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Third Molar Surgery

Wisdom teeth Epidemiology

• 96% of people develop at least one wisdom tooth
• 72% develop all 4
• 10% develop only 3
• 9% develop 2
• 5% develop only 1
• 4% develop none
• variably present depending on populations studied and are the most common congenitally absent tooth

Theories of impaction

• predominantly based on third molars being last to erupt and subsequent lack of space for eruption
  • differential growth of mesial/distal roots
  • inadequate arch length/space by the time third molars are erupting
  • third molar development lagging behind jaw growth
  • modern diet consists of highly processed food therefore teeth are less likely to wear
• 46% impaction rate for upper wisdom
• 72% have at least one lower wisdom impacted
• if left alone between 18 and 26, 55% of non impacted teeth will erupt and 33% of impacted teeth will erupt showing significant shift through the bone (some studies show movement still occurring between 20 and 32)

Indications

indications

• typically some type of progressive and non irreversible pathology
  • caries
  • periodontal disease
  • damage to adjacent tooth (root resorption, caries, perio)
  • pericoronitis
  • odontogenic cyst or tumour
• less common
  • impaction under dental prosthesis
  • reduce mandibular fracture
  • facilitate orthodontic healing
  • optimal periodontal healing

Pratt et al 1998

Pericoronitis

• acute localised soft tissue infection associated with impacted tooth
• pain, oedema, erythema, purulence, halitosis, trismus, dysphagia
• infection may spread to head and neck, posing risk to airway
• causative organisms
  • obligate and facultative anaerobes
  • mostly red and orange complexes
  • commonly, alpha-haemolytic streptococci, genera prevotella, veillonella, bacteroides, caphnophaga
• Nonsurgical treatment options
  • LA / debride / Oral hygiene
  • pain management
  • systemic antibiotics if at risk
• surgical treatment options
  • operculectomy
  • pericoronal ostectomy (removing bone to aid eruption)
  • extraction
    • opposing tooth, maybe in advanced case with long wait time for surgeon
    • involved tooth, definitive solution

Other reasons for removal

• other indications
  • PPD >5mm on adjacent 2nd molar
  • orthodontic/orthognathic surgery
  • interference under denture
  • food impaction discomfort
  • medical reason, organ transplant, radio, chemo, joint prosthesis, preventing potential pathology which may be more risky in certain groups
  • prevention of mandible fractures, can reduce 2.8X for high impact contact sports angle fracture
  • occupational indications
  • tooth which lines in line of an existing mandibualr fracture

AAOMS 2007 white paper on third molar data (Pogrel)

is it possible to predict the course of third molars?

• not possible in all cases, but adequate space between anterior border of ramus and 2nd molar distal appears necessary for successful eruption
• eruption to occlusal plane does not imply good state of health, as adequate osseous space is not the same as physiologic space
• third molars may still change in position after age of 25

periodontal considerations

• presence of impacted wisdom
  • adversely affects perio of adjacent sound 2nd molars as reflected in disruption of PDL, root resorption, PPD/CAL
• removal of impacted wisdom
  • can negatively impact periodontium of 2nd molars, preop assessment of intrabony defect, age level of plaque control can help to predict adverse outcomes
• reduction in postop CAL
  • no surgical approach can minimise loss more than others
  • GTR and/or DBP may be beneficial where there is already pre-existing CAL
  • NSPT and good OHI have potential to reduce postop CAL
• perio disease severity
  • patients with visible third molars have greater overall levels of perio severity
• perio disease progression
  • presence of wisdom associated with 5mm or greater PPD on 2nd molar distal, including progressive PPD even with asymptomatic wisdoms
• bacteria and mediators of inflammation
  • visible wisdoms are associated with bacteria that are responsible for severe and refractory periodontitis, and biochemical mediators of inflammation
• treatment
  • poorer treatment response when wisdoms are associated with perio, symptoms may reduce but microbial counts will not reduce to level of control
  • NSPT less effective when third molars present
• overall perio and thirs molar
  • wisdom associated with overall elevated perio in immediately adjacent teeth
  • adjacent teeth perio and wisdoms is progressive and only partially responsive to therapy

Microflora

• absence of symptoms does not indicate absence of disease or pathology
• red and orange complexes in clinically significant numbers can exist in and around asymptomatic wisdoms
• perio disease progresses in absence of symptoms

Age and wisdoms

• perio defects deteriorate with increasing age in presence of retained third molars
• caries in erupted third molars increases in prevalence with increasing age
• incidence of postop morbidity following wisdom removal is higher after 25 years
• germectomy (removal of wisdom <1/3 root formation) associated with lesser post morbidity

Is wisdom associated with crowding

• Likely that wisdom play role in etiology of crowding, but only one factor
• crowding is multifactorial and cannot easily predict with regards to wisdoms
• state of knowledge does not allow us to identify with accuracy who is at risk

To remove asymptomatic impacted third molars under rempros?

