L12 Introduction to Cysts of the Jaw

Question 1

What is a cyst?

Answer 1

A pathological cavity having fluid, semi-fluid or gaseous contents, not formed by the accumulation of pus.
May or may not have an epithelial lining.

Question 2

Describe the strutcure of a cyst.

Answer 2

• Cyst capsule: usually made of fibrous CT/granulation tissue, BVs
• Cyst lining: epithelial lining, not present in all cysts, usually non-keratinised stratified squamous
• Lumen: contains fluid/semi-fluid/solid/gaseous components

Question 3

What does the cyst wall refer to?

Answer 3

The cyst capsule and cyst lining

Question 4

What are the 2 categories cysts are divided into?

Answer 4

• Odontogenic: epithelial lining is derived from epithelial tissues associated with tooth development
• Non-odontogenic: epithelial lining is derived from sources other than the tooth forming organ

Question 5

What are the 2 categories odontogenic cysts are divided into?

Answer 5

• Inflammatory: stimulus for cyst development is inflammation, most commonly periapical inflammation
• Developmental: stimulus for cyst development is uncertain

Question 6

Name 3 odontogenic inflammatory cysts.

Answer 6

• Radicular
• Residual
• Paradental

Question 7

What is the alternative name for a radicular cyst?

Answer 7

Apical periodontal cyst

Question 8

Name 7 developmental inflammatory cysts.

Answer 8

• Follicular cysts
• Odontogenic keratocyst
• Gingival cyst
• Lateral periodontal cyst
• Botryoid odontogenic cyst
• Glandular odontogenic cyst
• Calcifying odontogenic cyst

Question 9

What are the 2 types of developmental inflammatory follicular cysts?

Answer 9

• Dentigerous cyst (encloses tooth crown)

- Eruption cyst

Question 10

What are the 3 categories of non-odontogenic cysts?

Answer 10

• Inclusion cysts
• Congenital cysts
• Cysts without epithelial lining

Question 11

Give examples of inclusion cysts.

Answer 11

• Nasopalatine
• Nasoalveolar
• Median palatal
• Globulomaxillary

Question 12

Give examples of congenital cysts.

Answer 12

• Thyroglossal duct
• Lymphoepithelial
• Dermoid cyst

Question 13

Give examples of cysts without an epithelial lining.

Answer 13

• Bone
• Salivary gland
• Stromal cysts in neoplasms

Question 14

Where are radicular cysts found?

Answer 14

At the apex of a non vital tooth.
Can be:
- Apical radicular
- Lateral redicular
- Residual radicular cyst: associated with extracted tooth

Question 15

Where are odontogenic keratocysts most commonly found?

Answer 15

At the angle of the mandible.

Not directly associated with a tooth.

Question 16

What are the 3 requirements for a cyst?

Answer 16

• Source of epithelium
• Stimulus for proliferation of epithelium
• Bone resorption for cavity of cysts to enalrge and grow

Question 17

Give examples of the origins of epithelial linings of odontogenic cysts.

Answer 17

• Hertwigs epithelial root sheath/Rests of Malassez = radicular cysts
• Reduced enamel epithelium = dentigerous cysts
• Dental lamina/Glands of Serres = odontogenic keratocysts, gingival cysts

Question 18

Describe a dentigerous cyst.

Answer 18

Odontogenic cyst formed from the reduced enamel epithelium, associated with the crown of an unerupted tooth, non-keratinised epithelium.

Question 19

Describe an odontogenic keratocyst.

Answer 19

Odontogenic cyst from the dental lamina/Glands of Serres, found in the angle of the mandible, multi-lobular, keratinised epithelium.

Question 20

Describe a radicular cyst.

Answer 20

Odontogenic inflammatory cyst from the epithelial rests of Malassez in the PDL as a consequence of inflammation, generally following death of the pulp.
Often develops from periapical granuloma.
Also known as apical periodontal cyst.

Question 21

Describe the incidence of radicular cysts.

Answer 21

• Peak age 4-5th decades
• Uncommon in deciduous teeth
• 63% men affected, 37% women

Question 22

Where are radicular cysts most likely to form?

