Pharmacology of Local Anaesthesia for Dental Practice

Importance of Pain Management

• Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage
• Effective control of orofacial pain facilitates the delivery of care and reduces anxiety about dentistry

Introduction to Local Anaesthetics

• Local anaesthetics are drugs that reversibly prevent the transmission of nerve impulses in the region to which they are applied, without affecting consciousness
• They prevent or relieve pain and interrupt nerve conduction by inhibiting the influx of sodium (Na+) ions through voltage-gated Na+ channels within nerve membranes
• Their effectiveness depends on lipid solubility and local pH

History of Local Anaesthetics

• The first local anaesthetic to be used was cocaine, but it was addictive and had psychogenic effects
• Procaine (novocaine) is no longer used, as more effective alternatives are available

Classification of Local Anaesthetics

• Local anaesthetics can be classified as amide-linked or ester-linked
• Examples of amide-linked local anaesthetics include lidocaine, prilocaine, articaine, and bupivacaine

Mechanism of Action

• Local anaesthetics work by preventing the transmission of nerve impulses by inhibiting the influx of sodium (Na+) ions through voltage-gated Na+ channels within nerve membranes
• The lipid-soluble base form of the anaesthetic penetrates the nerve membrane, where it is converted to the ionized form, which binds to the inactivation site of the Na+ channel, keeping the channel closed
• The pKa value of the anaesthetic determines the proportion of the ionized and non-ionized forms, which affects its potency and duration of action

Nociceptors

• Nociceptors are sensory receptors responsible for the detection of noxious stimuli, transforming them into electrical signals that are conducted to the CNS
• They are distributed throughout the body, including the skin, muscles, and joints, and can be stimulated by mechanical, thermal, or chemical stimuli