Third molars Flashcards
When do they erupt
18-24yrs
When do third molars start to form
Crown calcification begins between 7-10y and is completed by age 18y
Root calcification complete between 18-25y
What is meant by agenesis
absence of or failed development of a body part
Where is agenesis of the third molats more common
Maxilla in females
What is the most common reason for third molars failure to erupt
Impacted Third molars
What is meant by impacted molar
Tooth eruption is blocked
How can a third molar be impacted
Adjacent tooth, alveolar bone, surrounding mucossal soft tissue or a combo of these
What is the % of the incidence of impacted lower third molars
36-59%
What could a consequence of impaction be
Caries, pericoronitis or cyst formation
What nerves are at risk during a third molar surgery
Inferior Alveolar Nerve
Lingual Nerve
Nerve to Mylohyoid
Long Buccal Nerve
What ways on a radiograph would you be able to tell if theres risk to the inferior alveolar nerve canal
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
What is the location of the lingual nerve
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
What are the indications for a third molar extraction
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
What is pericoronitits
Inflammation around the crown of a partially erupted tooth
The tooth is normally PE and visible
What causes the inflammation of pericoronitis
Food and debris gets trapped under the operculum resulting in inflammation or infection
How long does pericoronitis happen and at what ages
Usually transient
Usually occurs 20-40yrs
What anaerobic microbes are most common in pericoronitis
Streptococci
Actinomyces
Propionibacterium
A beta-lactamase producing Prevotella
Bacteroides
Fusobacterium
Capnocytophaga
Staphylococci
What are the S&S of pericoronitis
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
What is the treatment of pericoronitis
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
When would you prescribe antibiotics
Generally do not prescribe antibiotics unless more severe pericoronitis, systemically unwell, extra-oral swelling, immunocompromised e.g. diabetic
What are the predisposing factors of pericoronitis
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
When would you take radiograph
Only if surgical intervention is being considered
What is meant by a superficially impacted tooth
crown of 8 related to crown of 7
What is meant by a deep impacted tooth
crown of 8 related to root of 7
What is meant by a moderatly impacted tooth
crown of 8 related to crown and root of 7
If your making a radiographic report of a patient with a third molar problem what should you include
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
What signs on a radiograph are associated with an increase of nerve injury during third molar surgery
diversion of the inferior dental canal
darkening of the root where crossed by the canal
interruption of the white lines of the canal
If on a radiograph there is a close relationship between nerve canal and third molar what would be the next step
Consider a cone beam computed tomograpgy (CBCT)
Or periapicals
How is angulation/orientation of a third molar measured
It is measured against the curve of spee
What are the Tx options for an impacted third molar
Common
-Referral
-Clinical review
-Removal of M3M
-Extraction of maxillary third molar
-Coronectomy
Less common
-Operculectomy
-Surgical exposure
-Pre-surgical orthodontics
-Surgical reimplantation/autotransplantation
How many will feel tempoary anaesthesia or paraesthesia of the IDN (lower lip/chin) after extraction
10-20%
How many will feel permanent anaesthesia or paraesthesia of the IDN (lower lip/chin) after extraction
<1%
How many will feel tempoary anaesthesia or paraesthesia of the lingual nerve (one side of tongue, taste) after extraction
0.25-23%
How many will feel permanent anaesthesia or paraesthesia of the lingual nerve (one side of tongue, taste) after extraction
0.14-2%
For the surgical removal of an 8 howis access achieved
gained by raising a buccal mucoperiosteal flap
+/- raising a lingual flap, there is some debate on this
What is the aim when achieving access to a 8 for surgical removal
Maximum access with minimal trauma
Larger flaps heal just as quickly as smaller ones
Minimise trauma to dental papillae
How would you start a access flap for removal of a 6
Use scalpel in one firm continuous stroke along the gingival margin of the 7
How do you reflect the gingiva
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
What instruments can be used in reflecting a flap
Mitchell’s trimmer
Howarth’s periosteal elevator
Ash Periosteal Elevator
Curved Warwick James elevator
Once the flap is reflected what is the next step
Flap retraction
What does flap retraction do
Provides access to the operative field and provides protection of soft tissues
What does flap design facilitate
retraction
What instruments are used in the retraction of a flap
Howarth’s periosteal elevator
rake retractor
Minnesota retractor
What instrument is used for bone removal and what is not used and why
Electrical straight handpiece with saline cooled bur
Round or fissure stainless steel & tungsten carbide burs
Air driven handpieces may lead to surgical emphysema
How is bone removal carried out in a surgical extraction
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
After bone removal what must the operator consider
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
In a horizontal tooth division where is the tooth seperated
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
After surgical tooth removal what is carried out and how
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
What is the aim of suturing
Reposition tissues
Cover bone
Prevent wound breakdown
Achieve haemostasis
When would you carry out a coronectomy
When there appears to be an increased risk of IAN damage with surgical removal
What are the stages of a coronectomy
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
With a coronectomy what must you warn the patient with
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
How would you remove a upper thord molar
Generally easier to remove
Removed by elevation only or elevation and forceps
Make sure to support tuberosity
A pt is getting there third molar surgically removed what is important to say to them for consent
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)
