Third Molars

Question 1

When do 3rd molars:
1. Erupt
2. Crown calcification
3. Root calcification

Answer 1

1. 18 - 24y
2. 7 - 10y (if not present at 14 then absent)
3. 18 - 25y

Question 2

Rate of Agenesis of third molars

Answer 2

• agenesis = failure of organ to develop
• 1 in 4 adults at least one absent 3rd molar

Question 3

What causes a 3rd molar to be impacted and impacts of this

Answer 3

1. Alveolar bone
2. Soft tissue
3. A tooth
4. A combination of these

• caries
• pericoronitis
• cyst formation

Question 4

Incidence of impacted 3rd molars

Answer 4

36 - 59 %

Question 5

Nerves at risk in M3M’s XLA

Answer 5

1. Inferior alveolar (large risk)
2. Lingual (medium risk)
3. Long buccal (low risk)
4. Mylohyoid (low risk)

Question 6

Signs of inferior alveolar intimacy with M3M’s

Answer 6

1. Interruption of corticated lines (lamina dura) of tooth or canal
2. Darkening of root where crossed by canal
3. Deflecting of IAC
4. Deflecting of root
5. Narrowing of IAC
6. Narrowing of the root
7. Dark and bifid root (wide apex opening)
8. Juxta apical area (well defined radiolucency with corticated margins, lateral to root rather than apex = not pathology but meant to be a continuation of lamina dura and corticated margins of IAC canal) thus close proximity

Question 7

Guidelines for XLA of wisdom teeth

Answer 7

NICE - guidance on extraction of wisdom teeth, 2000

Question 8

Indications for XLA of third molars

Answer 8

1. Undesirable Caries
2. Acute severe single / Recurrent pericoronitis
3. Periodontal disease
4. Cysts
5. Tumours
6. External resorption of 6/7/8

Other reasons

• orthognathic
• medical indications prophylaxis (immunosuppressed, awaiting cardiac surgery, bisphosphonates antiangiogenics, chemotherapy, )
• patient age / future ability to cope with tx
• auto transplantation
• g

Question 9

What is pericoronitis

Answer 9

PE tooth with operculum, inflammation around crown

As communication distal to 7 with food packing etc (can be barely visible)

20-40 year olds commonly

Question 10

Signs and symptoms of pericoronitis

Answer 10

Pain

Swelling

Suppuration

Bad taste

Bad breath

Dysphasia

Pyrexia

Malaise

Regional lymphadenopathy

Ulceration of operculum

Occlusal trauma to operculum

Question 11

Predisposing factors for pericoronitis

Answer 11

White race

A full dentition

Insufficient space between ascending ramus and distal of 7

Poor OH

Stress and fatigue

Vertical / distoangular impaction

Question 12

Treatment options for pericoronitis

Answer 12

Irrigation with warm saline water / chlorhexidine (anaphylaxis risk) with blunt needle

Analgesia advice

Dietary advice: Keep fluid levels up and eat soft food

Antibiotics*

If large extra oral swelling = maxfax urgent referral

Incision and drainage of abscess

XLA / coronectomy

Operculectomy

Surgical exposure (can allow to erupt)

Question 13

When provide antibiotics for pericoronitis

Answer 13

Severe pericoronitis:

Systemically unwell

Swelling extra orally

Immunocompromised (I.e. diabetic)

Question 14

What checking in OPT for XLA of third molars

Answer 14

Involvement of Sinus or IAN

Presence of disease

Anatomy for XLA (crown, root, condition)

Orientation of Impaction

Any associated pathology

Question 15

Types of impaction of 3rd molars

Answer 15

Done by angulation compared to curve of spee

• vertical (30 - 38%)
• mesial (40%)
• distal (6 - 15%)
• horizontal (3 - 15%)
• transverse (bucco lingual angulated) rare
• aberrant (can be up the ramus / completely ectopic) rare

Question 16

How are 3rd molars depths defined in surgical XLA planning

Answer 16

Superficial - crown only involved with crown of 7

Moderate - crown involved with crown and root of 7

Deep - crown only involved with root of 7

Question 17

Indications for NO XLA of 3rd molars

Answer 17

Symptomatic 8 with no associated disease ( consider other causes )
- TMD
- parotid disease
- lesions
- headaches
- referred angina pain
- oropharyngeal oncology

