Patient information about nerve injuries in relation to dentistry

Patient information about nerve injuries in relation to dentistry
Information Supplied by:
Professor Tara Renton
BDS MDSc PhD FRACDS FDS RCS FRACDS (OMS) MHEA
Consultant Oral Surgeon
Chair in Oral Surgery Kings College London Dental Institute
tararenton.dentistadvice.co.uk
Trigeminal nerve
Let’s start with a brief description of the main nerve – the trigeminal nerve - that
can, very occasionally, be injured during dental surgery.
The trigeminal nerve is the largest peripheral sensory nerve in the human body
and it is represented by over 50% of the sensory cortex in the brain. The
trigeminal nerve supplies the face, eyes, mouth and scalp with general sensation
such as touch, pain, temperature.
It has three divisions (hence the name trigeminal) called the Ophthalmic division,
the Maxillary division and the Mandibular division.
The trigeminal also gives nerve supply to make your chewing muscles work - the
muscles of mastication.
Below is a diagram of the nerve and its branches.
What happens when a sensory nerve is injured?
Most nerve injuries related to surgery are temporary (less than 3 months) some
continued repair/regeneration can occur up to 18 months later, however if the
initial injury is moderate to severe then it is less likely to get fully better, if at all.
After a nerve is injured during dentistry, many patients at first feel numbness in
the affected region and this may persist.
However, in some patients, instead of numbness, a troublesome sensation may
develop which may become painful. The patient may develop pain or discomfort
which may be constant or intermittent. The pain may start spontaneously or
started by moving, eating and touching. Bizarrely some patients feel numbness
but get pain on touching the area or with temperature changes (cold or warm).
The types of changed sensation includes; shooting pains, burning, aching,
stretching and pins and needles. Pain and discomfort can cause significant
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interference with daily function including eating, tasting, drinking, speaking,
sleeping, kissing, shaving and in applying makeup normally (Renton et al., 2006).
If you have had surgery or dental treatment and you notice any of the effects
listed above after a local anaesthetic should have worn off – say 6 hours later – it
is really you seek advice from the surgeon/hospital/dentist.
It is often very difficult for the patient to come to terms with injuries caused by
surgery especially if they have a major impact on their social and working life.
Treatment of these injuries is very difficult and they are best treated if identified
early on with referral to a specialist when necessary. Treatment usually involves
counselling and reassurance, medication for pain and rarely surgery.
Consent
If your dentist/surgeon feels there is a risk of damaging one of the nerves
described above, they should make you aware of this and discuss with you
alternative forms of treatment if that is appropriate.
Inferior alveolar nerve injury
What does this nerve supply sensation to?
Outside the mouth
The Inferior Alveolar Nerve (a branch of the mandibular division of the trigeminal
– see diagram above) supplies the skin over the whole side of chin, lower lip
and vermillion border of the lip (where the lip joins the cheek) on each side.
Inside the mouth
The Inferior Alveolar Nerve supplies all the lower teeth, the cheek side of the
gums and the skin on the inside of the lip.
Lower lip vermillion, skin and chin.
Inside the mouth supplies teeth and gums
Where is it? The Inferior alveolar nerve lies within a canal below the roots of the
teeth and emerges through and opening in the chin area (mental foramen).
Radiograph of the inferior alveolar nerve canal close to the lower wisdom tooth
A Clinical picture of damaged nerve exposed during reparative surgery.
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Causes of inferior alveolar nerve injury include:
• Implants
The incidence of implant related inferior alveolar nerve (IAN) nerve injuries
vary from 0-40% (Delcanho 1995; Rubenstein &, Taylor 1997; Wismeijer et al
1997; Bartling et al 1999; Walton 2000; von Arx et al 2005; Hegedus &
Diecidue 2006; Hillerup & Jensen 2006). There are rare reports of resolution
of implant related IAN neuropathies at over 4 years (Elian et al., 2005) but
these do not comply with normal reports of peripheral sensory nerve injuries
(Robinson 2000). Most of these injuries will be permanent if not treated within
24-48 hours.
• Endodontics
Any tooth requiring endodontic therapy that is in close proximity to the IAN
canal should require special attention. If the canal is over prepared and the
apex opened chemical nerve injuries from irrigation of canal medicaments is
possible. This will also lead to permanent nerve injury if not recognised and
treated within 48 hours.
• Third molar surgery
The inferior alveolar nerve (IAN) neuropathy related to third molar surgery
with a reported incidence of 1-20% temporary and 0-2% permanent Implants
If the tooth that requires extraction is close to the nerve as seen in the x-ray
picture, the likelihood of injury to the nerve increases to 20% temporary and
2% permanent. As a patient you will be warned of this increased risk and
possibly offered alternative types of surgery if appropriate (coronectomy).
• Local anaesthetic injections
Due to inferior alveolar block injections is very area (1 in 20-30 thousand and
is usually temporary but can persist and become permanent (at 3 months).
• Other causes
Include Trauma, Orthognathic surgery (cosmetic jaw surgery) and cancer
surgery
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Lingual nerve injury
What does this nerve supply sensation to?
The lingual nerve supplies sensation to each side of the tongue on the top and
underside of the tongue. It also supplies the floor of the mouth and lingual gums
of the lower teeth.
Where is it?
The lingual nerve lies in soft tissue inside the jaw bone so it cannot bee seen on
Xrays. However you can see from the diagram that the lingual nerve (black
dotted line) lies very close to the lower right wisdom tooth and can be easily
damaged (yellow line)
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Picture of the lingual nerve exposed surgically after injury
Causes of lingual nerve injury include:
•
Third molar surgery
•
The most common cause of Lingual Nerve Injuries is third molar (wisdom
tooth) surgery, with a reported incidence of 1-20% temporary and 0-2%
permanent (Mason 1988; Blackburn 1990; Renton & McGurk 2001). 88% of
lingual nerve injuries associated with third molar surgery resolve (Mason
1988; Blackburn 1990). Persistence of any peripheral sensory nerve injury
depends on the severity of the injury, increased age of the patient and the
time elapsed since the injury.
•
Dental local anaesthetic injections
•
Due to inferior alveolar block injections is very rare (1 in 20-30 thousand) and
is usually temporary but can persist and become permanent (at 3 months).
•
Intubation for general anaesthestic
There are several reports of nerve injury in relation to general anaesthetic but
this is extremely rare.
•
Ablative surgery
For cancer and other local surgeries including submandibular gland surgery.
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