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Minor Oral Surgery > M3Ms, CBCT, Coronectomy > Flashcards

M3Ms, CBCT, Coronectomy Flashcards

1
Q

What is the main purpose/aim of a coronectomy?

A

an evidence based procedure that is used in order to prevent IAN damage related to surgery for high risk M3M

all enamel must be removed!

M3M- mandibular 3rd molars

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2
Q

What is a coronectomy?

A

partial tooth removal, deliberate vital root retention and partial odontectomy.

a method of removing the crown of a totoh but leaving the roots untouched, which may be intimately related with the IAN, so that the possibility of injury is reduced.

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3
Q

Coronectomies are coded surgical procedures in what countries?

A
  • USA
  • Japan

OMFS- category service 2 in US

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4
Q

What are the most common complications related to M3Ms?

A
  1. dry socket
  2. nerve injury

(dry socket is the number 1 complication associated with M3Ms)

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5
Q

Outline the consequences for a patient with IAN injury

A
  • 70% of patients experience a combination of neuropathic pain, anaesthesia and altered sensation with mechanical allogynia and hyperalgesia
  • reduced daily function: eating, speaking, drinking, kissing and socialising
  • severe psychological impact due to pain, altered daily function. Iatrogenic nature of the injury can cause: depression, anger, PTSD, victim of abuse, loss of ability to trust
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6
Q

What are the reasons for increased incidence of IAN injury in patients >25 years old?

A
  • healing ability decreases with increasing age
  • more bone is removed during oral surgery owing to completely formed roots or increased bone mineralisation
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7
Q

Outline some factors that may influence development of IAN injury following M3M removal

A
  • Gender -Female
  • surgeon experience
  • eruption status and depth of impaction- unerupted M3M status is one of the strongest indicators for IANI
  • type of impaction
  • intra-operative nerve exposure and bleeding during surgery- clinical exposure of the IAN neurovascular bundle + bleeding of vessels associated with IAN
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8
Q

What type of M3M impaction saw increased incidence of IAN neurosensory deficit?

A

Horizontal impaction

(lowest was with vertical impaction)

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9
Q

What plain film radiographic signs on OPTs are indicative of possible risk of IAN injury?

A
  • roots crossing the superior border of mandibular canal
  • diversion of the mandibular canal (darkening of the root)
  • interruption of the lamina dura
  • juxta- apical area
  1. darkening of the root
  2. deflection of the root
  3. narrowing of the root
  4. narrowing of mandibular canal
  5. dark and bifid apexes of the root
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10
Q

What is the ONLY radiographic sign of significantly increased IAN injury risk?

A

darkening of the root

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11
Q

Panorals do not have high diagnostic accuracy in the assessment of IANI risk relating to the surgical extractions of M3Ms. Why is this?

A

this is because the presence or absence of these signs does not always determine the possibility of IANI

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12
Q

Following the identification of a radiological marker for close association between IAN and M3M on a panoral, what is recommended for further verification?

A

CT scan (computed tomography)

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13
Q

What is the benefit of CBCT over conventional CT?

A
  • reduced radiation dose
  • offers high spatial resolution
  • decreases cost
  • software associated with CBCT offers better imaging quality of M3Ms and surrounding structures
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14
Q

What are the radiographic signs that may indicate higher risk to IAN using a CBCT?

A
  • M3M root perforation by the mandibular canal- tooth root perforated
  • mandibular canal perforation or loss of the cortical line (LD)
  • LD (cortical line) interruption by the roots or crown of the M3M- cortical line associated with the mandibular canal
  • mandibular cortica defect length (distance) of at least 3mm has been associated with increased risk of IAN exposure
  • deformation of mandibular cancal at point of contact with M3M roots - indication of proximity
  1. Loss of mandibular cortex >3mm
  2. dumbbell distortion of mandibular canal
  3. lingual position of mandibular canal to roots
  4. perforation of tooth roots by mandibular canal
  5. inter- radicular mandibular canal with multiple roots
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15
Q

What is the impact of an intimate proximity of the M3M and mandibular canal on its oval configuration?

mandibular canal has an oval configuration

A
  • a dumbbell or tear drop shaped or concave configuration
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16
Q

What is a bifid mandibular canal?

A

structural variation of the mandibular canal

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17
Q

Bifid mandibular canals are common in the M3M region. True or false

A

true

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18
Q

If the M3M root is sandwiched between the mandibular canal and lost lingual cortex, what treatment would you consider?

