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BDS4 Oral Surgery > Third Molars (1) > Flashcards

Third Molars (1) Flashcards

1
Q

Radiographically, the crowns of upper third molars can be seen beginning to calcify at what age?

A

upper third molars = between 7 - 9yrs old

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2
Q

Radiographically, the crowns of lower third molars can be seen beginning to calcify at what age?

A

lower third molars = between 8 -10yrs old

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3
Q

By what age does the crown of third molars appear fully calcified radiographically?

A

usually by 18 years old

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4
Q

Between what ages can root calcification be seen?

A

18 - 25yrs old

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5
Q

What does agenesis mean?

A

Failure of an organ to develop

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6
Q

Why is there increased frequency of third molar agenesis?

A

It is an example of human evolution

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7
Q

Third molar agenesis incidence varies between populations - which population has reached nearly 100% third molar agenesis?

A

The Indigenous Mexicans

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8
Q

Which gene has been shown to be involved in third molar agenesis?

A

PAX9 gene

(there are other genetics involved also)

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9
Q

Is agenesis of third molars more common in the maxilla or mandible?

A

more common in the maxilla

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10
Q

Is agenesis of third molars more common in females or males?

A

more common in females

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11
Q

By which age - if you cannot see third molar development will it be almost always likely that they will completely fail to develop?

A

14 years old

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12
Q

What does M3M stand for?

A

Mandibular Third Molar

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13
Q

What does it mean if a third molar is impacted?

A

Failure of the third molar to erupt - either into full or partial functioning positioning or tooth fails to erupt at all

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14
Q

What is the most common reason for third molar failure to come through?

A

impacted third molar

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15
Q

Name 4 reasons why a third molar can be impacted?

A
  1. Impacted against adjacent tooth
  2. Impacted against alveolar bone
  3. Impacted by surrounding soft tissue
  4. Combination of all of these factors
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16
Q

Name 3 forms of eruption an impacted third molar can be found?

A
  1. Unerupted
  2. Partially erupted
  3. Fully erupted
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17
Q

Describe an unerupted impacted third molar

A

tooth completely enclosed around bone + soft tissue

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18
Q

Describe a partially erupted impacted third molar

A

Some of it has managed to erupt into the oral cavity, but not all of it

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19
Q

Describe a fully erupted impacted third molar

A

Whole occlusal surface right through the oral mucosa + exposed to oral cavity

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20
Q

Third molar partially erupted but no tooth evident on clinical examination. Radiograph shows caries in third molar - how?

A

This suggests that there is a communication between the oral cavity + third molar - allowing bacteria to pass through and cause caries

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21
Q

Name 3 problems related to impacted teeth

A
  1. Caries
  2. Pericoronitis
  3. Cyst formation
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22
Q

Name 4 nerves at risk during third molar surgery

A
  1. Inferior Alveolar Nerve
  2. Lingual Nerve
  3. Nerve to Mylohyoid
  4. Long Buccal Nerve
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23
Q

Which 2 nerves are much less commonly affected + effects are less obvious?

A
  1. Nerve to Mylohyoid
  2. Long Buccal Nerve
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24
Q

What type of nerve is the Inferior Alveolar Nerve?

A

peripheral sensory nerve

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25
Q

What nerve is the IAN formed from?

A

The mandibular division of the trigeminal nerve

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26
Q

What does the IAN supply?

A

All mandibular teeth on that side, mucosa of lower lip + chin

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27
Q

What is the Lingual nerve a branch of?

A

Branch of the mandibular division of the trigeminal nerve

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28
Q

What does the Lingual nerve supply?

A

Anterior 2/3rds of dorsal + ventral mucosa of tongue
Lingual gingivae
Floor of mouth

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29
Q

In Pogrel (1995) study, what was the mean vertical distance of the lingual nerve from the crest of the lingual plate + mean horizontal distance?

A

Distance from crest of lingual plate = 8.32mm

Mean horizontal distance = 3.45

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30
Q

In Kiesselbach (1984) study, what was the distance of the Lingual nerve vertically from the alveolar crest + from the lingual plate?

A

2.8mm (+/- 1.9mm) vertically from alveolar crest

0.58mm (+/- 0.9mm) from lingual plate

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31
Q

What structure does the lingual nerve have a close relationship to?

A

Lingual plate in the mandibular + retromolar area

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32
Q

What % of cases is the lingual nerve positioned at or above the level of the lingual plate?

A

15-18% of cases

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33
Q

What distance in mm does the lingual nerve run medial to the mandible?

A

the lingual nerve runs 0.3 - 5mm medial to the mandible

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34
Q

What 3 guidelines are related to third molars?

