3rd molars

Question 1

Most common reasons for 3rd molars failing to erupt

Answer 1

Impacted- by adjacent tooth, alveolar bone, surrounding mucosal soft tissues

Question 2

Nerves at risk during XLA8

Answer 2

Inferior alveolar
Lingual
Nerve to mylohyoid
Long buccal

Question 3

Anatomy of lingual nerve

Answer 3

Close relationship to lingual plate in mandibular and retromolar area
Between 0-3.5mm medial to mandible

Question 4

Indications for XLA8

Answer 4

Therapeutic indications: cysts, tumour, infection, external resorption of 7/8
Surgical indications: orthognathic
High risk of disease
Medical indication: immunosuppressed
Accessibility
Age
Autotransplantation
GA

Question 5

What is pericoronotis

Answer 5

Inflammation around crown of PE
Food/debris trapped under operculum causing inflammation/infection
Transient/self limiting/usually occurs 20-40 yrs
Anaerobic microbes: actinomyces, fusobacterium, beta lacatamase producing prevotella

Question 6

Signs and symptoms of pericoronitis

Answer 6

Pain, swelling, bad taste, pus discharge, occlusal trauma to operculum, ulceration of operculum, cheek biting, foetor oris, limited mouth opening, dysphagia, pyrexia, malaise, regional lymphadenopathy

Question 7

Treatment of pericoronitis

Answer 7

• Incision of localised pericoronal abscess if required
• +- LA depending on pain/pt
• irrigation with warm saline/CH MW( 0.1-0.25ml with syringe and blunt needle)
• XLA8 if traumatising operculum
• Instruct pt on frequent use of warm saline/CH MW
• Advice regarding analgesia
• Instruct pt on high fluid intake/soft diet
• No antibiotics unless more severe pericoronitis, systemically unwell, EO swelling, immunocompromised

Question 8

Predisposing factors to pericoronitis

Answer 8

• PE + vertical/distoangular impaction
• opposing molars causing mechanical trauma
• upper respiratory tract infection/stress
• poor OH
• white
• full dentition

Question 9

Why do some health boards recommend not to use CH MW to irrigate

Answer 9

Due to cases of anaphylaxis

Question 10

If considering surgery OPT take and Radiographic report for 3rd molars must include:

Answer 10

Presence/absence of disease
Anatomy of 3rd M
Depth/orientation of impaction
Working distance
Follicular width
Periodontal status
Relationship of U3M to maxillary antrum and lower to ID canal

Question 11

Radiographic signs that 3M lies close to ID canal

Answer 11

Interruption of white lines/lamina dura of canal
Darkening of root where crossed by canal/dark and bifid root
Diversion/deflection of ID canal/deflection of root
Narrowing of ID canal/root
Juxta apical area

Question 12

Radiographic signs associated with increased risk of nerve surgery during 3M surgery

Answer 12

Interruption of white lines of canal
Darkening of root where crossed by canal
Diversion canal

Question 13

What should be considered when 3M and ID canal are close

Answer 13

Cone Beam Computed Tomography (CBCT)

Question 14

Tx options for 3M

Answer 14

Common: referral, clinical review, XLA, coronectomy
Less common: operculectomy, surgical exposure, pre surgical ortho, surgical reimplantation/autotransplantation

Question 15

Basic principles of surgical removal of 3M

Answer 15

Risk assessment- planning/MH
Aseptic Technique
Minimal trauma to soft and hard tissues

Question 16

Surgical removal steps

Answer 16

Anaesthesia/access
Reflection
Retraction
Bone removal/tooth division as necessary
Debridement/suture/haemostasis/post-op instructions

Question 17

Access step

Answer 17

Raise buccal mucoperiosteal flap +/- lingual flap

Question 18

Reflection step

Answer 18

Raise flap at base of relieving incision
Free anterior papilla before proceeding with reflection distally
Reflect using periosteal elevator on bone- avoids disection occuring superficial to periosteum. Reduce st trauma
Instruments: mitchells trimmer, howarths pe, ash’s pe, wj e

Question 19

Retraction steps

Answer 19

Access to operative field
Protection of soft tissue
Facilitated by flap design
Atraumatic retraction: rest firmly on bone, aware of adjacent structures e.g. mental nerve
Instruments: howarth’s pe, rake retractor, minnesota retractor

Question 20

Bone removal

Answer 20

Electrical straight handpiece with saline cooled bur
Air driven handpieces may lead to surgical emphysema
Done on buccal side of tooth and distal aspect of impact
Intends to create deep, narrow gutter around crown of wisdom tooth
Allows correct application of elevators on mesial and buccal side of tooth

Question 21

Tooth division

Answer 21

Horizontal crown sectioning: remove entire tooth section above enamel cement junction- leave some tooth behind for orientation/elevation
Vertical crown sectioning: removal of distal portion of root and distal crown followed by elevation of mesial portion and root

Question 22

Debridement

Answer 22

Physical: bone file/handpiece to remove sharp bony edges- mitchells’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
Suture: approximate tissue and compress blood vessels
Aim- reposition tissue, cover bone, prevent wound breakdown, haemostatsis

Question 23

Coronectomy

Answer 23

Alternative to XLA when appears to be high risk of IAN damage

Question 24

Warn pt about retained roots/coronectomy

Answer 24

If roots mobilised during crown removal, entire tooth must be removed
May result in infection
Slow healing/painful socket
Roots may migrate at later date and begin to erupt though mucosa and require XLA

Question 25

Why would u preserve retained roots

Answer 25

Preserve bone height
Near IAN canal
Present for years with absence of disease
Gives pt options
Monitor to ensure caries free
Document discussion with pt