Third Molars Flashcards
When do third molars erupt?
Between 18-24 years old.
When do the crowns of third molars start to calcify and when do they stop calcifying?
Start- 7-10 years old
Finish- 18 years old.
When does root calcification finish for third molars?
18-25 years old.
What are the statistics for missing third molars?
1 in 4 adults will find that they have at least 1 third molar missing.
More common in the maxilla and in females.
If missing at age 14 on radiograph, almost always fail to develop.
What does it mean if a third molar is impacted?
Tooth fails to erupt, either completely or partially into the position that we would expect.
Descriptive term, not indication for surgery.
What might a third molar be impacted against?
Adjacent tooth, alveolar bone, surrounding mucosal soft tissue or a combination of factors.
What is the incidence of impacted lower third molars?
36-59%.
What are some of the potential consequences of impaction?
Caries, pericoronitis, cyst formation
Which nerves are at risk during third molar surgery?
Lingual nerve
Inferior Alveolar nerve
Nerve to Mylohyoid
Long buccal nerve
What does the IAN supply?
Pulpal tissue on that side
Lingual tissue on that side (through the lingual nerve)
Lower lip and chin (through the mental nerve)
Sensory to anterior 2/3 of the tongue
What does the lingual nerve supply?
Branch of the mandibular division of the trigeminal nerve.
Supplies the anterior 2/3 of the tongue (sensory) and FOM.
Lingual gingivae of that side.
Where is the lingual nerve located anatomically?
Close relationship to the lingual plate in mandibular and retro-molar area.
At or above level of lingual plate in 15-18% of cases.
Between 0-3.5mm medial to the mandible.
What guidelines can you use in relation to third molars?
NICE guidelines
SIGN guidelines
Royal College of Surgeons guidelines- parameters of care for patients undergoing mandibular third molar surgery.
What are the indications for extraction?
Caries- either in the 7 or 8
More than one episode of infection/pericoronitis in the tooth
Periodontal disease
Cysts
Tumours
External resorption of 7 or 8
High risk of disease
Surgical indications- i.e. within the surgical field
Medical indications- immunocompromised, awaiting cardiac surgery
Patient age- complications and recovery time increase with age, makes more sense to take the tooth out when the patient is still young.
What is pericoronitis?
Inflammation around the crown of a partially erupted tooth.
Food and debris gets trapped under the operculum resulting in inflammation or infection.
What are the signs and symptoms of pericoronitis?
Pain
Swelling- intra and extra-orally- commonly at angle of the mandible but can go laterally into the cheek or disto-buccally into the masseter (can cause truisms if infection in the masseter).
Bad taste
Pus discharge
Occlusal trauma to the operculum
Ulceration of the operculum
Evidence of cheek biting
Footer Boris
Limited mouth opening Dysphagia
Pyrexia
Malaise
Regional lymphadenopathy
Trismus
Extra-oral swelling may be present at the angle of the mandible and go laterally into the cheek or disto-buccally into masseter.
What age group of patients are most commonly affected by pericoronitis?
20-40 years old.
What are the predisposing factors for pericoronitis?
Partial eruption and vertical or distoangular impaction
Opposing maxillary third molar or maxillary second molar causing 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 mandibular third molar.
White race
A full dentition
What are the management options for pericoronitis?
+/- LA- IDB.
Irrigation with warm saline or chlorhexidine mouthwash- 10-20ml under the operculum.
Extraction of upper third molar be be indicated if traumatising the operculum.
POI- warm salty mouthrincses or chlorhexidine mouthwashes, regular paracetamol and ibuprofen, keep fluids up and keep eating.
Only prescribe antibiotics if the patient is systemically unwell, extra-oral swelling or immunocompromised.
If large extra-oral swelling, systemically unwell, trismus, dysphagia- refer to max-face or A&E.
What aspects of the history taking process would you want to know from a patient who you suspect has pericoronitis?
Look at their general appearance- do they look unwell? Do they have a visible extra-oral swelling?
C/O and HPC- SOCRATES, how many episodes of this have you had, how long do they last for, have you required antibiotics in the past?
Full medical history
Full dental history- history of extraction, dental anxiety, dental experience, oral hygiene measures.
