Third Molars

Question 1

When do 3rd molars erupt?

Answer 1

18-24

Question 2

When does crown calcification occur?

Answer 2

7-10

Question 3

What nerves are at risk?

Answer 3

IAN
Lingual
Mylohyoid
Long buccal

Question 4

Describe IAN anatomy + what it supplies

Answer 4

Peripheral sensory nerve
Branch of mandibular div of trigeminal
Supplies teeth gingivae lower lip chin and tongue on that side

Question 5

Describe Lingual nerve anatomy + what it supplies

Answer 5

Branch of mandibular div of trigeminal
Supplies anterior 2/3rds of tongue, lingual gingivae + FOM

Question 6

Name the 3rd molar guidelines

Answer 6

Nice 2020
Sign 43
FDS RCS 2020

Question 7

List indications for XLa of 8s (8)

Answer 7

• Caries in 8
• Caries in 7
• External resorption of 7 due to 8
• Periodontal disease in 8
• PA pathology in 8
• Cysts/tumours
• More than 1 episode of severe pericoronitis
• Render pt dentally fit: prior to radiotherapy tx/cardiac surgery

Question 8

List causes of external resorption

Answer 8

Trauma
Ortho pressure
Infection

Question 9

Most common cause of ERR in 7 due to 8

Answer 9

Not enough space between 7d and ascending ramus of mandible

Question 10

What is pericoronitis?

Answer 10

Inflammation around crown of PE tooth
Usually transient + self limiting

Question 11

Bacteria associated with pericorontiis

Answer 11

Actinomyces
Prevotella

Question 12

Signs + symptoms of pericoronitis

Answer 12

Pain
Swelling (I/O E/O_
Bad taste
Occlusal trauma to operculum
Ulceration to operculum
Cheek biting
Dysphagia - diff swallowing
Limited mouth opening
Fever
Halitosis
Regional lymphadenopathy

Question 13

Tx for pericoronitis

Answer 13

Irrigate with warm saline under operculum with blunt needle
XLa upper if impeding eruption
Advise regarding analgesia
Keep fluid levels up soft diet
No antibiotics unless severe systemic issues

Question 14

Predisposing factors to pericoronitis (6)

Answer 14

White
Full dentition
Opposing 8 causing trauma
Poor OH
Stress
Insufficient space between 7d and ascending ramus

Question 15

Medically relevant issues for XLa

Answer 15

Liver disease
Anticoagulants
Bisphosphonates
Contraceptive pill
Bleeding disorders

Question 16

Relevance of OPT for Xla planning

Answer 16

• Root morphology (apical hooks/ divergent/convergent)
• Crown morphology
• Bone levels/periodontal disease
• PA pathology
• Cysts/tumours
• Closeness to ID canal
• Depth of impaction
• Orientation of impaction (mesial, distal, horizontal transverse)

Question 17

Signs of close relationship with ID canal

Answer 17

• Interruption of tram lines (lamina dura)
• Dark root when crossed by canal
• Juxta-apical area
• Deflection of canal when passing root
• Deflection of root
• Narrowing of ID canal

Question 18

What is the juxta-apical area?

Answer 18

Well circumcised radiolucent region around root

Can appear corticated

Lamina dura still intact

Question 19

How is angulation measured

Answer 19

Curve of spee
Following occlusal surfaces

Question 20

What type of handpiece do we use for bone removal?

Answer 20

Straight handpiece avoids necrosis of bone

Question 21

Why can we not use an air driven handpiece?

Answer 21

Surgical emphysema risk

Question 22

Function of Mitchells trimmer

Answer 22

Remove soft tissue debris

Question 23

How to do a coronectomy (3)

Answer 23

Drill 3-4mm below crown then elevate

Decoronate

Reduce bone left so its below enamel and into dentine

Question 24

Warnings about a coronectomy

Answer 24

• Roots may migrate and erupt
• If roots mobilised need to remove
• Can get slow healing