cortical plate is thin, and maxillary anterior region which produces a palatal expansion. A cyst in the maxillary molar region may involve maxillary sinus and enlarge within the sinus without producing much expansion of cortical plates.
When the perforation of cortical plates occur, it appears as a window, or a radiolucency inside a radiolucency.
A large mandibular cyst may displace the shadow of inferior alveolar canal downward and laterally. Large cysts cause unequal resorption at different margins, and a scalloped or a lobulated margin may be formed.
If an unerupted tooth with a large follicular space is seen on a radiograph, it should be compared with the radiograph of opposite side before the diagnosis of a dentigerous cyst is made, because the size of follicular space can vary. A difference of more than three times that of the opposite side indicates a cyst.
Infection of a cyst causes a decrease in radiolucency and it blurs the radio-opaque margin. Rare malignant transformation also produces similar results. While the cyst heals after treatment, the radio-opaque line fades, as the cancellous bone deposits from the periphery.
Apart from signs, symptoms and radiologic feature, an important aid in the diagnosis of a cyst is aspiration technique. This also helps to distinguish between a cyst and the maxillary sinus.
A wide bore needle should be used for the procedure, which may be done under local anaesthesia. A diagnosis of a cyst can be confirmed if aspirate is light straw coloured fluid containing cholesterol crystals. These crystals appear shining when the fluid is taken on a dry swab.
When infected, the fluid becomes turbid and yellow. In OKC, the colour and consistency of fluid vary depending on the concentration of suspended keratin. Sometimes, it will be too thick. Aspiration of pure blood raises the possibility of central haemangioma or aneurysmal bone cyst. A serosanguinous fluid or gas may be withdrawn from simple bone cyst. Aspiration of air shows that needles may be in maxillary sinus. It can be confirmed by injection of 20 ml of sterile water, which would come at through the nostrils.
There is a risk of introducing infection during aspiration and ideally when this is performed, it should be at least 48 hours preoperatively and only under antibiotic cover.
Apart from the obvious problem of cystic enlargement causing weakness of jaw, certain particular potential complication, need to be mentioned, considering their clinical relevance.
Infection is the most complication of a cyst in the jaw. Normally, if the cyst is totally confined inside a bony cavity or within the soft tissues, there is no chance of it getting infected. Microbes gain access to the cyst through odontogenic passages (i.e. carious cavities, periodontal pockets etc.) or through minor external injuries. Cysts of inflammatory origin, like periapical cyst, are always infected. Infection causes the sclerotic border of the lesion to get blurred in radiograph.
Normally asymptomatic lesions are rendered painful by infection, which prompts the patient to seek treatment. Treatment includes antibiotic therapy and drainage, if necessary, followed by extraction or root filling of associated teeth, and complete curettage of cyst cavity. On opening into the cavity, an intact lining is not usually obtained.
II. Effects on associated teeth
Cysts usually do not cause resorption of the roots of associated teeth, and the vitality of these teeth is not affected in most of the cases. Surgical enucleation of large lesions is associated with teeth can cause disruption of blood supply leading to pulp death and non-response to vitality tests.
Odontogenic cysts are frequently found to cause displacement of the roots of associated teeth. Globulomaxillary cyst that causes divergence of maxillary lateral incisor and canine roots, is a typical example. Others like OKC also may cause displacement of multiple teeth even though externally discernible swelling may be minimal.
III. Pathologic fracture
This is a direct sequel of the jaw rendered weak by the expanding cyst. This may be caused by the duct enlargement and perforation of a cyst or from minor trauma, to the weakened bone. Surprisingly, some fractures may be asymptomatic since the cyst tissue acts as a splint between the fractured segments.
A pathologic fracture is also a possibility in case a large defect is not adequately managed by filling or grafting, after surgical enucleation.
IV. Recurrence after treatment
Recurrence of the lesion after treatment by enucleation is a relatively common occurrence. The odontogenic keratocysts are especially notorious for this. This complication has much to do with the perfection of surgical procedure. If the cyst lining is not completely removed during treatment, the remnants of the lining may proliferate to cause recurrence.
V. Malignant transformation
Most workers advise removal of the cyst lining as early as possible after the lesion is diagnosed, because of the capability to undergo pathologic change in course of time. The occurrences of ameloblastoma, squamous cell carcinoma and mucoepidermoid carcinoma have been well documented.
