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BDS4 Oral Surgery > Extraction of Third Molars 1 > Flashcards

Extraction of Third Molars 1 Flashcards

1
Q

What age does crown calcification of third molars start at? When does it finish?

A

Upper- 7-9

Lower- 8-10

Finishes age 18

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2
Q

What age do third molars tend to erupt?

A

Between 18-24

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3
Q

When is root calcification of third molars completed?

A

Between 18-25

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4
Q

What do missing 8s on a radiograph at age 14 tend to suggest?

A

They will not develop

-> 25% are missing 1 third molar

-> Agenesis is more common in females

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5
Q

What gene is agenesis of third molars related to?

A

PAX9 gene

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6
Q

What can pain/instability under denture in edentulous patients be caused by?

A

Unerupted 8s

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7
Q

What is meant by M3M?

A

Mandibular third molar

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8
Q

What is the most common reason for failure of eruption in third molars?

A

Impaction

-> can be unerupted, partially erupted or fully erupted

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9
Q

What structures can third molars be impacted against?

A

Adjacent tooth, alveolar bone, surrounding mucosal soft tissue or a combination

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10
Q

What are the consequences of impacted third molars?

A

Caries- bacteria passes through communications (can pass to other teeth)

Pericoronitis- inflammation around crown

Cyst formation- failure of follicle seperation

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11
Q

Which nerves are at risk during third molar surgery?

A

Inferior Alveolar Nerve
Lingual Nerve
Nerve to Mylohyoid*
Long Buccal Nerve*

*less common

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12
Q

What are the features of the IAN?

A

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)

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13
Q

What does the lingual nerve supply? (CNV3)

A

Anterior 2/3 of dorsal and ventral surfaces of tongue

Lingual gingivae

Floor of mouth

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14
Q

What structures are related to lingual nerve?

A

lies on superior attachment of mylohyoid muscle

Close relationship to lingual plate in mandibular (medially 0-3.5mm)

Retromolar area

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15
Q

How can lingual nerve be avoided in third molar surgery?

A

No identifiable pre-op factors- can only be avoided by good surgical technique

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16
Q

Which clinical guidelines are available for third molar extraction?

A

NICE, SIGN 43, FDS

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17
Q

What were the main takeaways from the updated FDS guidelines in 2020?

A

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

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18
Q

What are the therapeutic indications for extraction of third molars?

A

Infection (caries, pericoronitis, periodontal disease or local bone infection) – most common

Cysts

Tumours

External resorption of 7 or 8

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19
Q

What are the surgical indications for extraction of third molars?

A

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

20
Q

How many episodes of infection would prompt consideration of extracting a third molar?

A

1 or more

21
Q

Why are carious 8 more likely to be extracted than restored?

A

Difficult to achieve access and moisture control
 Small amounts of caries may be treatable esp occlusally

22
Q

What bone loss defects can impacted 8s cause typically?

A

Mesio-angular

23
Q

When do cysts usually present?

A

Between 20-50

24
Q

At what stage do cysts become symptomatic?

A

If they become very large or infected

25
Q

What is the most common cyst associated with third molars?

A

Dentigerous cyst (arises from reduced enamel epithelium separation from crown)

-> 10x more common in mandible

26
Q

How can cyst formation be prevented?

A

Prophylactic removal of disease free 8 would prevent cyst formation (but not usually an indication)

27
Q

Why may radiotherapy patients require their upper 8s removed before treatment?

A

To prevent ORN

28
Q

What is external resorption?

A

Destruction of tissue
-> Untreated is usually progressive

29
Q

What is an example of a medication that may require poor prognosis 8s to be removed before starting?

A

Bisphosponates

30
Q

When may autotransplantation utilising 8s used? Why is it not common?

A

To replace missing first molar

-> low success rate

31
Q

Why may all 8s be removed if patient going under GA?

A

Prevent need for future GA

32
Q

What is pericoronitis?

A

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)

33
Q

What is an operculum in pericoronitis? What are the issues it can cause?

A

Flap of gum sitting over tooth

-> food, bacteria, plaque can trap under gum (hard to keep clean)

34
Q

When does pericoronitis usually occur?

A

20-40 years

35
Q

What microorganisms are typically involved in pericoronitis?

A

Anaerobic microbes (Streptococci , Actinomyces, Propionibacterium, a beta-lactamase producing Prevotella, Bacteroides, Fusobacterium, Capnocytophaga and Staphylococci most common)

36
Q

What are the signs and symptoms of peri-coronitis?

A

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

37
Q

What can happen in the event of severe EO swelling due to pericoronitis?

A

Can spread to submandibular area and cheek

38
Q

What are the signs and symptoms of peri-coronitis? (2)

A

Foetor oris

Limited mouth opening (assoc. with sub masseteric spread)

Dysphagia (assoc. with sublingual/parapharyngeal spread)

Pyrexia

Malaise

Regional lymphadenopathy

39
Q

What are the predisposing factors for Pericoronitis?

A

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

40
Q

What can be done to treat pericoronitis?

A

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

41
Q

What general advice is given to patients with pericoronits?

A

Frequent saline and CHX mouthrinses

Analgesia

Instruct patient to keep fluid levels up and keep eating (soft/liquid diet if necessary)

42
Q

When may antibiotics for Pericoronitis be considered?

A

Severe pericoronitis

Systemically unwell

Extra-oral swelling

Immunocompromised e.g. diabetic

43
Q

When may a patient with pericoronitis require referral to MFU or A+E?

A

Large extra-oral swelling

Systemically unwell

Trismus

Dysphagia

44
Q

Why is operlucetomy not indicated?

A

As it usually grows back

45
Q

When should 8 be removed if patient has pericoronitis?

A

When it has been resolved

46
Q
A

BDS4 Oral Surgery (19 decks)

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