Dental Local Anesthesia

Study Notes

Local anesthesia is the loss of sensation in a circumscribed area of the body caused by a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nerves.

Should not be irritating to the tissue it is applied to.
Systemic toxicity should be low.
Must be effective regardless of whether it is injected into the tissue or applied locally to mucous membranes.
Time of onset of anesthesia should be as short as possible.
Duration of action must be long enough to permit completion of the procedure yet not so long as to require an extended recovery.
Should not cause any permanent alteration of nerve structure.

Develops when the blood level of the drug in a target organ (e.g. brain) becomes excessive.
Can cause central nervous system (CNS) and cardiovascular system (CVS) depression.
Reactions can range from mild tremor to tonic-clonic convulsions (CNS) and from a slight decrease in blood pressure and cardiac output to cardiac arrest (CVS).
Maximum recommended doses (MRD’s) of all drugs administered by injection should be calculated by body weight and should not be exceeded.

Based on chemical structure: ester group (e.g. cocaine, benzocaine, procaine, tetracaine) and amide group (e.g. lidocaine, mepivacaine, prilocaine, etidocaine, bupivacaine).
Based on duration of action: short acting (e.g. procaine), intermediate acting (e.g. lidocaine), and long acting (e.g. bupivacaine).

Local complications: hematomas, infection, trismus, nerve damage by the needle, needle breakage in soft tissues, and masticatory trauma.
Systemic complications: allergic reaction, cardiovascular and central nervous system dysfunction.
Management of soft tissue trauma involves reassuring the patient, allowing time for the anesthetic effects to diminish, and coating the involved area with lubricant.

Posterior superior alveolar nerve block: innervates the posterior maxillary deciduous molars.
Middle superior alveolar nerve block: innervates the premolars and the mesiobuccal root of the 1st permanent teeth.
Maximillary anterior region block: infiltration in the apical region of the anterior teeth provides satisfactory anesthesia in most cases.
Infraorbital nerve block: the infraorbital foramen in a 3-year-old is about 5 mm above the vestibular depth.
Palatal infiltration: anesthetic agent is injected into the depth of rugae as they contain less sensory endings.
Nasopalatine nerve block: nasopalatine nerve innervates the maxillary anterior teeth.
Greater palatine nerve block: greater palatine nerve innervates the maxillary posterior teeth in the palatal aspect.

Inferior alveolar nerve block: for anesthetizing the molars and premolars.
Factors to be considered: the mandibular foramen is located near the posterior border of the ramus in children.
Technique: the needle is penetrated into the pterygomandibular space and the solution is deposited close to the mandibular foramen.
Lingual nerve block: the needle has to be withdrawn and solution deposited half the distance from the inferior alveolar foramen.
Buccal nerve block: can be anesthetized by infiltration in the buccal sulcus distal to the permanent teeth.
Mental nerve block: anesthetizes the anterior teeth and premolar.