Anaesthesia is administered prior to a procedure to help dull pain or sedate a nervous or anxious patient. The most common form is local anaesthesia, meaning that it dulls pain in all or part of the mouth during dental work, but does not cause the patient to go to sleep. It usually wears off two to three hours after the procedure and is most often used when a patient is getting a filling or a root canal.

Some children or people with disabilities or severe anxiety may require conscious sedation. Nitrous oxide, also known as laughing gas, is often used, as are oral sedatives and oral injections.

On occasion, patients undergo general anaesthesia, in which drugs cause a temporary loss of consciousness. Deep sedation and general anaesthesia may be recommended in certain procedures, such as wisdom teeth extraction, or for children or adults who have severe anxiety or difficulty controlling their movements.


If you need local anaesthesia, your dentist will dry part of your mouth with air or use cotton rolls, then swab the area with a gel to numb the skin. Next, your dentist will slowly inject the local anaesthetic into the gum tissue. Most people don't feel the needle. Instead, the sting they feel is caused by the anaesthetic moving into the tissue. An injection of local anaesthesia can last up to several hours. After you leave the dentist's office, you may find it difficult to speak clearly and eat or drink for a few hours. Be careful not to bite down on the area that is numbed. You could cause damage to yourself without realising it. For the same reason it is best to avoid hot drink and foods straight after local anaesthesia.

If a patient requires nitrous oxide, the process is simple. Nitrous oxide is mixed with oxygen and administered through a mask that fits over the nose. The patient is asked to breathe through their nose. It works quickly to leave patients less agitated during the appointment.


  • Side effects from local anaesthetics are very rare, and the anaesthetic usually lasts for only a couple of hours.
  • Some possible side effects include:
  • A hematoma (a blood-filled swelling), which can form when the injection needle hits a blood vessel.
  • Numbness outside of the localised area. If this happens, your eyelid or mouth can droop. You will recover when the drug wears off.
  • An increased heart rate. This lasts only a minute or two. Tell your doctor if this has ever happened to you.
  • An injured nerve caused by the needle used to inject the anaesthesia. This can lead to numbness and pain for several weeks or months, but the nerve usually heals over time.
  • It is rare to have an allergic reaction to a local anaesthetic. Be sure to tell your dentist about all of the medication you take. This should include over-the-counter drugs and any herbs or vitamins you take. You should tell your dentist about any reactions you have had with medicines, no matter how minor the reaction was.
  • During the first trimester (three months) of pregnancy, it is best to avoid major dental treatment. After that time point, discuss your anaesthesia options with your dentist and your obstetrician or midwife. In general, most dentists say it is best to have dental treatment before pregnancy or postpone treatment that is not essential.