A
  1. NICE - Guidance on Extraction of Wisdom Teeth, 2000
  2. SIGN Publication Number 43 - Management of Unerupted + Impacted Third Molar Teeth, 2000
  3. FDS RCS - Patameters of Care for patients undergoing mandibular third molar surgery
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35
Q

Summarise the NICE and SIGN guidelines for extraction of wisdom teeth

A

Consensus from both documents - due to risk factors involved with third molar surgery, you must be able to justify surgical removal

36
Q

What is the most recent guidance on third molars

A

FDS RCS 2020 - parameters for care for patients undergoing mandibular third molar surgery

37
Q

Summarise the FDS RCS 2020 guidelines for third molars

A

acknowledges that by not removing impacted third molars - we are often postponing inevitable surgery, can result in procedure being more difficult
Recommend changing from solely therapeutic approach to mixed range of interventions for patients with M3M based on a more holistic + informed approach which should be agreed by patient

38
Q

Name 11 indications for third molar extraction

A
  1. Infection
  2. Cysts
  3. Tumours
  4. External reposition of 7 or 8
  5. Surgical indications
  6. High risk of disease
  7. Medical indications
  8. Accessibility
  9. Patient age
  10. Autotransplantation
  11. General Anaesthetic
39
Q

What is the most common reason for wisdom tooth extraction?

A

Infection

40
Q

Name 4 forms of infection in third molars

A
  1. Caries
  2. Pericoronitis
  3. Periodontal disease
  4. Local bone infection
41
Q

In what scenarios of ‘infection’ should third molar extraction always be considered

A
  1. Pericoronitis (acute or chronic)
  2. One or more episodes of infection (e.g. abscess)
  3. Untreatable pulpal or periapical disease
42
Q

Which is the more common reason for extraction - caries or pericoronitis?

A

caries

43
Q

What would make restoration of a third molar with caries difficult?

A

Limited access
Moisture control

44
Q

Why is peridontal disease an indication for third molar removal?

A

Because of the relative position of the lower 2nd + 3rd molars
Untreated horizontal, mesial angular impaction is prone to causing bone loss distal to 7

45
Q

What age are cysts related to third molars most common in patients

A

20-50yrs old

46
Q

What is the most common cyst associated with impacted third molars

A

dentigerous cyst

47
Q

How does a dentigerous cyst arise

A

arises from reduced enamel epithelium separation from the crown

48
Q

are cysts more common in the mandible or maxilla

A

mandible
(x10 more likely)

49
Q

When do symptoms of cysts usually occur?

A

often no symptoms associated until cyst becomes very large + infected

50
Q

Describe the management of a cyst related to third molars

A

Prophylactic removal or coronectomy of a disease free impacted M3M would often prevent development of a cyst - however number prevented small… therefore not usually an indication for removing a symptom free M3M

51
Q

What indications related to a tumour may third molars be extracted?

A
  • if close to 8
  • extracted as part of cancer (may be part of resection)
  • if patient diagnosed with cancer elsewhere in body + undergoing radiotherapy (extraction after tx commenced may result in osteoradionecrosis)
52
Q

What is external resorption

A

destruction of tissue

53
Q

What happens if resorption is left untreated

A

usually progressive

54
Q

How does resoprtion occur

A

Cause of inflammation usually unclear
Can be external resorption of third molar or second molar, caused by the third
Relatively rare

55
Q

Resorption is relatively rare, however what ages does it usually occur between?

A

21 - 30 years old
(risk of developing after 30 is small)

56
Q

Describe the management of resorption in third moalrs

A

should always consider removal of third molar in these cases

57
Q

Provide some surgical indications for third molar removal

A
  1. If the third molar is within the surgical field
    (if the M3M is in the line of the mandibular split - can lead to poorer outcome)
  2. If M3M is unerupted - extraction allows primary closure post-op
  3. If there is a fracture at the angle of the mandible - removal may be req. to allow adequate open reduction + internal fixation
58
Q

What medical indications may require removal of third molars

A
  1. patient awaiting cardiac surgery + need to be ‘dentally fit’ to avoid post-op complications
  2. Immunosuppression
  3. Starting course of bisphosphonates to avoid MRONJ
59
Q

How does accessibility affect indication for third molar removal?

A

If the patient has limited access to the dentist (e.g. astronaut, gap year, travelling) - may not be able to attend dentist for some time therefore removal of third molars may be indicated

60
Q

How might patient age be an indication for third molar extraction?

A

complications + recovery increase with age therefore may indicate removal before the patient gets older

61
Q

Describe the autotransplantation of third molars

A

If a third molar is sound it can occasionally, but rarely, but used for autogenous transplantation.
Usually third molar –> first molar socket site.
Low incidence of success, therefore only used in specific circumstances

62
Q

How may general anaesthetic indicate removal of a third molar

A

If patient is undergoing third molar removal under GA, may indicate also removing opposing/contralateral third molars as you dont want to have to carry out this similar procedure down the line

63
Q

What is pericoronitis

A

inflammation around the crown of a partially erupted tooth

64
Q

what is the operculum?

