About Trigeminal Nerve Injuries 

 

Patients with nerve injuries are often distressed, angry and confused about why the nerve ijury has happened. They will often be extra nervous about dental treatment due to the previous nerve injury and afraid that it will happen again. No sensory nerve injury prevents you from treating the patient. They may have additional sensitivity due to the nerve injury so just be patient and careful. The patients are provided the card below.

 

 

 

What to tell your doctor and dentist

Dear Dentist....I am a patient who has suffered nerve injury, following previous dental treatment.

Dear Dentist 4.doc

 

 

What are they and how are they caused?

 

The trigeminal nerve is the large sensory nerve that supplies feeling to your face, mouth, eyes, nose and scalp (Figure 1). 

 

Nerve injury can sometimes result from dental treatments such as dental injections, root canals, insertion of dental implants and removal of teeth or other surgical treatments. These dental injuries affect the trigeminal nerve  usually the lower lip or tongue areas— causing a mixture of pain, numbness and strange sensations that may be present all the time or intermittently.

Trigeminal nerve injuries can be extremely distressing for patients. Although the majority of patients regain normal sensation and function within a few weeks or months, some are left with abnormal sensation or pain, which can cause problems with speech and chewing.

 

 

Trigeminal nerve injury is the most problematic consequence of dental surgical procedures with major medico-legal implications and many complaints to the General Dental Council are related to dental implant treatment. The incidence of lingual nerve injury has remained static in the UK over the last 30 years, however the incidence of inferior alveolar nerve injury has increased; the latter being due to implant surgery and endodontic therapy.

 

 

Iatrogenic (caused by doctors or dentists) injuries to the third division of the trigeminal nerve remain a common and complex clinical problem. Altered sensation and pain in the orofacial region may interfere with speaking, eating, kissing, shaving, applying make up, tooth brushing and drinking; in fact just about every social interaction we take for granted. Usually after oral rehabilitation, the patient expects and experiences significant improvements, not only regarding jaw function, but also in relation to dental, facial, and even overall body image. Thus these injuries have a significant negative effect on the patient’s self-image and quality of life and the iatrogenesis of these injuries lead to significant psychological effects.

 

Signs and symptoms – What you may be experiencing

Trigeminal nerve injuries can cause episodes of intense, stabbing, electric shock-like pain in the areas of the face where the branches of the trigeminal nerve are distributed — the lips, eyes, nose, scalp, forehead, upper jaw and lower jaw. Sometimes you may notice pain with touch or when a cold breeze hits your face.

 

Eating, speaking, drinking, brushing your teeth, shaving or applying makeup may all be difficult because of the changes in feeling. Examples of some patients with these nerve injuries.

 

What are the risks of nerve injury in relation to dentistry?

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 in 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 surgery, 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 with certain stimulation. 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 interference with daily function including eating, tasting, drinking, speaking, sleeping, kissing, shaving and in applying makeup normally (Renton et al., 2006).

 

Have you been injured?

URGENT treatment (within 30 hours) is indicated in endodontic (Root canal) and implant related nerve injuries. Link

 

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.

 

There are 2 main nerves that can be injured by dental treatment;

  • Inferior alveolar (lip and chin) 
  • Lingual (tongue) nerve

  

Both are sensory nerves (supply feeling) and do not mive muscles (motor nerves)

Inferior alveolar (lip and chin) 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.

 

Sensory supply area of inferior alveolar nerve Inside the mouth

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. 

 

Where is it? 

Radiograph of the inferior alveolar nerve canal close to the lower wisdom tooth

 

Causes of inferior alveolar nerve injury include: 

Implants (Featured in the BBC Health News and Dental Tribune)

 

Nerve injuries related to dental implant treatment is becoming an increasing problem. The incidence of implant related inferior alveolar nerve (IAN) nerve injuries varies from 0-40%. 25% of edentulous patients present with a degree of altered IAN function, thus reinforcing the guidelines on the necessity of preoperative neurosensory evaluation. 

Some hints for the patient

 

  • Great care must be taken when selecting your clinician (avoid non specialists for complicated treatments and if you are in doubt contact the general dental council. We also suggest caution in seeking ‘cheap’ implant treatment abroad!).

 

  • You should be advised regarding alternative treatments before you go ahead with implant.   

 

  • You should have at least 2 visits including written and explicit consent that you should fully understand before signing

 

  • You should be assessed using xrays and sometimes special scans to see exactly where the nerve is and whether there is enough bone for the implant

 

  • Scanning now introduced to many specialist practises and dental hospitals will provide low radiation dosage and improved imaging for planning implant treatment. Several

papers have drawn attention to the weakness of CT evaluation in identifying the IAN canal with poorer sensitivity and specificity compared with pantomogram radiography (big Xray) 

 

Have you been injured?

