Cysts

Question 1

Describe what a cyst is

Answer 1

A fluid filled sac. Rounded and smooth and removed by enucleation. Epithelial lined.

Question 2

What are the clinical features of a cyst?

Answer 2

• Slow growing
• Commonly associated with non vital or unerupted tooth
• Slow bony expansion
• Tooth displacement or tooth mobility

Question 3

What are the radiological features of a cyst?

Answer 3

• Radiolucent
• Round or oval, scalloped margin
• Well defined, smooth, well corticated
• Tooth displacement and occasional root resorption
• Thinning, expansion and perforation of cortical plates
• Displacement of anatomical margins e.g. ID canal, maxillary floor sinus

Question 4

What are some ways that cysts can be treated?

Answer 4

1) Enucleation (scoop out)
2) Marsupialization (hole made in cyst to reduce pressure)
3) Excision (cut out with a margin)

Question 5

What cells do radicular cysts come from?
What are some characteristics of radicular cysts?

Answer 5

Cell rests of Malassez from the apical third of the root.
- Epithelial cavity on non-vital tooth
- Apical, lateral or residual
- upper laterals in males are most common

Question 6

Explain the process of a radicular cyst forming

Answer 6

1) Non vital tooth
2) Inflammation extends into PDL around tooth apex
3) Inflammation causes widening of lamina dura
4) Cell rests of mallassez in the apical third of the tooth
5) Epithelium proliferates in response to inflammation
6) Basal cells proliferate around the edge, mature and move to centre of island
7) The cavity contains cells such as inflammatory exudate that exerts osmotic pressure on the cyst causing expansion

Question 7

What are the radiological features of a radicular cyst?

Answer 7

• Radiolucent
• Apex of non vital tooth
• Circular at first and gets ovoid as it expands
• Well defined surface, rounded, smooth and often corticated
• Tooth displacement, expansion and thinning of the cortical plate

Question 8

What bodies are seen in histological features of radicular cysts?

Answer 8

Rushtom bodies

Question 9

What are the differences in histology between a residual radicular cyst and a radicular cyst?

Answer 9

Residual radicular cyst = inflammation subsides as cause removed, epithelium is less hyperplastic, thinner and better organized.

Question 10

What is the definition of an inflammatory collateral cyst?
What are the radiological features?

Answer 10

Cyst arising on the side of a tooth from epithelium near the furcation of the molars.
Tooth tends to be vital.

Radiological:
- Unilateral or bilateral
- Radiolucent
- Affected tooth may be tipped out of alignment

Question 11

What is the definition of a dentigerous cyst?

Answer 11

• A cyst which contains the crown of an unerupted tooth and has an epithelial lining attached at the CEJ
• Reduced enamel epithelium seperates from enamel to form the cyst cavity

Question 12

Explain the process of a dentigerous cyst formation

Answer 12

1. The impacted tooth crown is surrounded by reduced enamel epithelium
2. If the tooth does not erupt, the space between the epithelium and the tooth enlarged due to fluid leakage into this space
3. Lots of small molecules are generated in this space causing an osmotic pressure
4. Orthodontic pressure exerted on surrounding structures
5. Cyst enlarges and anatomical structures are placed under orthodontic pressure
6. Cyst pushes out to form a round shape putting pressure on ID canal

Question 13

What are the radiological features of a dentigerous cyst?

Answer 13

• Radiolucent
• Centered around crown of an unerupted tooth
• Appears attached at CEJ
• Round shape when small, elongates when larger

Question 14

What are the clinical features of an odontogenic keratocyst?

Answer 14

• Common sites = angle and posterior body of mandible
• Unilocular
• May replace a tooth
• Arises from dental lamina rests (cell rests of serres)
• May reoccur following treatment

Question 15

What are the radiological features of a keratocyst?

Answer 15

• Radiolucent
• Posterior mandible
• Well defined, corticated margin
• Round when small and then elongates
• Unilocular, scalloped margin

Question 16

How do odontogenic keratocysts grow?

Answer 16

• No internal pressure
• Grow by lining
• Lining has high mitotic activity and the wall secretes bone resorbing factors
• Growth is along path of least resistance
• Teeth are no displaced, cortical bone is not resorbed

Question 17

What condition is associated with multiple odontogenic keratocysts?

Answer 17

Basal cell naevus syndrome

Question 18

What is the classification of a nasopalatine cyst?

Answer 18

• Developmental and non-odontogenic

Question 19

What are the clinical features of a nasopalatine cyst?

Answer 19

• Swelling over incisive canal
• Prone to being burst due to trauma
• All teeth are vital
• Age range 30-60 years

Question 20

What are some radiological features of a nasopalatine cyst?

Answer 20

• Radiolucent
• Midline is centered between apices of two central incisor roots
• May displace the central incisor root apices away from each other
• Round/oval shape
• Root resorption is rare