Third Molar Flashcards
eruption
- approx 18-24yrs, varies
- may still be present and begin to erupt in elderly/edentulous pt
CO denture rocking/no longer fits
crown and root calcification
- crown: begins 7-10yo, completed by 18yo
- root: completed btw 18-25yo
stats of missing
- at least 1 missing in 25% adults
- maxilla
- female
guidance and their summary
SIGN 43 2000 - must justify the need of surgical removal
NICE 2000 - discourage removal unless pathology assoc.
most up to date (currently in use):
FDS RCS 2020 (Faculty of dental surgery, royal college of surgeons) - change from soley therapeutic approach to mixed intervention
nerves at risk during SR L8s
lingual
IAN
mylohyoid and long buccal - less common and effects less obvious
location of lingual n
varies
- lies on superior attachment of mylohyoid muscle
- at level of lingual plate in 15-18%
- 0-3.5mm medial to mandible
impacted meaning
tooth eruption is blocked
- full/ partial functional position
incidence of impacted lower third molar
around 50%
consequence of impaction
- caries
- periconronitis
- cyst formaiton
U removal indications
cheek biting/buccally erupted overeruption traumatising L operculum PE and impacted non-fct pt undergoing GA
therapeutic indication of wisdom extraction
- caries (8/7)
- pericoronitis
- periodontal disease (7d)
- local bone infection
- Dentigerous cyst
- tumours
- external root resorption of 7/8
SIGN vs NICE
SIGN - ≥1 episode of infection
NICE >1
imaging
OPT
(+/- PA)
+/- CBCT (3D relationship to nerve)
clinical assessment of M3M
eruption status - how many cusps seen
PD status - pockets distal to 7?
TMJ - rule out TMJ, similar pain to pericoronitis
exclude other causes
local infection
caries/resorption
occlusal relationship
regional LNs
any associated pathology
degree of surgical access
working space
STs
Types of imapction
- plus transverse (buccal / lingual)
- aberrant ( in odd place)
working space
distance between L7 and ascending ramus
radiological assessment
- orientation and position (impaction)
- impaction depth
- relationship to IDC/MS
follicular width
working distance
crown - size, shape, caries
roots - number, morphology, apical hooks
bone levels
adjacent tooth
any surrounding pathology
- dentigerous cyst
- loss of bone distal to crown
when to consider when follicle turning to dentigerous cyst?
if follicle > 3mm size
3 key radiographic signs of M3M - possible increased risk to IAN
diversion/deflection of canal
darkening of root where crossed by canal
interruption of tram line / lamina dura of canal
8 radiographic signs of possible increased risk to IAN - M3M removal
diversion/deflection of canal darkening of root interruption of white lines/LD of canal deflection of root narrowing of IDC narrowing of root dark and bifid root juxta apical area?
juxta apical area
well-defined radiolucent area adjacent that isn’t related to PA pathology
can appear corticated
lamina dura round tooth intact
lateral to root rather than apex
what is the most common orientation of impaction? M3M
mesial 40%
what is orientation of impaction measured against?
the curve of spee
- curve of occlusal plane
- draw lines through long axis of 7 and 8 and compare
what are the types of depth of impaction and what does it indicate?
- superficial - 8 crown relate to 7crown
- moderate - 8 crown to 7 crown+root
- deep - 8 crown to 7 root
- amount of bone removal required