3rd Molars Flashcards
when 3rd molars erupt and calcify
erupt = 18-24
crown = 7-18
root = 18+
what is the rate of “missing”
1 in 4 will be missing at least one
agenesis more common in maxilla + females
if missing @ 14, likely will not develop
incidence of impacted M3M
35-59%
indications of M3M removal
caries, perio
infection
recurrent pericoronitis
cyst
local bone infection
tumour
external resorption 7/8
surgical; orthognathic, fracture, resection
high risk of disease
medical; cardiac surgery, immunosuppressed, prevent ORN
accessibility, age, already GA
autotransplantation into 6
when would you take an OPT?
what is it used to assess
only when considering surgery
disease, anatomy, impaction depth, follicular width
working distance [7d->ramus]
IAN relationship
pathology
what 7 signs on an OPT would indicate close relationship with IAN?
put significantly risk 3 at top
- interruption of white lines/lamina dura of canal
- darkening of root where crossed by canal
- diversion/reflection of IAC
- deflection of root
- narrowing of IAC
- narrowing of root
- juxta apical area
what is a juxta apical area
radiolucent region lateral to apex
NOT just absolute apex
not pathological area
what nerves are at risk of damage
inferior alveolar nerve
lingual nerve
nerve to mylohyoid
long buccal
discuss IAN and the risks
peripheral sensory nerve to lower teeth, mucosa, lip and chin
temporary = 10-20%
permanent = <1%
discuss lingual nerve and the risks
anterior 2/3 tongue
located at/above lingual plate 15-18%, 0-3.5mm medial to mandible
temporary = 0.25-23%
permanent = 0.14-2%
discuss nerve to mylohyoid and long buccal
nerve to mylohyoid =
from IAN, motor to mylohyoid and anterior belly of digastric
long buccal =
from IAN, sensory to skin of cheek, buccal mucosa and gingiva of lower molars
how could taste be altered
damage to chorda tympani fibres via lingual nerve
rare
how long can be expected for nerves to recover before no more
18-24mths
pericoronitis
what
symptoms
inflammation of the operculum of a partially erupted tooth
pain, swelling, pus, halitosis, ulceration
occlusal trauma to operculum
limited opening
dysphagia
pyrexia
malaise
lymphadenopathy
usually self limiting
20-40
what microbes cause pericoronitis
prevotella
actinomyces
fusobacterium
pericoronitis predisposing factors
PE + vertical/distal angle
opposing causing occlusal trauma
respiratory infections
stress
fatigue
white
poor OH
insufficient space
full dentition
pericoronitis tx
incise if localised abscess
LA, irrigate saline/chx 10-20ml syringe and blunt needle
MW, analgesia, soft diet
abx if systemic, swelling, immunocompromised
pt presents with severe pain LR8 and associated swelling of the face
O/E you notice inflamed operculum
she has a large EO swelling, is systemically unwell, cannot open her mouth and is having difficulty swallowing
what do you expect this is
what will you do
Ludwigs angina
urgent maxfax referral
when/why would you consider taking a CBCT?
if close relationship with IAC is shown on OPT
how can angulation of 8 be determined?
what is the incidence and which is most common
vertical = 30-38%
mesial = 40% **
- most common
distal = 6-18%
horizontal = 3-15%
transverse/aberrant
how can the depth of 8 be determined and describe them
gives indication of bone removal required
superficial = crown 8 + crown 7
moderate = crown 8 + crown/root 7
deep = crown 8 + root 7
tx options in pt presenting with pericoronitis
refer
clinical review
xla
xla upper 8
coronectomy
operulectomy
surgical exposure
pre-surgical ortho
surgical preimplantation/autotransplantation
what is a coronectomy
why would you consider it
procedure
alternative to full xla if increased risk of nerve damage
removal of crown and leaving roots in situ
- flap
- transect tooth 3-4mm below CEJ
- elevate without mobilising roots
- irrigate socket
- reposition flap + suture
follow up 1-2 weeks, xray 6m + 1yr
warnings to give pt about coronectomy
if roots become mobile then will need full xla
infection, slow healing, painful socket, jaw pain
roots may migrate later and erupt, necessitating full removal with another procedure
how do you create a flap
buccal mucoperiosteal +/- lingual flap
max access with min trauma
one firm continuous stroke to minimise trauma
describe a 2-sided flap and how to suture
distal relieving incision, around margin of 7 + 8
1 interrupted suture around the back of 7 and distal relieving suture
describe a 3-sided flap and how to suture
distal relieving incision on 8 with mesial relieving incision 8
2/3 sutures
how do you reflect the access flap
raise at base of relieving incision, undermine free papillae before distal to avoid teas
periosteal elevator firmly on bone
Mitchells trimmer, howard/ash periostea elevator, carved Warwick James
how do you retract the access flap and what is the point
access to operation field and protect soft tissues
atraumatic/passive by resting firmly on bone
Mitchells, periostea, rake retractor, Minnesota
how do you remove bone
straight handpick, saline cooled tungsten carbide/ss bur
round/fissure
without air as will cause surgical emphysema
DEEP NARROW GUTTER around crown
how do you/can you divide the tooth
as necessary
crowns + root sectioned
horizontal crown section;
above CEJ
vertical crown section;
separate roots, distal crown + root then mesial crown + root
how do you debride the socket
physical via removing sharp bony edges with Mitchells on bone and Victoria soft tissue
irrigation with sterile saline
suction under flap, check for sequestra
clean debris
curette follicular tissue
how do you suture the tissues and what is the aim
aim = reposition tissues, cover bone, prevent wound breakdown, achieve haemostasis
approximate tissues, compress blood vessels
discuss maxillary third molar removal
easier xla, elevation only or with forceps
straight/curved Warwick James, coiplands, upper 3rd bayonets
procedure =
support tuberosity, +/- buccal flap
don’t underestimate [grossly carious, PE, diverging roots]
