So What Is Pain?

The International Association for the Study of Pain (IASP)^* defines pain as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage’.

Pain experience is dependent upon:

• Age.
• Gender.
• Ethnicity.
• Culture.
• Pain experience.
• Personality.
• Stress.
• Depression.
• Anxiety.

Pain:

• May have an organic and psychological causation.
• Is an entirely individual response.
• May be assessed by psychological questionnaires to investigate functionality, disability and behaviour.
• May be superficially ‘scored’ using the Likert scale (https://simplypsychology.org/likert‐scale.html).
• Is near impossible to measure due to the individuality of the pain experience which is different for every patient.

Assessment

As considered in Chapter 6, assessing a patient in pain requires specific skills, knowledge and excellent communication. Communication is key to eliciting the necessary history from a patient in pain. The clinician must be a good listener. Certain patients, however, may not be able to communicate the nature and severity of the pain they are experiencing. This greatly increases the challenge of completing an effective assessment.

The clinician is beholden to take a full and comprehensive history to build trust and understanding of the patient and their complaint. Acute pain will have onset in the last few days, or possibly weeks, but generally has been present for less than 3 months. The pain may be associated with key inflammatory signs (tumor, dolor, calor, rubor and loss of function) but if caused by a ‘cold bacterium’ may not have the traditional inflammatory signs (dry socket, for example). Acute pain is inflammatory pain that responds to anti‐inflammatories (e.g. paracetamol and non‐steroidal anti‐inflammatory drugs – NSAIDs).

Management of Dental Pain

The management of dental pain includes:

• The management of patients presenting with pain as a symptom. The pain may be acute pain (usually of sudden or recent onset, possibly lasting <3 months) or chronic trigeminal pain (lasting >3 months). Pain is usually a symptom of some pathology or trauma or referred pain (cancer must be always excluded in recent onset pain not responding to normal interventions).
• The management of patients undergoing surgical and operative procedures of the face, jaws, teeth and mouth, requiring anaesthesia (local or possibly general). The management, while typically preoperative, may be intraoperative.
• Postsurgical pain management.

Management of Acute Symptomatic Pain

The management of acute symptomatic pain, which is often pulpal in origin or caused by infection or trauma, typically begins with the management of the causation. This may involve a dental extraction, an endodontic procedure, the management of a dental abscess or wound, or measures to control various forms of infection.

Management of Intraoperative Pain

Intraoperative pain is typically managed by means of local anaesthesia with or without adjunctive sedation (for anxiolysis) or general anaesthesia when undertaking prolonged or extensive surgical procedures.

Management of Postoperative Pain

Post‐operative pain is typically managed by means of education, reassurance and analgesics.

Management of Chronic Trigeminal Pain

According to Woda et al. (2005), chronic trigeminal pain may be classified as:

• Neurovascular pain conditions.
• Neuropathic pain conditions.
• Idiopathic (better now referred to as centralised or dysfunctional) pain conditions.

The management of chronic trigeminal pain involves a range of procedures and pain management regimens. Patients with chronic trigeminal pain may require specialist care.

Treatment Planning

The cornerstones of treatment planning for a patient in pain, as in all other aspects of dentistry are:

• Thorough history.
• Careful examination.
• Appropriate special tests.
• Eliciting the correct diagnosis.

In pain management the standard history and examination should be augmented with specific questions, observations and special tests (Table 9.1).

There is no absolute measure of pain because it is a purely subjective experience. However, pain assessment is essential in diagnosing and monitoring patients’ response to treatment. Pain rating scales are often used in assessing pain intensity. A useful tool for remembering pain history questions is SOCRATES – Site, Onset, Character, Radiation, Associated features, Timing, Exacerbating and alleviating factors, Severity.

Management of Acute Pain

Acute orofacial pain refers to pain initiating from the teeth or their supporting structures, the mucosa, gingivae, maxilla, mandible or periodontal membrane. It is one of the commonest reasons for individuals to seek dental care

Aetiology

There is a wide range of causes of acute orofacial pain, including:

• Most commonly, pulpitis causing dental pain (toothache).
• Infection of the soft tissues, most commonly pericoronitis.
• Periapical periodontitis.
• Dentine hypersensitivity.
• Dry socket.
• Acute trauma.

