Third Molars Flashcards
Between what ages do third molars usually erupt into the mouth?
Between 18-24yrs
At what age does crown calcification of upper third molars begin?
between 7-9y/o
At what age does crown calcification of lower third molars begin?
between 8-10y/o
If third molars are missing at age 14 on a radiograph, what will likely happen?
unlikely to develop
What is agenesis in terms of third molars?
Failure of an organ to develop eg failure of third molars to develop
In which jaw is agenesis of third molars more likely to occur?
Maxilla
What does an impacted third molar mean?
tooth eruption is blocked
What are the most common reasons for impacted third molars?
- blocked by adjacent tooth
- alveolar bone
- surrounding mucosal soft tissue
- combination of above
What are some potential consequences of impacted third molars?
- caries
- pericoronitis
- cyst formation
What nerves are at risk during third molar surgery?
- inferior alveolar nerve
- lingual nerve
- nerve to mylohyoid
- long buccal nerve
Why do we almost ALWAYS need an OPT radiograph before third molar surgery on lowers?
To see how close third molar lies in relation to the inferior alveolar nerve canal
Where does the lingual nerve lie roughly in relation to the mandible?
between 0-3.5mm medial to the mandible
What guidelines are referred to for third molar surgery?
- NICE = guidance on extraction of wisdom teeth 2000
- SIGN Publication 43 = management of unerupted and impacted third molar teeth, 2000
- FDS, RCS 2020 = parameters of Care for patients undergoing mandibular third molar surgery
What are therapeutic indications for extractions of third molars?
- infection (caries, pericoronitis, local bone infection)
- cysts
- tumours
- external resorption of 7 or 8
What are some other indications for extractions of third molars?
- surgical indications eg orthognathic, fractured mandible
- high risk of disease
- medical indications
- accessibility limited for restorative work
- patient age
- autotransplantation
- general anaesthetic
Give examples of medical indications for extraction of third molars:
- awaiting cardiac surgery
- immunosuppressed
- prevent osteonecrosis
What is pericoronitis?
Inflammation around the crown of a partially erupted tooth
- food and debris gets trapped under the flap resulting in inflammation & infection
In what age groups is pericoronitis most commonly seen?
20-40 yrs
What type of microbes are typically found in pericoronitis infections?
Anaerobic microbes
- streptococci
What are the signs and symptoms of pericoronitis?
- pain & swelling
- bad taste
- pus discharge
- occlusal trauma to gum flap
- evidence of cheek biting
- limited mouth opening
- dysphagia
- pyrexia
- malaise
- foetor oris
- regional lymphadenopathy
What is the operculum of third molar?
Gum flap covering PE third molar
How is pericoronitis treated?
- incision of localised pericoronal abscess
- LA sometimes depends on patient
- irrigation with warm saline or chlorhexidine mouthwash
What advice should be given to patients with pericoronitis?
- advice regarding analgesia
- instruct patient to keep fluid levels up & keep eating
- generally do not prescribe antibiotics unless systemic symptoms
- if large extra-oral swelling, severly systemically unwell/trismus/dysphagia… refer to maxfax
What type of radiograph would you get to assess the third molars?
OPT
What would you look at on an OPT when assessing third molars?
- anatomy of 3M
- depth of impaction
- orientation of impaction
- working distance
- follicular width
- perio bone levels
- surrounding anatomy (IAN/maxillary sinus)
What are some signs on the OPT that may suggest that lower third molars lie close to the inferior dental canal?
- interruption of lamina dura of canal
- darkening of the root where crossed by the canal
- diversion/deflection of the inferior dental canal
- deflection of root
- narrowing of IAN canal
- narrowing of root
- dark & bifid root
What are the 3 HIGHEST RISK SIGNS on an OPT of risk to inferior alveolar dental nerve during 3M surgery?
- diversion of IAN canal
- darkening of the root where crossed by canal
- interruption of the white lines of the canal
If you take an OPT, and there is suspected close relationship of 3M to IAN canal what might you do next?
take CBCT
What different types of angulation may third molars be situated in?
- vertical
- mesial
- distal
- horizontal
- transverse (sideways)
What is the angulation/orientation of third molars measured against?
curve of Spee
What orientation of third molars are the most difficult to remove?
distally impacted third molars
How can the depth of impaction of third molars be described?
