3rd Molars

Question 1

when 3rd molars erupt and calcify

Answer 1

erupt = 18-24
crown = 7-18
root = 18+

Question 2

what is the rate of “missing”

Answer 2

1 in 4 will be missing at least one
agenesis more common in maxilla + females
if missing @ 14, likely will not develop

Question 3

incidence of impacted M3M

Answer 3

35-59%

Question 4

indications of M3M removal

Answer 4

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

Question 5

when would you take an OPT?
what is it used to assess

Answer 5

only when considering surgery

disease, anatomy, impaction depth, follicular width
working distance [7d->ramus]
IAN relationship
pathology

Question 6

what 7 signs on an OPT would indicate close relationship with IAN?

put significantly risk 3 at top

Answer 6

1. interruption of white lines/lamina dura of canal
2. darkening of root where crossed by canal
3. diversion/reflection of IAC
4. deflection of root
5. narrowing of IAC
6. narrowing of root
7. juxta apical area

Question 7

what is a juxta apical area

Answer 7

radiolucent region lateral to apex
NOT just absolute apex
not pathological area

Question 8

what nerves are at risk of damage

Answer 8

inferior alveolar nerve
lingual nerve
nerve to mylohyoid
long buccal

Question 9

discuss IAN and the risks

Answer 9

peripheral sensory nerve to lower teeth, mucosa, lip and chin

temporary = 10-20%
permanent = <1%

Question 10

discuss lingual nerve and the risks

Answer 10

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%

Question 11

discuss nerve to mylohyoid and long buccal

Answer 11

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

Question 12

how could taste be altered

Answer 12

damage to chorda tympani fibres via lingual nerve
rare

Question 13

how long can be expected for nerves to recover before no more

Answer 13

18-24mths

Question 14

pericoronitis
what
symptoms

Answer 14

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

Question 15

what microbes cause pericoronitis

Answer 15

prevotella
actinomyces
fusobacterium

Question 16

pericoronitis predisposing factors

Answer 16

PE + vertical/distal angle
opposing causing occlusal trauma
respiratory infections
stress
fatigue
white
poor OH
insufficient space
full dentition

Question 17

pericoronitis tx

Answer 17

incise if localised abscess
LA, irrigate saline/chx 10-20ml syringe and blunt needle
MW, analgesia, soft diet

abx if systemic, swelling, immunocompromised

Question 18

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

Answer 18

Ludwigs angina

urgent maxfax referral

Question 19

when/why would you consider taking a CBCT?

Answer 19

if close relationship with IAC is shown on OPT

Question 20

how can angulation of 8 be determined?
what is the incidence and which is most common

Answer 20

vertical = 30-38%
mesial = 40% **
- most common
distal = 6-18%
horizontal = 3-15%
transverse/aberrant

Question 21

how can the depth of 8 be determined and describe them

Answer 21

gives indication of bone removal required

superficial = crown 8 + crown 7
moderate = crown 8 + crown/root 7
deep = crown 8 + root 7

Question 22

tx options in pt presenting with pericoronitis

Answer 22

refer
clinical review
xla
xla upper 8
coronectomy
operulectomy
surgical exposure
pre-surgical ortho
surgical preimplantation/autotransplantation

Question 23

what is a coronectomy
why would you consider it
procedure

Answer 23

alternative to full xla if increased risk of nerve damage
removal of crown and leaving roots in situ

1. flap
2. transect tooth 3-4mm below CEJ
3. elevate without mobilising roots
4. irrigate socket
5. reposition flap + suture
   follow up 1-2 weeks, xray 6m + 1yr

Question 24

warnings to give pt about coronectomy

Answer 24

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

Question 25

how do you create a flap

Answer 25

buccal mucoperiosteal +/- lingual flap max access with min trauma one firm continuous stroke to minimise trauma

Question 26

describe a 2-sided flap and how to suture

Answer 26

distal relieving incision, around margin of 7 + 8 1 interrupted suture around the back of 7 and distal relieving suture

Question 27

describe a 3-sided flap and how to suture

Answer 27

distal relieving incision on 8 with mesial relieving incision 8 2/3 sutures

Question 28

how do you reflect the access flap

Answer 28

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

Question 29

how do you retract the access flap and what is the point

Answer 29

access to operation field and protect soft tissues atraumatic/passive by resting firmly on bone Mitchells, periostea, rake retractor, Minnesota

Question 30

how do you remove bone

Answer 30

straight handpick, saline cooled tungsten carbide/ss bur round/fissure without air as will cause surgical emphysema DEEP NARROW GUTTER around crown

Question 31

how do you/can you divide the tooth

Answer 31

as necessary crowns + root sectioned horizontal crown section; above CEJ vertical crown section; separate roots, distal crown + root then mesial crown + root

Question 32

how do you debride the socket

Answer 32

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

Question 33

how do you suture the tissues and what is the aim

Answer 33

aim = reposition tissues, cover bone, prevent wound breakdown, achieve haemostasis approximate tissues, compress blood vessels

Question 34

discuss maxillary third molar removal

Answer 34

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]