General information about local anaesthetics in dentistry

Local anaesthetics are commonly used in dentistry. They provide effective pain control (analgesia), and have a low incidence of adverse effects. However, before administering a local anaesthetic clinicians must have an understanding of the local and systemic complications that can arise from their use.

In dentistry, the most common methods of administration are:

• infiltration—local anaesthetic is injected adjacent to the site where analgesia is required. Infiltration is sufficient for most teeth, except the lower molars
• regional block—local anaesthetic is injected adjacent to the nerve, proximal to the site where analgesia is required. A regional block aims to prevent pain being experienced in the area of nerve distribution distal to the site of injection (eg mandibular [inferior alveolar nerve] blocks are required for procedures of the lower molars).

Topical administration of a local anaesthetic¹ is indicated for minor painful procedures (eg band removal, crown placement, mucosal incision). It may also be used to facilitate injection of local anaesthetic in anxious or needle-phobic patients by eliminating pain on the mucosal surface; however, patients may experience discomfort upon injection of local anaesthetic into the deeper tissues.

The onset of effect depends on the method used; analgesia occurs approximately 2 to 3 minutes after an infiltration injection, 4 to 5 minutes after a block injection, and 3 minutes after topical administration. Pulp analgesia takes longer than analgesia of the soft tissues. The duration of effects depends on the local anaesthetic used, the dose and the method of administration. Advise patients of the likely duration of effects and that they should seek advice if they have not recovered after this time.

Medical practitioners who are experienced in the use of local anaesthetic via infiltration or regional block may use these techniques for temporary relief of acute severe dental pain (eg irreversible pulpitis). Some local anaesthetics are available in single-use dental cartridges, which may be easier to use.