Specific cyst types
Odontogenic keratocyst (OKC; primordial cyst)
In earlier literature, the keratocyst is described as a cholesteatoma (Hauer- 1926; Kostecka-1929). The first account is by Mikulicz in 1876 and the term odontogenic keratocyst was introduced by Philipsen (1956).
Previous authors have tended to denote all cysts containing keratin as keratocysts. But the one under discussion here is a distinct entity of developmental origin, arising from primordial odontogenic epithelium.
Browne (1969,1972) has shown that the OKC has a particular age distribution, the mean age being 32.1 years with a peak in 2nd and 3rd decades. 40-60% of all patients falls in this age group. It is estimated that OKC account for about 11 percent of all the cysts of the jaws. It occurs more in whites than in blacks.
Keratocysts are generally found more frequently in males than in females and this sex predilection is more pronounced in blacks than in whites. The mandible is found to be involved far more frequently than the maxilla (about 75%). About one-half of all keratocysts occur at the angle of the mandible extending to various distances.
Patients with keratocysts complain of pain, swelling or discharge. Paresthesia of lower lip and teeth and pathologic fractures do occur, but are rare. Many patients are free of symptoms until the cyst has reached a large size, involving the entire maxillary sinus or mandibular ramus, including the condylar and coronoid processes. This is because the keratocyst tends to extend in the medullary cavity and clinically observable expansion of bone occurs late.
The occurrence of large keratocysts that involved the maxillary sinus and led to destruction of the floor of the orbit and caused proptosis of the eyeball have been reported (Voorsmit-1984).
Maxillary cysts may cause buccal expansion, but palatal expansion is also rarely seen. Mandibular lesions may cause buccal or lingual expansions.
Gorlin-Goltz syndrome (first described by Binkley and Johnson –1951) is transmitted as an autosomal dominant trait and is characterised by
- cutaneous anomalies including basal cell carcinoma, other benign dermal cysts and tumours, palmar pitting, palmar and plantar keratosis and dermal calcinosis
- dental and osseous anomalies including odontogenic keratocysts (often multiple), mild mandibular prognathism, rib anomalies (often bifid), vertebral anomalies and brachymetacarpalism.
- ophthalmologic abnormalities including hypertelorism with wide nasal bridge, dystopia canthorum, congenital blindness and internal strabismus.
- neurologic anomalies including mental retardation, dural calcification, agenesis of corpus callosum, congenital hydrocephalus and occurrence of medulloblastomas with greater than normal frequency and
- sexual abnormalities including hypogonadism in males and ovarian tumours.
The keratocyst has a particular tendency to recur after surgical treatment. The recurrence rate in various reported series is found to vary between 11 and 62%. A high recurrence rate was noticed when cysts were located in the angle or ascending ramus of the mandible. Those whose radiographic appearances are multilocular have a higher recurrence rate than those with a unilocular appearance.
Possible reasons for recurrences are
- occurrence of satellite cysts, which are retained during enucleation procedures,
- thin and fragile linings, which causes difficulty to enucleate completely,
- epithelial linings of OKCs have intrinsic growth potential (Toller-1967) and they may be regarded as benign neoplasms,
- innate tendency in some patients to develop OKC from remnants of dental lamina and
- new cysts may develop from epithelial offshoots of the basal layer of the oral epithelium.
Toller (1967) viewed keratocysts as benign neoplasms. They tend to extend along cancellous component of the bone without producing noteworthy expansion of cortical plates. They frequently reach a large size, particularly at the angle of the mandible, before they are diagnosed. Main (1970) showed that the mitotic value of the keratocyst linings ranged from 0 to 19 with a mean of 8.0. this figure is similar to that in ameloblastomas and in dental lamina, and higher than that found in non-odontogenic cysts (2.3) and radicular cysts (4.5).
While Toller postulated that the raised osmolarities (when compared to serum osmolarity) play an important part in expansive growth of keratocysts, Main felt that mural growth in the form of epithelial proliferation is the essential process involved.
Radiologically, early keratocysts appear as small, round or ovoid radiolucent areas that are well demarcated with a distinct sclerotic margin. Some of these unilocular lesions have scalloped margins and these may be misdiagnosed as multilocular lesions. However, true multilocular lesions are not uncommon. Various studies have shown about 23% of all OKCs to be multilocular. Generally, these are significantly larger than the unilocular ones. The multilocular variety is liable to be misdiagnosed as ameloblastoma.
