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BDS4 CDS Oral Surgery > 8. Third Molars > Flashcards

8. Third Molars Flashcards

1
Q

At what age do third molars usually erupt into the mouth ?

A

18-24

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2
Q

When does crown calcification of third molars begin ?

A

7-10

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3
Q

When is crown calcification of third molars completed ?

A

18

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4
Q

When is root calcification of third molars completed ?

A

18-25

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5
Q

What gene is agenesis of third molars related to ?

A

PAX9 gene

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6
Q

Is agenesis of third molars more common in men or women ?

A

Women

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7
Q

At what age, if third molars are not present on the radiograph, are patients unlikely to present ?

A

14

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8
Q

What can cause third molars to become impacted ?

A

Adjacent tooth.
Alveolar bone.
Surrounding mucosal soft tissue.

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9
Q

What are the complications associated with third molars that might lead to them being extracted ?

A

Caries.
Pericoronitis.
Cyst formation.

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10
Q

What are the four nerves associated with third molar surgery ?

A

IAN
Lingual nerve
Nerve to mylohyoid
Long buccal nerve

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11
Q

What are four therapeutic indications for extraction of third molars ?

A

Infection, cysts, tumours, external resorption of 7 or 8

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12
Q

What are other indications for extraction of third molars ?

A

Surgical indications - orthognathic, fractured mandible.
High risk of disease.
Medical indications.
Accessibility to care.
Patient age.
Autotransplantation.
GA

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13
Q

What are 3 medical indications for extraction of third molars ?

A

Awaiting cardiac surgery,
Immunosuppressed.
Prevention of osteoradionecrosis.

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14
Q

Define pericoronitis.

A

Inflammation of tissues around the crown of a partially erupted tooth. Caused by food trapping and debris under operculum resulting in inflammation and infection.

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15
Q

What one condition is related to incidence of pericoronitis ?

A

URTI

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16
Q

What type of microbes are associated with pericoronitis ?

A

Anaerobic microbes.
Examples - streptococci, actinomycetes, beta-lactamase prevotella.

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17
Q

What are the common symptoms and signs of pericoronitis ?

A

Pain.
Swelling.
Bad taste.
Pus discharge.
Occlusal trauma to operculum.
Limited mouth opening.
Dysphagia.
Pyrexia.
Regional lymphadenopathy.

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18
Q

What treatment is given for pericoronitis ?

A

LA - usually IDB.
+/- incision of localised pericoronal abscess if required.
Irrigation under operculum with (10-20ml needle) blunt needle with warm saline or chlorhexidine mouthwash.

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19
Q

What advice should be given to patient with pericoronitis ?

A

Advice on analgesia.
Warm saline mouth rinse.
Keep fluid levels and eating up.

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20
Q

What are predisposing factors associated with pericoronitis ?

A

Partial eruption with vertical or disto-angular impaction.
URTI
Stress and fatigue.
Poor OH.
White race.
Full dentition.
Insufficient space between the ascending ramus and distal aspect of M2M.

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21
Q

Why is an OPT indicated prior to third molar surgery ?

A

Disease.
Anatomy of tooth.
Anatomy of root.
Depth of impaction.
Orientation.
Working distance.
Follicular width.
Periodontal status.
Relationship to significant structures.

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22
Q

Define working distance with relation to removal of third molars.

A

Distance between distal of lower 7 and ramus of the mandible.

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23
Q

How many mm of widening of dental follicle is associated with formation of cyst related to third molar tooth ?

A

2.5-3mm

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24
Q

Where is the dental follicle ?

A

Tissue surrounding crown of developing tooth.

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25
Q

What are the 3 signs which have been demonstrated to be associated with significantly increased risk of nerve injury during third molar surgery ?
SIGN and FDS guidelines.

A

Diversion of canal.
Darkening of root where crossing the canal.
Interruption of lamina dura of canal.

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26
Q

What is a Juxta apical area seen on radiograph of a third molar ?

A

Well circumscribed radiolucent region lateral to root of third molar.
Lamina dura still intact.
Non-pathological.

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27
Q

What further imaging may be required if you are concerned about the extraction of a third molar ?

A

CBCT
PA

28
Q

Why is CBCT useful ?

A

Assess exact relationship between tooth and canal - whether there is bone separating them or if tooth is compressing canal.

29
Q

Why is PA useful ?

A

Caries assessment.

30
Q

What is the most common angulation of impaction of third molars ?

A

Mesial (40%)

31
Q

Define aberrant angulation.

A

Located in strange place where you would not expect to see a third molar - ramus of mandible or lower border.

32
Q

Define superficial impaction.

A

Crown of 8 related to crown of 7.

33
Q

Define moderate impaction.

A

Crown of 8 related to crown and root of 7.

34
Q

Define deep impaction.

A

Crown of 8 related to root of 7.

