Third Molars Flashcards
(39 cards)
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