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BDS4-oral Surgery > Third molars > Flashcards

Third molars Flashcards

1
Q

When do they erupt

A

18-24yrs

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2
Q

When do third molars start to form

A

Crown calcification begins between 7-10y and is completed by age 18y

Root calcification complete between 18-25y

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3
Q

What is meant by agenesis

A

absence of or failed development of a body part

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4
Q

Where is agenesis of the third molats more common

A

Maxilla in females

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5
Q

What is the most common reason for third molars failure to erupt

A

Impacted Third molars

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6
Q

What is meant by impacted molar

A

Tooth eruption is blocked

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7
Q

How can a third molar be impacted

A

Adjacent tooth, alveolar bone, surrounding mucossal soft tissue or a combo of these

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8
Q

What is the % of the incidence of impacted lower third molars

A

36-59%

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9
Q

What could a consequence of impaction be

A

Caries, pericoronitis or cyst formation

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10
Q

What nerves are at risk during a third molar surgery

A

Inferior Alveolar Nerve

Lingual Nerve

Nerve to Mylohyoid

Long Buccal Nerve

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11
Q

What ways on a radiograph would you be able to tell if theres risk to the inferior alveolar nerve canal

A

Darkening of the roots over the canal

Deflection of the roots

Narrowing of the roots

Interruption of the white line of canal

Dark and bifid apex of root

Narrowing of the canal

Diversion of the canal

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12
Q

What is the location of the lingual nerve

A

Close relationship to the lingual plate in mandibular and retromolar area

At or above level of lingual plate in 15-18% of cases

Between 0-3.5mm medial to mandible

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13
Q

What are the indications for a third molar extraction

A

Theraputic:
-Infection (caries, pericoronitits, perio etc)
-Cysts
-Tumour
-External resorption of 7 or 9

Surgical indications:
-Orthognathic surgery
-Fractured mandible
-In resection of diseased tissue

High risk of disease

Medical indications:
-Awaiting cardiac surgery
-Immunosuppressed
-To prevent osteonecrosis

Patients age

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14
Q

What is pericoronitits

A

Inflammation around the crown of a partially erupted tooth

The tooth is normally PE and visible

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15
Q

What causes the inflammation of pericoronitis

A

Food and debris gets trapped under the operculum resulting in inflammation or infection

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16
Q

How long does pericoronitis happen and at what ages

A

Usually transient

Usually occurs 20-40yrs

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17
Q

What anaerobic microbes are most common in pericoronitis

A

Streptococci

Actinomyces

Propionibacterium

A beta-lactamase producing Prevotella
Bacteroides

Fusobacterium

Capnocytophaga

Staphylococci

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18
Q

What are the S&S of pericoronitis

A

Pain

Swelling – Intra or extraoral

Bad taste

Pus discharge

Occlusal trauma to operculum

Ulceration of operculum

Evidence of cheek biting

Foetor oris

Limited mouth opening

Dysphagia

Pyrexia

Malaise

Regional lymphadenopathy

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19
Q

What is the treatment of 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

Patient instructed on frequent warm saline or chlorhexidine mouthwashes

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20
Q

When would you prescribe antibiotics

A

Generally do not prescribe antibiotics unless more severe pericoronitis, systemically unwell, extra-oral swelling, immunocompromised e.g. diabetic

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21
Q

What are the predisposing factors of pericoronitis

A

Partial eruption and vertical or distoangular impaction

Opposing maxillary M3M or M2M causing mechanical trauma contributing to recurrent infection

Upper respiratory tract infections as well as stress and fatigue pericoronitis

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

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22
Q

When would you take radiograph

A

Only if surgical intervention is being considered

23
Q

What is meant by a superficially impacted tooth

A

crown of 8 related to crown of 7

24
Q

What is meant by a deep impacted tooth

A

crown of 8 related to root of 7

25
Q

What is meant by a moderatly impacted tooth

A

crown of 8 related to crown and root of 7

26
Q

If your making a radiographic report of a patient with a third molar problem what should you include

A

Presence or absence of disease (in 3M or elsewhere)

Anatomy of 3M (crown size, shape, condition, root formation)

Depth of impaction

Orientation of impaction

Working distance (distal of lower 7 to ramus of mandible)

Follicular width

Periodontal status

The relationship or proximity of upper third molars to the maxillary antrum and of lower third molars to the inferior dental canal

Any other assoc pathology

27
Q

What signs on a radiograph are associated with an increase of nerve injury during third molar surgery

A

diversion of the inferior dental canal

darkening of the root where crossed by the canal

interruption of the white lines of the canal

28
Q

If on a radiograph there is a close relationship between nerve canal and third molar what would be the next step

A

Consider a cone beam computed tomograpgy (CBCT)

Or periapicals

29
Q

How is angulation/orientation of a third molar measured

A

It is measured against the curve of spee

30
Q

What are the Tx options for an impacted third molar

A

Common
-Referral
-Clinical review
-Removal of M3M
-Extraction of maxillary third molar
-Coronectomy