A

coronectomy

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19
Q

Buccal position of M3M roots in contact with a lingually placed mandibular canal is associated with an increased IANI rate. True or false

A

true

20
Q

Cortical perforation of the mandibular canal correlates with what radiographic sign observed on a panoral?

A

darkening of the root

21
Q

If there is high risk of association between the M3M and mandibular canal determined by a panoral, what should be the next step?

A

CBCT

22
Q

How can you minimise radiation when undertaking a CBCT?

A
  • smallest field of view (FOV)
  • where compatible, a reduced rotation (180 instead of 360)
  • higher speed rotation - has been de
23
Q

Outline the criteria on CBCT that may indicate coronectomy rather than removal

A
  • tooth root perforating mandibular canal
  • lingual position of the mandibular canal in relation to the M3M
  • direct contact
  • decortication: cortical defect size >3mm
  • altered shape of the mandibular canal
  • loss of lingual cortex
24
Q

What has multivariate analysis shown to be the strongest predictor of IAN injury?

A

narrowing of the mandibular canal

25
Q
A
26
Q

A cortical defect >/= 3mm is associated with…

A
  • increased risk of intra-operative visualisaition of the IAN
  • there is high sensitivity and specificity for this
27
Q

What are the indications of a coronectomy?

A
  • when there is an indication for extraction
  • the tooth in question has been identified as high risk of IAN injury
  • patient is healthy
  • dentally vital tooth
28
Q

What are the contraindications for a coronectomy?

A
  • active caries into the pulp/demonstrating periapical abnormality
  • Mobile M3Ms
  • M3Ms associated with tumours
  • horizontally impacted M3Ms- difficult to obtrain a successful coronectomy due to placement of retained root in relation to alveolus
  • immunocompromised patients- poor healing- at risk of infection with retained roots
  • patients understanding is compromised
  • travelling/difficult to access healthcare
  • patients schedulres for future surgery involving the site
29
Q

Why are coronectomies contraindicated in mobile M3Ms?

A

they can act as a foreign body and become a nidus for infection or migration

nidus - place for

30
Q

Suggest possible reasons why a coronectomy was converted to an extraction during surgery

A
  • root loosening
  • mobilisation
31
Q

Suggest reasons why re-operation may be required following coronectomy

A
  • persistent pain
  • root exposure
  • persistent apical infections
  • retained root migration
32
Q

What factors can contribute to easier mobilisation of M3Ms?

A
  • narrowing of roots
  • vertical impactions
33
Q

Root migration has been shown to be of a short distance and away from the nerve. True or false

A

true

34
Q

Describe a surgical technique that minimises risk of mobility of the roots

A
  • wider groove of pulpal depth is drilled using a fissure bur (surgical drill)
  • crown elevated off the roots with less force

mobilisation can be prevented by taking a more expansive section of the crown from the roots! (first bulletpoint)

35
Q

When is a repeat coronectomy recommended?

A

in cases where enamel retention is diagnosed in order to prevent retained roots from infection

36
Q

Migration of roots was often found in what kinds of patients ?

A

younger patients

37
Q

What does re-operation following coronectomy refer to?

A

extraction of the retained root

38
Q

What authoritative body concluded that it was a breach of duty to not offer a patient with high risk M3M a cornonectomy?

A
  • National Health Service Litigation Authority (NHSLA)
39
Q

Why is it important to carry out coronectomies on vital/health teeth?

A

vital pulp allows dentine and bone integration and healing

40
Q

During a coronectomy, what increases the risk of lingual nerve damage?

A

reduced/ missing lingual plate

41
Q

What type of drills are not recommended for coronectomies ?

A

high speed front exhaust drills

42
Q

________ closure is recommended by most studies following coronectomies as it optimises healing

A

Primary closure

43
Q

What treatment is postulated to prevent root migration?

A

Bone grafting

Bone graft over exposed root surface

44
Q

There is an indication for pulpectomy/pulpotomy/RCT following coronectomy. True or false

A

False

this is because the root remains vital
vitality of root is maintained at it is essential for healing/integration with the bone

45
Q

What has been the postulated reasons for post operative panoral radiographs following coronectomies?

A
  • check for complete removal of enamel
  • monitor root migration

Minor Oral Surgery (36 decks)

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