• position and disposition of unerupted teeth is dynamic and unpredictable
• ultimate decision must be under clinical exam and review of age, position of tooth, anticipated difficulty of removal, type of prosthesis and risk associated with removal

CT and wisdoms

• in 2007, unable to tell

Coronectomy

• should be considered in cases where tooth must be removed and IAN close association

Lingual flap elevation and retraction

• raising and retraction lingual flap is acceptable where clinicians see fit
• periosteal elevator must remain subperiosteal at all times, and no sharp edges on lingual retractor

Should anything be placed in the socket following third molar removal

• GTR, DBP, PRP work in high risk or near high risk third molars

Nerve damage

• occasional damage to IAN and lingual nerve occurs following lower wisdom removal
• at least 50% of cases recover spontaneously
• nerve surgery results are variable, 50% improvement when performed between 4.5-7months
• later repairs can still show some recovery

Contemporary Management of Third Molars ADA Hyam 2018

Classification

Decision matrix

Prophylactic removal (six main groups)

• sport or military
  • contact sport
  • peak performance
• reduce physical dexterity
  • tremors
  • neuromuscular disease
• altered mental capacity
  • dementia
  • cognitive development
• pre medication
  • bisphosphonates
  • anticoagulants
• pre treatment
  • radiotherapy
  • chemotherapy
• immunomodifier therapy
  • bacteraemia
  • tissue transfer patients

Considerations of prophylactic removal

• judge likelihood of tooth needing removal will acquire disease/symptoms in particular future period, balance this risk against surgical removal
• must feel that the patient will be better for having had surgery at this time versus surgery at a later time where procedure may be more complex, recovery more tenuous and complication rate higher

Surgical assessment

• WHARFE
• winters lines
• height of mandible
• angulation
• root form
• follicular sac size
• exit pathway of tooth

risk of complication

• experience, IAN proximity, lingual nerve, age, recovery

Current health modifiers

• cardiac state, immunocompromise, coagulation function,
• bisphosphonates and denosumab
• respiratory function
• fitness for type of anaesthesia and pregnancy status

Future health modifiers

• commence medication, tissue transfer procedure, become pregnant

Social modifiers

• access to care and support post surgery
• transport/home help

Financial Modifiers

• insurance plans
• loss on income due to recovery period

Complications

Contraindications

• patient too young <12yo, difficult to predict future eruption potential
• older patient group, >40y, risk potentially outweighs benefits
• medically compromised patients who are unfit for surfery
• extreme limitation in mouth opening
• unacceptable risk of IAN injury
• lack of surgery experience

Types of complications

• inadequate assessment
• inadequate premedication/preparation
• inadequate anaesthesia
• incorrect surgical techniques
• immediate postop complications
• delayed postop complications

Minimising complications

• proper patient preparation
• asepsis
• meticulous management of hard and soft tissue
• controlled force when applying instruments
• haemostasis
• adequate postoperative instruction

Patient Assessment

Patient level factors

• age, sex, race
• radiograph, CT scan
• presence of infection, swelling, lymphadenopathy, trismus, purulent discharge
• pt anxiety
• access, degree of mouth opening, size of tongue, oral cavity, crowdinging
• pericoronitis and soft tissue
• anatomy

Radiographic Assessment/ Classification

Elements of difficult surgery

• distoangular
• class 3 ramus (tooth completely in ramus)
• class C depth
• long, thin roots
• divergent curved roots
• narrow PDL
• thin follicle
• dense, inelastic bone
• contact with second molar
• close to IAN
• complete bone impaction

Gregory and pell

• degree of impaction of third molar in vertical (ABC) and horizontal dimensions (123)
• vertical/ABC, comparing occlusal surface to occlusal plane and neck of 2nd molar
  • A: at or above occlusal plane
  • B: between occlusal plane and neck of 2nd molar
  • C: below neck of 2nd molar
• horizontal/123, comparing distance from distal2nd molar to anterior ramus, to AP size of wisdom
  • 1: ramus to 2nd molar is larger than wisdom
  • 2: ramus to 2nd molar is smaller than wisdom
  • 3: no space between ramus and 2nd molar (wisdom completely in ramus)
• 
• 

Winters classification of angulation impaction

Relationship to the inferior alveolar nerve

• 5 main radiographic markerrs on OPG
  • radiolucency across roots
  • deviation of mandibular canal
  • interruption of canal cortication continuity
  • deflection of roots by canal
  • narrow of roots
• 
• 
  