Management

The management of the conditions which give rise to acute orofacial pain is dealt with in different chapters of this manual. Common features of the different management strategies include:

• Thorough assessment, including special tests as indicated clinically.
• Differential and definitive diagnosis.
• Elimination of the causation.
• Remedial or surgical measures.
• Prevention of recurrence.

Management of Intraoperative Pain

Local Anaesthesia

Local anaesthesia is defined as a drug, administered for medical or surgical purposes, that induces reversible partial or total loss of sensation and may be topical, local, regional or general, depending on the method of administration and area of the body affected.

Key considerations include:

• Local anaesthesia is always the first choice of anaesthesia providing there are no contraindications.
• Application may be topical or injected by infiltration or block.
• An understanding of the pharmacology of local anaesthesia drugs is a prerequisite to the administration of local anaesthesia.
• Familiarity with the relevant anatomy and the variety of methods of administering local anaesthesia is a further prerequisite.
• The simplest local anaesthesia technique which is likely to be effective is usually the most appropriate.
• All patients must be monitored in accordance with current recommendations.
• Patients must be discharged and cared for appropriately.
• Medicolegal considerations, including consent, patient instructions and detailed clinical notes, help to protect the patient and also minimise the risk of litigation.
• To provide local or regional pain relief for dental and surgical procedures with minimal discomfort to the patient whilst minimising complications.
• To minimise the need for sedation or general anaesthesia in the provision of routine dentistry.

The ideal local anaesthetic does not yet exist. The properties of the ideal local anaesthetic, compared to those of existing local anaesthetics, are listed in Table 9.2.

The advantages of local anaesthesia over general anaesthesia in the provision of dental care include:

• Convenience, speed of administration and good patient acceptance.
• Significantly lower mortality.
• High patient satisfaction.
• Well tolerated in patients with pulmonary disease.
• The patient’s airway is maintained.
• Selective muscle relaxation.
• Reduced blood loss.
• Decreased incidence of dep vein thrombosis and pulmonary embolism – both complications of general anaesthesia and prolonged immobilisation.

The disadvantages of local anaesthesia in dentistry include:

• Patient remains conscious.
• Patient anxiety.
• Not reliable for surgery or operative procedures which may take more than 2 hours to complete.
• Risk of bradycardia, hypotension and fainting – vasovagal syncope.

Contraindications of local anaesthesia in dentistry include:

• Patient:
  • Refusal.
  • Inability to collaborate with treatment (mental or physical disability, or < 7 years of age) or severe anxiety in adults.
• Surgical:
  • Procedure lasting more than 1–2 hours.
  • Large surgical domain – would require an overdose of local anaesthesia, let alone multiple injections, to gain surgical analgesia.
  • Previous failed attempts under local anaesthesia.
• Medical:
  • Bleeding dyscrasia causing additional haemorrhage and associated complications.
  • Hypovolaemia may increase toxicity of local anaesthetic.
  • Presence of sepsis/bacteraemia.
  • Certain neurological conditions and disease.
  • Increased intracranial pressure.
  • Fixed cardiac output states.

Patient Assessment

A satisfactory first visit is crucial to the success of subsequent treatment under local anaesthesia. Remember that for some patients even discussing dentistry can be frightening. The assessment should include:

• A full medical history. If in doubt, consult the patient’s general medical practitioner or individuals providing any specialist care.
• A baseline recording of blood pressure with the result recorded in the patient’s notes.
• To clarify operative risk, the patient may be classified according to the American Society of Anesthesiologists (ASA) scale (Box 9.1). Patients classified ASA I or ASA II are generally suitable for treatment in primary dental care. ASA III–IV patients should be referred to a specialist centre.
• A dental history, including details of many adverse experiences with, in particular, local anaesthesia.
• The patient’s level of anxiety. Marked anxiety may be an indication for conscious sedation.
• Examination of the site(s) for the administration of the lopcal anaesthesia, together with an assessment of the sufficiency of the access.

Treatment Options

The following treatment options, as detailed in Figure 9.1, may then be considered and discussed with the patient:

• Local anaesthesia alone.
• Local anaesthesia with inhalational sedation (RA).
• Local anaesthesia with intravenous conscious sedation.
• Local anaesthesia with oral sedation.
• General anaesthesia as an outpatient.
• General anaesthesia as an inpatient.