A

flap of gum sitting over the tooth - often the source of the problem in pericoronitis

65
Q

how does the operculum often cause pericoronitis

A

difficult to clean, food/plaque/bacteria can get trapped underneath

66
Q

How can pericoronitis be described

A

transient + self limiting

67
Q

What age group are usually affected by pericoronitis

A

20 - 40 yrs

68
Q

Which health condition can impact the incidence of pericoronitis?

A

Upper Respiratory Tract Infection (URTI)

(seems to be an increase in cases of pericoronitis)

starts off as URTI then develops into pericoronitis
(reason unclear)

69
Q

What is the second most common indication for M3M extraction?

A

pericoronitis

70
Q

what are the majority of microbes involved in pericoronitis?

A

anaerobes

(e.g. streptococci, actinomyces, staphylococci etc.)

71
Q

Signs + Symptoms of pericoronitis

A
  • pain + swelling (most common)
  • bad taste
  • pus discharge
  • occlusal trauma to operculum
  • ulceration of operculum
  • cheek biting
  • foetor oris
  • limited mouth opening
  • dysphagia
  • pyrexia
  • malaise
  • regional lymphadenopathy
72
Q

How can the pain associated with pericoronitis be described?

A

very variable
often ‘throbbing’
often increases in intensity as it develops

73
Q

In severe cases of pericoronitis which result in extra-oral swelling, where can the swelling occur?

A

commonly starts at the angle of the mandible + extend…
- usually to submandibular area
- laterally into cheek
- disto-bucally under masseter (sub-masseteric abscess)
- sublingually
- around tonsils + pharyngeal space

74
Q

If swelling due to pericoronitis extends under the masseter - what is this known as and what are the associated characteristics?

A

= sub-masseteric abscess

characteristic signs: profound trismus (unable to open mouth)

75
Q

If swelling due to pericoronitis extends to tonsils / pharyngeal space - what difficulty can the patient experience?

A

can lead to dysphagia
(difficulty swallowing)

Patient may present with drooling if unable to swallow comfortably

76
Q

how might a patient present if they are systemically unwell due to pericoronitis

A

pyrexia (fever)
malaise (generally run down)
lymphodenopathy (swollen lymph nodes)

77
Q

What are tx options if a patient is acutely symptomatic due to pericoronitis?

A
  • incision of local area of infection
  • irrigation with warm saline (or perhaps chlorhexidine mouthwash)
  • removal of upper third molar
78
Q

How would you irrigate to treat pericoronitis?

A
  • LA may/may not be indicated (patient preference)
  • use syringe + blunt needle
  • fill syringe with warm saline
79
Q

Why may chlorhexidine be contraindicated for irrigation in pericoronitis

A

Previous reports of anaphylaxis (rare - but some health boards are wary of use)
Therefore check with health board / use saline

80
Q

How does removal of upper third molar relieve pericoronitis of M3M?

A

eases trauma to lower operculum
may also give space for M3M to erupt

81
Q

Post op instructions after tx of pericoronitis

A
  • tell Pt to frequently rinse with warm saline or chlorhexidine (to prevent reoccurrence of pericoronitis)
  • give advise regarding analgesia (do not exceed dose / check MH)
  • advise patient to drink plenty fluids + eat at regular intervals (soft diet may help)
82
Q

Can lower 8 be removed during pericoronitis episode?

A

Generally, we don’t remove lower 8 until acute episode of pericoronitis has resolved

83
Q

What is an operculectomy?

A

removal of the operculum causing pericoronitis

84
Q

Why are operculecomties not carried out nowadays?

A

because the operculum just grows back to where it was within weeks/months therefore not much to be gained from an operculectomy. (although may be indicated in specific cases)

85
Q

when would you consider referral to A&E or maxfax during pericoronitis?

A
  • large extra-oral swelling
  • Pt systemically unwell (significant cases of dysphgia, breathing difficulty, trismus)
86
Q

Pre-disposing factors for pericoronitis

A
  • Partially erupted tooth
  • Vertical or distoangular impaction
  • Opposing 2nd/3rd maxillary molar causing trauma
  • Upper Respiratory Tract Infection
  • Stress
  • Fatigue
  • Poor OH
  • Insufficient space between ascending ramus of lower jaw + distal aspect of lower 7 - more likely to have impacted tooth - more likely to suffer from pericoronitis
  • White race
  • Full dentition

BDS4 Oral Surgery (2 decks)

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