Less common
-Operculectomy
-Surgical exposure
-Pre-surgical orthodontics
-Surgical reimplantation/autotransplantation

31
Q

How many will feel tempoary anaesthesia or paraesthesia of the IDN (lower lip/chin) after extraction

A

10-20%

32
Q

How many will feel permanent anaesthesia or paraesthesia of the IDN (lower lip/chin) after extraction

A

<1%

33
Q

How many will feel tempoary anaesthesia or paraesthesia of the lingual nerve (one side of tongue, taste) after extraction

A

0.25-23%

34
Q

How many will feel permanent anaesthesia or paraesthesia of the lingual nerve (one side of tongue, taste) after extraction

A

0.14-2%

35
Q

For the surgical removal of an 8 howis access achieved

A

gained by raising a buccal mucoperiosteal flap

+/- raising a lingual flap, there is some debate on this

36
Q

What is the aim when achieving access to a 8 for surgical removal

A

Maximum access with minimal trauma

Larger flaps heal just as quickly as smaller ones

Minimise trauma to dental papillae

37
Q

How would you start a access flap for removal of a 6

A

Use scalpel in one firm continuous stroke along the gingival margin of the 7

38
Q

How do you reflect the gingiva

A

Once finished with the scalpel commence the raising of the flap starting at the relieving incision, but make sure to undermine/free anterior papilla before this to avoid any tears normally with a warick james, Reflection is achieved with the periosteal elevator firm against bone and raise in 1 piece to avoid trauma

39
Q

What instruments can be used in reflecting a flap

A

Mitchell’s trimmer

Howarth’s periosteal elevator

Ash Periosteal Elevator

Curved Warwick James elevator

40
Q

Once the flap is reflected what is the next step

A

Flap retraction

41
Q

What does flap retraction do

A

Provides access to the operative field and provides protection of soft tissues

42
Q

What does flap design facilitate

A

retraction

43
Q

What instruments are used in the retraction of a flap

A

Howarth’s periosteal elevator

rake retractor

Minnesota retractor

44
Q

What instrument is used for bone removal and what is not used and why

A

Electrical straight handpiece with saline cooled bur

Round or fissure stainless steel & tungsten carbide burs

Air driven handpieces may lead to surgical emphysema

45
Q

How is bone removal carried out in a surgical extraction

A

It is carried out on the buccal aspect of the tooth and onto the distal aspect of the impaction with bur keeping a close contact the whole way round

The intention is to create a deep, narrow gutter around the crown of the wisdom tooth not a shallow, broad gutter

Bone should be removed to allow correct application of elevators on the mesial and buccal aspects of the tooth

46
Q

After bone removal what must the operator consider

A

assess the possibility of removing the tooth in its entirety with elevators or a combination of elevators and forceps

If this is not possible and adequate bone has been removed the tooth should then be sectioned with the drill/burs

47
Q

In a horizontal tooth division where is the tooth seperated

A

When sectioning to remove entire tooth section above the enamel-cementum junction this leaves some crown behind and allows orientation and elevation

When carrying out coronectomy below enamel–cementum junction

48
Q

After surgical tooth removal what is carried out and how

A

Debridement:

Physical
-Bone file or handpiece to remove sharp bony edges
-Mitchell’s trimmer or Victoria curette to remove soft tissue debris

Irrigation
-Sterile saline into socket and under flap

Suction
-Aspirate under flap to remove debris
-Check socket for retained apices etc

49
Q

What is the aim of suturing

A

Reposition tissues

Cover bone

Prevent wound breakdown

Achieve haemostasis

50
Q

When would you carry out a coronectomy

A

When there appears to be an increased risk of IAN damage with surgical removal

51
Q

What are the stages of a coronectomy

A

Flap design as necessary to gain access to tooth. Generally – standard wisdom tooth flap designs

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

If necessary – further reduction of roots with a rose head bur to 3-4mm below alveolar crest

Socket irrigated

Flap replaced

52
Q

With a coronectomy what must you warn the patient with

A

If the 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

Can get a slow healing/painful “socket”

The roots may migrate later and begin to erupt through the mucosa; and may require extraction

53
Q

How would you remove a upper thord molar

A

Generally easier to remove

Removed by elevation only or elevation and forceps

Make sure to support tuberosity

54
Q

A pt is getting there third molar surgically removed what is important to say to them for consent

A

Discuss option of LA/Conscious sedation/GA (and referral if required)

Regarding procedure:
Pain, Swelling, Bleeding, Infection, Jaw stiffness, Dry socket

Temporary (2-20%) or Permanent (<1%) damage to nerve, with possibility of numbness, tingling or painful sensation

Areas affected could include side of chin, lip, tongue, gums or cheek

Small risk of loss of taste sensation

Surgical approach: cut in gum, bone removal which will feel like vibration/water, pressure, stitches (dissolving)

BDS4-oral Surgery (13 decks)

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