Social history- smoking, alcohol, occupation, carer support.
What aspects of the clinical examination would you want to look at for a pericoronitis patient?
Extra-oral- TMJ, MOM, lymph nodes, facial asymmetry, trismus.
Intra-oral- soft tissue examination, dentition, M2M, eruption status of M3Ms, condition of remaining dentition, occlusion, oral hygiene, caries status, perio status (of M2M), look at working space- distance from the distal aspect of the M2M to the ascending ramus.
Probe behind the distal of the M2M and see if you can feel the 8.
When would radiographs be indicated and what ones would you take?
Sectional OPT and only indicated if you are considering surgical intervention.
What would you look for on the OPT?
Presence or absence of disease in 3M or elsewhere
Anatomy of 3M- crown, roots, condition of it in general, any pathology.
Depth of impaction
Orientation of impaction
Working distance- distance from the distal aspect of the M2M to the ascending ramus.
Follicular width
Periodontal states
Relationship of M3M to the inferior alveolar canal
Any other associated pathology
What radiographic signs would suggest that there is a significantly increased risk of nerve injury during third molar surgery?
Diversion of the inferior dental canal- canal appears to bend over the roots of the M3M
Darkening of the root where crossed by the canal
Interruption of the white lines of the canal
What other signs might suggest a close relationship of the roots of a M3M with the inferior dental canal?
Deflection of roots
Narrowing of the inferior dental canal
Narrowing of the root
Dark and bifid root
Juxta-apical area
If conventional imaging has shown a close relationship between the third molar and inferior dental canal, what would you do?
Request CBCT
If CBCT unavailable- you can use CT instead.
What angulation can the M3M be at if it is impacted?
Mesial
Distal
Vertical
Horizontal
Transverse or aberrant
Measured against the curve of speed.
Why are distally impacted third molars difficult to remove?
Must remove distal bone first.
How do you measure depth of impaction?
Superficial- crown of 8 related to crown of 7
Moderate- crown of 8 related to crown and root of 7
Deep- crown of 8 related to root of 7
What are the treatment options for an impacted third molar?
Leave and monitor
Referral to OS
Removal of M3M
Removal of maxillary third molar
Coronectomy
Less common
- operculectomy
- Surgical exposure
- pre-surgical orthodontics
- Surgical re-implantation/autotransplantation
What must you discuss with the patient in order to make a decision about treatment options?
Discuss all options with patient.
Risks and benefits of all options.
Potential complications
Access to treatment- how long they will likely wait for the surgery.
Record conversation in the notes.
What factors should you take into consideration when deciding treatment options for a patient?
Patient’s access to treatment
Presence of any other third molars
Patient’s age
Is the patient symptomatic?
Is there any disease present?
Risk of complications.
Under what circumstances might you opt to extract a M3M that is asymptomatic?
In the field of surgery- orthognathic.
In the field of radiation for head and neck
What methods of anaesthesia might you consider for removal of an impacted M3M?
LA
Sedation
GA
How would you gain consent for this procedure?
Explain procedure in layman’s terms
- Explain the potential need for surgical access, sectioning of the tooth and sutures.
Discuss risks and benefits
Discuss potential complications of the surgery and for after care.
- Ensure to mention risk of nerve damage and show patient the radiograph.
- If a close relationship is present, offer CBCT.
What post-op complications would you mention to the patient?
Pain
Bleeding
Bruising
Swelling
Jaw stiffness/limited mouth opening
Altered sensation
Numbness- either temporary or permanent
Dysaesthesia
Hypoaesthesia
Hyperaesthesia
Damage to adjacent teeth
Dry socket
Infection
What are the chances of temporary or permanent numbness following extraction of a lower third molar?
Temporary damage to IDN- 10-20% (literature suggests 2.7-36%).
Permanent- less than 1%
Lingual nerve-
- Temporary- 0.25-23%
- permanent- 0.14-2%.
If patients did have numbness in the IDN or lingual nerve, what symptoms would they have?
IDN- numbness to lower lip and chin on the same side and loss of taste in the anterior 2/3 of the tongue.