The simplest technique that will enable the proposed treatment to be carried out safely and effectively is generally best.

Once the most appropriate treatment option has been agreed with the patient, pre‐ and postoperative instructions should be provided and discussed with the patient and consent obtained.

Regulations

There are specific regulations pertaining to practitioners who provide dental local anaesthesia. All such practitioners must be resuscitation–basic life support (BLS) trained, work in an environment with facilities for sterilising the syringes, and adhere to health and safety regulations with regard to sharps disposal and cross‐infection control regulations.

Local Anaesthetics

The range of local anaesthetic agents available for, and commonly used in dentistry (British National Formulary – https://www.bnf.org/) includes:

• Lidocaine (lignocaine) – most commonly used.
• Prilocaine.
• Benzocaine – surface anaesthesia.
• Marcaine.
• Articaine.

Information on the duration and maximum doses of these anaesthetics is set out in Table 9.3.

The drug of first choice is lidocaine with adrenaline (1:80 000 UK; 1:100 000 (epinephrine) Europe and USA). The adrenaline acts as a vasoconstrictor, extending the duration of the action of the lidocaine.

Lidocaine has the following properties:

• Non‐irritant to tissue.
• Spreads effectively and rapidly through tissues.
• Has few or no vasodilator effects.
• Anaesthesia is more rapid than with procaine.
• Good duration of anaesthesia.
• Has some topical action as a spray or gel.
• Maximum safe dose 200 mg (500 mg with vasoconstrictor).
• Non‐allergenic.
• Without adrenaline, there are no contraindications for dental use.

Safety of Local Anaesthesia

Local anaesthesia is considered to be very safe, if appropriately administered and within maximum dose levels. However, prior to administration it is important to:

• Check for allergy.
• Check for history of poorly controlled hypertension.
• Check doses at extremes of age.
• Excercise caution in those with uncontrolled cardiac arrhythmias and severe hypertension.
• Avoid high doses in patients with severe liver disease as metabolism is impaired.
• Assess the risk of psychogenic side effects.

Pharmacokinetics

Local anaesthetics cannot block sodium channels from outside the axon; only uncharged local anaesthetics can cross the axon membrane.

pH

Most local anaesthetics, with the exception of benzocaine, are weak bases (pKa 8–9). pKa = pH when the local anaesthetic is 50% charged/uncharged. The smaller the difference between pKa and pH, the more non‐ionised molecules. The more non‐ionised molecules, the quicker the onset of action. The rate of diffusion of non‐ionised molecules through the nerve cell membrane depends upon:

• Nerve morphology.
• Concentration of the anaesthetic solution.
• Lipid solubility.

Onset of Action

pKa ↓ (= ionisation ↓) = time to onset ↓.

Potency

Lipid solubility ↑ = potency ↑.

Duration of Action

Protein binding ↑ and lipid solubility ↑ = duration of action↑.

Diffusion of the anaesthetic agent away from the nerve depends on:

• Protein binding.
• Concentration of the anaesthetic.
• Lipid solubility.

Duration Times

These are listed in Table 9.4.

Effect of Increasing the Dose (Volume and/or Concentration)

• Time to onset ↓.
• Duration of action ↑.
• More profound motor block.
• But, risk of ↑toxicity.

Adjunctive Components

The most commonly used anaesthetic solutions contain several components, for example:

Xylocaine® 2% with Adrenaline (1:80 000)

• Lidocaine hydrochloride BP 21.4 mg – the anaesthetic agent.
• Adrenaline tartrate BP 22.7 mg – the vasoconstrictor.
• Sodium chloride 6 mg – to make the solution isotonic.
• Sodium metabisulfite 0.5 mg – to prevent oxidation of the adrenaline when exposed to light.

Citanest® with Octapressin®

• Prilocaine hydrochloride BP 30 mg – the anaesthetic agent.
• Felypressin 0.03 i.u. – the vasoconstrictor.
• Sodium chloride BP 6 mg – to make the solution isotonic.

Sodium Bicarbonate

Sodium bicarbonate is added to lidocaine with adrenaline to neutralise the solution, reduce the pain of injection and increase effectiveness. Buffered solutions should be discarded after one week, because the effectiveness of the adrenaline decreases by almost 25% during this time.

