Friday, August 7, 2009

Dental anesthesia

Forms of dental anesthesia are similar to general medical anesthesia except for the use of nitrous oxide, relatively uncommon outside of the dental field in the U.S.

Local anesthetics

The most commonly used local anesthetic is lidocaine (also called xylocaine), a modern replacement for novocaine and procaine. Its half-life in the body is about 1.5-2 hours. Other local anaesthetics in current use include septocaine, marcaine (a long-acting anesthetic), and mepivacaine. A combination of these may be used depending on the situation. Also, most agents come in two forms: with and without epinephrine.

The most common technique, effective for the lower teeth and jaw, is inferior alveolar nerve anaesthesia. An injection blocks sensation in the inferior alveolar nerve, which runs from the hinge of the jaw down the back of the mandible, connecting to the lower teeth, lower lip, chin, and tongue. The inferior alveolar nerve probably is anesthetized more often than any other nerve in the body. To anesthetize this nerve, the dentist inserts the needle somewhat posterior to the patient’s last molar. Several nondental nerves are usually anesthetized during an inferior alveolar block. The mental nerve, which supplies cutaneous innervation to the anterior lip and chin, is a distal branch of the inferior alveolar nerve. When the inferior alveolar nerve is blocked, the mental nerve is blocked also, resulting in a numb lip and chin. Nerves lying near the point where the inferior alveolar nerve enters the mandible often are also anesthetized during inferior alveolar anesthesia. For example, the lingual nerve can be anesthetized to produce a numb tongue. The facial nerve lies some distance from the inferior alveolar nerve, but in rare cases anesthetic can diffuse far enough posteriorly to anesthetize that nerve. The result is a temporary facial palsy (paralysis or paresis), with the injected side of the face drooping because of flaccid muscles, which disappears when the anesthesia wears off. If the facial nerve is cut by an improperly inserted needle, permanent facial palsy may occur.

The superior alveolar nerves are not usually anesthetized directly because they are difficult to approach with a needle. For this reason, the upper are usually anesthetized locally by inserting the needle beneath the oral mucosa surrounding the teeth.

Other anaesthetics

  • Nitrous oxide (N2O), also known as "laughing gas", binds to the hemoglobin in the lungs, where it travels to the brain, leaving a dissociated and euphoric feeling for most patients. N2O is typically used in conjunction with Procaine. Nitrous oxide is used in combination with Oxygen. Often (especially with children) a sweet smelling fruity scent similar to an auto scent is used with the gas to inspire deep inhalation. Nitrous oxide nose respirators are available to dentists pre-scented with a fruity smell and used by some dentists especially on children.
  • Eugenol — made from clove oil, this is a topical anesthetic also used in the common dental material ZOE (zinc oxide eugenol).
  • Topical anastethics — benzocaine, eugenol, and forms of xylocaine are used topically to numb various areas before injections or other minor procedures
  • General anesthesia — drugs such as versed, ketamine, propofol and fentanyl are used to put the patient in a twilight sleep or render them completely unconscious and unaware of pain.
  • Versed a drug that represses memories of the procedure is usually given two hours prior to the procedure in combination with Tylenol in General anesthesia so the patient will go home with no memories of being in surgery.
  • Sevoflurane gas in combination with Nitrous oxide and Oxygen is often used during General anesthesia followed by the use of isoflurane gas to maintain anesthesia during the procedure. In children sweet fruity scents are often used with the gases to inspire deep inhalation. Scents come in cherry, apple, bubblegum, watermelon, etc...
  • Propofol a drug with similar effects to Sodium Pentathol is often used through intravenous infusion through an IV during General anesthesia after gasses are initiated.
  • Morphine is often used to control pain during the dental surgery under General anesthesia. The morphine is usually administered through IV.
  • Ketorolac is often administered through IV to suppress both pain and inflammation while under General anesthesia. *Ketorolac is often administered through IV to suppress both pain and inflammation while under General anesthesia.

Other Drugs Often used During General Anesthesia

  • Decadron a steroid is often administered through IV to suppress inflammation and swelling resulting during the surgery while under General anesthesia.
  • Ondansetron brand named Zofran is often administered to prevent nausea during the surgery which may result from the blood draining into the stomach while under General anesthesia. Or it is given to the patient after the procedure for postoperative nausea which may result from the anesthesia itself which was administered.


  • Electrical nerve blocks — a technology that involves using electrical current to block the reception or generation of pain signals.
  • Branch block — a common form of local dental anesthesia, blocks the reception of pain for one quadrant of the mouth at a time. Typically given in the buccal surface (cheek). (IAB, MNB are types of this block)
  • Dental block — given below the tooth in question. Used usually for minor procedures such as fillings.
  • Palatal block— given into the hard palate, useful in numbing the upper teeth.
  • Intraosseous — an injection of local anesthetic given directly into the osseous (bone) structure of the tooth.
  • Intrapulpal — an injection of local anesthetic given directly into the pulp of the tooth to completely desensitize the tooth.
  • An alternative to chemical or electrical blocks, acupuncture or acupressure is rarely used.

Dental syringe

A dental syringe is a syringe used by dentists for the injection of an anesthetic. It consists of a breech-loading syringe fitted with a sealed cartridge containing anesthetic solution.

The ancillary tool (generally part of a dental engine) used to supply either water or air to the oral cavity for the purpose of cleaning debris away from the area the dentist is working on, is also referred to as a dental syringe. A 3-way syringe has separate internal channels supplying air, water or a mist of air and water, created by combining the pressurized air with the waterflow. The syringe tip can be separated from the main body and replaced when necessary.

General anesthesia

Dentists who have completed a training program in anesthesiology may also administer general IV and inhalation anesthesthetic agents.

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