When do 3rd molars:
1. Erupt
2. Crown calcification
3. Root calcification
- 18 - 24y
- 7 - 10y (if not present at 14 then absent)
- 18 - 25y
Rate of Agenesis of third molars
- agenesis = failure of organ to develop
- 1 in 4 adults at least one absent 3rd molar
What causes a 3rd molar to be impacted and impacts of this
- Alveolar bone
- Soft tissue
- A tooth
- A combination of these
- caries
- pericoronitis
- cyst formation
Incidence of impacted 3rd molars
36 - 59 %
Nerves at risk in M3M’s XLA
- Inferior alveolar (large risk)
- Lingual (medium risk)
- Long buccal (low risk)
- Mylohyoid (low risk)
Signs of inferior alveolar intimacy with M3M’s
- Interruption of corticated lines (lamina dura) of tooth or canal
- Darkening of root where crossed by canal
- Deflecting of IAC
- Deflecting of root
- Narrowing of IAC
- Narrowing of the root
- Dark and bifid root (wide apex opening)
- Juxta apical area (well defined radiolucency with corticated margins, lateral to root rather than apex = not pathology but meant to be a continuation of lamina dura and corticated margins of IAC canal) thus close proximity
Guidelines for XLA of wisdom teeth
NICE - guidance on extraction of wisdom teeth, 2000
Indications for XLA of third molars
- Undesirable Caries
- Acute severe single / Recurrent pericoronitis
- Periodontal disease
- Cysts
- Tumours
- External resorption of 6/7/8
Other reasons
- orthognathic
- medical indications prophylaxis (immunosuppressed, awaiting cardiac surgery, bisphosphonates antiangiogenics, chemotherapy, )
- patient age / future ability to cope with tx
- auto transplantation
- g
What is pericoronitis
PE tooth with operculum, inflammation around crown
As communication distal to 7 with food packing etc (can be barely visible)
20-40 year olds commonly
Signs and symptoms of pericoronitis
Pain
Swelling
Suppuration
Bad taste
Bad breath
Dysphasia
Pyrexia
Malaise
Regional lymphadenopathy
Ulceration of operculum
Occlusal trauma to operculum
Predisposing factors for pericoronitis
White race
A full dentition
Insufficient space between ascending ramus and distal of 7
Poor OH
Stress and fatigue
Vertical / distoangular impaction
Treatment options for pericoronitis
Irrigation with warm saline water / chlorhexidine (anaphylaxis risk) with blunt needle
Analgesia advice
Dietary advice: Keep fluid levels up and eat soft food
Antibiotics*
If large extra oral swelling = maxfax urgent referral
Incision and drainage of abscess
XLA / coronectomy
Operculectomy
Surgical exposure (can allow to erupt)
When provide antibiotics for pericoronitis
Severe pericoronitis:
Systemically unwell
Swelling extra orally
Immunocompromised (I.e. diabetic)
What checking in OPT for XLA of third molars
Involvement of Sinus or IAN
Presence of disease
Anatomy for XLA (crown, root, condition)
Orientation of Impaction
Any associated pathology
Types of impaction of 3rd molars
Done by angulation compared to curve of spee
- vertical (30 - 38%)
- mesial (40%)
- distal (6 - 15%)
- horizontal (3 - 15%)
- transverse (bucco lingual angulated) rare
- aberrant (can be up the ramus / completely ectopic) rare
How are 3rd molars depths defined in surgical XLA planning
Superficial - crown only involved with crown of 7
Moderate - crown involved with crown and root of 7
Deep - crown only involved with root of 7
Indications for NO XLA of 3rd molars
Symptomatic 8 with no associated disease ( consider other causes )
- TMD
- parotid disease
- lesions
- headaches
- referred angina pain
- oropharyngeal oncology
Asymptomatic with low disease risk
- just review at intervals
Complications / risks post 3rd molar XLA (with % chance)
Pain
Bleeding
Swelling
Bruising
Infection
Jaw stiffness
Dry socket (osteitis)
Surgical procedure
Damage to adjacent teeth / rests.
Altered sensation (HYPO/HYPER/ana/para/dysaethesia)
IDN
- temporary 10-20%
- Permanent <1%
Altered taste from lingual nerve very rare
- temp 0.25-23%
- perm 0.14-2%
How long for nerve damage from XLA is diagnosed as permanent
18-24 months, not going to heal
Special investigation if PA shows close relationship between IAC and 8 to be XLA
Cone beam computed tomography (CBCT)
Benefit of local anaesthetic in an XLA even if GA
Haemostasis easier
How to cut flap for M3Ms XLA
Buccal mucoperiosteal flap
Can do lingual but risk lingual nerve damage
Larger flap heals just as fast
One continuous stroke with scalpel
Minimise trauma to dental papillae
How to reflect surgical flap
Instruments
- Mitchell’s trimmer
- hearths periosteal elevator (holds out way)
- ash periosteal elevator
- curved Warwick James elevator (asking papillae flaps, others for while flap)
Raise from base of releasing incision
Full tissue done to bone
How is bone removal facilitated for XLA
Electrical straight hand piece with saline cooled bur (surgical emphysema)
Round or fissure stainless steel and tungsten carbide burs
Round = remove bone
Fissure = separating tooth
Bone removal = buccal to distal
DEEP and NARROW gutter around tooth
work distal to medial as if slip = lingual nerve
