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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 APeer-Reviewed CEActivity by Approved PACE Program Provider FAGD/MAGDCredit Approval Dentistry Today, Inc, is an ADA CERP Recognized Provider. ADA CERP is does not imply acceptance a service of the American Dental Association to assist dental professionals by a state or provincial board of in indentifying quality providers of continuing dental education. ADA CERP dentistry or AGD endorsement. does not approve or endorse individual courses or instructors, nor does it June 1, 2009 to May 31, 2011 imply acceptance of credit hours by boards of dentistry. Concerns or AGDPaceapproval number:309062 complaints about a CE provider may be directed to the provider or to ADACERPatada.org/goto/cerp. Opinions expressed by CE authors are their own and may not reflect those of Dentistry Today. Mention of specific product names does not infer endorsement by Dentistry Today. Information contained in CE articles and courses is not a substitute for sound clinical judgment and accepted standards of care. Participants are urged to contact their state dental boards for continuing education requirements. 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 1 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 2 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 1 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 3 technique. For example, following a maxillary infiltration known as the intraligamentary injection (ILI) and the 4 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). 2 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 7 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 8 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). 9 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 3
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