Further, OKCs may occur in the periapical regions of vital standing teeth, giving the appearance of a radicular cyst. In other cases, they may impede the eruption of related teeth and this results in a ‘dentigerous’ appearance radiologically.
It is generally agreed that a keratocyst is a developmental abnormality arising from odontogenic epithelium, the sources being dental lamina or its remnants. The term ‘primordial cyst’ was first used by Robinson to describe a cyst of the jaw which he suggested was derived from the enamel organ in its early stages of development by degeneration of stellate reticulum before any calcified structures had been laid down. It is now generally agreed that most of the so-called primordial cysts may, in fact, be keratocysts.
The linings of odontogenic keratocysts are rarely received intact in the laboratory. They are usually thin-walled, collapsed and folded. The histologic features are characteristic.
- They are lined by a regular keratinised stratified squamous epithelium, which is usually about 5-8 cell layers thick and without rete pegs. The tyre of keratinisation is parakeratin in 80-90% of cases.
- The epithelium is uniformly thick, with a well-defined, often palisaded basal layer consisting of columnar or cuboidal cells, or a mixture of both.
- The nuclei of columnar basal cells tend to be oriented away from the basement membrane, and in the majority of cases, are intensely basophilic.
- Desquamated keratin is present in most of the cyst cavities.
Because of the high recurrence rate, simple enucleation is not considered to be sufficient. Excision of the lesion along with a small margin of surrounding bone would be a more reasonable plan.
Gingival cyst and midpalatine raphae cyst of infants
These two cyst types are discussed together because of the clinical features they share, although one is of odontogenic origin and the latter, of developmental non-odontogenic origin. Two specific varieties which may be included in this category are ‘Epstein’s pearls’ which occur along midpalatine raphae and Bohn’s nodules, which are seen around dental ridges.
The frequency of gingival cysts is high in new-born infants but they are rarely seen after 3 months of age. It is apparent that most of them undergo involution and disappear, or rupture though the surface epithelium and exfoliate.
The nodules are 2-3 mm in diameter. They are white or cream-coloured.
Some of the gingival cysts open into the surface or may be involved by developing teeth. Very few become clinical problems.
Gingival cysts of infants arise from the dental lamina. The epithelial remnants of dental lamina (glands of Serres) have the capacity, from as early a stage in development as 10 weeks in utero to proliferate, keratinise and form small cysts.
In the morphodifferentiation stage (late bell stage) of tooth development, the disintegration of dental lamina begins to occur and many islands and strands of odontogenic epithelium are seen between the tooth germ and oral epithelium. The epithelial remnants which have already formed microcysts, expand rapidly at this stage (15-20 weeks in utero)
The cysts along midpalatine raphae arise from epithelial inclusions at the line of fusion of the palatal folds and the nasal process. These usually atrophy and become resorbed after birth. Some may, however, produce keratin-containing microcysts.
Both the types of cysts under discussion have similar histologic features. The cysts are round or ovoid and may have a smooth or undulating outline in histologic sections. There is a thin lining of stratified squamous epithelium, and keratin fills the cavity. The basal cells are flat.
There is no indication for treatment of gingival cysts or midpalatine raphae cysts.
Gingival cysts of adults
This rare condition accounts for only 0.5% of all the cysts of the jaws. The actual incidence may be more, as many patients do not report for treatment. Most cases occur in 5th and 6th decades and there has been no significant gender predilection. Gingival cysts occur much more frequently in mandible than in maxilla.
The patient may give a history of a slowly enlarging, painless swelling. The cysts are well-circumscribed swellings, usually less than 1 cm in diameter and may occur in attached gingiva or interdental papilla, always on the facial aspect. There may be no radiographic change or only a faint round shadow indicating superficial bone erosion.
A number of suggestions have been made about the pathogenesis. The most favoured theory is that they arise from odontogenic epithelial nest cells derived from dental lamina.
Gingival cysts have a variable histologic pattern. The epithelium may be thin, of thicker stratified squamous nature, or even atrophic. Some may have epithelial thickenings, which may be small and flat, or may protrude into the cyst lumen. The fibrous connective tissue wall is usually relatively uninflamed.
