Radiology-odontogenic tumours

Question 1

What is characteristic of an odontogenic tumour ?

Answer 1

They are benign (100:1 chance of malignancy)
Asymptomatic (only painful if infected or causing pathological fracture)
Mostly found within the bones of the jaw.

Question 2

Give example(s) of epithelial odontogenic tumours?

Answer 2

Ameloblastoma.
Adenomatoid odontogenic tumour
Calcifying epithelial odontogenic tumour

Question 3

Give example(s) of mesenchymal odontogenic tumours

Answer 3

Odontogenic myxoma

Question 4

Give example(s) of mixed odontogenic tumours?

Answer 4

Odontome (This contains dental hard tissues due to the concept of induction- you cannot have enamel without dentine)

Question 5

What are the most common odontogenic tumours?

Answer 5

Ameloblastomas & odontomes (50% of all tumours)

Question 6

What causes the formation of odontogenic tumours?

Answer 6

Leftovers in the jaw of:
* Rests of serres
* Rests of Malassez
* Reduced enamel epithelium.

Question 7

What is an ameloblastoma and give some characteristics ?

Answer 7

A benign epithelial tumour.
It is locally destructive but slow growing and typically painless (80% of these occur in the posterior mandible)

Question 8

Give the radiographic features of an ameloblastoma?

Answer 8

Margins -Corticated & well defined.
Can be mutlicystic (scalloped margins) or uni-cystic.
Radiolucent.
The mutlicystic type may have thick curved septa with white lines causing a soap bubble appearance.
Causes:
Displacement of adjacent structures.
Thinning of bony cortices
Knife edge external root resorption (clean cut of the tooth)

Question 9

Name 2 different types of ameloblastoma and compare their histological appearance?

Answer 9

Follicular (Ameloblasts like cells are arranged in islands)
Plexiform (ameloblasts like cells are arranged in strands)

Question 10

Discuss the recurrence rate of an ameloblastoma?

Answer 10

This has a high recurrence rate (15%) because there is no connective tissue capsule so cells can grow and infiltrate into the jawbone.

Question 11

How do we manage an ameloblastoma

Answer 11

Resect the tumour with large margins
and review

Question 12

What is an adenomatoid odontogenic tumour and some characteristics of this?

Answer 12

Benign epithelial tumour.
It is commonly found in the anterior maxilla.
Mostly associated with unerupted maxillary canines.

Question 13

How does an adenomatoid odontogenic tumour present radiographically?

Answer 13

75% are associated with an unerrupted tooth.
Tumour is typically attached apically to the ACJ-

Radiolucency around the ACJ of the tooth
Corticated margins.

Question 14

Discuss the histology of an adenomatoid odontogenic tumour?

Answer 14

• Epithelial cells surround the tumour making it look like a duct.
• There is a fibrous tissue capsule around the cells

Question 15

Discuss the recurrence of an adenomatoid odontogenic tumour?

Answer 15

Because of the fibrous tissue capsule around the cells the surgical removal is more straightforward and there is a lower reccurence rate)

Question 16

What is a calcifying odontogenic tumour and discuss the characteristics of it?

Answer 16

a benign epithelial tumour,
Most common site is the posterior mandible
50% are associated with an unerupted tooth.

Question 17

What is an odontogenic myxoma and discuss the characteristics of it?

Answer 17

This is a benign mesenchymal tumour.
It can be unilocular (smaller lesion) or mutlilocular as it becomes bigger- soap bubble appearance.
There is slow growth along the bone before causing notable bucco-lingual expansion- it takes a while before they are noticed clinically.

Question 18

Discuss the radiographic presentation of an odontogenic myxoma?

Answer 18

Well defined radiolucency (can have a thin corticated margin)
When this grows it scallops between the teeth but as it gets bigger the teeth are displaced.

Question 19

Discuss the histology of an odontogenic myxoma?

Answer 19

Loose myxoid tissue with stellate cells
May contain islands of inactive odontogenic epithelium
There is no fibrous tissue capsule (it is locally invasive 25% recurrence rate)

Question 20

Discuss the recurence of an odontogenic myxoma ?

Answer 20

There is no fibrous tissue capsule- it is locally invasive (25% recurrence rate)

Question 21

How do we manage an odontogenic myxoma?

Answer 21

Curettage for smaller lesions (scrape it out)
Resection (take a block of bone away)
Follow up due to the recurrence risk

Question 22

What is an odontoma and discuss the characteristics of it ?

Answer 22

This is a benign mixed epithelial and mesenchymal tumour.
This is a malformation of dental tissue (enamel/ dentine/ cementum/ pulp)
It can be associated with other odontogenic lesions (e.g. dentigerous cysts).
It can be surrounded by a dental follicle
It lies above the inferior alveolar canal

Question 23

Name and compare the different types of odontoma?

Answer 23

Compound odontoma- Ordered dental structures. May appear as small teeth.This is more common in the anterior maxilla.
Complex odontoma- disorganised mass of dental tissues- this is more common in the posterior border of the mandible.

Question 24

Discuss the histology of an odontoma?

Answer 24

It contains dental tissues because it originates from both epithelial and mesenchymal hard tissues.
You see:
Soft tissue that resembles the tooth germ.
Dentine
The enamel space- A slide preparation dissolves the enamel as it is fully calcified)

Question 25

How do we manage an odontoma?

Answer 25

Remove the odontoma.