third molar Flashcards
when do third molars usually erupt
18-24yrs
when is crown and root calcification of third molar
crown calcification 7yrs completed by 18
root calcification 18-25yrs
at what age is 3rd molars are not on radiograph would they not be expected to ever appear
14
what is what is partially erupted
partially eupted is defined as when some of the tooth has erupted into the oral cavity
consequences of impacted 3rd molars
caries
periodontitis
cyst formation
what is most common reason third molars dont erupt
impaction (blocked)
what nerves are at risk during third molar surgery
- inferior alveolar nerve
- lingual nerve
- nerve to mylohyoid - less commonly affected
- long buccal nerve - less commonly affected
where is inferior alveolar nerve from
mandibular division of trigeminal nerve
what does inferior alveolar nerve supply
- mandibular teeth on that side
-mucosa
-lip and chin
lingual nerve (location, supply, and origin)
location
- superior attachment of mylohyoid
-closer to lingual plate and alveolar crest
origin
- mandibular division of Trigeminal nerve
supplies
-anterior two thirds of dorsal and ventral mucosa of the tongue
guidelines for wisdom teeth
- NICE
- SIGN publication 43
- FDS, RCS 2020
indications for extraction of third molar
- cysts
-tumours - external resorption
- infection
- local bone infection
- caries- hard to restore caries or caries on adjacent tooth
- perio -untreated mesio angular impaction prone to cause bone loss distal to lower 7
-medical indications - starting bisphosphonates
cysts common in third molar
- aged 20-50
- dentigenous cyst - reduced enamel epithelium separation from crown
-common in mandible
what is pericoronitis
inflammation around the crown of a partially erupted tooth
food and debris trapped under operculum
usually transient and self limiting
usually occurs 20-40 yrs
second most common indication for M3M extraction
what microbes present in pericoronitis
(streptococci, actinomyces, propoionbacterium, a beta lactamase producing prevotella, bacteriocides, fusobacterium , capnocytophages and staphylococci most common)
signs and symptoms of pericoronitis
- pain
-swelling - intra/extraoral
(can give truisms if spread under masseter)
-bad taste
-pus
-ulceration and occlusal trauma of operculum
-foetor iris
-dysphagia
-pyrexia
-malaise
-lympadenopathy
Tx of pericoronitis
- incision of localised pericoronal abscess if needed
- +/- LA (IDB) depends on pain or patient
- irrigation with warm saline or chlorhexidine mouthwash (10-20ml syringe with blunt needle - under the operculum)
- painkillers
-fluid levels up
how to treat if systemically unwell or extremely swollen
refer to maxfax and antibiotics
pre-disposing factors for pericoronitis
- partial eruption and vertical or distoangular impaction
- opposing maxillary M3M or M2M causing mechanical trauma contributing to recurrent infection
- upper respiratory tract infection as well as stress and fatigue periocoronitis
- poor OH
- white race
- full dentition
- insufficient space between ascending ramus of the lower jaw and distal aspect of M2M
what radiograph usually taken for third molar
OPT
what does OPT help determine
- presence of disease
- anatomy of 3M
- depth of impaction
-orientation of tooth
-working distance (distal of lower 7 to ramus of mandible)
-follicular width - perio status
- relationship to maxillary antrum or inferior alveolar canal
what are the depths of impaction
superfically impacted (crown of 8 at same height as 7)
moderately impacted (anywhere between this)
deeply impacted ( crown of 8 at same level as roots of adjacent 7)
what would be suggested if follice is bigger than 3mm
cyst
signs of close proximity to ID canal
- interruption of white lines/lamina dura of the canal
- darkening of root where crossed by the canal
- diversion/deflection of the inferior dental canal
- deflection of root
- narrowing of inferior dental canal
- narrowing of root
- dark and bifid root
- juxta apical area ?
what is further imaging for 3M
- CBCT
-periapical - caries detection
types of angulation of 3M
vertical - around 30-38% of impacted lower 8s
mesial - around 40%
distal - around 6-15%
horizontal - around 3-15%
transverse or aberrant - less common
treatment options for third molar
- referral
- clinical review - reviewing signs and symptoms, dont need extra radiographs if no symptoms , routine bitewings should show if adjacent 7 is affected
- removal of M3M
- extraction of maxillary third molar
- coronectomy - removing crown and leaving roots
- operculectomy - removing operculum , generally grows back
- surgical exposure - encourage unerupted tooth to come into mouth
- pre-surgical ortho
- surgical re-implantation/autotransplantation - limited sucess, often moved to sight of lower 6
risks and complications of 3M extraction
- risk of fracture
-pain
-swelling
-brusing
-jaw stiffness/limited mouth opening
-bleeding
-infection - dry socket
-nerve damage
nerve damage and 3M extraction
- numbness or tingling (anaesthesia/parasthesia)
-dysaesthesia
-reduced or increased sensation
IDN(lower lip/chin)
- temp - 10-20%
- permanent <1%
lingual (one side of tongue, taste)
-temp - up to 23%
- permanent - 1%
what is coronectomy
- crown is removed and retention of root adjacent to IAN to reduce damage
- transection of tooth 3-4mm below enamel of crown
- leave pulp and try not to mobilise root
warnings for patients for coronectomy
- if root is mobilised during crown removal the entire tooth must be removed (more likely with conical fused roots)
- leaving roots behind could result in infection (rarely seen
- can get slow healing/painful socket
- roots may migrate later and begin to erupt through mucosa, may need extraction
access for wisdom tooth extraction
- buccal mucoperiosteal flap
-maximum access minimal trauma
-distal relieving incision
-create a buccal gutter
how to debride after 3m extraction
- bone file
-saline - suction
account for all apices
