In: Anesthesia24 Sep 2009
Local anesthesia is defined as a loss of sensation in a circumscribed area of the body by a depression of excitation in nerve endings or an inhibition of the conduction process in the peripheral nerves. In clinical practice a localized loss of pain sensation is desired. Although the terms dental anesthesia and dental analgesia are used synonymously in dentistry, local analgesia is more accurate. Local anesthesia can be achieved by a number of mechanisms including mechanical trauma, anoxia, and use of neurolytic agents in addition to traditional local anesthetic drugs. However, clinically only reversible local anesthetic agents and other reversible techniques such as temperature reduction or electronic stimulation are useful to prevent pain.
The use of reversible local anesthetic chemical agents is the most common method to achieve pain control in dental practice. Some ideal properties of local anesthetics are as follows:
In spite of the major advances made in the field of anesthesia, the ideal local anesthetic agent does not exist.
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Local anesthetic agents can be classified in several ways (as shown in the Table):
The injectable local anesthetics used in dentistry have a common core structure consisting of
The combination of hydrophilic and lipophilic properties in 1 molecule is essential for an injectable local anesthetic to be effective. The hydrophilic portion of the molecule consists of a substituted secondary or tertiary amine. Solubility in water is essential for 2 reasons—to allow for the dissolution in a solvent to permit injection, and to allow penetration through interstitial fluid following administration. buy tadalafil online
The intermediate chain consists of either an amide or ester linkage. This allows spatial separation of the hydrophilic and lipophilic components of the molecule. The older agents, procaine and cocaine, are ester-based drugs but are no longer widely used as dental anesthetics due to their unwanted side effects, such as toxic or allergic reactions.
The lipophilic part of the local anesthetic agent is an aromatic residue that is essential for its ability to penetrate fatty tissue such as the lipid sheath of nerves in order to gain access to the nerve cell membrane to reach its site of action.
Different drugs have different proportions of hydro-philic and lipophilic components. These differences modify the characteristics and/or the properties of the anesthetic agents in the following ways:
The general constituents of a dental cartridge of anesthetic solution are:
MOLECULAR BASIS OF LOCAL ANESTHESIA
All local anesthetic agents used in dentistry work by obstructing the exchange in Na+ permeability, which is essential for the initial phases of a neuronal action potential. This mechanism prevents the development and propagation of the action potential by preventing the wave of depolarization.
Blog invites submissions of review articles, reports on clinical techniques, case reports, conference summaries, and articles of opinion pertinent to the control of pain and anxiety in dentistry.