The gingival cyst is removed by local excision.
Lateral periodontal cyst
The designation is confined to those cysts which occur in the lateral periodontal position, which is not of inflammatory origin and in which case, a diagnosis of OKC is excluded. This is also a rare condition, accounting for less than 1% of all cysts of the jaws. The patients are usually adults (mean of 50 years) with a peak in the age group of 40-69 years.
The most frequent location is the mandibular premolar area, followed by the anterior region of maxilla. The lateral periodontal cyst may be symptomless. Sometimes, a gingival selling may arise in the facial aspect. Pain and tenderness at the site have been reported.
Radiographs show a round or oval well-circumscribed radiolucent area, usually with a sclerotic margin. The cysts lie between the apex and cervical margin of the tooth.
The lateral periodontal cyst is of odontogenic origin and the general agreement is that they are of developmental origin. An expanded follicle on the lateral surface of the erupting crown may be the cause.
Microscopically, it is lined by a thin, non-keratinising layer of squamous or cuboidal epithelium with small and pyknotic nuclei. Localised plaques and thickenings are common.
The lesion is treated by surgical enucleation without, if possible, removing the associated tooth.
Botryoid odontogenic cyst
Widely regarded as a variant of lateral periodontal cyst, the botryoid odontogenic cyst is multilocular and hence the term ‘botryoid’ which means ‘cluster of grapes’. This cyst occurs in adults, mainly in anterior region of the mandible.
The cyst cavities are varied in size and are lined by thin non-keratinising epithelium with thin fibrous connective tissue septa.
The lesion requires careful excision because there have been numerous reports of recurrences.
Glandular odontogenic cyst
This has some characteristics of lateral periodontal cyst and botryoid odontogenic cyst, but has fairly typical histologic features. Secretory elements and stratified squamous epithelium are seen in the lining.
Dentigerous (follicular) cyst
This type of cyst typically encloses the crown of an unerupted tooth by expansion of its follicle and is attached to the neck of the tooth.
The dentigerous cyst accounts for about 16% of all jaw cysts. It is seen more in2nd and 3rd decades of life and the frequency is greater in males and in whites. A very substantial majority involve the mandibular 3rd molar.
Clinical and radiographic presentation
Dentigerous cysts may grow to a large size before they are diagnosed. Many patients first become aware of the cyst as a slowly enlarging swelling. An unerupted tooth is a mandatory feature.
Radiographically, the common finding is a unilocular radiolucent area associated with crowns of unerupted teeth. They have well-defined sclerotic margins unless they become infected. There are three radiological variants.
- The crown is enveloped symmetrically.
- Expanded follicle is seen on one side of the crown (lateral dentigerous cyst).
- Entire tooth is involved (circumferential dentigerous cyst).
Dentigerous cyst has a greater tendency than other cysts to produce resorption of roots of adjacent teeth.
It has been suggested that dentigerous cysts may be of either extra-follicular or intra-follicular origin, and the latter may develop by accumulation of fluid between the reduced enamel epithelium and enamel or within the enamel organ itself. It is suggested that the pressure exerted by a potentially erupting tooth on an impacted follicle obstructs the venous outflow thereby inducing rapid transduction of serum across the capillary walls.
The thin fibrous cyst wall, being derived from dental follicle, consists of young fibroblasts widely separated by stroma and ground substance rich in acid mucopolysaccharide. The epithelial lining consists of 2-4 cell layers of flat or cuboidal cells. Characteristically, the epithelial lining is keratinised.
Small lesions can be surgically removed in their entirety. Larger cysts that involve serious loss of bone are often treated by the insertion of a surgical drain or marsupialisation.
Several relatively potential complications exists, which can arise from the dentigerous cysts, apart from the possibility of recurrence. These include
- development of ameloblastoma,
- development of epidermoid carcinoma and
- development of mucoepidermoid carcinoma.
A dentigerous cyst occurring in soft tissues, the eruption cyst is formed when a tooth is impeded in its path of eruption with in the soft tissues overlying the bone.
This cyst is found in children of different ages. Deciduous and permanent teeth may be involved, most frequently anterior to the first permanent molar.