Hyaluronidase

Hyaluronidase is a bovine‐derived enzyme that hydrolyses hyaluronic acid in the connective tissue and facilitates the diffusion of local anaesthetic. Although this increases the spread of anaesthesia, hyaluronidase decreases the duration of action and increases the risk of toxic reactions.

Sodium Metabisulfite

Sodium metabisulfite is added as a stabiliser. It makes the solution more acidic and may contribute towards pain (‘burn’) on injection. It may also provoke an allergic reaction.

Vasoconstrictors

The functions of a vasoconstrictor in an anaesthetic solution are to:

• Increase the duration of action by 30–50%, but only in combination with short‐acting local anaesthetics (lidocaine‐, prilocaine and marcaine).
• Increase the depth of anaesthesia.
• Decrease intravascular uptake.
• Reduce operative bleeding through vasoconstriction.
• Reduce systemic toxicity.

Vasoconstrictors are unstable in direct sunlight and heat, therefore local anaesthetic solutions containing a vasoconstrictor should be stored in a dark, cool place.

Adrenaline

Adrenaline is the most widely used vasoconstrictor in dentistry, because:

• It is a very potent vasoconstrictor.
• It has low systemic toxicity in concentrations below 1:50 000 (1:80 000 used in dentistry).
• It is slowly absorbed, and therefore very safe.

However, adrenaline must not be injected intravenously because it may cause tachycardia, increased blood pressure, arrhythmia, or ventricular fibrillation. Also, the administration of adrenaline may be contraindicated in patients with thyrotoxicosis and pre‐existing cardiovascular disease. It must not be given in conjunction with general anaesthetic agents such as halothane.

Octapressin®

Octapressin® is:

• A relatively weak vasoconstrictor.
• Available only with prilocaine in a dose of 1:200 000 (0.3 i.u.).
• Safe to use in patients with thyrotoxicosis.
• Contraindicated in pregnancy.

Patients with ischaemic heart disease must only be given a small dose of Octapressin®, because >8 ml of Citanest® with Octapressin® may induce coronary vasoconstriction.

If anaesthetising a structure with end arteries – an ear or finger – only plain (non‐vasoconstrictor containing) local anaesthetic solution should be used.

Patient‐Related Factors

Age and Size

Careful dosage monitoring is required at extremes of age (<1 and >70 years of age). In very young and older patients, reduced elimination of the anaesthetic agent may allow a 10–20% reduction in dose.

Body Size

In very small patients (<50 kg), the dose for regional anaesthesia should be reduced by <30%. Larger doses are not normally required for dental purposes in larger patients.

Pregnancy

In pregnancy there is a hormonally increased sensitivity to local anaesthetic agents, together with an increased risk of toxicity.

Presence of Infection

Local anaesthesia is relatively ineffective in the presence of infection, given low tissue pH and vasodilation, notwithstanding the risk of spreading the infection.

Medical Considerations

• Local anaesthesia is very safe.
• The commonest problems are psychogenic.
• Check for allergy.
• Check for history of cardiac arrhythmias.
• Check for history of hypertension.
• Check for hepatic and renal dysfunction.

Such medical complications may require dose reductions relative to degree of dysfunction, possibly <50%.

Myths

Common myths include the need to avoid the use of adrenaline‐containing local anaesthetic in:

• Patients on monoamine oxidase (MAO) inhibitors.
• All hypertensive patients.
• All patients who have angina or have had a myocardial infarction.
• All patients with liver disease.

Also, bilateral inferior dental blocks are not necessarily dangerous, and evidence is limited in that Citanest® may induce labour in pregnant females.

Antinociceptive Effects

Other unsubstantiated effects of local anaesthesia include:

• Antiarrhythmic.
• Improved bowel function.
• Antithrombotic.
• Reduction of inflammation processes.
• Antibacterial.
• Influence on wound healing.
• Neuroprotection.
• Accumulation of metabolites – risk of methaemoglobinaemia.

Equipment

Syringes

Local anaesthetic syringes are amongst the most commonly used types of dental equipment. These syringes may be reusable, with the need to decontaminate and sterilise between patients, or single‐use, disposable syringes, which minimise the risk of cross‐infection and, given integral sheath protection, reduce the incidence of needlestick injuries. Aspiration may be achieved by means of aspirating tip plungers, as part of the design of the syringe, or by means of an aspirating bug as part of the design of the local anaesthetic cartridge. Reusable and single‐use, disposable syringe systems may be:

• Self‐aspirating.
• Aspirating.
• Non‐aspirating.

