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Third Molars > Third Molars > Flashcards

Third Molars Flashcards

1
Q

What is the usual eruption age of third molars

A

18-24 years

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2
Q

When is the calcification of the crown begin and complete in third molars e

A

7-10. Years and complete by 18 years

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3
Q

At what age if the third molar is missing on a radiograph would you expect it to. Never develop

A

14

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4
Q

Where does the lingual. Nerve lie

A

On the superior attachment of the mylohyoid

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5
Q

What is the incidence of impacted M3M

A

36–30%

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6
Q

What are the 4 therapeutic indications for c extraction of M3M

A

Infection
Cysts
Tumours
External resorption of 7 and 8

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7
Q

What is the most common cyst arise from M3M

A

Dentigenergous cyst arising from the reduced enamel epithelium separating from the crown

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8
Q

What two ways of impaction are higher risk of disease

A

Mesial-angular
Horizontal

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9
Q

What is pericornitis

A

Inflammation around a partially erupted tooth
Food and debris gets trapped under the operculum and causes inflammation and infection

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10
Q

Name three anerobic Microbes involved in pericornitis

A

Actinomyces
Streptococci
Beta lactamase producing prevotella intermedia

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11
Q

What two kinds of impaction predispose a patient to pericornitis

A

Vertical and distoangular

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12
Q

Insufficient space between what two structures can result in pericornitis

A

Ascending ramus of lower jaw and distal aspect of M2M

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13
Q

What is the risk of temporary numbness following extraction of a lower third molar

A

10-20%

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14
Q

What is the risk of permanent numbness following XLA of lower 3rd molar

A

<1%

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15
Q

Name 4 reasons for Indication of extraction of a lower third molar

A

Infection - caries, periodontal dsieae or local bone infection
Cyst
Tumour
External respotion of 7 0r 8
Impaction leading to high risk of disease
Medical indications

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16
Q

What muscle does the lingual nerve lie on the superior attachment of

A

The mylohyoid muscle

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17
Q

What 4 nerves are at risk during extraction of a mandibular third molar

A

Inferior alveolar nerve
Lingual nerve
Nerve to mylohyoid
Long buccal nerve

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18
Q

What are 5 predisposing factors to periocoronitis

A

Partial eruption and vertical or distoangular impaction
Opposing M3M or M2M causing mechanical trauma contributing to recurrent infection
Upper respiratory tract infections
Poor oral hygiene
Insufficient space between the ascending ramus of the lower jaw and the distal aspect of the M2M
A full dention
White race

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19
Q

Why is it so important to check the TMJ on patients with third molar pain

A

Often patients that are referred in for third molar pain aren’t actually having third molar pain it is instead TMD pain

20
Q

What is the working space distance when discussing M3M

A

Distance between distal of the M2M and the ascending ramus

It is essentially the space you have to get it out

21
Q

When assessing follicular width above what measuremt would you be concerned that there is pathology

A

Anything more than 2-3mm

22
Q

There are many radiographic signs that can indicate a close relation ship of the ID canal to the roots of the M3M
What three are we most worried about that have been identified to carry the most increased risk of nerve injury during molar surgery

A

Diversion of the inferior dental canal
Darkening of the root where crossed by the canal
Interruption of the white lines of the canal

23
Q

What is the angulation/ortientaion of an impaction measured against

A

Measured against the curve of spee

24
Q

The depth of an impaction gives us an indication of what

A

The amount of bone removal required

25
Q

There are 3 categories for depth of an impacted M3M what are they and what do they mean

A

Superficial - crown of 8 related to the crown of the 7
Moderate - crown of 8 related to crown and root of 7
Deep - crown of 8 related to root of 8

26
Q

What percentage of people require consious sedation for routine dental treamtent

A

7%

27
Q

When discussing numbness with the patient what areas do u refer to

A

Lower lip, chin and side of tongue

28
Q

After what period of time would there not be much hope for nerve recovery

A

18-24 months

29
Q

What acronym can be used for refferals and explain it

A

SBAR

S - situation ; 23/m pain LL8
B - background ; HPC, episodes of periocornitis>?, any antibiocos
A - assessment ; LL8 PE, moderate mesial impaction, caries, food packing, MH SH DH
R - recommendation ; pt keen for surgical removal and i believe it is indicate here

30
Q

Three basic principles of surgical removal

A

Risk assessment
Aseptic technique
Minimal trauma to hard and soft tissues

31
Q

What are the 8 steps in surgical removal

A

Anaesthesia
Access
Bone removal as necessary
Tooth divsion as necessary
Debridement
Suture
Achieve haemostatis
Post operative instructions ; verbal and written

32
Q

What is the aim of the surgical access in removal of M3M

A

Maximum access with minimal trauma

33
Q

Name 3 instruments that can be used to reflect the mucosa during surgical extraction

A

Mitchell’s trimmer
Howarths periosteal elevator
Ash periosteal elevator

34
Q

Name 2 instruments that can be used for retraction

A

Minnesota
Rake retractor

35
Q

What kind of handpiece and bur do we use for bone removal and why

A

Electrical straight handpiece with saline cooled bur - to avoid necrosis of teh bone

Air driven hand pieces may lead to surgical emphysema

Tungsten carbide burns

36
Q

What’s is the aim of bone removal

A

Create a deep narrow gutter around the crown of the wisdom tooth

37
Q

What must we be wary of when removing bone

A

Tissues behind the 3rd molar contain the lingal nerve

38
Q

What are the 3 kinds of surgical debridement

A

Physical ; bone file or handpiece to remove sharp bony edges ( mitchell’s trimmer)

Irrigation ; sterile saline into socket and under mucoperiosteal flap

Suction ; aspirate to remove debris and check socket for retained apices

39
Q

What are 4 aims of suturing

A

Reposition tissues
Cover bone
Prevent wound breakdown
Achieve haemostatis

40
Q

If a patients roots are in close proximity to the IAN canal what treamtent option can we offer

A

Coronectomy

41
Q

What is the aim of a corenecotmy

A

The crown is removed with the deliberate retention of the root adjacent to the IAN

The aim is to reduce the risk of IAN damage

42
Q

How far down should you take off in a corenectomy

A

Transection of tooth 3-4mm below the enamel of he crown into dentine

43
Q

When should we review a corenectomy patient

A

Review 1-2 weeks
Further 3-6 months
1 year

Radiographic review at 6 months or a year or both

44
Q

What are the 3outcomes for the roots left behind in a corenectomy

A
  1. Roots remain where they are and the gum heals - 70%
  2. Roots migrate to surface, will feel like they tooth is coming through and they then need to be extracted - 20-30%
  3. Roots become infected 5-10%
45
Q

What 4 things must you warn a patient about if you are going to do a corenecotmy

A

If the roots are mobilised during the crown removal the entire tooth needs to be removed - risk of infection too high.

Leaving roots behind can result in infection - rare

Can get slow painful healing - dry socket

They roots may migrate and begin to erupt through mucosa so need to be extracted

Third Molars (1 decks)

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