What pain is

Pain is a defence reaction that tends to be associated with actual or perceived injury. A key feature of pain is that it conditions avoidance. It must be unpleasant to be effective. Not all pain, however, is the same. The distinction between the sharp pain of a needle prick and the ache of overworked muscles is all too obvious and the separation of these two examples into fast, type 1, or acute pain and slow, type 2 or more chronic pain is fairly easy. It is also of considerable therapeutic advantage because the latter responds well to analgesics, but the former does not. However, there are almost as many types or descriptions of pain as there are conditions that cause it. Colicky abdominal pain, the throbbing pain of an abscess and the dull ache of myofascial pain are remarkably different in nature.

Pain may result from a range of stimuli: penetrating injury, pressure, heat, electrical stimulation, inflammation, muscular fatigue, etc. Almost any tissue (excluding dental enamel) may be the source.

This chapter is concerned with pain associated fairly closely with surgery. This includes the pain that would be associated with the surgery if no measures (such as local anaesthesia) were taken to prevent it and the pain so often experienced after surgery, which is more associated with inflammation.

Although we have said that pain is a defence reaction, there is little evidence that it is in any other way beneficial and for that reason we should do all that we can to prevent it during and after any surgery.

It is important to remember that only one individual is in a position to define pain: the patient. Therefore when a patient says that they have pain, they have—it is of no practical benefit to debate with them whether their experience is pressure, movement or whatever! It is wise to remember also that pain requires consciousness to be experienced, and that it is influenced by emotional state, tiredness and anticipation. Local sensitization of the peripheral nerves by inflammatory mediators considerably increases pain experience and can cause difficulty in controlling the pain of patients who have been in pain for several days. This is probably one of the commonest reasons for failure of local anaesthesia in such patients.

How to recognize pain

Your patient will tell you when they are in pain. However, there are some situations where a patient has difficulty in communicating or might not wish to worry you about their pain. Some will even think it is ‘normal’ to experience pain during a surgical procedure.

Pain tends to elicit certain reactions, which can be noted. Bodily movement, tensing of the body, wide opening or screwing shut of the eyes, dilation of the pupils, skin pallor and sweating are all readily recognizable. Noises (ranging from grunts to screams) can be illustrative—and may require immediate action.

What anxiety is

Anxiety is also a defence reaction, ranging from disquiet, through apprehension and anxiety, to fear and downright terror. Like pain, we must accept that anxiety is a factor that may need to be measured, rather than simply noted as present. Anxiety is the anticipation of an unpleasant event that conditions avoidance.

Some anxiety or fear is clearly advantageous. For example, finding oneself at the edge of a cliff or having misjudged the speed of an oncoming car makes one move swiftly to reduce the danger (many people will also go out of their way to cause anxiety by bungee jumping or fairground rides). But anxiety associated with dental treatment is often unhelpful because it not only causes great suffering but also creates barriers to dental care. It is the dental practitioner’s obligation to aim to minimize their patients’ suffering’and that includes their anxiety.

Some anxiety may even be frankly damaging. For example, in a patient with moderate to severe ischaemic heart disease, the increase in work done by the heart as a result of the fear might not be matched by an increase in coronary blood flow. This can precipitate angina or worse.

Where fear of a particular thing, event or concept is unreasonably excessive it may be described as a phobia. The distinction between what is a somewhat exaggerated concern about dental treatment and what is a true phobia is rather blurred.

How to recognize anxiety

The patient’s description is again of great value, and many people will openly discuss their concerns about dental treatment. However, embarrassment or loss of face can be experienced (particularly amongst men) by admitting to fear, particularly when the patient feels that their fear may be irrational. There is therefore an underreporting of anxiety and considerable variation in the weight that individuals place on their own fear. For this reason it is important that you actively look for and assess the level of anxiety.

Clues can be found in body language: posture and facial expression. Overt signs of sympathetic nervous system activity such as pallor and sweating may be diagnostic. Behaviour such as failing to attend or cancelling appointments, aggressive behaviour or tearful episodes may also be clues. If you need more evidence, the patient’s pulse and blood pressure would show considerable increases.

Why use local anaesthetics?

Local anaesthetics have become the most widely used form of pain relief in dentistry. A variety of techniques and drugs are available and can be varied depending on the patient’s medical and dental history and the pharmacology of the agent.

The drugs are safe to use. Tens of millions of cartridges of local anaesthetics are administered by dentists in the UK each year. The mortality rate associated with dental treatment that does not involve general anaesthesia is about one case per annum and even amongstsuch cases local anaesthesia is rarely regarded as causative of the death. Few drug systems in medicine have such a good safety record.

The drugs are effective. In almost all dental applications it is possible to completely abolish pain during the procedure and, with care, pain on administration of the drug can be kept to an acceptable level.

Reducing pain on administration

The application of lidocaine or benzocaine in the form of a paste, gel or spray to the oral mucosa can result in loss of sensibility to a depth of a few millimetres in a few minutes. This can abolish the pain of needle penetration and, for superficial injections, dramatically reduce the discomfort on injection. This can also have a major impact on the anticipation of pain in those particularly frightened by injections.

The use of topical local anaesthetics does have disadvantages, however. By spreading widely around the mouth they can induce numbness in a much wider area than would otherwise be necessary. Also, they cannot penetrate to the depth at which the inferior alveolar nerve block or greater palatine nerve block injections are given.

For procedures involving the skin topical lidocaine is of no value. However, EMLA cream does penetrate deeply enough to be effective. It should be left on the skin for at least one hour before the procedure. Amethocaine gel can also be effective on skin, and possibly over a time period shorter than that of EMLA, but is more likely to cause skin irritation.

Pain of injection can also be reduced by injecting slowly, distracting the patient and perhaps by stimulating nearby tissues (such as by compressing the cheek between finger and thumb) to activate the central neurological ‘gate mechanism’. Rapid penetration of the mucosa by the needle results in far less discomfort than that experienced on slow pressure. This is made easier in lax tissues by tensing the mucosa before needle penetration.

Extent of anaesthesia required

In preparing for surgical procedures you should plan carefully the area of anaesthesia. If a mucoperiosteal flap is to be raised, the extent of anaesthesia required must include the area at the centre of the surgery, the whole of the distribution of the flap itself and all the areas of mucosa through which a suture needle will eventually pass. Where surgery is to involve more than one quadrant you should consider exactly how much local anaesthetic will be required; for example, if you were attempting to extract three molar teeth in each quadrant in one session, it may not be possible to achieve satisfactory anaesthesia without exceeding the recommended maximum dose.

Failure

Failure to achieve satisfactory pain relief for surgical procedures at the first attempt is not uncommon. Failure may be associated with pain and local inflammation, which result in local neural sensitization (see p. 13). This is a difficult problem in a patient who is particularly anxious about dental treatment and who puts off attending until their pain is unbearable. There may also be a relationship between failure and severe anxiety, which is a common problem in the latter type of patient.

Failure is more common with regional block anaesthesia, probably for anatomical reasons. Although anatomical landmarks provide a guide, no two patients are the same shape and variation should be expected. If you experience repeated failures in regional block anaesthesia you should revise the anatomical guidance in textbooks and consider the accuracy with which you are following recommendations. Rarely, there may be failure due to aberrant innervation. How to manage local anaesthetic failure is described well by Meechan (1999).