third molars 1 Flashcards
what age radiographically is crown calcification begin for 3rd molars
between 7-10 years old
what age is crown calcification finished in 3rd molars
18
what age is root calficiation finished
18-25
what is agenesis
failure of an organ to develop
who is agenesis more common in
females and more common in maxilla
1 in 4 adults have at least 1 3rd molar missing
at what age would you suspect no 3rd molar to be present
if missing radiographically by age 14 would almost always fail to develop
what are M3Ms usually impacts against
adjacent teeth, alveolar bone, surrounding mucosal soft tissue or a combination of these factor
what is the incidence of impacted M3M
36-59%
what are the consequence of impacted M3M
caries, pericoronitis or cyst formation
what nerves are at risk during 3rd molar surgery
IAN
lingual nerve
nerve to mylohyoid
long buccal nerve
what does lingual nerve suply
anterior 2/3 of dorsal surface and central mucosa of the tongue and gives off a branch to supply the gingiva of lingual
where is lingual nerve situated
close relationship to lingual plate in mandibular retromolr pad area
what are the pre-op identifiable factors for lingual nerve injury
none - injury is largely down to surgical technique
what is the guidance regarding removal of M3M
previously discouraged removal unless there was pathology associated with it
new evidence states that not removing them could just be delaying the inevitable surgery and could make pathology worse
what are the indications for extraction
infection - caries, pericoronitis, periodontal disease
cysts
tumours
external resorption of the 7 or 8
pericoronitis
what is most common cyst
dentinogenesis
is mandible or maxilla more common for a cyst
mandible - 10x more common
what ages is extneral resorption of 7 or 8 more common
21-30
if pt has a tumour why would you extract the 8’s before starting treatment
if need to remove it after radiotherapy then there is a risk of osteoradionecrosis
what is the surgical indications for removal of M3M
for orthognathic surgery, fractured mandible
may need extracted to allow for primary closure
what are the medical indications for extraction
awaiting heart surgery
immunosuppressed
before starting Bisphosphonates
how are 3rd molars used for auto transplantation
if pt missing 1st molars can remove 8’s and put into the space of 6’s
very low success rate
what is pericoronitis
inflammation around the crown of a partially erupted tooth
what is the operculum
flap of gum sitting over the tooth
what can the operculum cause
food trapping and debris getting stuck under it as hard to clean
what age range gets pericoronitis
20-40
what general health condition can increase case of pericoronitis
upper respiratory tract infection - unclear why
what bacteria are involved in pericoronitis
anaerobic microbes mainly
streptococci, actinomyces, prevotella, bactericides, fusobacterium, staphylococci
signs and symptoms of pericoronitis
pain on biting - variable
swelling - intra/extra-oral
bad taste
pus discharge
occlusal trauma to operculum
ulceration of operculum
evidence of cheek biting
limited mouth opening
dysphagia
pyrexia
malaise
regional lymphadenopathy
in severe cases of pericoronitis what swelling can occur
extra-oral
starts at the angle of the mandible and commonly travels into the submandibular area, or laterally into the cheek, or disto-buccaly under the masseter
what is swelling going under the masseter called
sub-masseteric abscess and main sign is unable to open mouth, severe trismus
treatment of pericoronitis
- LA depends on pt and pain
- irrigate with warm saline or CHX mouthwash = 10-20ml syringe with blunt needle under the operculum
- extract upper 3rd molar stop traumatising operculum
- pt instructed on frequent warm saline/CHX
- advice regarding analgesia
- soft/liquid diet if necessary
- used to do operculectomy
- if large swelling and systemically unwell refer to max fax or A&E
are antibiotics prescribed for pericoronitis
generally no, unless systemically unwell, e/o swelling, immunocompromised
what are the predisposing factors for pericoronitis
partial eruption and vertical ditto-angular impaction
opposing maxillary 3rd molar causing trauma
upper respiratory tract infections as well as stress and fatigue
poor OH
insufficient space between the ascending ramus of the lower jaw and the distal aspect of the M2M
white race
a full dentition