URGENT treatment (within 30 hours) is indicated in endodontic (Root canal) and implant related nerve injuries

 

Endodontics  (Root canal) see RCS endodontics guidelines

 

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. Reports on endodontic nerve injuries which may not be limited to those teeth proximal to the IAN canal but may occur in maxillary teeth as well. The largest series reported to date was Pogrel (2007) who reported on 61 patients with endodontic nerve injury over an 8 year period.  The risk factors for endodontic inferior alveolar nerve injury include;

 

  • Proximity of the tooth to the mandibular canal
  • Over instrumentation
  • Overfill
  • Chemical nerve injury (including sodium hypochlorite)

 

Again caution is recommended in seeking specialist care for root canal should the tooth ne high risk

 

Have you been injured? URGENT treatment (within 30 hours) is

indicated in endodontic (Root canal) related nerve injuries

 

Some hints for the patient

  • Great care must be taken when selecting your clinician (avoid non specialists for complicated treatments and if you are in doubt contact the general dental council. We also suggest caution in seeking ‘cheap’ dentalt treatment abroad!). 

 

  • You should be advised regarding alternative treatments before you go ahead with treatment

 

  • You should have at least 2 visits including written and explicit consent that you should fully understand before signing

 

  • You should be assessed using xrays before treatment

 

Third molar surgery related inferior alveolar nerve injury is reported to occur in up to 3.6 % of cases permanently and 8% of cases temporarily. Factors associated with IAN injury are age, difficulty of surgery and proximity to the IAN canal. If the tooth is closely associated with the IAN canal radiographically; ie. superimposed on the IAN canal, darkening of roots, loss of lamina dura of canal, deviation of canal Figure 8 (Howe and Poynton 1969; Rood et al., 1983; 1986; Rud 1988) then 20% of patients having these teeth removed are at risk of developing temporary IAN nerve injury and 1-4% are at risk of permanent injury (Howe and Poynton 1969; Rood et al., 1983; 1986; Rud 1988; Renton et al 2005).

 

Radiographs illustrating 2 cases of ‘high risk’ mandibular third molars. In both cases the lower thord molar is crossing the IAN canal completely, there is darkening of the tooth roots and loss of lamina dura of the canal roof and floor

 

Again caution is advised about who you seek treatment from. Oral surgery specialists (Registered as so on the General Dental Council list) are best trained to carry out this work. Therefore the prevention of inferior alveolar nerve injuries in relation to third molar surgery is paramount and must be based upon:

 

Do you need the wisdom tooth removed?

The National Institute of Clinicial Excellence has made guidelines about whether your wisdom tooth needs removal.

  

A clinical decision that the tooth needs to be extracted must be based on NICE guidelines. Prophylactic surgery should only be undertaken when specifically indicated i.e. pre radiotherapy, pre chemotherapy or pre IV bisposphonates, none of which are included in NICE guidelines.

 

  • The clinician specialist must identify mandibular teeth at high risk of IAN injury based on plane radiographic features and/ or cone beam CT scanning. If deemed at high risk the patient must be made aware of the increased nerve injury incidence (increased risk 2% permanent and 20% temporary) and perhaps offered alternative procedures that may in course reduce the risk of injury. 

 

  • If the tooth is in close proximity to the IAN on plain film then;
  • You should be warned of higher nerve injury risk (up to 10 times higher=20% temporary and 2% permanent compared with 2% temporary and 0.2% permanent form low risk wisdom teeth)

 

  • You may be sent for Cone beam CT scanning which may further elucidate the relationship between IAN and tooth roots. If the tooth is non vital, or pathology associated with it, then tooth removal has to take place and the roots should be sectioned appropriately to minimise trauma to the adjacent IAN.

 

  • You may be offered a coronectomy procedure rather than removal of the tooth if appropriate.

 

Some hints for the patient

  • Great care must be taken when selecting your clinician (avoid non specialists for complicated treatments and if you are in doubt contact the general dental council. We also suggest caution in seeking ‘cheap’ dental treatment abroad!). 

 

  • You should be advised regarding alternative treatments before you go ahead with implants

 

  • You should have at least 2 visits including written and explicit consent that you should fully understand before signing

 

  • You should be assessed using xrays before surgery

 

  • Scanning now introduced to many specialist practises and dental hospitals will provide low radiation dosage and improved imaging for planning implant treatment. Several papers have drawn attention to the weakness of CT evaluation in identifying the IAN canal is close to your wisdom tooth 

 

Dental extraction of other teeth proximal to IAN canal

The clinician should be aware that any mandibular tooth (lower 8,7,6,5 or 4) that if the tooth root is crossing the IAN canal, and displays the radiographic signs is associated with increased risk of IAN injury, there is increased possibility of damageto the IAN on removal of the tooth. The the patient must be assessed accordingly, consented and treated similarly to high risk third molar teeth. The same assessment should be applied for these high risk teeth as above.

