Third Molars Flashcards
At what age do third molars usually erupt?
between 18 and 24
when does crown calcification of third molars begin and end?
begins 7-10
completed by age 18
when does root calcification complete in third molars?
18-25
what proportion of adults have at least one third molar missing?
1 in 4
- more common in maxilla and females
- almost always fail to develop if missing at 14 in radiograph
impacted third molars - what does this mean?
tooth eruption is blocked
What are mandibular third molars usually impacted against?
adjacent tooth
alveolar bone
surrounding mucosal soft tissues
a combination of these factors
incidence of impacted lower third molars
36-59%
consequences of impacted third molars
caries
pericoronitis
cyst formation
what nerves are at risk during mandibular third molar surgery?
inferior alveolar
lingual
nerve to mylohyoid
long buccal
indications for extracting third molars
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
what is pericoronitis?
inflammation around the crown of a partially erupted tooth
how does pericoronitis occur?
food and debris gets trapped in the operculum resulting in inflammation and infection
what type of microorganisms are responsible for periocoronitis?
anaerobic microbes
e.g. streptococci, actinomyces, fusobacterium
pericoronitis signs and symptoms
pain
swelling
bad taste
pus discharge
ulceration of operculum
evidence of cheek biting
limited mouth opening
dysphagia
malaise
regional lymphadenopathy
pericoronitis treatment
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
pericoronitis - instructions to give patient
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
pericoronitis predisposing factors
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
XLA 3rd molars - radiographic examination features
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
radiographic signs which may indicate close proximity of the root and the IAN
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
3 radiographic signs associated with a significant increased risk of nerve injury during third molar surgery
diversion of the inferior dental canal
darkening of the root where crossed by the canal
interruption of the white lines of the canal
What other imaging is possible if conventional imaging has shown a close relationship between the third molar and the inferior dental canal?
cone beam CT
post operative complications of third molar surgery
pain
swelling
bruising
jaw stiffness/limited mouth opening
bleeding
infection
dry socket
what percentage of patients may experience temporary numbness or parasthesia to the lower lip/chin following lower third molars extraction?
10-20%
may take weeks or months to improve
< 1% permanent
surgical extraction - steps
anaesthesia
access
bone removal as necessary
tooth division
debridement
suture
achieve haemostasis
post op instructions
surgical removal - anaesthesia options
LA
IV sedation and LA
general anaesthetic
how is access gained during a surgical extraction
mucoperioesteal flap is raised
- lingual flap may also be raised
use scalpel in one firm continuous stroke
surgical removal - reflection
rinse flap at base of relieving incision
reflect with periosteal elevator firmly on bone
surgical removal - retraction principles
access to operative field
protection of soft tissues
atraumatic/passive retraction
- rest firmly on bone
- awareness of adjacent structures e.g. mental nerve
surgical extraction - bone removal
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
how is tooth division done?
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
When sectioning to remove the entire tooth section, why should you remove the crown at just above the ACJ?
leaves some crown behind allowing orientation and elevation
surgical removal - debridement
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
aims of suturing
reposition tissues
cover bone
prevent wound breakdown
achieve haemostasis
what is a coronectomy?
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
aims of a coronectomy
to reduce risk of damage to inferior alveolar nerve
coronectomy steps
flap design as necessary to gain access
transection of tooth 3-4mmm below crown
elevation of crown without mobilising roots
socket irrigated
flap replaced
coronectomy follow up
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
coronectomy - warnings to patient prior to procedure
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
upper third molar extraction - things to take care with when extracting
support tuberosity with finger and thumb
if access difficult a buccal flap can be raised followed by appropriate bone removal
