Oral and maxillofacial surgery/Local anesthesia

Learning resources:

Oral and maxillofacial surgery
School of Medicine
School of Dentistry

General points edit

  • The most common local anesthetic (LA) used in dentistry and oral surgery depends to a degree on geographic location, as does the available cartridges. Common formulations are:
    • 2% Lidocaine with 1:80,000 (or 1:100,000) Epinephrine in 2.2 mL cartridges
    • 4% Articaine with 1:100,000 Epinephrine in 2.2 mL cartridges

Maximum doses edit

The maximum dose of any given LA depends on many factors.

The basic maximum dose is calculated according to the per kg body-weight. If this works out to be higher than the absolute ceiling, do not go above the absolute ceiling.

  • Elderly (>65)

Duration of anesthesia edit

  • Time of exposure
  • Concentration of LA solution
  • Volume of solution in vacinity of nerve
  • Size of nerve fiber

Intra-vascular injection edit

Signs and symptoms:

  • Tachycardia
  • Sweating

Causes of inadequate LA: In any LA injection, the reasons that inadequate anesthesia is not obtained can be considered under the following headings:

Block vs Infiltration edit

  • Accurate placement of infiltrations is helped by knowledge of average root lengths and root completion dates

Put the needle on a clean surface and covered with a sterile sheet to hide it from view. The sight of the needle increases patient anxiety, so don't wave it in-front of them.

  • Check it is safe to do the procedure. It is impossible to be allergic to epinephrine, which is an endogenous vasoconstrictor. Allergy to the LA is uncommon. When allergy does occur, it is most likely due to other components of the LA solution like the preservative methyl paraben. Some dental LA cartridges contain rubber latex. Unstable thyrotoxicosis is a contra-indication for

Most often, needle phobia is the reason that the IANB cannot be performed on an awake patient.

  • Check what is the maximum does you can administer. This step can usually be ignored until the first injection has not given adequate anesthesia, when you might be thinking about giving more LA. Maximum doses of LA are calculated according to weight and depend on the drug used, and whether a constrictor is present. Hepatic metabolism is another factor. Physiologic decreased efficiency of the hepatic metabolism occurs in the very young and the very old. Pathologic liver damage should also be noted, such as cirrhosis. Generally speaking you would halve the maximum dose calculated by weight in persons with impaired hepatic metabolism.
  • Describe to patient in non-threatening terms what is going on. Pain has a psychologic component, and research demonstrates people who are told that a procedure will hurt experience more pain. Therefore, describe the procedure as something like this: "I'm going to numb up the bottom teeth, you might feel some coldness at the back of the mouth for a moment." Do not say something like this: "I'm going to stick this huge needle deep into the back of your throat. It's going to hurt like crazy."
  • Lay the patient flat on an examination bed or dental chair with available bright light. Ideally they would be wearing eye-protection
  • Ask the patient to close their eyes. This prevents them seeing the needle, and also prevents them from being dazzled by the examination light,
  • Positioned examination light