Factors associated with less complicated surgeries

• mesioangular
• class 1 ramus
• class A depth
• roots 1/3-2/3 formed
• fused conical roots
• wide PDL
• large follicle
• elastic bone
• separated from 2nd molar
• separated from IAN
• soft tissue impaction

FOR MAXILLARY WISDOMS

• 1st level: fully or partially erupted
• 2nd level: crown margin below apices of adjacent 2nd molar
• 3rd level: crown above apices of adjacent second molar (high risk of displacement into infratemporal fossa or antrum)

Surgical Process

recipe

• adequate prep
  • patient prep
  • anaesthesia
  • positioning
  • prepare instruments
• raise flap
• bone removal
• tooth sectioning, delivery
• wound toilet
• wound closure

Raising a flap

• 4 types of incision
• distal reliving incision
• envelope incision
  • limited access for deep impaction
• buccal extension flap
  • increased access
  • potential perio issues
• triangular flap

Bony removal

• high power airless handpiece, protect flap with Minnesota
• round or flat fissure surgical bur
• gutter around tooth
  • expose entire crown/furcation point/ height of contour
  • create purchase point
• removal of distal bone (if ramus is capturing)
• make sure lingual flap retracted

Sectioning tooth

• depends on angulation of impaction and depth of impaction
• section of crown in horizontal impaction
• division along longitudinal axis in mesioangular impaction
• sectioning distally impacted tooth with caution

Wound toilet

• may be filled with bony debris, cystic lining, dental follicle lining, granulation tissue
• irrigation with normal isotonic saline
• special attention to space under flap
• removal of all surgical debris and loose bony dust
• adequate haemostasis so no postop haematoma

Wound closure

• key suture directly behind second molar
• accurate apposition of wound edge
• second suture across distal relieving incision
• avoid water tight closure
• resorbable sutures

Minimising complications

• antibiotics placed in alveolar socket to decrease bacterial plaque (Olech 1953, Verbic 1953)
• use of preop antibiotics
  • little gain with postop ab alone martin et al 2005
• use of chlorhexidine mouth rinse prior to surgery (Rango and Szkutnik 1991)
• Improving oral hygiene preoperatively (Penarrocha et al 2001)

Maxillary molars

• flap design
  • distal incision sagittally along maxillary tuberosity and diagonally across tuberosity
  • mesial incision across buccal attached gingival extension according to heigh of impaction
• removal of buccal bone
  • should be quite membranous and easy to remove
• elevation
  • fine curved elevator
  • elevate buccodistally
  • protect with retractor to prevent displacement
• wound toilet

Prophylactic corticosteroids

• to be effective at minimising oedema steroids must be given in doses exceeding physiological levels
  • decrease levels of lymphokines, prostaglandins, bradykinin, serotonin, cortisol and perhaps histamine
• using a steroid with maximum antiinflammatory and minimum gluco and mineralocorticoid properties seems best
• fluorinated steroids such as dexamethason are well fit, with dexamethasone having only minimal immunosuppressive functions
• contraindications
  • active or treated TB, fungal or viral infection (especially ocular herpes), glaucoma, psychosis
  • peptic ulcer disease, cushings, diabetes, hypertension, pregnancy, myasthenia gravis
• Pederson et al, Bierne et al support significantly decreased swelling without increased infection or orthoer complication, dexamethasone has a long half life and is useful as prolonged courses up to 1day postop are recommended to reduce rebound swelling

Dry socket

• chlorhex rinse for streptokinases

Nerve Injuries

Causes

• inadequate assessment
• incorrect surgical techniques

Seddon 1943 classification

• neuropraxia
• axonotmesis
• Neurotmesis
  

Pattern of sensory loss Merrill 1979

• hypoaesthesia - decrease sensitivity
• hyperaesthesia - increase sensitivity
• paraesthsia - abnormal sensation (pins and needles/tingling)
• dysaesthesia - unpleasant abnormal sensation (burning, sharp, aching pain)
• anaesthesia - total loss

Treatment options

• in case of witness transection
  • immediate referral for surgical repair is necessary
• if anaesthesia post wisdom teeth surgery
  • referral for assessment and possible nerve repair
• altered sensation in lip and chin
  • just monitor and map for 6months
• • if anaesthesia persists >6months
    • further XR to assess continuity of mandibular canal
• consider surgical exploration and decompression or repair of nerve

Nerve repair options

• 3 types
  • perineurial repair
  • group funicular repair
  • epineural repair -> most logical choice
• trigeminal branches are polyfasicular without grouping
• using 8-0 to 11-0 monofilament nylon, with minimal number (3-6 optimal) and close approximation
• 

Lingual nerve paraesthesia

• ranges from 0.278%-13%
• clinically there is sensory disturbance
  • hypoesthesia, hyperesthesia, anaesthesia, dysesthesia
• mechanisms of injury controversial