Extraction of Third Molars 1 Flashcards
What age does crown calcification of third molars start at? When does it finish?
Upper- 7-9
Lower- 8-10
Finishes age 18
What age do third molars tend to erupt?
Between 18-24
When is root calcification of third molars completed?
Between 18-25
What do missing 8s on a radiograph at age 14 tend to suggest?
They will not develop
-> 25% are missing 1 third molar
-> Agenesis is more common in females
What gene is agenesis of third molars related to?
PAX9 gene
What can pain/instability under denture in edentulous patients be caused by?
Unerupted 8s
What is meant by M3M?
Mandibular third molar
What is the most common reason for failure of eruption in third molars?
Impaction
-> can be unerupted, partially erupted or fully erupted
What structures can third molars be impacted against?
Adjacent tooth, alveolar bone, surrounding mucosal soft tissue or a combination
What are the consequences of impacted third molars?
Caries- bacteria passes through communications (can pass to other teeth)
Pericoronitis- inflammation around crown
Cyst formation- failure of follicle seperation
Which nerves are at risk during third molar surgery?
Inferior Alveolar Nerve
Lingual Nerve
Nerve to Mylohyoid*
Long Buccal Nerve*
*less common
What are the features of the IAN?
Peripheral sensory nerve (mandibular division of trigeminal nerve)
Supplies all teeth on that side, lip and chin mucosa
-> Position in relationship to 3rd molar varies (but radiograph helps determine)
What does the lingual nerve supply? (CNV3)
Anterior 2/3 of dorsal and ventral surfaces of tongue
Lingual gingivae
Floor of mouth
What structures are related to lingual nerve?
lies on superior attachment of mylohyoid muscle
Close relationship to lingual plate in mandibular (medially 0-3.5mm)
Retromolar area
How can lingual nerve be avoided in third molar surgery?
No identifiable pre-op factors- can only be avoided by good surgical technique
Which clinical guidelines are available for third molar extraction?
NICE, SIGN 43, FDS
What were the main takeaways from the updated FDS guidelines in 2020?
3rd molars can be removed:
If there is pathology (caries, perio, infection, cysts)
If not removing impacted molars is delaying inevitable surgery and can make surgery more difficult
-> Change from therapeutic approach to more holistic and patient lead approach
What are the therapeutic indications for extraction of third molars?
Infection (caries, pericoronitis, periodontal disease or local bone infection) – most common
Cysts
Tumours
External resorption of 7 or 8
What are the surgical indications for extraction of third molars?
Within surgical field (orthognathic, fractured mandible, in resection of diseased tissue)
High risk of disease
Medical indications egawaiting cardiac surgery, immunosuppressed or to prevent osteonecrosis
Accessibility- limited access
Patient age- complications and recovery time increase with age
Autotransplantation
General Anaesthetic
How many episodes of infection would prompt consideration of extracting a third molar?
1 or more
Why are carious 8 more likely to be extracted than restored?
Difficult to achieve access and moisture control
Small amounts of caries may be treatable esp occlusally
What bone loss defects can impacted 8s cause typically?
Mesio-angular
When do cysts usually present?
Between 20-50
At what stage do cysts become symptomatic?
If they become very large or infected
What is the most common cyst associated with third molars?
Dentigerous cyst (arises from reduced enamel epithelium separation from crown)
-> 10x more common in mandible
How can cyst formation be prevented?
Prophylactic removal of disease free 8 would prevent cyst formation (but not usually an indication)
Why may radiotherapy patients require their upper 8s removed before treatment?
To prevent ORN
What is external resorption?
Destruction of tissue
-> Untreated is usually progressive
What is an example of a medication that may require poor prognosis 8s to be removed before starting?
Bisphosponates
When may autotransplantation utilising 8s used? Why is it not common?
To replace missing first molar
-> low success rate
Why may all 8s be removed if patient going under GA?
Prevent need for future GA
What is pericoronitis?
Inflammation around the crown of a partially erupted tooth (usually transient and self limiting)
-> Tooth is usually partially erupted but sometimes there is little evidence of communication (probe)
What is an operculum in pericoronitis? What are the issues it can cause?
Flap of gum sitting over tooth
-> food, bacteria, plaque can trap under gum (hard to keep clean)
When does pericoronitis usually occur?
20-40 years
What microorganisms are typically involved in pericoronitis?
Anaerobic microbes (Streptococci , Actinomyces, Propionibacterium, a beta-lactamase producing Prevotella, Bacteroides, Fusobacterium, Capnocytophaga and Staphylococci most common)
What are the signs and symptoms of peri-coronitis?
Pain- increases, throbbing, pain on chewing
Swelling – Intra or extraoral
Bad taste
Pus discharge
Occlusal trauma to operculum
-> Ulceration of operculum
Evidence of cheek biting
What can happen in the event of severe EO swelling due to pericoronitis?
Can spread to submandibular area and cheek
What are the signs and symptoms of peri-coronitis? (2)
Foetor oris
Limited mouth opening (assoc. with sub masseteric spread)
Dysphagia (assoc. with sublingual/parapharyngeal spread)
Pyrexia
Malaise
Regional lymphadenopathy
What are the predisposing factors for Pericoronitis?
Partial eruption and vertical/distoangular impaction
Opposing maxillary 7/8 causing mechanical trauma contributing to recurrent infection
Upper respiratory tract infections
Stress and fatigue
Poor oral hygiene
Insufficient space between the ascending ramus of the lower jaw and the distal aspect of the M2M
White race
A full dentition
What can be done to treat pericoronitis?
Incision of localised pericoronal abscess if required
-> +/- local anaesthetic (IDB) – depends on pain/patient
Irrigation with warm saline or chlorhexidine mouthwash (10-20ml syringe with blunt needle – under the operculum)
Extraction of upper third molar if traumatising the operculum
What general advice is given to patients with pericoronits?
Frequent saline and CHX mouthrinses
Analgesia
Instruct patient to keep fluid levels up and keep eating (soft/liquid diet if necessary)
When may antibiotics for Pericoronitis be considered?
Severe pericoronitis
Systemically unwell
Extra-oral swelling
Immunocompromised e.g. diabetic
When may a patient with pericoronitis require referral to MFU or A+E?
Large extra-oral swelling
Systemically unwell
Trismus
Dysphagia
Why is operlucetomy not indicated?
As it usually grows back
When should 8 be removed if patient has pericoronitis?
When it has been resolved
