Jaw disease Flashcards
What is a cyst?
A cyst is a pathological cavity filled with fluid, semi-fluid or gaseous contents and which is not created by the accumulation of pus. It is usually but not always lined by epithelium. A cyst has a wall, lumen and lining.
How are cysts classified?
- Epithelial cysts
- Odontogenic cysts
- Inflammatory
- Developmental
- Non-odontogenic
- Nasopalatine duct cyst
- Nasolabial cyst
- Odontogenic cysts
- Cyst like lesions
What are the types of odontogenic cyst?
Inflammatory:
- Radicular cyst
- Residual cyst
- Paradental/collateral cyst
Developmental:
- Follicular
- Dentigerous cyst
- Eruption cyst
- Odontogenic keratocyst
- Gingival cyst
- Lateral periodontal cyst/Botryoid odontogenic cyst
- Calcifying odontogenic cyst
- Glandular odontogenic cyst
- Orthokeratinised odontogenic cystWhat is the frequency of the different cyst types?
- Radicular 65%
- Follicular 20%
- Keratocyst 5%
- Nasopalatine 5%
- Others 5%
What do cysts need in order to form?
- A source of epithelium
- A stimulus for proliferation
- Growth and bone resorption
What are the sources of epithelium for the different cyst types.
Radicular cysts develop from remnants of Hertwigs Root sheath (periodontal ligament contains epithelial remnants called rest cells of Malassez). Follicular cysts develop from the reduced enamel epithelium. Odontogenic keratocysts and gingival cysts develop from remnants of the dental lamina (enamel organ develops from this)
What is the stimulus for proliferation for cysts?
Inflammation and an apical granuloma for radicular cysts. Periodontitis for inferior lateral periodontal cysts and pericoronitis for paradental cysts. For developmental cysts the factors are largely unknown. For a dentigerous cyst it may be eruptive force, proliferation and hydrostatic pressure. For a keratocyst it may be epithelial proliferation, hydrostatic pressure and tumour.
How do cysts grow and expand (three ways)?
Osmosis and hydrostatic pressure:
- Cytokines cause cyst to grow
- Ball of cells exceeds capacity of blood supply to keep alive so cells in the centre break down forming a rim of viable cells and hypertonic centre
- Hypertonic centre wants to bring water in to make it isotonic so water drawn in by osmosis
- Hydrostatic pressure increases so cyst expands - unicentric expansion
- E.g. radicular and dentigerous cyst
Proliferation of the lining:
- Enlargement of the cyst at the peripheries due to active division of the cells of the epithelium of the lining of the cyst
- Finger like projections are zones of active cell division or proliferation
- e.g. Odontogenic keratocyst
Bone resorption:
- IL1 and IL6 (cytokines)
- Prostaglandins
- Endotoxins
- Stimulation and activation of osteoclasts
- All incorporate methods whereby they stimulate bone to be resorbed
What is a radicular cyst?
They arise in the periodontal ligament from the epithelial cell rests of malassez as a result of inflammation following death of the pulp. It is always associated with a non-vital tooth. It can be apical at the apex of a tooth associated with the opening of a root canal. It can be lateral at the side of a tooth associated with a lateral branch of the root canal. It can be residual which is a radicular cyst which has persisted after extraction of the associated tooth. Radicular cysts are mostly in younger patients, in the maxilla and mostly affect incisors. It always develops in a periapical granuloma. Proliferating odontogenic epithelium leads to a cyst.
What features are seen in the histology of a radicular cyst?
Mucous metaplasia is seen in 15%. Cholesterol is a bi-product of the cells breaking down and it tends to gather as crystals. Cholesterol crystals are seen in 30%. Mucous cells are seen in 15%, hyaline bodies in 10%, cilia in 10% and keratin in 2%.
Non-keratinised stratified squamous epithelium is seen.
How can you tell the difference between cysts and granulomas?
Cysts tend to be larger, more radiolucent, well-defined, corticated and painless. But only 50% are diagnosed correctly pre-operatively. The larger the lesion the more likely it is to be a radicular cyst. At 1-1.4cm 50% are cysts, at 1.5-1.9cm 65% are cysts and at 2cm+ 90% are cysts.
What is a collateral/paradental cyst?
It is a cyst which arises on the lateral aspect of a tooth as a result of inflammation in a periodontal pocket. It arises from pocket epithelium. A particular type of paradental cyst arises at the buccal aspect of partially erupted molars. The histology is similar to the radicular cyst.
What is a follicular cyst?
They surround the crowns of unerupted teeth and arise from the reduced enamel epithelium. Dentigerous cysts are associated with an impacted tooth and eruption cysts are associated with an erupting tooth. It forms due to the follicular epithelium proliferating. An eruption cyst lies just beneath the oral mucosa and attaches at the ACJ.
What is an odontogenic keratocyst?
It is a cyst arising in the tooth bearing area from remnants of the dental lamina. It is characterised by a thin lining of parakeratinised stratified squamous epithelium. It may replace a tooth. There is epithelial proliferation which may be due to genetics or trauma. There is often little or no bucco-lingual expansion of the jaw. The recurrence varies between studies. Daughter cysts can form in the connective tissue and these can be left behind which can lead to recurrence. There is fragility of the lining.