35
Q

Define coronectomy.

A

Removal of crown and leaving the roots in situ.

36
Q

When is a coronectomy indicated ?

A

When very close relation of roots to IA canal - confirmed by OPT and CBCT.

37
Q

Name common post-op complications of third molar surgery.

A

Pain
Swelling
Bruising
Jaw stiffness
Limited mouth opening
Bleeding
Infection
Dry socket
Numbness or tingling tongue - lingual nerve
Numbness or tingling lip and chin - mental nerve/IAN
Altered taste - lingual nerve (chorda tympani)
Dysaesthesia
Hypaesthesia

38
Q

When will maximum swelling occur in patient following 3M surgery ?

A

48 hours.

39
Q

Name 5 predisposing factors which might contribute to dry socket.

A

Females.
Smokers.
Previous dry socket.
Lower 8s.
Contraceptives.

40
Q

A patient has a restored 7 adjacent to 8 to be extracted - what specific risk should you mention to the patient ?

A

Damage restoration.
Will be temporised and new filling can be placed at later date once socket has healed.

41
Q

A patient has a edentulous/atrophic mandible, aberrant lower 8 close to lower border of mandible and a large cystic lesion associated with 8 - what specific risk should you mention to the patient ?

A

Jaw fracture.

42
Q

Between how long should nerves recover if damaged during third molar surgery before permanent damage occurs ?

A

18-24 months
24+ months - usually remains permanent.

43
Q

What nerve is responsible for taste from anterior two thirds of the tongue ?

A
  • Chorda tymapni.
  • Branch of facial nerve CNVII.
  • Runs with lingual nerve.
44
Q

Define dysaesthesia.

A

Painful, uncomfortable, unpleasant sensation.
Rare complication of third molar surgery - chin, tongue, sometimes neuralgia type pain.

45
Q

Define hypoaesthesia.

A

Reduced sensation.

46
Q

What alternative type of imaging can a patient be referred for if there is concerns over the close proximity of IDC and tooth/roots ?

A

CBCT scan.

47
Q

Name four instruments which can be used for reflecting mucoperiosteal flaps.

A

Mitchell’s trimmer.
Howarth’s periosteal elevator.
Ash periosteal elevator.
Curved Warwick James elevator.

48
Q

Name three types of retractor used when retracting a surgical flap.

A

Howarth’s retractor.
Rake retractor.
Minnesota retractor.

49
Q

What are the two functions of retraction ?

A

Access to operative field.
Protection of soft tissues.

50
Q

What type of handpiece is used in surgical bone removal ?

A

Electrical straight handpiece with saline cooled bur.

51
Q

What complication can arise if air driven handpieces are used to remove bone ?

A

Surgical emphysema.

52
Q

What is a round bur used for in surgical bone removal ?

A

Create gutter in bone surrounding tooth to gain access.

53
Q

What is a fissure bur used for in surgical XLA ?

A

Sectioning tooth.

54
Q

What is the aim of bone removal ?

A

Create deep, narrow gutter around crown to allow correct application of elevators on mesial and buccal aspects of the tooth.
Bone should be removed on buccal aspect of tooth and onto distal aspect of the impaction.

55
Q

What material are surgical bone removal burs made of ?

A

Tungsten carbide.

56
Q

What are the aims of suturing ?

A

Repositioning of tissues, cover bone, prevent wound breakdown, achieve haemostasis.

57
Q

When giving post-op instructions, how long should patients not smoke for post-XLA ?

A

24 hours.

58
Q

When giving post-op instructions, how long should patients not drink alcohol for post-XLA ?

A

24 hours.

59
Q

When giving post-op instructions, how long should patients avoid vigorous exercise for post-XLA ?

A

24 hours.

60
Q

What advice should you give a patient regarding eating and drinking post-surgical XLA ?

A

Take care with hot - LA.
Avoid hard or jaggy foods i.e. crisps.
Chew on opposite side of the mouth.
Soft diet to reduce pressure on muscles and mouth opening.

61
Q

How long can a patient expect to be sore post-op after surgical XLA ?

A

24-48 hours.

62
Q

When should a patient contact you post-XLA ?

A

If they notice pus/bad taste.
Pain or swelling after 3 days post-XLA.
Bleeding for >30mins biting on dampened gauze.
Persistent numbness after 24 hours.

63
Q

How long should a patient expect jaw stiffness post-XLA of 8s ?

A

2-3 weeks.

64
Q

How long does anaesthesia normally last from IDB ?

A

3 hours.
Sensation will return in tongue before mouth.

65
Q

How often should a patient use warm, salty water mouthrinse ?

A

2-3x daily for first week.
Give it 6-8 hours post-op to rinse.

66
Q

What is the aim of a coronectomy ?

A

Reduce the risk of IAN damage.

BDS4 CDS Oral Surgery (18 decks)

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