Answer 22

• More likely in maxilla (60), mandible 40%

- Maxillary anterior tooth commonly affected (37%), due to being more likely to be traumatised

Question 23

Describe the symptoms of a radicular cyst.

Answer 23

• Many are symptomless
• Larger cysts will present as slowly enlarging swellings
• May present with signs of acute inflammation due to secondary infection
• May be more than 1 cysts, suggestion of cyst prone individuals

Question 24

Describe the signs of a radicular cyst.

Answer 24

• Labial or buccal swelling associated with a non-vital tooth
• May be palatal swelling (e.g. with upper incisors), but rarely lingual swelling
• Small cysts may produce bony hard swellings
• Larger cysts may be spring with eggshell crackling
• Large cysts may erode bone

Question 25

Describe the radiological presentation of an apical periodontal cyst.

Answer 25

- Uniformally radiolucent round or oval lesion at root apex - Well demarcated periphery - Surrounded by a narrow radiopaque margin extending from the lamina dura of the affected tooth

Question 26

How can you differentiate between a radicular cyst and periapical granuloma radiographically?

Answer 26

Cysts tend to be: - Larger - More radiolucent - Well defined - Corticated outline - Painless Cysts tend to be larger than granulomas

Question 27

Describe the composition of a radicular cyst.

Answer 27

- Spherical or ovoid - Cyst wall of variable thickness (can be very thin or up to 5mm thick) - May be yellow nodules of cholesterol - Brown fluid contents with shimmering cholesterol crystals

Question 28

Describe the histological features of the epithelium of an apical periodontal (radicular) cyst.

Answer 28

- Non-keratinised stratified squamous epithelium - Epithelium often discontinuous, between 1-50 cells thick - Epithelial lining may be proliferating and show arcading, or be quiescent - Mucous cells present in 40% of cysts - Some cysts have pseudo-stratified ciliated epithelium, more common in maxillary cysts - Rarely have keratinised epithelium

Question 29

Describe the histological features of the capsule of an apical periodontal cyst.

Answer 29

- Condensed fibrous CT - Variable inflammatory cell infiltrate - Cholesterol clefts with associated foreign body giant cell reaction and haemosiderin deposits

Question 30

Describe the cysts contents of a radicular cyst.

Answer 30

- May be straw coloured, but often stained brown by heamorrhage - Usually contains cholesterol crystals giving a shimerring appearance

Question 31

What are the 3 stages of apical periodontal cyst pathogenesis?

Answer 31

1) Initiation 2) Cyst formation 3) Cyst enlargement

Question 32

Describe radicular cyst initiation.

Answer 32

1) Epithelial proliferation of rests of Malassez in a periapical granuloma following pulp necrosis 2) Proliferation possibly caused by products of pulp necrosis or by local changes in the supporting CT e.g. reduction in pH, increased CO2 tension 3) The proliferating epithelium has a characteristic histological appearance with arcades and rings of epithelium encircling cores of vascular connective tissue

Question 33

Describe radicular cyst formaiton.

Answer 33

3 possible mechanisms: - Cavity forms within a proliferating mass of epithelium due to epithelial degeneration and necrosis - Epithelium proliferates to line a cavity formed as a result of CT breakdown due to proteolytic activity - Epithelium proliferates to line the CT surface of an abscess cavity

Question 34

Describe radicular cyst enlargement.

Answer 34

- Appear to expand equally in all directions - Suggest increased pressure in cyst lumen causing expansion - Alveolar bone must resorb to allow expansion

Question 35

Describe the increased pressure in the radicular cyst lumen and its effects on bone.

Answer 35

- Pressure in the cyst lumen is higher than the capillary pressure - High pressure caused by lysis of epithelial and inflammatory cells, and inflammatory exudate - Fluid also flows into lumen via semi-permeable membrane also increasing pressure - Pressure against surrounding alveolar bone causes bone resorption

Question 36

What is the management of a radicular cyst?

Answer 36

- Many resolve following extraction or endodontic treatment of extracted tooth - Surgical intervention: enucleation (removal of cyst capsule) - Marsupialisation: used for larger cysts, decompression by cutting open cyst and draining into oral cavity