Odontogenic cysts Flashcards
Describe the 2 possible ways that the cyst may proliferate
- Developmental stimulus: nasopalatine duct cysts
- Inflammatory stimulus: inflammatory cytokines release growth factors, and this causes development of remaining odontogenic epithelial remnants
Describe the ways the cyst “lumen” forms
Epithelial degeneration:
Three possible mechanisms:
1. Within the body of the epithelium, the cells in the centre die, mainly due to ischemia (less access to vascular supply)
2. Cell adhesion may be lost, proteolytic enzymes may be switched on
3. Apoptosis may occur within the epithelium
Stromal degeneration:
• More common
• Epithelia surrounds degenerated connective tissue, isolating them from the surrounding vasculature, causing lumen formation
Explain how cysts cause expansion and removal of bone
- There is an enclosed area of the epithelium
- These epithelial cells shed into the cyst lumen as they begin to degenerate
- They serve as a source of osmotically active particles
- Since the epithelial lining is semi-permeable, H20 and inflammatory oedema are attracted to the osmotically active particles within, causing inflammation
- As water begins to inflate the cyst, this increases the hydrostatic pressure and consequently, the inflated cysts places pressure on surrounding cells
- This causes pressure- induced apoptosis of surrounding cells and resorption of bone
- The cyst enlarges and causes bone resorption centrally
- Increments of new subperiosteal bone are laid down to maintain integrity of the cortex, producing a bony-hard expansion
- However, the rate of expansion is faster than the rate of subperiosteal deposition, leading to progressive thinning of the cortex which can be deformed on palpation producing the clinical signs of “oil-can bottoming” and “egg-shell crackling
Describe radicular cysts in terms of:
- Origin of the epithelium
- How the cyst occurs
Origin of the epithelium:
• Cell rests of Malassez, which are remnants of the Hertwig epithelial root sheath
How the cyst occurs:
• Its epithelial lining comes from the epithelium of the periapical granuloma
• The chronic inflammation which is likely to be rich in cytokines like growth factors, stimulates the rests of Malassez to proliferate
Describe radicular cysts in terms of its histological features
• Lined by non-keratinized stratified squamous epithelium supported by a chronically inflamed fibrous tissue capsule
• Capsule may contain collections of cholesterol (appears as clefts histologically)
• Rushton’s bodies
Collagen fibres and fibroblasts
Describe radicular cysts in terms of its:
- Clinical features
- Radiographic features
Clinical features:
• Can appear apically, laterally. This depends on the root canals (if there are lateral canals etc.)
• Can occur as a residual cyst (where the offending tooth is removed but the cyst remains behind)
• Tooth is non- vital
• Mostly asymptomatic
Radiographic features:
• Apical radicular cyst presents as a round or ovoid radiolucency at the root apex
• Lesion is often well circumscribed
• May be surrounded by a peripheral radiopaque margin continuous with the lamina dura of the involved tooth
Describe dentigerous cysts in terms of:
- Origin of the epithelium
- Process of cyst formation
Origin of the epithelium:
• The reduced enamel epithelium (which surrounds the crown of the of a fully formed, but unerupted tooth)
Process of cyst formation:
• The potentially erupting tooth compresses against the follicle
• This increases the venous pressure in the follicle
• This causes leakage of fluid into the follicle
Describe dentigerous cysts in terms of its histological features
- The lining of dentigerous cysts is typically thin, regular layer of non-keratinized epithelium
- Usually cuboidal epithelium OR stratified squamous epithelium
- Filled with watery fluid
- It is attached to the cementoenamel junction
- NO inflammatory cell infiltration
- Cholesterol clefts may be presentand associated foreign body-type giant cells
Describe dentigerous cysts in terms of its:
- Clinical features (where its most common)
- Associated complications
Clinical features of a dentigerous cyst:
• Twice as common in the mandible, especially the crown of impacted molars
• The cysts most frequently involve teeth which are commonly impacted or erupt late
Complications associated with a dentigerous cyst:
• When large, it is capable of displacing teeth or causing a fracture of the mandible
Describe eruption cysts in terms of:
- Description
- Clinical features (which teeth are mostly involved, the mucosa)
Description:
• Found in the soft tissue around the crown of an erupting tooth
• Because the tooth erupts through the cyst, this condition usually does not require treatment
Clinical features:
• Eruption cysts involve both the deciduous and permanent dentitions (mainly molars and incisors)
• Present as fluctuant swellings on the alveolar mucosa and are often bluish in colour
• Haemorrhage into the cyst cavity is common as a result of trauma
Describe odontogenic keratocysts in terms of:
- Origin
- How it results in multilocular cysts
Origin:
• Develops from the epithelial rests or glands of Serres, which persist after dissolution of the dental lamina
How it results in multilocular cysts:
• The epithelium can separate from the wall, resulting in islands of epithelium
• These can go on to form ‘satellite’ or ‘daughter’cysts, leading to an overall multilocularcyst.
Describe odontogenic keratocysts in terms of its histological features
- The surrounding epithelium lack rete ridges
- Well-defined basal epithelial layer which may be columnar or cuboidal
- Often reverse polarity: nucleus orientated away from the basement membrane
- Satellite cysts in the fibrous capsule, especially in Gorlin Syndrome- associated keratocyst.
- Artefactual separation from their basement membrane
Describe odontogenic keratocysts in terms of its:
- Clinical features (which teeth are most commonly affected)
- Associated complications
- Radiographic features
Clinical features:
• Mandibular third molars mostly affected
• Keratocysts enlarge predominantly in an anteroposterior direction and can reach large sizes
Associated complications:
• Can move teeth and resorb tooth structure
• High recurrence rate
Radiographic features:
• Radiolucent expansion of jaws, often multilocular, but can be unilocular
• Many present in apparent dentigerous relationship
For Gorlin Goltz Syndrome, state:
- What it is
- The type of inheritance
- Affected gene
What it is:
• A rare, inherited disorder that affects many organs and tissues in the body
• People with this disorder have a very high risk of developingbasal cellskin cancer during adolescence or early adulthood
Type of inheritance:
• Autosomal dominant trait
Affected gene:
• Mutation of a tumour suppressor gene which plays an important role in the normal growth and development of tissues and organs
For Gorlin Goltz Syndrome, state the clinical features of its associated odontogenic keratocysts:
- Skeletal abnormalities
- Oral features
Skeletal abnormalities: • Ribs are bifid, fussed or missing • Short metacarpals • Ocular hypertelorism • Developmental malformations
Oral features:
• Multiple cysts
• High recurrence
• Usually multiple and asymmetrically bilateral
• 80% in mandible, affects 3’s, 4’s and 7’s