It produces a smooth swelling over the erupting tooth which may be either the colour of normal gingiva or blue. It is usually painless unless infected, and is soft and fluctuent. There is no bone involvement, but the cyst may throw a soft tissue shadow in radiographs. Transillumination would help to distinguish it from an eruption haematoma.
The pathogenesis is similar to that of the dentigerous cyst
The superficial part is covered by the keratinised stratified squamous epithelium of the overlying gingiva. This is separated from the cyst by a strip of dense connective tissue which usually shows a chronic inflammatory cell infiltrate.
Calcifying odontogenic cyst (COC)
Though a well-recognised lesion, a COC is not commonly encountered (about 1% of all jaw cysts). This cyst occurs over a wide age range but here is a distinct peak in the 2nd decade. There is an equal sex distribution and no racial predilection is apparent. Maxilla and mandible are involved with almost equal frequency but anterior part of either is a more common site.
Swelling is the most frequent symptom. Intra-osseous lesions may produce a hard bony expansion, which may be extensive. Occasionally, cortical plate may be perforated. Pain is a rare symptom and many cases have been asymptomatic.
The calcifying odontogenic cyst appears in the radiographs essentially as a radiolucent area with regular or poorly defined margins. Irregular calcified bodies of varying size and opacity may be seen in the radiolucent area.
Histologically, the epithelial lining has characteristic odontogenic features with a prominent basal layer consisting of palisaded columnar or cuboidal cells and hyperchromatic nuclei, polarised away from the basement membrane. the most remarkable feature of COC is the presence of ghost cells, which are enlarged, ballooned, ovoid or elongated cells with thin epithelium. Calcification may occur in some of the ghost cells, initially as fine powdery or coarse basophilic granules and later as spherical bodies.
The COC is treated by surgical enucleation. If associated with an odontogenic tumour, a wider excision is required.
Nasopalatine duct (incisive canal) cyst
Derived from embryonic epithelial residues in the nasopalatine canal or from epithelium included in the lines of fusion of facial processes, it occurs within the nasopalatine canal or in the soft tissues of the palate.
This is the most common of the non-odontogenic cysts. Majority occurs in 4th, 5th and 6th decades. The most common symptom is swelling, usually in the anterior region of the midline of the palate. Swelling may also occur in the midline on the labial aspect of alveolar ridge. There may be a bulge on the floor of the nose. There may be pain and /or discharge. Salty taste and displacement of teeth may be other features.
It may be difficult to determine Radiographically whether a radiolucency in the area is a cyst or a large incisive fossa. Any radiograph of the fossa which shows a shadow less than 6 mm wide can be considered to be within normal limits. Incisive canal cysts are found in the midline of the palate, above or between the roots of the central incisor teeth. They are round, ovoid or sometimes heart-shaped. The margins are well-demarcated.
The incisive canal cyst is treated by surgical enucleation.
Median palatine and median alveolar cysts
In recent years, the existence of these cysts as separate entities have been questioned and they have subsequently been excluded from the WHO classification (1992). Previously it was thought that these cysts developed from epithelium entrapped in the process of fusion of embryonic processes. It is now felt that they represent posterior extension of an incisive canal cyst in the case of a median palatal cyst, and anterior extension in case of median alveolar cyst. The so-called median alveolar cyst may also, in a number of instances, be a keratocyst derived from dental lamina in the midline of the maxilla.
Median mandibular cyst
A cyst occasionally occurs in the midline of the mandible. It produces a well-defined round, ovoid or irregular radiolucent area and may separate the roots of the lower teeth. The presence of such a cyst associated with vital teeth tempted some to propose its origin from epithelial inclusions trapped in the area during embryonic development. The concept is not tenable as the as the mandible forms in the mandibular process which develops as a single unit. Most of the cysts considered to be median mandibular cysts are of radicular, lateral periodontal , intra-osseous dermoid or keratocyst variety.
This has been traditionally described as a fissural cyst found within the bone between upper lateral incisor and canine. It causes the roots of these teeth to diverge. There is now considerable opinion against the theory that it is a fissural cyst.
A wide variety of lesions presenting clinically and radiographically as globulomaxillary cyst have been found to be OKCs, adenoameloblastoma, myxoma and heamorrhagic bone cyst.
Nasolabial (nasoalveolar) cyst
The nasolabial cyst occurs outside the bone in the nasolabial folds below the alae nasi. These are very rare lesions with a wide age distribution (peak in 40-60 years age group) and a predilection to occur in females (75-80%).
