third molars Flashcards
what age do third molars usually erupt
18-24
what age does crown and root calcification of 3rd molars occur
crown - begins age 7/10 finishes age 18
root - complete by age 15-18
what proportion of adults will be missing at least 1 3rd molar
1 in 4
at what age, if no third molar on radiograph, are no 3rd molar likely to develop
14
what is the most common reason 3rd molars fail to erupt
impacted by adjacent tooth , alveolar bone, surrounding mucosa or combination of these
name 3 potential complications of 3rd molar impaction
caries
pericoronitis
cyst formation
what 4 nerves are at risk during 3rd molar surgery
IAN
lingual
nerve to mylohyoid
long buccal
what does the IAN supply
all mandibular teeth on that side, mucosa and skin of lower lip and chin on that side
what does the lingual nerve supply
sensory innervation to anterior 2/3 of tongue (both dorsal and ventral)
branch that supplies lingual gingivae and floor of mouth on that side
what location to the mandible is the lingual nerve
0-3.5mm medial to mandible
name 3 therapeutic indications for extraction of 3rd molars
infection - caries, pericoronitis, perio disease
cysts
tumours
external resorption of 7 or 8
pericoronitis
inflammation around the crown of a partially erupted tooth
Food and debris get trapped under operculum and cause inflammation and infection
operculum
piece of gum tissue present over occlusal surface of tooth after eruption
name 3 bacteria that may be implicated in pericoronitis
anaerobes:
prevotella intermedia
streptococci
actinomyces
what age group are normally affected by pericoronitis
20-40
what is the only general health condition that increases risk of pericoronitis
upper respiratory tract infection - unclear why
signs and symptoms of pericoronitis
pain - often throbbing
swelling - intra or extra oral, usually intra oral over impacted tooth
bad taste/ pus discharge
occlusal trauma to operculum
ulceration of operculum
evidence of cheek biting
foetor oris (bad breath/ halitosis)
dsphagia (difficulty swallowing)
systemically unwell - pyrexia, malaise, regional lymphadenopathy
trismus is a characteristic sign of what type of abscess
sub masseteric
what is the usual treatment for pericoronitis
usually self limiting and transient (non permanent and self recovering)
irrigation with warm saline or chlorhexidine
incision of localised pericoronal abscess if required
frequent warm saline or chlorhexidine mouth rinses
antibiotic of choice for pericoronitis
metronizadole four hundred mg 3x daily for 3 days
antibiotic for pericoronitis if patient cant have metronizadole
amoxicillin 500mg tablets, 1 tablet, 3x daily for 3 days
predisposing factors for pericoronitis
partially erupted and vertical or distoangular impaction
opposing maxillary molar causing mechanical trauma contributing to recurrent infection
upper respiratory tract infection as well as stress and fatigue
insufficient space between mandibular ramus and distal aspect of M2M
white race
full dentition present
