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Continuing Education
Course Number: 123
Local Anesthesia
Reversal
Authored by Stanley F. Malamed, DDS
Uponsuccessful completion of this CE activity 2 CE credit hours may be awarded
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Continuing Education
RecommendationsforFluorideVarnishUseinCariesManagement
LocalAnesthesiaReversal hydrogen chloride (HCl) in 1948 led to an explosion of new
drugs that have provided the dentist and dental patient with
the opportunity to experience both pain-free treatment and
LEARNINGOBJECTIVES a pain-free post-treatment period. However, many patients
AFTERREADINGTHISARTICLE,THEINDIVIDUAL complain that lingering numbness of residual soft-tissue
WILL LEARN: anesthesia (STA) following completion of a dental
procedure is inconvenient, uncomfortable, and can lead to
• Thetypesoflocal anesthesia and mechanisms of action soft-tissue injury due to the inability to detect pain,
• The clinical use of a new agent that reverses soft especially in children.
tissue anesthesia. This article reviews the types of LA and mechanisms of
action, and discusses a new agent that reverses STA.
ABOUTTHEAUTHOR The LA armamentarium today consists of drugs
Dr. Malamed is a professor of anesthesia providing a range of durations of pain control, from short-
andmedicine at the School of Dentistry at acting drugs (~30 minutes pulpal anesthesia) to long-acting
the University of Southern California. He drugs providing pulpal anesthesia up to 7 hours and STA of
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graduated from New York University upto12hours’duration. Short-durationdrugsprovidepulpal
College of Dentistry in 1969. He then anesthesia for approximately 30 minutes and include
completed a dental internship and mepivacaine HCl 3% and prilocaine HCl 4%. The long-
residency in anesthesiology at Montefiore Hospital and duration category consists of bupivacaine HCl 0.5% with
Medical Center in the Bronx, NY before serving for 2 years epinephrine 1:200,000, providing pulpal anesthesia for up to
in the US Army Dental Corps at Ft.Knox, Kentucky.In 1973, 7 hours (commonly from 90 to 180 minutes) with STA for up
hejoined the faculty of the University of Southern California to 12 hours. Interestingly, bupivacaine HCl is a long-acting
School of Dentistry (Los Angeles) where today he is a anesthetic when administered by nerve block (NB) (eg,
professor of anesthesia and medicine. He is also a inferior alveolar NB) only. It is not nearly as long acting when
Diplomate of the American Dental Board of Anesthesiology. administered by supraperiosteal (infiltration) injection.
He has authored more than 120 scientific papers and 16 Astheusuallengthofdentaltreatmentisapproximately
chapters in various medical and dental journals and 44 minutes, the short-duration anesthetics fail to meet the
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textbooks in the areas of physical evaluation, emergency pain control needs of many patients.
medicine, local anesthesia, sedation, and general anesthesia. The intermediate-duration category is most often used.
He authored the textbooks Handbook of Local Anesthesia With the inclusion of a vasopressor (epinephrine or
(5th ed.), Emergency Medicine in Dentistry (6th ed.), and levonordefrin [in the US]), the drugs in this group provide
Sedation: A Guide to Patient Management (4th ed.). He can pulpal anesthesia of approximately 60 minutes’ duration.
be reached at (213) 740-1081 or malamed@usc.edu. Intermediate-duration drugs include articaine HCl 4% with
epinephrine 1:100,000 and 1:200,000; lidocaine HCl 2% with
Disclosure: Dr. Malamed is a paid consultant for Novalar epinephrine 1:50,000 and 1:100,000; mepivacaine HCl 2%
Pharmaceuticals, Inc. with levonordefrin 1:20,000 (with epinephrine 1:100,000 in
Canada);and prilocaine HCl 4% with epinephrine 1:200,000.
INTRODUCTION Table 1 summarizes these drugs based upon expected
duration of pulpal anesthesia.
Local anesthesia (LA) forms the backbone of pain control It is pulpal anesthesia that allows the doctor to
techniques in dentistry. The introduction of lidocaine painlessly treat the tooth. Anesthesia of the associated soft
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Continuing Education
Local Anesthesia Reversal
tissues occurs hand-in-hand with pulpal anesthesia. usually limited to nerve blocks (inferior alveolar [Gow-
Though necessary for many treatments such as curettage, Gates]), large areas of STA develop along with the desired
periodontal surgery, extractions, implants, and subgingival pulpal anesthesia.The anterior two thirds of the tongue, the
tooth preparation, in order for these procedures to be lower lip, and cheek are left without sensation for many
completed painlessly, the duration of STA is of considerably hours following completion of dental treatment.
longer duration than that of pulpal anesthesia, averaging 3 to Recently, new techniques (actually the reinvention of very
5 hours in the intermediate-duration group of LAs (Table 1). old techniques) have been introduced which provide localized
Another factor determining not just the duration of areasofpulpalanesthesiawithaminimumofassociatedSTA.
anesthesia but its extent is the choice of local anesthetic These include the periodontal ligament (PDL) injection (also
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technique. For example, following a maxillary infiltration known as the intraligamentary injection (ILI) and the
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over the lateral incisor, the tooth will be anesthetized (pulpal intraosseous injection. Anesthesia of the tongue or lip is
anesthesia) along with the localized soft tissues in that essentially nonexistent following these injections.
