M3Ms, CBCT, Coronectomy Flashcards
What is the main purpose/aim of a coronectomy?
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
What is a coronectomy?
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.
Coronectomies are coded surgical procedures in what countries?
- USA
- Japan
OMFS- category service 2 in US
What are the most common complications related to M3Ms?
- dry socket
- nerve injury
(dry socket is the number 1 complication associated with M3Ms)
Outline the consequences for a patient with IAN injury
- 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
What are the reasons for increased incidence of IAN injury in patients >25 years old?
- healing ability decreases with increasing age
- more bone is removed during oral surgery owing to completely formed roots or increased bone mineralisation
Outline some factors that may influence development of IAN injury following M3M removal
- 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
What type of M3M impaction saw increased incidence of IAN neurosensory deficit?
Horizontal impaction
(lowest was with vertical impaction)
What plain film radiographic signs on OPTs are indicative of possible risk of IAN injury?
- 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
- darkening of the root
- deflection of the root
- narrowing of the root
- narrowing of mandibular canal
- dark and bifid apexes of the root
What is the ONLY radiographic sign of significantly increased IAN injury risk?
darkening of the root
Panorals do not have high diagnostic accuracy in the assessment of IANI risk relating to the surgical extractions of M3Ms. Why is this?
this is because the presence or absence of these signs does not always determine the possibility of IANI
Following the identification of a radiological marker for close association between IAN and M3M on a panoral, what is recommended for further verification?
CT scan (computed tomography)
What is the benefit of CBCT over conventional CT?
- reduced radiation dose
- offers high spatial resolution
- decreases cost
- software associated with CBCT offers better imaging quality of M3Ms and surrounding structures
What are the radiographic signs that may indicate higher risk to IAN using a CBCT?
- 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
- Loss of mandibular cortex >3mm
- dumbbell distortion of mandibular canal
- lingual position of mandibular canal to roots
- perforation of tooth roots by mandibular canal
- inter- radicular mandibular canal with multiple roots
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 dumbbell or tear drop shaped or concave configuration
What is a bifid mandibular canal?
structural variation of the mandibular canal
Bifid mandibular canals are common in the M3M region. True or false
true
If the M3M root is sandwiched between the mandibular canal and lost lingual cortex, what treatment would you consider?
coronectomy
Buccal position of M3M roots in contact with a lingually placed mandibular canal is associated with an increased IANI rate. True or false
true
Cortical perforation of the mandibular canal correlates with what radiographic sign observed on a panoral?
darkening of the root
If there is high risk of association between the M3M and mandibular canal determined by a panoral, what should be the next step?
CBCT
How can you minimise radiation when undertaking a CBCT?
- smallest field of view (FOV)
- where compatible, a reduced rotation (180 instead of 360)
- higher speed rotation - has been de
Outline the criteria on CBCT that may indicate coronectomy rather than removal
- 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
What has multivariate analysis shown to be the strongest predictor of IAN injury?
narrowing of the mandibular canal
A cortical defect >/= 3mm is associated with…
- increased risk of intra-operative visualisaition of the IAN
- there is high sensitivity and specificity for this
What are the indications of a coronectomy?
- 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
What are the contraindications for a coronectomy?
- 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
Why are coronectomies contraindicated in mobile M3Ms?
they can act as a foreign body and become a nidus for infection or migration
nidus - place for
Suggest possible reasons why a coronectomy was converted to an extraction during surgery
- root loosening
- mobilisation
Suggest reasons why re-operation may be required following coronectomy
- persistent pain
- root exposure
- persistent apical infections
- retained root migration
What factors can contribute to easier mobilisation of M3Ms?
- narrowing of roots
- vertical impactions
Root migration has been shown to be of a short distance and away from the nerve. True or false
true
Describe a surgical technique that minimises risk of mobility of the roots
- 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)
When is a repeat coronectomy recommended?
in cases where enamel retention is diagnosed in order to prevent retained roots from infection
Migration of roots was often found in what kinds of patients ?
younger patients
What does re-operation following coronectomy refer to?
extraction of the retained root
What authoritative body concluded that it was a breach of duty to not offer a patient with high risk M3M a cornonectomy?
- National Health Service Litigation Authority (NHSLA)
Why is it important to carry out coronectomies on vital/health teeth?
vital pulp allows dentine and bone integration and healing
During a coronectomy, what increases the risk of lingual nerve damage?
reduced/ missing lingual plate
What type of drills are not recommended for coronectomies ?
high speed front exhaust drills
________ closure is recommended by most studies following coronectomies as it optimises healing
Primary closure
What treatment is postulated to prevent root migration?
Bone grafting
Bone graft over exposed root surface
There is an indication for pulpectomy/pulpotomy/RCT following coronectomy. True or false
False
this is because the root remains vital
vitality of root is maintained at it is essential for healing/integration with the bone
What has been the postulated reasons for post operative panoral radiographs following coronectomies?
- check for complete removal of enamel
- monitor root migration
