OS- Cysts

Question 1

What is a cyst?

Answer 1

A pathological cavity containing fluid/ semi fluid or gaseous contents which is not created by the accumulation of pus.

Question 2

How can you differentiate between an infected cyst and an abscess?

Answer 2

Because infected cysts lose their cortication they look similar to abscesses so we need to consider the shape/size of the radiolucency.

Cysts will often be round and displace the teeth/bone around them.

Abscesses often have more irregular shapes and don’t displace the surrounding hard tissues. (but they can cause tissue breakdown)

Question 3

What are the symptoms of a cyst in the jaw?

Answer 3

Pain
Tenderness
Slow growing swelling.
Displacement of teeth.
Mobility of teeth.
Discoloration of the tooth.

Although cysts are often asymptomatic until they get infected.

Question 4

How can we tell if a cyst comes from the tooth or the periodontium?

Answer 4

Sensibility testing the tooth.
If the cyst comes from the tooth- the tooth will be non-vital.
If the cyst comes from the periodontium- the tooth will be vital.

Question 5

What initial radiographs do we select to investigate a cyst?

Answer 5

Oblique occlusal/ Periapical / OPT (not for anterior)

Question 6

What are the radiographic features we look for in a cyst?

Answer 6

• Shape (spherical or egg shaped)
• Margins (defined and corticated unless infected)
• Locularity- often unilocular
• Multiplicity- single/ bilateral (multiple would indicate a syndrome)
• Effect on the surrounding anatomy-
  How aggressive is it- Displace (cortical plates/ adjacent teeth/ maxillary sinus/ inferior alveolar canal)
  Root resorption?
• Inclusion of unerupted teeth in the cyst.

Question 7

How can we classify cysts?

Answer 7

Structure (epithelial or non epithelially lined)
Pathogenesis (Inflammatory or pathological)
Origin (Odontogenic or non-odontogenic)

Question 8

What is an odontogenic cyst?

Answer 8

The most common type of bony swelling in the jaw (>90% of bony swellings are odontogenic cysts)
This is an epithelial lined cyst that arises from tooth tissue and is formed in a tooth bearing area.

Question 9

How do ontogenic cysts form?

Answer 9

From leftover tooth tissue when it is broken down in the jaw.
Rests of mallasez- remnants of hertwigs epithelial sheath (dentine production)
Rests of Seres- remnants of the dental lamina (produces the dental papilla)
Reduced enamel epithelium- remnants of the enamel organ .

Question 10

What are the two most common types of odontogenic cyst?

Answer 10

Radicular and residual.

Question 11

What is a radicular cyst?

Answer 11

This is an inflammatory odontogenic cyst that is always associated with a non vital tooth.

Question 12

What is the presentation of a radicular cyst?

Answer 12

Often asymptomatic (unless infected)
Typically slow growing with limited expansion.

Question 13

How does a radicular cyst form?

Answer 13

There is proliferation of the epithelial rests of malassez at the apex due to the inflammatory change caused by pulp necrosis:
Either through
- Proliferating epithelium with central necrosis.
- The centre gets cut off from the blood supply & becomes necrotic. (This cyst inside is known as a microcyst which brings fluid into the granuloma)
- The epithelium surrounds the fluid area.

Question 14

How do periapical granulomas differ from a radicular cyst?

Answer 14

**Peri apical granulomas could be treated by RCT of the tooth, A radicular cyst could not. (Conflicting information) **
Radicular cysts are larger than periapical granulomas. (>15mm diameter then 2/3 of cases would be a radicular cyst)

Question 15

What are the radiographic features of a radicular cyst ?

Answer 15

• Well defined round/oval radiolucency.
• Corticated margin continuous with the lamina dura of the non-vital tooth.
• Larger lesions may displace the adjacent structures.
• Long standing lesions may cause external root resorption &/ contain dystrophic calcification.

Question 16

What are the histological features of a radicular cyst?

Answer 16

stratified squamous epithelial lining.
Connective tissue capsule (with inflammation in the capsule)

Question 17

What is a residual cyst?

Answer 17

When the radicular cyst remains after removal of the tooth or treatment via root canal

Question 18

What is a lateral reticular cyst?

Answer 18

This is a radicular cyst that is associated with an accessory canal. This is located at the side of the tooth instead of the apex.

Question 19

What are inflammatory odontogenic cysts?

Answer 19

These are odontogenic cysts associated with a vital tooth.

Question 20

Give and describe two examples of inflammatory odontogenic cysts?

Answer 20

Radicular (and residual)- cyst occuring at the apex of a non vital tooth.
Paradental cyst- Cysts typically occuring at the distal aspect of a partially erupted mandibular third molar.
Buccal bifurcation cyst- typically occuring at the buccal aspect of the mandibular first molar.

Question 21

What is a dentigerous cyst?

Answer 21

A cyst associated with the crown of an unerupted (and usually impacted tooth)
(Most common with the 3rd molars in the mandible)

Question 22

What are the radiographic signs of a dentigerous cyst?

Answer 22

Corticated margins attached to the ADJ of the tooth.
Larger cysts may begin to envelope around the root of the tooth.
Tend to expand symmetrically initially but larger cysts may expand unilaterally.

Question 23

Discuss the histology of a dentigerous cyst?

Answer 23

Thin non-keratinised Stratified squamous epithelium.
No significant inflammation- BUT may resemble a radicular cyst if inflamed

Question 24

What do we measure when diagnosing a dentigerous cyst?
And how do we interpret the results?

