6 - Third molars Flashcards

1
Q

When do third molars typically erupt?

A

18-24 years

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2
Q

When does third molar crown calcification begin?

A

7-10 years

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3
Q

When does third molar crown calcification finish?

A

18 years

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4
Q

When does third molar root calcification finish?

A

18-25 years

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5
Q

Define agenesis.

A

Failure to develop

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6
Q

At what age can you determine if third molars agenesis is present?

A

14 years

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7
Q

Define M3M.

A

Mandibular third molar

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8
Q

What are the consequences of impacted M3Ms?

A
  • caries
  • pericoronitis
  • cyst formation
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9
Q

What causes pericoronitis?

A

Failure of the follicle to break down

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10
Q

What nerves are at risk during third molar surgery?

A
  • IAN
  • lingual nerve
  • nerve to mylohyoid
  • long buccal nerve
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11
Q

Describe the location of the IAN in relation to the M3M.

A

Lies within the inferior alveolar nerve canal that passes close to the roots of M3Ms

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12
Q

Describe the location of the lingual nerve in relation to the M3M.

A
  • close relationship to the lingual plate
  • lingual to the mandible in the retromolar pad area
  • lies on the superior attachment of the mylohyoid muscle
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13
Q

What does the FDS RCS 2020 guidance state for third molar surgery?

A
  • consensus document after reviewing SIGN and NICE guidance which suggest that third molar surgery should only be carried out if there is visible pathology
  • new guidance suggests a holistic and intervention approach to avoid postponing inevitable surgery
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14
Q

What are the therapeutic indications for extraction of third molars?

A
  • infection (caries, pericoronitis, perio, or local bone infection)
  • cysts
  • tumours (prevent ORN)
  • ERR of 7 or 8
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15
Q

What are the holistic indications for extraction of third molars?

A
  • surgical (ie within surgical field)
  • high risk of disease
  • medical indications (ie dentally fit)
  • accessibility
  • age
  • autotransplantation (rare)
  • GA (if already undergoing tx)
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16
Q

What is pericoronitis?

A
  • inflammation around the crown of a partially erupted tooth
  • food and debris get trapped under the operculum resulting in infection and inflammation
17
Q

What microbes are associated with pericoronitis?

A
  • anaerobic microbes
  • eg streptococci, actinomyces, prevotella
18
Q

What are the signs and symptoms of pericoronitis?

A
  • pain
  • swelling IO or EO
  • bad taste or pus
  • occlusal trauma to operculum, ulceration of operculum
  • trismus and dysphagia
  • regional lymphadenopathy
19
Q

What is the treatment for pericoronitis?

A
  • incision of localised abscess +/- LA
  • irrigation with warm saline or chlorheixidine under operculum
  • XLA of M3M if trauma
  • analgesia and stay hydrated
20
Q

When are antibiotics appropriate for pericoronitis?

A
  • evidence of spreading infection
  • systemically unwell
  • EO swelling or severe trismus
21
Q

What are predisposing factors to pericoronitis?

A
  • partial eruption
  • vertical or distal impaction
  • opposing maxillary teeth causing trauma to operculum
  • URTI
  • poor OH
  • full dentition