Local anaesthetic injections (deep dental injections)

 

Injuries to inferior alveolar and lingual nerves are caused by local analgesia block injections and have an estimated injury incidence of between 1:26,762 to 1:800,000 inferior alveolar nerve blocks (Pogrel and Thamby, 2000; Haas and Lennon, 1995). More recently the incidence of nerve injury in relation to IDBs has been calculated as 1:609,000 but with a sig increase in injury rate with 4% agents (Gaffen & Haas 2009). These injuries are associated with a 34% incidence of neuropathic pain which is high when compared with other causes of peripheral nerve injury (Pogrel and Thamby, 2000). However the true incidence is difficult to gauge without large population surveys. The problem with these injuries that the nerve will remain grossly intact and surgery is not appropriate as one cannot identify the injured region.

 

You may be at increased risk of nerve injury

  • If you experience pain on injection during treatment 
  • If you have multiple deep injections
  • Or a high concentration anaesthetic agent ( Articaine, Prilocaine, Mepivicaine) is used for deep injections  (check with your dentist)

 

Some hints for the patient, please see the BDJ LA nerve injury paper here

  • Suggest caution in seeking ‘cheap’ implant treatment abroad!).
  •  
  • Many clinicians are using a low risk injection technique wherebye they give infiltrations (non deep injections next to the tooth) rather than deep block injections using higher concentration or normal agents in order to avoid uncessary deep injections.

 

  • Ask your clinician as this is not always possible

 

  • If you need a deep injection, avoidance of high concentration agents for deep block injections is recommended

 

  • There isn’t much we can do with these nerve injuries aside for sitting and waiting for their recovery which may or may not happen. But we can see and advise the patients to reassure them

 

Other causes 

Include Trauma, Orthognathic surgery and Ablative surgery

Lingual (tongue) 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 doesn’t show up on xray as it isn’t in a bony canal. It runs very closely to the wisdom teeth in soft ling tissue running forward to supply feeling to the anterior 2 thirds of the tongue

 

Picture of a lingual nerve being operated on after injury

 

Causes of lingual nerve injury include:

Third molar surgery (see Renton & McGurk 2001; Renton & Yilmaz, 2011 papers)

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. There are specific  guidelines from the Royal College of Surgeons and NICE regarding whether you need your wisdom tooth removed out

 

Some hints for the patient

  • Great care must be taken when selecting your clinician (avoid non specialists for complicated treatments and if you are in doubt contact the general dental council. We also suggest caution in seeking ‘cheap’ dental treatment abroad!). 

 

  • You should be advised regarding alternative treatments before you go ahead with wisdom tooth removal. DO you need it removed?

 

  • You should have at least 2 visits including written and explicit consent that you should fully understand before signing

 

  • You should be assessed using xrays before surgery

 

  • If you have an injury…Ideally these injuries should be assessed and surgically treated (if required) before 3 months after surgery

 

Dental local anaesthetic injections 

Due to inferior alveolar block (deep dental) injections is very rare (1 in 10 thousand and is usually temporary but can persist and become permanent (at 3 months). There is very little we can do for these injuries but just to sit and wait to see if they improve.

 

You may be at increased risk of nerve injury

  • If you experience pain on injection during treatment 
  • If you have multiple deep injections
  • Or a high concentration anaesthetic agent ( Articaine, Prilocaine, Mepivicaine) is used for deep injections  (check with your dentist)

 

Some hints for the patient (link to BDJ LA nerve injury paper)

  • Great care must be taken when selecting your clinician (avoid non specialists for complicated treatments and if you are in doubt contact the general dental council. We also suggest caution in seeking ‘cheap’ implant treatment abroad!). 

 

  • Many clinicians are using a low risk injection technique where bye they give infiltrations (non deep injections next to the tooth) rather than deep block injections using higher concentration or normal agents in order to avoid unnecessary deep injections.

 

  • Ask your clinician as this is not always possible

 

  • If you need a deep injection, avoidance of high concentration agents for deep block injections is recommended

 

  • There isn’t much we can do with these nerve injuries aside for sitting and waiting for their recovery which may or may not happen. But we can see and advise the patients to reassure them

 

Intubation for general anaesthetic in hospital can rarely cause lingual (tongue) nerve injuries when the breathing tube is passed behind the tongue when you are asleep. There is very little we can do for these injuries but just to sit and wait to see if they improve.

 

 

Ablative (extensive) surgery

For other local surgeries including submandibular gland surgery which may be avoided by being seen in a specialist salivary gland clinic where you may be treated by ultrasound of the stones causing gland problems. Surgery for oral cancer may cause nerve injuries but these cannot be avoided.