Asymptomatic with low disease risk
- just review at intervals

Question 18

Complications / risks post 3rd molar XLA (with % chance)

Answer 18

Pain
Bleeding
Swelling
Bruising
Infection
Jaw stiffness
Dry socket (osteitis)
Surgical procedure
Damage to adjacent teeth / rests.
Altered sensation (HYPO/HYPER/ana/para/dysaethesia)

IDN
- temporary 10-20%
- Permanent <1%

Altered taste from lingual nerve very rare
- temp 0.25-23%
- perm 0.14-2%

Question 19

How long for nerve damage from XLA is diagnosed as permanent

Answer 19

18-24 months, not going to heal

Question 20

Special investigation if PA shows close relationship between IAC and 8 to be XLA

Answer 20

Cone beam computed tomography (CBCT)

Question 21

Benefit of local anaesthetic in an XLA even if GA

Answer 21

Haemostasis easier

Question 22

How to cut flap for M3Ms XLA

Answer 22

Buccal mucoperiosteal flap

Can do lingual but risk lingual nerve damage

Larger flap heals just as fast

One continuous stroke with scalpel

Minimise trauma to dental papillae

Question 23

How to reflect surgical flap

Answer 23

Instruments

• Mitchell’s trimmer
• hearths periosteal elevator (holds out way)
• ash periosteal elevator
• curved Warwick James elevator (asking papillae flaps, others for while flap)

Raise from base of releasing incision

Full tissue done to bone

Question 24

How is bone removal facilitated for XLA

Answer 24

Electrical straight hand piece with saline cooled bur (surgical emphysema)

Round or fissure stainless steel and tungsten carbide burs

Round = remove bone
Fissure = separating tooth

Bone removal = buccal to distal

DEEP and NARROW gutter around tooth

work distal to medial as if slip = lingual nerve

Question 25

Types of tooth division for XLA of M3Ms

Answer 25

Horizontal
- NOT coronectomy as want enamel to grasp

Root division for XLA individually (vertical)
- if impacted so can’t XLA whole

ALWAYS cut distal to medial

Question 26

Types of debridement

Answer 26

Hard or soft tissues:

Physical
- handpiece / bone files
- soft tissue = Mitchell’s trimmer / Victoria curette)

Irrigation
- sterile saline

Suction
- aspirate under flap

Question 27

Aims of suturing following XLA and flap

Answer 27

Reposition tissue

Cover bone

Prevent wound breakdown

Achieve haemostats (compress Blood vessels)

Approximate tissue (don’t cover socket)

Question 28

Types of flap design for M3Ms XLA

Answer 28

3 sided flap (with medial releasing flap)

2 sided envelope flap (only distal releasing flap)

Question 29

Post op instructions for XLA

Answer 29

Careful with numbness not to bite self

Don’t touch area with finger, tongue or toothbrush

Don’t rinse mouth 6 hours after surgery / not that day

Warm salt mouth rinse 3-4 times daily (teaspoon of salt)

Cut down smoking for next week

Try not elevate heart rate for few days

Ice pack for swelling (wrapped in towel)

Over the counter analgesia

If pain worsens 2-3 days contact dentist

If antibiotics = finish

Contact us if swelling spreads, pus, numbness, jaw stiffness > 3 weeks

Question 30

Coronectomy procedure

Answer 30

Reduce chance of IAN damage

Transection 3-4mm bellow enamel and this distance bellow bone crest at least

Cut then elevate off

Pulp left

Irrigation then flap left open over XLA (some fully cover)

Question 31

Coronectomy follow up and warnings

Answer 31

Follow up
- review 1-2 weeks
- then 3-6m then 1 year
- radiograph at 6m-1y

Warnings
- if root mobilised, needs removed
- can get infection with roots left
- slow healing of painful socket
- may need XLA of roots if migrate to gingiva

Question 32

How to remove upper 8s

Answer 32

Usually very easy but can be very hard

Straight or curved Warwick James

Upper third molar bayonet forceps

SUPPORT tuberosity and if not budging will fracture this so only use forceps here

Can do buccal flap