Third Molars

Question 1

What does impacted mean?

Answer 1

Tooth eruption is blocked

Question 2

What is the incidence of impacted lower third molars?

Answer 2

36-59%

Question 3

What is unerupted defined as?

Answer 3

Tooth is completely enclosed in bone and soft tissue

Question 4

What is partially erupted defined as?

Answer 4

When some of the tooth has erupted into the oral cavity but not all

Question 5

What are the indications for extraction of a third molar?

Answer 5

Infection (caries, pericoronitis, periodontal disease)
Cysts
Tumours
External resorption of 7 or 8

Question 6

What is Pericoronitis?

Answer 6

Inflammation around the crown of a partially erupted tooth
Food and debris gets trapped under the operculum resulting in inflammation or infection

Question 7

What are the signs and symptoms of pericoronitis?

Answer 7

Pain
Swelling- intra or extra oral
Bad taste
Bad smell
Pus discharge
Occlusal trauma to operculum (opposing arch teeth occlude with the operculum)
Ulceration of operculum
Evidence of cheek biting
Limited mouth opening
Dysphagia
Pyrexia (fever)
Malaise
Regional lymphadenopathy

Question 8

What is the treatment for pericoronitis?

Answer 8

Treat if patient is acutely symptomatic
-Incision of localised pericoronal abscess if required
-Irrigation with warm saline or chlorhexidine mouthwash (blunt needle under the operculum)
antibiotics if there is an infection present- Pen V
Extraction of upper third molar if traumatising the operculum

Question 9

What are the predisposing factors for pericoronitis?

Answer 9

Partial eruption and vertical or distoangular impaction
Opposing maxillary 3rd molars or 2nd molars causing trauma
Upper respiratory tract infections
Stress and fatigue
Poor oral hygiene
Insufficient space between the ascending ramus of the lower jaw and the distal aspect of 2nd molar
A full dentition

Question 10

What are the categories of depth of impaction?

Answer 10

Superficially, moderately or deeply impacted

Question 11

What nerves are at risk during third molar surgery?

Answer 11

Inferior alveolar nerve
Lingual nerve
Nerve to mylohyoid
Long buccal nerve

Question 12

What does the lingual nerve supply?

Answer 12

Anterior two third of the dorsal and ventral mucosa of the tongue and also gives off a branch that supplies the floor of the mouth and the gingivae

Question 13

What are some guidelines for third molars?

Answer 13

Sign Publication Number 43, 2000
FDS, RCS revised in 2020- Parameters of Care for patients undergoing mandibular third molar surgery

Question 14

What in the history of presenting complaint should you investigate for third molars?

Answer 14

How long the problem has been occurring
SOCRATES
How many episodes
How often
severity
If there has been previous requirement for antibiotics

Question 15

Why is it important to check the TMJ during an exam before extracting third molars?

Answer 15

Large number of patients who are referred for extractions already have TMJ pain, the presenting pain is similar to pericoronitis
If there are clicks present before the surgery
If the patient has limited mouth opening - can affect surgical access
Muscles of mastication- spasm of muscles can cause pain

Question 16

What is superficial impaction?

Answer 16

Crown of the 8 is sitting next to the crown of the 7

Question 17

What is deep impaction?

Answer 17

Crown of the 8 is sitting next to the roots of the 7

Question 18

What is moderate impaction?

Answer 18

Crown of the 8 is sitting next to both the crown and root of the 7

Question 19

What are some signs of close proximity to the inferior alveolar canal in a radiograph?

Answer 19

Interruption of the white lines/lamina dura of the canal
Darkening of the root where crossed by the canal
Diversion/deflection of the inferior alveolar canal (change in the pathway the canal was taking)
Deflection of root (curving away from canal)
Narrowing of inferior alveolar canal
Narrowing of the Root
Dark and bifid root
Juxta apical area

Question 20

What is a Juxta Apical Area?

Answer 20

A well circumscribed radiolucent region lateral to the root of the third molar rather than the apex
Not usually at the tip of the apex but normally somewhere around the root
Lamina dura is intact and appearance is not pathological

Question 21

What further imaging can be done if a close relationship to the IAN is suspected?

Answer 21

CBCT
Tells us whether there is bone between the tooth and the canal or if the tooth is actually compressing the canal- helps to inform patient

Question 22

What types of angulation of 8’s can you get?

Answer 22

Vertical
Mesioangular
Distal
Horizontal
Transverse or aberrant

Question 23

How is the angulation measured?

Answer 23

It is measured against the curve of spee
Can also look at orientation of the teeth next to the 8’s to see where it sits in relation

Question 24

When is a coronectomy performed and what is it?

Answer 24

It is performed in lower 8’s that have a close relationship between the roots and the IAN
Involves removing the crown and leaving the roots in situ- less risk of damaging the nerve

Question 25

What complications should the patient be informed of in a surgical removal of an 8?

Answer 25

Minor surgical procedure if tooth needs sectioned
Possibly leaving some of the apex behind if the tooth fractures
Pain
Swelling
Bruising
Jaw stiffness/limited mouth opening (trismus)
Bleeding
Infection
Dry socket (localised osteitis)
Numbness (anaesthesia) or tingling/pins and needles sensation (paraesthesia) of the lower lip, chin, side of tongue (taste can be affected)

Question 26

What is the likelihood of temporary or permanent damage to the IAN in XLA of lower 8’s?

Answer 26

Temporary- (may take weeks/months to improve) counted as temporary if it resolves within 2 years
–10-20%
Permanent - 1%

Question 27

What nerve is damaged if the patient experiences altered or loss of taste sensation?