Lingual nerve- loss of taste to anterior 2/3 of the tongue and loss of sensation to the lingual gingivae on that side.
If you decide to refer the patient to your local OS department, what would you include in the referral letter?
Patient demographics- name, age, DOB, address, CHI number, phone number.
Your details- name, practice address, practice phone number.
Reason for referral- surgical extraction of partially erupted LL8.
Background- history of disease.
Details of assessment and copy in radiographs that were taken.
Your recommendation.
Describe the process of surgical removal of a lower wisdom tooth.
Anaesthesia- LA, sedation, GA
Access- raising a mucoperiosteal flap
Bone removal
Tooth division
Debridement
Suture
Achieve haemostasis
Post-opo instructions
Describe the process of raising a flap.
Full thickness mucoperiosteal flap- can be one sided, 2 sided or 3 sided.
Wide base
Larger flaps heal just as quickly as smaller flaps
Ensure minimal trauma to the dental papillae
Reflection of the flat should be done at the relieving incision
- Use the Ash, Howarth’s, Mitchell’s trimmer or Warwick James.
- Free the dental papilla before reflecting the flap further.
- Reflection should be done with the periosteal elevator strictly on bone.
Why do you need to retract the tissues?
Access to operative field
Protect the soft tissues
Access for bone removal
Improve visibility
What instruments might you use for retraction of soft tissues?
Minnesota
Rake retractor
Howarth’s
Ensure you rest firmly on bone.
What do you use for bone removal?
Electric handpiece- do not use air turbine because of the risk of surgical emphysema.
Bone removal done distal to mesial- going buccally as well.
- Aim to create a narrow and deep buccal gutter.
- Allows correct application of elevators on the medial and distal aspects of the tooth.
After bone removal, what decision does the operator have to make?
Decide whether you think the tooth will be able to be extracted whole or if the tooth needs sectioned.
Describe how you would section the tooth.
Use fissure bur to horizontally section the tooth just above the ACJ- ensure the bur doesn’t come out the lingual aspect.
Warwick James into the section and crack off the crown- warn this patient of this.
May then require the roots to be sectioned vertically and elevate the roots individually.
Can also vertically section the whole tooth.
How would you debride the socket?
Ensure no sharp bits of bone are left- bone file.
Mitchell’s trimmer or Victoria curette to remove the soft tissue debris.
Irrigations into socket and under the flap.
Suction- aspirate under the flap, check the socket for retained apices.
Once the tooth was out, what would you check?
Check that the apices are intact
Check in the socket- any sharp bits of bone, granulation tissue, parts of the tooth left in situ.
What are the aims of suturing?
Approximate tissues
Achieve haemostasis
Healing by primary intention
Cover bone
Prevent wound breakdown
After suturing has taken place, what would you do?
Get the patient to bite down on a damp piece of gauze.
Post-op instructions given verbally and in writing.
Ensure haemostasis has been achieved before the patient leaves.
Why might a coronectomy be carried out?
To reduce risk of damage to the IAN.
Crown is removed with the deliberate retention of the root adjacent to the IAN.
Describe the process of a coronectomy.
Raise a flap
Transection of the tooth 3-4mm below the enamel of the crown into dentine.
Elevate/lever the crown off without mobilising the roots
Pulp left in place.
Irrigate the socket.
Flap repositioned to leave the socket open.
Follow up- review 1-2 weeks post op
- further review 3-6 months then 1 year.
- Take radiographs at 6 months and 1 year.
What must you warn the patient about with regards to a coronectomy?
If the roots become mobile, then we need to extract them.
Leaving roots behind could lead to infection
Can get a slow healing socket
The roots may mobilise later on and require extraction further down the line. m
Which teeth wouldn’t be suitable for a coronectomy?
Grossly carious
Medical contraindications- poorly controlled diabetes, immunocompromised, bleeding risk.
What are the SIGN guidelines for removal of lower wisdom teeth?
More than one episode of infection or problems in the wisdom tooth.
Caries in the 8 or 7
Pathology- PA pathology, cyst, perio disease. z
What would you use to extract an upper wisdom tooth?
Elevate with Warwick James or Couplands
Upper third molar forceps.
Ensure you support the tuberosity with your finger and thumb.
