Third Molars Flashcards
give 2 causes of lack of space in dental arch - causing impaction.
evolutionary changes & lack of an abrasive diet
what are the top 5 most commonly impacted teeth?
- lower 8s
- upper 3s
- lower 3s, 4s and 5s
- upper 1s and 2s
- upper 8s
why are lower 8s the most commonly impacted?
they erupt the latest
what causes malpositioning of ectopic and displaced teeth?
ectopic - congenital factors
displaced - nearby pathology
what happens to teeth at the level of a jaw fracture?
they are rendered non vital
when is it not necessary to XLA impacted lower 8s?
asymptomatic, pt has no complaints, XLA risks nerve damage
what is pericorinitis?
inflammation of tissues around crown of partially erupted or impacted tooth
symptoms of pericorinitis & when to refer
pain, swelling, dysphagia, bad taste, malaise, may lead to cellulitis - if 2 or more cases then refer
is operculotomy recomended?
no as will just re-grow
list local measures for pericoronitis
irrigate w/ saline, OH measures, remove trauma
what can be done if indentations/trauma seen on operculum?
XLA or grind down cusps of opposing 8
when should pt be given antibiotics for pericorinitis? (3) what antibiotic & dose?
is systemically unwell
immunocompromised
if cannot drain locally - trismus, pt uncompliant
metranidazole 400mg 3x daily for 3 days
what microbes are involves in pericoronitis?
what 2 bacteria are involved in increased pocket depths between 2nd & 3rd molars?
anaerobic
prevotella intermedia & campylobacter rectus associated w/ inc pocket depths of 2nd and 3rd molars
list tx options for impacted lower 8s
do nothing, XLA, coronectomy
what radiograph is used to assess lower 8s?
half/whole DPT - PA is 2nd choice
what indicates close proximity of 8 to ID canal?
darkening, deflection or loss of lamina dura of ID canal as roots pass
roots of teeth get darker or deflect as they pass ID canal
juxta apical area - radiolucent area lateral to tooth
what is the most common type of impaction?
mesial 1st
vertical 2nd
when may CBCT be used to assess impacted 8?
when DPT suggests 8 close to IDC/high risk for XLA
what is neuropraxia and when is it caused?
apex of tooth rubbing against IDC - mildest form of nerve damage
how common is change in sensation to lower lip and tongue post XLA?
when should pt be informed of a risk?
lower lip - 5% short term, <1% long term
tongue - 10% short term, <1% long term
pt should be informed when risk >5%
review pt after 3 months to assess if long term damage has occured
what procedure is indicated when high risk/tooth too close to IDN for XLA? what are risks of this procedure
coronectomy - leave roots behind
root migration and infection
what flap should be done for lower impacted 8s?
explain design of this flap
triangular (3 sided)
distal relieving incision - up ascending ramus
round crown of 8 and half of 7 - include papilla between 7 and 8
mesial relieving incision - from centre of 2nd molar down depth of sulcus
when is a 2 sided flap used? what incisions are made?
used if pericoronal pathology or cyst
distal relieving incision - up ascending ramus
round crown of 8 and all of 7 - ends just distal to 6
what is used to remove bone? why and where is bone removal carried out?
round bur in surgical hand piece (chisels no longer used)
create a point of elevator application
create a narrow gutter mesiobuccally
when are crown/roots sectioned/divided? (3)
horizontally impacted
distoangular crown
pincer roots w/ diff paths of removal
what flap should be used for horizontally impacted 8? what must be done after flap raised? (3)
triangular
bone removal, section crown at ACJ, section roots at furcation
intrinsic & extrinsic obstacles for XLA
intrinsic - root morphology
extrinsic - bone, adj teeth, ID canal
what should you never do when elevating?
use adj tooth as fulcrum
what is the most important suture of the flap?
suture placed from buccal to lingual tissues immediately distal to 7
what material is used for suturing? when are sutures removed?
3/0 vicryl rapide
dissolve after 1 week
maxillary 8s - thickness of bone, root shape/number, angle/impaction, positioning
thin cortical bone
short single conical fused root
mesioangled or vertically impacted - often very buccally placed
what should be done to manage impacted upper 8? how many sutures to reposition flap?
buccal flap
remove thin friable bone w/ couplands
use elevator to move tooth down, back and buccally
use one suture to reposition flap
what is the order of tx planning?
- path of withdrawal
- obstacles
- point of application
- bone removal
- flap design
backwards to how it is carried out
POPBF