- superficial
- moderate
- deep
Where would a third molar that is considered superficial in terms of depth be positioned?
crown of 8 related to crown of 7
Where would a third molar that is considered moderate in terms of depth be positioned?
crown of 8 related to crown and root of 7
Where would a third molar that is considered deep (in terms of depth) be positioned?
crown of 8 related to root of 7
What are the common treatment options for problematic third molars?
- referral
- clinical review
- XLA of M3M
- coronectomy
What are some less common treatment options for problematic third molars?
- operculectomy
- surgical exposure
- pre-surgical orthodontics
- surgical reimplantation/autotransplantation
What are the different methods of anaesthesia used for third molar treatment?
- LA alone
- conscious sedation
- general anaesthetic
What type of consent is needed for GA and IV sedation?
written consent form (done at different appt)
What post-op complications may arise from third molar surgery?
- pain
- swelling
- bruising
- jaw stiffness/trismus
- bleeding
- infection
- dry socket
- numbness or tingling of lower lip, chin, tongue
What is dysaesthesia?
painful, uncomfortable, unpleasant sensation of lower lip, chin, tongue
- sometimes neuralgia type pain
What is hypoaesthesia?
reduced sensation
what are the basic principles of surgery in dentistry?
- risk assessment (good planning & medical history)
- aseptic technique
- minimal trauma to hard & soft tissues
what are the steps of surgical removal of third molars?
- anaesthesia
- access
- bone removal as necessary
- tooth division as necessary
- debridement
- suture
- achieve haemostasis
- post-op instructions
How is surgical access to third molars achieved?
- raise a buccal mucoperiosteal flap
- sometimes raise a lingual flap
What factors apply to surgical flaps?
- larger flaps heal just as well as smaller ones
- use scalpel in one firm continuous stroke
- avoid trauma to dental papillae
How should flaps be reflected during surgical extractions?
- commence raising flap at base of relieving incision
- undermine/free anterior papillae before proceeding with reflection distally
- reflect with periosteal elevator firmly on bone
what is often used to raise papillae during a surgical extraction?
(curved) warwick james elevator
what instruments are used to raise flap from bone during a surgical extraction?
- mitchell’s trimmer
- howarth’s periosteal elevator
- ash periosteal elevator
why are flaps retracted during surgical extractions?
- better access to operative field
- protection of soft tissue
what instruments are used to retract flaps during surgical extractions?
- Howarth’s periosteal elevator
- Rake retractor
- Minnesota retractor
how do you ensure you achieve atraumatic/passive retention of flaps?
- rest firmly on bone
- have awareness of surrounding structures
- avoid crushing
what is used to remove bone during a surgical extraction?
- electrical straight handpiece with saline cooled burr
- round or fissure stainless steel & tungsten carbide burs
why are air driven handpieces not used in surgical extractions?
risk of surgical emphysema
what should you try to achieve when removing bone during surgical extractions of third molars?
- carried out on buccal aspect of tooth & onto distal aspect of impaction
- create a deep narrow gutter around crown of wisdom tooth (avoid shallow, broad gutter)
when removing bone around third molars, why do you start distally and move mesially?
if burr slips travelling distally you risk damaging the lingual nerve
What is the horizontal tooth division method during surgical extractions?
divide the crown from the roots
- some crown left (can be elevated out with roots)
- full coronectomy when divided below enamel cementum junction
What are the different modes of debridement in oral surgery?
- physical
- irrigation
- suction
How is physical debridement carried out?
- bone file or handpiece to remove sharp bony edges
- Mitchell’s trimmer or Victoria curette to remove soft tissue debris
How is irrigation debridement carried out?
sterile saline into socket and under flap
how is suction debridement carried out?
- aspirate under flap to remove debris
- check socket for retained apices etc.
what are the aims of suturing?
- reposition tissues
- cover bone
- prevent wound breakdown
- achieve haemostasis
Why is a coronectomy used in third molar surgery?
alternative to surgical removal of entire tooth when there appears to be an INCREASED RISK OF IAN DAMAGE
How is a coronectomy carried out?
- flap raised
- transection of tooth 3-4mm below the enamel of the crown into dentine
- elevate/lever crown off without mobilising the roots
- pulp left in place (untreated)
- sometimes reduce roots futher with rose head burr
When do you follow-up with a patient after coronectomy surgery?
- review 1-2 weeks
- further review 3-6 months
- then review 1 year later
What must you warn the patient of prior to coronectomy surgery?
- if root is mobilised during crown removal the entire tooth must be removed
- leaving roots behind could result in infection
- can get a slow healing/painful socket
- the roots may migrate later and begin to erupt through mucosa (and need XLA)