- 62% occur in males
- 75% in the mandible
- 50% in the lower third molar area
- 50% associated with an unerupted tooth
What syndrome is associated with odontogenic keratocysts?
Gorlin Goltz/basal cell naevus syndrome.
What is basal cell naevus syndrome?
Don’t confuse with Gardner’s - multiple osteomas
It is autosomal dominant, chromosome 9q, prevalence is 1:60000. The features are:
- Multiple and recurrent odontogenic keratocysts (tend to occur before 25, recurrence common)
- Basal cell carcinomas of the skin (not limited to sun exposed areas, scarring on face and neck)
- Frontal bossing (frontal region of skull is wide) and hypertelorism (eyes are wide set)
- Skeletal abnormalities e.g. bifid ribs - like a wishbone
- Cervical rib - rib coming off cervical vertebrae, compresses nerves passing to arms so there will be problems with sensation and motor function of arms
- Cranial abnormalities e.g. calcification of falx cerebri (between right and left hemisphere of brain, if calcified there will be greater conduction leading to epilepsy
What is the evidence that an odontogenic keratocyst may be a benign neoplasm?
- High proliferation rate in the epithelial lining
- High rate of recurrence
- Aggressive and infiltrative growth
- Association with basal cell carcinoma in Gorlin Goltz
- Molecular changes similar to basal cell carcinoma
- PTCH (chromosome 9q) mutation in BCC and Gorlins
How have odontogenic keratocysts been classified and reclassified?
WHO classification 2005 renamed keratocyst as keratocystic odontogenic tumour. It was not widely accepted. In 2017 WHO classification reverted to odontogenic keratocyst.
What is a lateral periodontal cyst?
They occur on the lateral aspect or between the roots of vital teeth. It is developmental in origin from the rests of Serres. Occasionally it is multilocular and is called botryoid odontogenic cyst. Localised thickening of the lining is common.
What are gingival cysts?
In infants they arise from the dental lamina rests in the alveolar mucosa of infants (alveolar cysts) and are lined by thin parakeratinised epithelium.
In adults they arise from the dental lamina rests in the attached gingiva. They are lined by non-keratinised epithelium.
What is a glandular odontogenic cyst?
A cyst characterised by cuboidal or columnar epithelium with mucous production. Forms duct-like or glandular structures.
What is a calcifying odontogenic cyst?
There was a change in the 2017 classification and it is no longer a tumour. It is most common in aged 10-30 in the mandible and maxilla. Radiolucencies but may have calcifications. The histology shows a cyst lined by ameloblastoma like epithelium with ghost cells and dentine in the wall. It may be solid - odontogenic ghost cell tumour.
What is a nasopalatine duct cyst?
Nasopalatine duct cysts arise in the nasopalatine (incisive) canal from epithelial residues of the nasopalatine duct. They are lined by respiratory epithelium or stratified squamous epithelium or often both. The hard palate forms by the fusion of three processes. The point where they meet is where the nasopalatine duct arises and this is shown by the inciisve papilla.
What is a nasolabial cyst?
It arises in the soft tissue overlying the alveolar process at the base of the nostril deep to the nasolabial fold. It probably arises from remnants of the nasolacrimal duct and is usually lined by pseudostratified columnar epithelium.
What are cystic lesions of the jaws?
They don’t have an epithelial lining. It can be a solitary (simple) bone cyst or Stafne’s bone cavity.
What are the ways of removing cysts?
- Enucleation - removal of the cyst in its entirety without cutting, blunt dissecting it out
- Curettage - Removal of tissue by scraping and scooping in portions
- Resection - removal of part of an organ, takes pathology and margin of normal tissue
- Marsupialisation - creation of a pouch by suturing the cyst lining to the external surface, the pouch can heal from the base upwards
The approach for most cysts is enucleation.
When would you apicect a tooth?
- Anterior tooth (mainly)
- Acceptable orthograde RCT
- Patient accepts risks e.g. recession
- Consider implant first
What are the indications for apicectomy (need both)?
- Persistent symptoms/pathology in a non-vital tooth
- Re-RCT is unfeasible
Apicectomy more likely to work in short term than re-RCT but re-RCT more successful in longterm.
What may the persistent symptoms of a tooth requiring apicectomy be?
- Apical cyst
- Swelling
- Discharge
- Mobility
- Pain
When is re-RCT unfeasible?
- Adequate re-RCT has failed
- Sclerotic canals, cannot instrument
- Canal morphology e.g. curvature, accessory canals
- Post-crown, cannot remove
- Complex crown/bridge, perforation more likely than instrumentation
- Root perforation
- Fractured instrument, cannot retrieve
- Fractured root
What are the relative and absolute contraindications to apicectomy?
Relative: - Previous apicectomy - Poor OH - Molars - Active caries - Advanced perio - Implant - Unwilling to have LA - High mobility index - Sinus disease (recurrent sinusitis) Absolute: - Severe bleeding disorder - Endocarditis risk - Unrestorable tooth - Post-crown retrievable
How is an apicectomy done?
- Ideally enucleate, may have to curettage if friable
- Apical 3mm of root removed (apical delta)
- Don’t need to remove to base of bone cavity
- 90 degrees to long axis of tooth
- IRM vs MTA as retrograde RCT
What are the types of flap design?
- Mucoperiosteal
- Semi-lunar
- Leubke-Oschenbein
