Third Molars

Question 1

At what age do third molars usually erupt?

Answer 1

between 18 and 24

Question 2

when does crown calcification of third molars begin and end?

Answer 2

begins 7-10
completed by age 18

Question 3

when does root calcification complete in third molars?

Answer 3

18-25

Question 4

what proportion of adults have at least one third molar missing?

Answer 4

1 in 4
- more common in maxilla and females
- almost always fail to develop if missing at 14 in radiograph

Question 5

impacted third molars - what does this mean?

Answer 5

tooth eruption is blocked

Question 6

What are mandibular third molars usually impacted against?

Answer 6

adjacent tooth
alveolar bone
surrounding mucosal soft tissues
a combination of these factors

Question 7

incidence of impacted lower third molars

Answer 7

36-59%

Question 8

consequences of impacted third molars

Answer 8

caries
pericoronitis
cyst formation

Question 9

what nerves are at risk during mandibular third molar surgery?

Answer 9

inferior alveolar
lingual
nerve to mylohyoid
long buccal

Question 10

indications for extracting third molars

Answer 10

infection
- caries
- pericoronitis
- periodontal disease
- local bone infection
cysts
tumour
external resorption of 7 or 8
high risk of disease
medical indications e.g.g immunosuppressed
accessibility
autotransplantation

Question 11

what is pericoronitis?

Answer 11

inflammation around the crown of a partially erupted tooth

Question 12

how does pericoronitis occur?

Answer 12

food and debris gets trapped in the operculum resulting in inflammation and infection

Question 13

what type of microorganisms are responsible for periocoronitis?

Answer 13

anaerobic microbes
e.g. streptococci, actinomyces, fusobacterium

Question 14

pericoronitis signs and symptoms

Answer 14

pain
swelling
bad taste
pus discharge
ulceration of operculum
evidence of cheek biting
limited mouth opening
dysphagia
malaise
regional lymphadenopathy

Question 15

pericoronitis treatment

Answer 15

incision of localised pericoronal abscess if present
- LA IDB - depends on pain/patient
irrigation with warm saline or chlorhexidine mouthwash (10-20ml syringe with blunt needle under the operculum)
XLA of upper third molar if traumatising the operculum
patient instructions on frequent warm saline or chlorhexidiene mouthwashes

Question 16

pericoronitis - instructions to give patient

Answer 16

analgesia
instruct patient to keep fluid levels up and keep eating
- soft diet if necessary
generally do not prescribe antibiotics unless more severe case, systemically unwell, e/o swelling or immunocompromised e.g. diabetes
if large e/o swelling, scenically unwell, trsimus or dysphagia - refer to max fax or A&E

Question 17

pericoronitis predisposing factors

Answer 17

partial eruption and vertical or distoangular impaction
opposing maxillary 2nd or 3rd molar causing mechanical trauma contributing to recurrent infection
poor oH
insufficient space between ascending ramus of lower jaw and distal aspect of mandibular 2nd molar
white race
full dentition

Question 18

XLA 3rd molars - radiographic examination features

Answer 18

only if surgical intervention is being considered
OPT to determine
- presence or absence of disease
- depth and orientation of impaction
working distance
periodontal status
any associated pathology
relationship of upper third molars to maxillary sinus or lower third molars to inferior dental canal

Question 19

radiographic signs which may indicate close proximity of the root and the IAN

Answer 19

diversion of the inferior dental canal
darkening of the root where crossed by the canal
interruption of the white lines of the canal
deflection of root
narrowing of inferior dental canal
dark and bifid root
narrowing of the root

Question 20

3 radiographic signs associated with a significant increased risk of nerve injury during third molar surgery

Answer 20

diversion of the inferior dental canal
darkening of the root where crossed by the canal
interruption of the white lines of the canal

Question 21

What other imaging is possible if conventional imaging has shown a close relationship between the third molar and the inferior dental canal?

Answer 21

cone beam CT

Question 22

post operative complications of third molar surgery

Answer 22

pain
swelling
bruising
jaw stiffness/limited mouth opening
bleeding
infection
dry socket

Question 23

what percentage of patients may experience temporary numbness or parasthesia to the lower lip/chin following lower third molars extraction?

Answer 23

10-20%
may take weeks or months to improve
< 1% permanent

Question 24

surgical extraction - steps

Answer 24

anaesthesia
access
bone removal as necessary
tooth division
debridement
suture
achieve haemostasis
post op instructions

Question 25

surgical removal - anaesthesia options

Answer 25

LA IV sedation and LA general anaesthetic

Question 26

how is access gained during a surgical extraction

Answer 26

mucoperioesteal flap is raised - lingual flap may also be raised use scalpel in one firm continuous stroke

Question 27

surgical removal - reflection

Answer 27

rinse flap at base of relieving incision reflect with periosteal elevator firmly on bone

Question 28

surgical removal - retraction principles

Answer 28

access to operative field protection of soft tissues atraumatic/passive retraction - rest firmly on bone - awareness of adjacent structures e.g. mental nerve

Question 29

surgical extraction - bone removal

Answer 29

electrical straight handpiece with saline cooled bur used - as air driven handpicks may cause surgical emphysema round or fissure stainless steel and tungsten carbide burs used bone removal carried out on buccal aspect of tooth and onto distal aspect of impaction intention is to create a deep narrow gutter around the corn of the wisdom tooth bone should be removed to allow correct application of elevators on the mesial and buccal aspects of the tooth

Question 30

how is tooth division done?

Answer 30

most commonly - crown of tooth is sectioned from the roots crown and roots are elevated as individual items - sometimes further of separation of roots is required following elevation of the crown

Question 31

When sectioning to remove the entire tooth section, why should you remove the crown at just above the ACJ?

Answer 31

leaves some crown behind allowing orientation and elevation

Question 32

surgical removal - debridement

Answer 32

physical - bone file or handpiece to remove sharp bony edges - Mitchell's trimmer or Victoria curette to remove soft tissue debris irrigation - sterile saline into socket and under flap - must irrigate below flap before repositioning suction - aspirate under flap to remove debris - check socket for retained apices

Question 33

aims of suturing

Answer 33

reposition tissues cover bone prevent wound breakdown achieve haemostasis

Question 34

what is a coronectomy?

Answer 34

removal of the crown of the tooth with deliberate retention of root adjacent to the inferior alveolar nerve alternative to surgical removal of entire tooth where there appears to be an increased risk of IAN damage with surgical removala

Question 35

aims of a coronectomy

Answer 35

to reduce risk of damage to inferior alveolar nerve

Question 36

coronectomy steps

Answer 36

flap design as necessary to gain access transection of tooth 3-4mmm below crown elevation of crown without mobilising roots socket irrigated flap replaced

Question 37

coronectomy follow up

Answer 37

review in 1-2 weeks further 3-6 monthly review then 1 year radiographic review - 6 months or 1 year or both - some take immediate or 1 week post op radiograph

Question 38

coronectomy - warnings to patient prior to procedure

Answer 38

if root is mobilised during crown removal the entire tooth must be removed leaving roots behind can result in infection (rare) can get a slow healing/painful 'socket' roots may migrate later and begin to erupt through mucosa - may require extraction

Question 39

upper third molar extraction - things to take care with when extracting

Answer 39

support tuberosity with finger and thumb if access difficult a buccal flap can be raised followed by appropriate bone removal