Third Molars Flashcards
(45 cards)
What is the usual eruption age of third molars
18-24 years
When is the calcification of the crown begin and complete in third molars e
7-10. Years and complete by 18 years
At what age if the third molar is missing on a radiograph would you expect it to. Never develop
14
Where does the lingual. Nerve lie
On the superior attachment of the mylohyoid
What is the incidence of impacted M3M
36–30%
What are the 4 therapeutic indications for c extraction of M3M
Infection
Cysts
Tumours
External resorption of 7 and 8
What is the most common cyst arise from M3M
Dentigenergous cyst arising from the reduced enamel epithelium separating from the crown
What two ways of impaction are higher risk of disease
Mesial-angular
Horizontal
What is pericornitis
Inflammation around a partially erupted tooth
Food and debris gets trapped under the operculum and causes inflammation and infection
Name three anerobic Microbes involved in pericornitis
Actinomyces
Streptococci
Beta lactamase producing prevotella intermedia
What two kinds of impaction predispose a patient to pericornitis
Vertical and distoangular
Insufficient space between what two structures can result in pericornitis
Ascending ramus of lower jaw and distal aspect of M2M
What is the risk of temporary numbness following extraction of a lower third molar
10-20%
What is the risk of permanent numbness following XLA of lower 3rd molar
<1%
Name 4 reasons for Indication of extraction of a lower third molar
Infection - caries, periodontal dsieae or local bone infection
Cyst
Tumour
External respotion of 7 0r 8
Impaction leading to high risk of disease
Medical indications
What muscle does the lingual nerve lie on the superior attachment of
The mylohyoid muscle
What 4 nerves are at risk during extraction of a mandibular third molar
Inferior alveolar nerve
Lingual nerve
Nerve to mylohyoid
Long buccal nerve
What are 5 predisposing factors to periocoronitis
Partial eruption and vertical or distoangular impaction
Opposing M3M or M2M causing mechanical trauma contributing to recurrent infection
Upper respiratory tract infections
Poor oral hygiene
Insufficient space between the ascending ramus of the lower jaw and the distal aspect of the M2M
A full dention
White race
Why is it so important to check the TMJ on patients with third molar pain
Often patients that are referred in for third molar pain aren’t actually having third molar pain it is instead TMD pain
What is the working space distance when discussing M3M
Distance between distal of the M2M and the ascending ramus
It is essentially the space you have to get it out
When assessing follicular width above what measuremt would you be concerned that there is pathology
Anything more than 2-3mm
There are many radiographic signs that can indicate a close relation ship of the ID canal to the roots of the M3M
What three are we most worried about that have been identified to carry the most increased risk of nerve injury during 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 is the angulation/ortientaion of an impaction measured against
Measured against the curve of spee
The depth of an impaction gives us an indication of what
The amount of bone removal required