Clinically, a swelling in the nasolabial fold is the most common complaint. Some patients complain of pain and difficulty in nasal breathing. The cyst grows slowly.
Radiographically, there may be a localised increased radiolucency of the alveolar process which results from a depression on the labial surface of the maxilla.
The pathogenesis of nasolabial cyst is unresolved, though it is generally agreed to be of developmental origin.
Histologically, it is lined by non-ciliated pseudo-stratified columnar epithelium and has collaginous or loose connective tissue walls.
Radicular (periapical) and residual cysts
A radicular cyst is one which arises from the epithelial remnants in the periodontal ligament as a result of inflammation. The inflammation usually follows the death of the dental pulp and the cysts arising in this way are found most commonly at the apices of involved teeth.
The radicular cyst is the most common type among jaw cysts. They occur in all tooth-bearing areas, but more commonly they seem to occur in maxillary anterior region. Many radicular cysts are symptomless but slowly enlarging swellings are often complained of. At first, the swelling is bony-hard but as it becomes bigger, sponginess and fluctuence are elicited. In the maxilla, the swelling may be buccal/labial. Pain and infection are other likely features. A non-vital tooth is a central finding. In the case of residual cysts, a history of extracted tooth.
Radiologically, it is difficult to differentiate between radicular cysts and periapical granulomas. But when the lesion is 2 mm in diameter or larger, the diagnosis of a cyst may be made.
The pathogenesis of radicular cysts may be considered in three phases
- phase of initiation – inflammatory infiltrate from non-vital cause proliferation of epithelial cells.
- phase of cyst formation – a cyst cavity is formed within the proliferating epithelial mass by degeneration and death of cells in the centre.
- phase of enlargement – osmolarity difference between the cystic fluid and serum plays a part in the enlargement of the cyst.
Radicular cysts are lined by stratified squamous epithelium. Inflammatory infiltrate is a common finding. Hyaline bodies and secretory cells are also frequently found.
Radicular cysts are treated by enucleation with extraction or root-filling of associated teeth. An intact lining may not be obtained because of infection.
Solitary bone cyst
This lesion, which occurs in mandible and very seldom in maxilla, is very rare and it occurs in young individuals (peak frequency in second decade).
Swelling, pain and labial paresthesia are the presenting symptoms but in most cases, there will not be any symptoms. More than half of the patients have given a history of trauma to the region.
Radiographically, the cyst appears as a radiolucent area with an irregular but definite edge, and slight cortication. Marginal condensation and scalloping also may be seen.
Pathogenesis of the solitary bone cyst is not known, though general agreement is of a traumatic aetiology. This states that (Olech, Sicher and Weinmann) following trauma to a bone, which causes intramedullary haemorrhage, a failure of early organisation of the haematoma in marrow spaces and subsequent liquefaction of the clot, lead to the formation of traumatic bone cyst.
When the cyst cavity is opened at operation, they are frequently found to be empty. The cyst consists of a loose vascular fibrous tissue membrane. Adjacent bone may show osteoclastic resorption.
Aneurysmal bone cyst
This is an uncommon lesion occurring in the first three decades of life. More cases are seen in the mandible than in the maxilla.
Clinically, the aneurysmal bone cyst produces a firm swelling which is painful in some of the cases. Sometimes the swelling and malocclusion becomes progressively worse. This cyst produces a radiolucent area which produces an ovoid of fusiform expansion of bone. Some are multilocular or honeycomb-like.
The pathogenesis of the lesion is controversial. A number of workers are of the view that the cyst results from a vascular disturbance in the form of a sudden venous occlusion or development of an arteriovenous shunt, while some feel that the lesion is a secondary phenomenon arising from a pre-existing bone lesion.
When the covering bone is removed, the bleeding may be profuse.
It is generally agreed that the treatment is curettage. Usually there is no communication with any large vessels.
Management of cysts
Some small radicular cysts regress if the necrotic pulp remnants and/or bacteria are removed from the root canal of the causative tooth and the canal effectively filled. This approach should be used only in small lesions with discretion and has to be monitored by careful follow-up.
Surgical treatment should be based on conservation of dental and osseous structures as far as possible. Wherever possible, the functional teeth should be preserved. This will require careful assessment of all teeth related to the cyst. Pulpless teeth should be root-filled within 24 hours prior to the operation.