Answer 24

The radius of the follicle.
If it is >4mm consider that it is a cyst.
If it is >10mm assume it is a dentigerous cyst.

Question 25

Give an example of a variant of a dentigerous cyst?

Answer 25

An eruption cyst where the cyst is contained in the soft tissues rather than bone. There is enlargement of the follicle around the tooth. This is more commonin incisors and almost exclusively in children.

Question 26

What is an odontogenic keratocyst?

Answer 26

This is a cyst that originates from tooth structure but has no specific relationship to the teeth.

Question 27

How does an odontogenic keratocyst present radiographically ?

Answer 27

It has scalloped margins. Can be multilocular. Often causes the displacement of adjacent teeth. Doesn't have very good growth pottential.

Question 28

How do we diagnose an odontogenic keratocyst?

Answer 28

Aspiration biopsy- it should contain squames and has a low soluble protein content.

Question 29

Discuss the histology of an odontogenic keratocyst.

Answer 29

No rete pegs with the epithelium and connective tissues- this means the epithelium can separate from the wall allowing bits to remain in bone after surgery. Multicentric growth Production of daughter cysts (satelite cysts- that can be left behind)

Question 30

What type of cyst has the biggest problem with recurrence and why?

Answer 30

Odontogenic keratocyst - it has no rete pegs with the epithelium and connective tissue which allows the epithelium to separate from the wall- allowing bits to remain in bone after surgery

Question 31

What is the presentation of Basal Naevus syndrome?

Answer 31

multiple odontogenic keratocyst Multiple basal cell carcinomas Palmar and plantar pitting. .

Question 32

What is the nasopalatine duct cyst?

Answer 32

A developmental non-odontogenic cyst which arises from the nasopalatine duct remnants.

Question 33

How does a nasopalatine duct cyst present?

Answer 33

Often asymptomatic- Patients can note a salty taste in the patient's mouth without infection. Larger cysts can displace the teeth or cause swelling in the palate. Cyst always involves the midline but is not always symmetrical.

Question 34

Discuss the histology of a nasopalatine duct cyst.

Answer 34

Non-keratinised stratifed squamous with modified respiratory epithelium

Question 35

How does a Nasopalatine duct cyst present on a radiograph.

Answer 35

Corticated radiolucency between/ over the roots of the central incisors Often unilocular May appear Heart shaped- due to the superimposition of the anterior nasal spine.

Question 36

How do we differentiate between a cyst and the incisive fossa on a radiograph?

Answer 36

If <6mm assume incisive fossa. 6-10mm monitor >10mm suspect cyst.

Question 37

What is a solitary bone cyst?

Answer 37

non-odontogenic cyst without an epithelial lining. e.g. a simple/traumatic or haemorrhagic bone cyst.

Question 38

How does a solitary bone cyst present?

Answer 38

Usually asymptomatic (incendental finding) Rarely pain or swelling.

Question 39

Discuss the radiographic features of a solitary bone cyst?

Answer 39

Most commonly found in the premolar/molar region of the mandible. Variable definition & cortication.

Question 40

What is an anerusymal bone cyst?

Answer 40

A cyst in which blood is aspirated during an aspiration biopsy.

Question 41

What is a Stafne cavity?

Answer 41

This is not a cyst. This is a depression in the bone which contains salivary or fatty tissue. (although cortical bone is preserved) It only occurs in the mandible (almost exclusvely lingual.

Question 42

Discuss the presentation of a stafne cavity.

Answer 42

Often in the angle or posterior body of the mandible. Well defined & corticated Inferior to the inferior alveolar canal Asymptomatic Rarely displaces adjacent structures.

Question 43

How do we take an aspiration biopsy.

Answer 43

Using a 5-10ml wide bore needle to drain the contents in the GDP.

Question 44

How do we take an incisional biopsy?

Answer 44

This is partial removal under LA. A mucoperiosteal flap is raised with bone removal if required. We incise and remove a section of the lining to obtain a sample.

Question 45

What is an excisional biopsy?

Answer 45

Complete removal of the cyst.

Question 46

What are the two cyst treatments. Compare them. Their indications. Advantages and disadvantages.

Answer 46

**Enucleation**- Removal of the whole cystic lesion under GA. *Indications*: Dependent on patient healing ability and adjacent structures. Advantages- Whole lining can be examined pathologically. Limited closure. Little aftercare needed. Bone healing should happen after removal. Disadvantages- Risk of mandibular fracture with large cysts. Chance of leaving some of the lining (causing recurrence) If it is a dentigerous cyst we want to preserve the tooth. Can damage adjacent structures. Clot filled cavity may become infected. Contraindications- old age/poor health. **Marsupilisation**- Creation of a surgical window in the wall of the cyst to remove the contents and suture it to the surrounding epithelium. To encourage the cyst to decrease in size for later enucleation. *Indications*- If enucleation would damage the surrounding structures. If access to the area is difficult. To allow eruption of the teeth affected by a dentigerous cyst. Elderly or medically compromised patients unable to withstand extensive surgery. Very large cysts that would be at risk of jaw fracture with enuclceation. *Advantages*- Simple to perform. May spare vital structures. Can combine with enucleation at a later date. *Disadvantages*- Opening may close and cyst can reform. Complete lining is not available for histology. It is difficult to keep clean and lots of aftercare needed.