Pharmaceutical manufacturers use color coding systems to assist clinicians in
the identification of various anesthetics used in their practice. The
concentration of vasoconstrictors, for example, is identified by color coding,
either the rubber stopper in each cartridge or by colored rings around the
cartridge. It is advisable that the dental specialist become familiar with the
different color coding systems.
VASOCONSTRICTORS IN LOCAL ANESTHETICS
Local anesthetics usually contain a vasoconstricting drug, such as epinephrine or
levonordefrin (Neo-Cobefrin). The addition of vasoconstrictors to local anesthetics is
beneficial for the following reasons:
a. The anesthetic is retained in the area longer, resulting in a greater time and
depth of anesthesia.
b. The toxic effect of the anesthetic is reduced since it is released into the
general circulation more slowly.
c. The area of the injection will have less tendency to bleed.
METHODS OF ADMINISTRATION OF LOCAL ANESTHETICS
a. Topical. Topical anesthetics are applied to the mucous membrane or skin
surface. They penetrate through the surface layers of the mucous membrane or skin,
contact the nerve endings, and produce a loss of pain and sensation. Topical
anesthetics may be used to anesthetize the buccal mucosa at the site of injection, to
temporarily abolish a gag reflex, to relieve pain of certain lesions, or to relieve pain and
discomfort of oral prophylaxis procedures. Topical anesthetics used most commonly
are benzocaine and lidocaine (Xylocaine).
b. Block Anesthesia (Conduction Anesthesia). The local anesthetic is
injected into the area next to the nerve trunk (a major undivided portion of a nerve
trunk). This blocks the passage of impulses to the brain from the area involved. This
technique is most commonly employed in the mandible where the density of the bone
renders infiltration ineffective. In the mandibular block, the anesthetic solution is placed
near the mandibular foramen (where the inferior alveolar nerve trunk enters the
mandible) to innervate the mandibular teeth. Thus, all of the mandibular teeth are
anesthetized by the blockage of nerve impulses at a point some distance away from the