third molars 1

Question 1

what age radiographically is crown calcification begin for 3rd molars

Answer 1

between 7-10 years old

Question 2

what age is crown calcification finished in 3rd molars

Answer 2

18

Question 3

what age is root calficiation finished

Answer 3

18-25

Question 4

what is agenesis

Answer 4

failure of an organ to develop

Question 5

who is agenesis more common in

Answer 5

females and more common in maxilla
1 in 4 adults have at least 1 3rd molar missing

Question 6

at what age would you suspect no 3rd molar to be present

Answer 6

if missing radiographically by age 14 would almost always fail to develop

Question 7

what are M3Ms usually impacts against

Answer 7

adjacent teeth, alveolar bone, surrounding mucosal soft tissue or a combination of these factor

Question 8

what is the incidence of impacted M3M

Answer 8

36-59%

Question 9

what are the consequence of impacted M3M

Answer 9

caries, pericoronitis or cyst formation

Question 10

what nerves are at risk during 3rd molar surgery

Answer 10

IAN
lingual nerve
nerve to mylohyoid
long buccal nerve

Question 11

what does lingual nerve suply

Answer 11

anterior 2/3 of dorsal surface and central mucosa of the tongue and gives off a branch to supply the gingiva of lingual

Question 12

where is lingual nerve situated

Answer 12

close relationship to lingual plate in mandibular retromolr pad area

Question 13

what are the pre-op identifiable factors for lingual nerve injury

Answer 13

none - injury is largely down to surgical technique

Question 14

what is the guidance regarding removal of M3M

Answer 14

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

Question 15

what are the indications for extraction

Answer 15

infection - caries, pericoronitis, periodontal disease
cysts
tumours
external resorption of the 7 or 8
pericoronitis

Question 16

what is most common cyst

Answer 16

dentinogenesis

Question 17

is mandible or maxilla more common for a cyst

Answer 17

mandible - 10x more common

Question 18

what ages is extneral resorption of 7 or 8 more common

Answer 18

21-30

Question 19

if pt has a tumour why would you extract the 8’s before starting treatment

Answer 19

if need to remove it after radiotherapy then there is a risk of osteoradionecrosis

Question 20

what is the surgical indications for removal of M3M

Answer 20

for orthognathic surgery, fractured mandible
may need extracted to allow for primary closure

Question 21

what are the medical indications for extraction

Answer 21

awaiting heart surgery
immunosuppressed
before starting Bisphosphonates

Question 22

how are 3rd molars used for auto transplantation

Answer 22

if pt missing 1st molars can remove 8’s and put into the space of 6’s
very low success rate

Question 23

what is pericoronitis

Answer 23

inflammation around the crown of a partially erupted tooth

Question 24

what is the operculum

Answer 24

flap of gum sitting over the tooth

Question 25

what can the operculum cause

Answer 25

food trapping and debris getting stuck under it as hard to clean

Question 26

what age range gets pericoronitis

Answer 26

20-40

Question 27

what general health condition can increase case of pericoronitis

Answer 27

upper respiratory tract infection - unclear why

Question 28

what bacteria are involved in pericoronitis

Answer 28

anaerobic microbes mainly streptococci, actinomyces, prevotella, bactericides, fusobacterium, staphylococci

Question 29

signs and symptoms of pericoronitis

Answer 29

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

Question 30

in severe cases of pericoronitis what swelling can occur

Answer 30

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

Question 31

what is swelling going under the masseter called

Answer 31

sub-masseteric abscess and main sign is unable to open mouth, severe trismus

Question 32

treatment of pericoronitis

Answer 32

- 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

Question 33

are antibiotics prescribed for pericoronitis

Answer 33

generally no, unless systemically unwell, e/o swelling, immunocompromised

Question 34

what are the predisposing factors for pericoronitis

Answer 34

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