Regardless of aetiology, nature or location of the cyst, two methods of treatment are generally accepted. They are
- enucleation of the cyst sac and
- marsupialisation (Partsch operation).
The name of Partsch (1892) is normally associated with this operation although he also described enucleation. Very large cysts may be treated by making an opening into the cyst as large as is practical and packing the cavity. This ensures complete drainage and decompression.
- Technically simple
- Local anaesthesia is enough even for large cysts since anaesthesia for deeper tissues is not necessary.
- Associated vital structures are not damaged.
- Tooth in a dentigerous cyst may be conserved and its eruption permitted.
- Since the pack may act as a splint, it may be a favourable procedure in case of pathologic fractures.
- The need for regular post-operative care.
- Long duration of treatment.
- Pathologic tissue is left behind, which may result in unfavourable complications.
- Normal contour may not be achieved leading to a depression which is not self-cleansing. This may lead to recurrence.
A U-shaped incision outlines the area which is slightly larger than the eventual bony opening. This will leave a narrow rim of oral mucosa which can roll over the edge of the bone to become united to the cut edge of the cyst lining. Elevation of the mucoperiosteal flap starts on intact bone. In case of perforation, periosteum should be carefully dissected off the cyst lining without damaging it. A cross incision is made in the lining to expose the cyst lumen and cystic contents are evacuated. The cavity is flushed gently with saline.
The flap is now turned into the cavity and is sutured to the cyst lining along the bony margin. The excess flap and cyst lining are trimmed away. The cavity is flushed again with sterile saline and is packed with iodoform or tincture benzoate pack. Whitehead varnish pack may also be used.
After completely flushing the gauze with the chemical (iodoform etc.), excess fluid is squeezed out. The pack is then unrolled and carefully placed into the cavity with two pairs of forceps. The gauze strip is first laid along the floor of the cavity and the remainder is inserted systematically in layers running from side to side. This pack is left in place for 7- 14 days. By this time, the junction between the lining and mucosal flap will be healed and an acrylic plug can be fabricated.
This plug maintains the patency of the opening and prevents the foods particles from entering the cavity. If the patient is denture wearing, this plug can be attached to the denture. The plug should be stable, adequately retained and large enough to prevent accidental swallowing.
After this, daily irrigation should be done for a prolonged period.
Waldron (1941) recommended enucleation of cystic lining after the cavity is partially filled following marsupialisation. That is when considerable thickness of bone is formed or when the cyst becomes relatively smaller and there is no danger of damaging important structures or rendering the jaw weaker by enucleation. This will reduce the healing time and help to avoid the chance of residual defect.
This is the most rational and most popular method employed for the treatment of cysts. After removal of the cyst lining and primary closure, the bony cavity fills with blood clot, which eventually organises to form normal bone.
- Whole lining is removed and comprehensive histopathologic examination is possible.
- Less chance of occurrences of residual deformity.
- Lessens patient’s discomfort (of using a plug).
- Less overall treatment time
- No need of frequent follow-ups and irrigation.
- Less chances of future complications like malignant transformation.
Enucleation can be done under general or local anaesthesia. In any case, before the incision is demarcated, the area should be infiltrated with a local anaesthetic solution with a vasoconstrictor. This helps in easy separation of cystic lining from the periosteum. Whenever possible, a buccal or labial approach is preferable because of superior visibility and accessibility. However, a cyst causing palatal expansion alone should be approached through this direction the associated pulpless teeth should be extracted or root-filled.
A wide mucoperiosteal flap with margins on intact bone should be reflected. If the bone is intact, a window cut is made with chisel or bur without perforating the cystic wall. If the bone is thin, it can be peeled off with a periosteal elevator. Further clearance is done using bone roungers till adequate access is obtained.
The cyst lining is gently separated from the cavity with the broad end of periosteal elevator. Depending upon the size of the cyst and its position, other instruments such as spoon escavator and Mitchell’s trimmer can be used. Edge of the instrument is applied on cavity wall with the concave surface facing the lining.
Careful dissection should be done to separate the lining from the structures like periosteum, nasal cavity wall, maxillary sinus, neurovascular bundles etc. Undue pressure should not be used while doing this.