area, such as those in the buccal fold and the lip. Following
the anterior superior alveolar nerve block a large area on RESIDUALSTA
the anterior portion of the maxilla, including the lower eyelid
to the lateral border of the nose to the upper lip extending The long duration of residual STA may be desirable
from the midline to the corner of the mouth on that side, will following some dental treatments; examples include
beanesthetized. surgical procedures (oral surgical, periodontal, and
In the mandible, where anesthesia in the adult is endodontic). However, most operative dental care requires
Table 1. Expected Durations of Pulpal and SoftTissue Anesthesia (STA)
Vasopressor Pulpal anesthesia (minutes) STA (minutes)
SHORT-DURATION
Mepivacaine hydrogen None 20to30(infiltration) 90to120
chloride (HCl) 30to45(nerveblock)
Prilocaine HCl None 10to15(infiltration) 60to120(infiltration)
45to65(nerveblock) 120to240(nerveblock)
INTERMEDIATE-DURATION
Articaine HCl 1:100,000 60(infiltration) 180to240
1:200,000 up to 120 (nerve block)
Lidocaine HCl 1:50,000 55to65(infiltration) 180to300
1:100,000 80to90(nerveblock)
Mepivacaine HCl 1:20,000 levonordefrin 40to60(infiltration) 180to300
60to90(nerveblock)
Prilocaine HCl 1:200,000 35to45(infiltration) 180to480
50to70(nerveblock)
LONG-DURATION
Bupivacaine HCl 1:200,000 Upto7hours(infiltration) 240to720
Upto7hours(nerve block)
Sources: Malamed SF. Handbook of local anesthesia. 5th edition. St. Louis, Mo: CV Mosby; 2003;79 and Malamed SF,Yagiela JA.Pain Control in Dentistry. ADA News.
September 2007 (supplement).
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Continuing Education
Local Anesthesia Reversal
profound anesthesia (pulpal) during the relatively brief
treatment period while the patient is in the dental chair.
Once treatment is completed there is no longer a need for
continued anesthesia of the tissues, either hard or soft.
However, the need for effective intraoperative pain control Figure 1.
normally mandates the use of LA containing a vasopressor Soft-tissue injury
such as epinephrine or levonordefrin, which has become following inferior
a routine part of dentistry.5,6 Patients are commonly alveolar nerve block.
discharged from the dental office with residual numbness to
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their lips and tongue, typically persisting for 3 to 5 hours. Table 2. Incidence of Lip Injury
Residual STA presents as an inconvenience or Following Inferior Alveolar Nerve Block
embarrassment to the patient who is unable to function
normally for many hours after leaving the dental Age (years) %with soft tissue injury to lip
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appointment. In a survey by Rafique, et al of patients
receiving intraoral LA, the authors stated that there were <4 18
several aspects of the post-LA experience that were 4to7 16
disliked by patients, including 3 major areas—functional, 8to11 13
sensory, and perceptual.
Functionally, the patients disliked their diminished >12 7
ability to speak (lisping), to smile (asymmetric), to drink Source: College C, Feigal R, Wandera A, Strange M. Bilateral versus
(liquid runs from the mouth), and the inability to control unilateral mandibular block anesthesia in a pediatric population.
drooling while still numb. Sensorially, the lack of sensation Pediatr Dent. 2000;22:453-457.
was described as quite discomforting, while the perception
that their body was distorted (eg, swollen lips) was equally
unpleasant. For many patients these sequelae become a hurts, and then test the still-numb side—which doesn’t hurt.
significant detriment to their quality of life, making it difficult Where the adult would normally not proceed beyond this
for them to return to their usual activities for hours after point, the younger child may “play” with this “feeling” and
treatment. When the dental appointment concludes at a continue to bite ever harder and harder, not realizing the
time approaching a meal, either lunch or dinner, patients damage that is being inflicted. Mentally handicapped adults
must consider whether to eat while numb or postpone their are just as likely to incur self-inflicted soft-tissue injury. This
dining until the residual STA resolves. author was surprised to learn from dentists who treat geriatric
Though not normally a significant problem, residual STA patients that another group—the geriatric patient with
may occasionally lead to self-inflicted injury in any patient. dementia—presents a risk of soft-tissue injury following LA
Self-inflicted injury to soft tissues—most commonly the lip or injection equal to or greater than that of children and mentally
tongue—is more apt to be noted in younger children and in challenged adults.
1,9
mentally disabled adult and pediatric patients (Figure 1).
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A study of pediatric patients by College, et al revealed HOWLASWORK—ANOVERVIEW
that a significant percentage of inferior alveolar nerve
blocks were associated with inadvertent biting of the lips. By In a simplistic description of how LAs work to block nerve
age group, the frequency of trauma to the lips was 18% (< 4 conduction and prevent pain, consider a dynamite stick and
years), 16% (4 to 7 years), 13% (8 to 11 years), and 7% (> 12 a fuse (Figure 2). The dynamite stick represents the brain
years) (Table 2). This can be explained by the fact that the (central nervous system); the fuse the peripheral nerve, for
younger patient will test (by biting) their un-numb lip—which example the inferior alveolar nerve. When the fuse is lit
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