Quality Resource Guide

Local Anesthetics 5th Edition

www.metdental.com

descriptions of these techniques can be found in

textbooks on local anesthesia4, and are described

only briefly here. Intraosseous injection requires

perforation of the cortical bone on the lateral aspect

of an interdental septum. A needle is then inserted

through this hole and a local anesthetic injected

into the cancellous bone. Diffusion of the drug from

the site of injection can produce pulpal and surgical

anesthesia of the adjacent teeth and gingiva. The

onset is usually achieved with seconds and may

last up to 30 minutes or more. In the periodontal

ligament injection, the needle is advanced vertically

into the gingival sulcus on a proximal surface until

the tip is wedged tightly in the periodontal ligament

space. A small amount of anesthetic solution is then

injected and pulpal anesthesia is usually achieved

almost instantaneously. The drug reaches the apical

area either by diffusion through the periodontal

ligament, the adjacent cancellous bone or both.

Although

intraosseous

injection

can

accomplished with a standard round bur and

27- gauge needle, disposable units consisting

of a bone-perforating bur and a size-matched

needle are available (

e.g.,

Stabident System™;

X-Tip System™). For the intraligamentary injection,

special syringes capable of generating high

injection pressures are available but offer little

advantage over a 27-gauge needle on a standard

aspirating syringe.

Table 3 - Duration of Action Proﬁles of Dental Local Anesthetics*

Category

Duration



Preparations

Short

Inﬁltration:

up to 30 minutes

Nerve block:

up to 2 hours

• Lidocaine 2% plain

• Mepivacaine 3% plain

• Prilocaine 4% plain

Intermediate

Inﬁltration:

up to 2.5 hours

Nerve block:

up to 3.5 hours

• Articaine 4% with 1:100,000 or 1:200,000 epinephrine

• Lidocaine 2% with 1:50,000 or 100,000 epinephrine

• Mepivacaine 2% with 1:20,000 levonordefrin

• Prilocaine 4% plain or with 1:200,000 epinephrine

Long

Inﬁltration:

Up to 4 hours

Nerve block:

Up to 8 hours

• Bupivacaine 0.5% with 1:200,000 epinephrine

* Duration of local anesthesia depends upon multiple factors.

In addition to type (supraperiosteal inﬁltration or nerve

block) and quality of injection, anatomic deviations, variations in patient response to the anesthetic agent, local tissue

environment, dose, and rate of clearance from the site of injection will inﬂuence duration.

†

Estimated period of soft tissue anesthesia; duration of pulpal anesthesia is typically less.

Mepivacaine has been used for local anesthesia in

dentistry for many years. It has a shorter duration of

action than lidocaine with epinephrine, particularly

in the absence of a vasoconstrictor, and has been

advocated for brief procedures. The vasoconstrictor

most

commonly

used

with

mepivacaine

levonordefrin (Neocobefrin™), a synthetic alpha-

adrenergic amine. Levonordefrin is less potent than

epinephrine and a much higher concentration is

required for adequate vasoconstriction.

Articaine was approved in 2000 in the U.S. for local

anesthesia. Initial reports that articaine penetrated

alveolar bone to a greater extent and diffused

more widely than other agents have not been

substantiated. Its duration of action and other clinical

properties are similar to lidocaine, and articaine

offers no particular advantage. It is available only

with epinephrine. Use in children under 4 years of

age is not recommended.

The local anesthetic features of prilocaine are

also similar to lidocaine. An advantage is lesser

vasodilation, which permits use of a lower

concentration of epinephrine. A drawback is a

dose-related formation of methemoglobin, which

reduces oxygen binding and transport and can

lead to cyanosis and respiratory distress. Although

this effect is ordinarily not clinically significant

at recommended dosages, prilocaine should be

avoided in patients with existing methemoglobinemia,

severe anemia, chronic hypoxia related to cardiac or

pulmonary disease, or patients taking drugs with

oxidant properties,

e.g.

, nitrites, sulfonamides or

acetaminophen.

Bupivacaine is distinguished from the other amide-

type agents by its considerably greater lipid

solubility. This property makes bupivacaine more

potent (and toxic) and gives it a much longer duration

of action. Soft tissue anesthesia up to 4 hours

following infiltration and up to 8 hours following

nerve block may be achieved with bupivacaine.

However, pulpal anesthesia in the maxilla may be

relatively short after supraperiosteal infiltration.

The

greater duration of anesthesia makes bupivacaine

useful for longer procedures, particularly surgical.

Bupivacaine is the only anesthetic used in dentistry

for which dosage on the basis of body weight has

not been established. However, a total dose of

90 mg should not be exceeded in adults. Use in

children is not recommended.

In mid-2003, local anesthetic manufacturers

participating in the ADA Seal program agreed to

a system for color-coding and uniform contents

labeling of anesthetic cartridges (

Table 4

). This

welcome

change

makes

recognition

easier

and reduces chances of errors in anesthesia

administration.

Alternative Delivery Methods

Most dental anesthesia is achieved using either

infiltration or block injections in soft tissue. These

techniques are straightforward, easily mastered

and when used correctly are safe and effective.

However, the need to deliver an anesthetic by a

different route occasionally arises. For example, it

may be desirable to anesthetize a single mandibular

tooth without numbing the tongue, lip and other soft

tissues. There are also instances,

e.g.,

infection,

where usual injection techniques fail to produce

sufficient anesthesia, and an alternate or “rescue”

method is required.

There are several alternatives to soft tissue

injections with which practitioners should be familiar.

These include the intraosseous and periodontal

ligament (intraligamentary) injections. Detailed