After removing the cyst lining, the cavity is irrigated and well debrided and inspected for any remnants of cyst lining. Hemostasis should be achieved before closing. In large cysts, immediate control of bleeding may not be enough and further oozing is managed by placing a gauze pack in the cavity till complete hemostasis occurs. This pack is removed after 24 hours.
An alternate way is to pack the cavity loosely with iodoform gauze and to keep the pack for 7-10 days. A low-pressure suction drainage system may be used.
Voorsmit, Stoelinga and van Haelst (1981) advised devitalising any fragments of lining left in the cavity after enucleation, either by swabbing the cavity with Carnoy’s solution or by freezing the bony wall. Carnoy’s solution is a powerful histological fixative made by mixing chloroform (3 parts), absolute alcohol (6 parts) and glacial acetic acid (1 part).
An approach that recently has gained popularity in the management of keratocysts is a combination of methods. The first step is to decompress the cyst. A plastic (or other suitable material) drain is secured in place to ensure that the opening remains patent. After 6 to 8 weeks, the lining of the cyst becomes generally thick and tough. The second step is to carefully enucleate the cyst. At this time, the thickened cyst wall is much more easily removed than is the usual OKC. The next step is to perform a peripheral ostectomy with a large bone bur. A margin of 2 to 3 mm is taken, depending on adjacent vital structures involved. The final step is to treat the residual bone bed with chemical cautery (Carnoy’s solution). This systematically thorough method, although time consuming and demanding much patient co-operation, has achieved good results.
To obliterate the cavity after cyst enucleation, various filling materials have been recommended for packing into the defect prior to closure of the wound. Primarily, these are forms of haemostatic resorbable sponge, some of which may be soaked in a solution containing an antibiotic or thrombin. These materials are inserted to prevent excessive bleeding and to form a scaffold into which granulation tissue can migrate.
It is now recognised that grafting with autogenous cancellous bone can be performed successfully within oral wounds. In case of large defects, when pathologic fractures are possible or there would be considerable loss of contour in a future denture-bearing area, this procedure can be used to obliterate the cavity and stimulate osteogenesis. Should grafting be indicated, autogenous bone provides the best results if a second wound is not a major consideration (Boyne-1970; Flint-1964; Mowlem-1944; Scott, Peterson and Grant-1949).
A risk of bone grafting cyst cavities is the possibility of bone fragments becoming infected if wound breakdown occurs. The risk of failure in these cases is greater than when grafts are introduced after resection of a segment of mandible, because of the greater difficulty in ensuring watertight wound closure.
Enucleation and package
This is an improvised method devised to combine the advantages of the two main techniques, but in fact it combines the disadvantages of both enucleation and marsupialisation, yet the advantages of primary closure are not achieved.
Treatment of large maxillary cysts
Marsupialisation and complete removal of cyst lining and opening the cystic cavity into nose, was described by Seward (1969). It is done through an intra-oral incision on either buccal/labial or palatal aspect. After reflecting the flap, the cyst lining is carefully detached from maxillary sinus and from the floor of the orbit. Care should be taken not to damage the floor of the orbit and infra-orbital nerve.
Along with the cyst lining, the whole adjacent antral mucosa is removed. The cavity is packed with iodoform gauze. An intranasal antrostomy is done just below the anterior part of inferior turbinate. The end of the pack or a drainage tube can be drawn through this and pasted over skin. The intraoral flap is sutured by interrupted mattress suture. The drain or gauze can be removed after 24 hours.
All the patients treated for cysts should be observed post-operatively for a long time to make sure proper healing occurs. This includes clinical examination, and radiographic examination at regular intervals. The vitality of the retained teeth should be checked during recall visits. If vitality is not regained, adequate treatment should be given.
Cystic lesions are very common in jawbones and it includes those of both odontogenic and non-odontogenic origin. Odontogenic cysts are unique to the jawbones, and it often results in considerable destruction of these bones. The diagnosis of these lesions is often delayed because of their innocent presentation. By the time of diagnosis, most of the cyst will be enlarged considerably weakening the bones. This leads to various sequelae such as fractures. Other complications eventhough rare such as malignant transformation of cystic lining is of considerable importance of various surgical modalities available, enucleation with primary closure should be treatment of choice wherever possible because of the least unfavourable sequelae.
- C. Killey & Kay
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