Answer 27

Lingual Nerve
Runs across the front two thirds of the tongue and carries nerve fibres that are responsible for normal sensation and taste. Trauma to this nerve can cause loss of sensation, altered sensation, pain and loss of taste

Question 28

How should you structure a referral of a lower third molar?

Answer 28

SBAR
Situation - what patient is presenting with
Background- History of presenting complaint
Assessment- what were your assessment findings, social history, medical history, dental history and any other relevant findings or investigations
Recommendation- opinion on what should be done (XLA/advice)

Question 29

What is the working area?

Answer 29

Space from the distal of the 7 to the ramus of the mandible

Question 30

When is surgical removal required?

Answer 30

When the tooth cannot be removed with forceps alone

Question 31

What are the stages in a surgical removal?

Answer 31

Anaesthesia
Access
Bone removal as necessary (buccal guttering)
Tooth division as necessary
Debridement
Suture (after placing soft tissues back in original position)
Achieve haemostasis
Post-op instructions

Question 32

How is access achieved in a surgical extraction?

Answer 32

Raising a buccal mucoperiosteal flap
+/- raising a lingual flap (depends on surgeon and clinical situation)
Maximum access with minimal trauma
Larger flaps heal just as quickly as smaller ones
Use scalpel in one firm continuous stroke
Minimise trauma to dental papillae

Question 33

What instruments can you use for raising the flap from the bone?

Answer 33

Mitchell’s trimmer
Howarths periosteal elevator
Ash periosteal elevator
Curved warwick james elevator

Question 34

What is involved in reflecting a flap?

Answer 34

Raise flap at base of relieving incision
Undermine/free anterior papilla before proceeding with reflection distally
Reflect with elevator firmly on bone
–avoid dissection occuring superficial to periosteum
–reduce soft tissue bruising/trauma

Question 35

What is the intention of bone removal?

Answer 35

Carried out on the buccal and distal aspect of the impacted tooth
Intention is to create a deep, narrow gutter around the crown of the wisdom tooth
Bone should be removed to allow correct application of elevators on the mesial and distal aspects of the tooth

Question 36

What burs are used for bone removal?

Answer 36

Round stainless steel and tungsten carbide burs (around the margin to create buccal gutter)
Fissure stainless steel and tungsten carbide burs (to section the tooth)

Question 37

When would you section a tooth after creating the buccal gutter?

Answer 37

If the tooth cannot be mobilised with elevators and forceps
If this is not possible and adequate bone has been removed then the tooth should be sectioned

Question 38

Where is sectioned in horizontal crown sectioning?
In complete XLA?
In coronectomy?

Answer 38

When sectioning to remove the entire tooth sectio above the enamel-cementum junction. This leaves behind some crown and allows orientation and elevation
In a coronectomy- section below the enamel-cementum junction (no enamel can be left behind in this procedure)
DO NOT use bur to go all the way through the tooth to the lingual side to avoid excess damage, when the hole is created an elevator can be used to break the crown off the tooth
Can further section the roots after horizontal crown section if required- the roots are elevated individually

Question 39

When is a vertical crown section used?
What does this allow?

Answer 39

Where the roots are separate, the tooth may be sectioned longitudinally/vertically
This allows removal of the distal portion of the crown and distal root, followed by elevation of the mesial portion of the crown and mesial root

Question 40

Why do you need to debride the socket after XLA?

Answer 40

Must account for all the apices of the tooth and that none of the tooth has been left behind
Must clean the socket and ensure that there are no bony spicules left around the socket

Question 41

What kinds of debridement are performed?

Answer 41

Physical
–Bone file or bone nibblers (bone rongeure or handpiece to remove sharp bony edges)
–Mitchells trimmer to remove soft tissue debris
Irrigation
–sterile saline into the socket and under the flap
–irrigate underneath the flap
Suction
–Aspirate under flap to remove debris

Question 42

What are the aims of suturing?

Answer 42

Reposition tissues
Cover bone
Prevent wound breakdown
Achieve haemostasis

Question 43

List post operative instructions to give patient.

Answer 43

No vigorous exercise for 24 hours
No alcohol for 24 hours
No smoking for 48 hours
When eating and drinking careful of hot foods before anaesthesia wears of
Avoid agitating the gum with fingers or toothbrushes or tongues (dislodges blood clot)
Advise on analgesia
Swelling is normal (if spreads to underside of jaw or upto eye then be concerned)
Normal for socket to bleed (if bleeds more than 30 mins, number to phone)
Infection- if pain is worsening or they notice a bad taste or pus from site contact dentist
Bruising is normal
Jaw stiffness (from prolonged mouth opening, muscles spasm)
Soft diet and limited mouth opening can be helpful
IDB generally lasts 3 hours
Rinse with warm salty water 2-3 times a day, 24 hours after the extraction

Question 44

What is involved in a coronectomy?

Answer 44

Crown is removed with the deliberate retention of the root adjacent to the IAN
Transection of tooth 3-4mm below the enamel (and the height of the bone) of the crown into the dentine
Elevate/lever crown off without mobilising the roots
Pulp left in place untreated (majority heals over unaffected)
Socket irrigated with saline

Question 45

What must you warn the patient in a coronectomy?

Answer 45

If the root is mobilised during crown removal the entire tooth must be removed (more likely with conical fused roots)
Leaving roots behind could result in infection (rare)
Can get a slow healing/painful socket
The roots may migrate later and begin to erupt through the mucosa and a second extraction may be required
Similarly the roots can migrate further into the IAN