It is a legal requirement to aspirate during block anaesthesia in the UK.

Conventional reusable syringes continue to be the most widely used form of syringe in the clinical practice of dentistry. There are several methods of reducing the risk of needlestick injuries when using such syringes. These include:

• Immediate removal of the used needle, using an artery clip, and disposal of the needle in a sharps disposal bin, which should be to hand.
• The use of a block of foam into which the needle is inserted immediately following use.
• The use of specially designed needle mounts, sheaths and removers.

Needles

Length and Gauge

The three standard dental needle lengths are:

• Long (~35 mm).
• Short (~25 mm).
• Ultra‐short (~12 mm).

In general, it is suggested that long needles should be used for deep injections such as blocks of the inferior dental nerve to improve accuracy. Short needles are used for most other forms of local anaesthetic injection in dentistry. Ultra‐short needles tend to be used for injections such as periodontal ligament injections.

The three standard dental needle gauges, or thicknesses, are:

• 25‐gauge.
• 27‐gauge.
• 30‐gauge.

The higher the gauge, the finer the needle.

The choice of gauge depends on two main factors:

1. The need for a stiff needle. The thicker the needle, the more stable it is, and the less it deflects when pushed into tissue. A practitioner may decide to use a thicker needle when planning to inject on heavier‐set individuals.
2. The need to aspirate. Neither 27‐gauge nor 30‐gauge needles are reliable for the aspiration of blood. Whenever the practitioner is injecting into an area where there is the possibility of entering a blood vessel, a 25‐gauge needle should be used. Patients are not able to discern the difference between the prick of a 25‐, 27‐ or 30‐gauge needle. The key to reducing pain during injection, regardless of the needle gauge, is to inject slowly and steadily.

Needles – Key Points of Safety

• Never inject directly into nerves.
• Never place your hand or any other part of your anatomy over the sharp end of the needle.
• Always immediately dispose of the used needle.
• Never bend a needle.
• Never insert the needle up to the hub of the syringe.

Cartridges (Figure 9.2)

Local anaesthetic cartridges are labelled according to:

• Volume – UK 2.2 ml (USA and Europe 2 ml).
• Name of drug, with or without a vasoconstrictor.
• Expiry date.

Prior to use, it is essential to check the contents and expiry date of a cartridge. The cartridge should also be checked for any evidence of damage. If a cartridge is found, or merely suspected, to have suffered damage, it should be rejected. The batch number of the cartridge should be recorded in the patient’s notes.

All local anaesthetic cartridges should be stored in accordance with manufacturer’s instructions to prevent contamination and denaturing.

Clinical Procedure

Success in local anaesthesia is underpinned by:

• The patient being fully prepared – briefed, consented and reassured.
• The dental team being fully prepared – there is nothing worse for an anxious patient than having to wait for missing items to be located.
• The procedure being undertaken efficiently, effectively and safely.
• The capability of the dental team to deal with any untoward event which occurs during the procedure.

Before any clinical procedure is started, typically with the administration of local anaesthetic, it is important to check the patient’s:

• Identity – name, date of birth, address, hospital number, etc.
• Medical history.
• Blood pressure.
• Intended procedure.
• Consent.
• Comfort, including a preoperative visit to the toilet.

Then, always check:

• The cartridge loaded in the syringe – the anaesthetic agent, the presence or absence of vasoconstrictor and date of expiry.
• The suitability of the needle, and that it has been correctly fitted to the syringe and ready for use.
• And record the cartridge batch number in the patient notes.

Routes of Application

Local anaesthetics for dental purposes may be applied:

• Topically.
• By infiltration.
• To effect block anaesthesia.

Topical

Timing

• Prior to infiltration or block injection.
• Incision and drainage of superficial abscesses.
• Prior to cannula insertion.

Agents

• Benzocaine 20%.
• Xylocaine 4%.
• Ethylchloride spray.
• Eutetic mixture of lidocaine (2.5%) and prilocaine (2.5%) – EMLA.