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Successful Local Anesthesia for Restorative and Endodontic Treatment
School of Dentistry
University of Alabama at Birmingham
February 2016
John Nusstein, DDS, MS
Professor and Chair, Division of Endodontics
The Ohio State University, Columbus, Ohio
Diplomate, American Board of Endodontics
Introduction
We have published a number of our anesthesia articles in the Journal of Endodontics. There are a number of reasons for this. The JOE is one of the most respected journals in dentistry. Additionally, in the past, oral surgeons have been the resource for local anesthesia. By publishing our articles in the JOE, the current knowledge endodontists have made us the authorities for local anesthesia. This should come as no surprise since we deal with failures of pulpal anesthesia on a daily basis. We should take advantage of this benefit by working with our referrals regarding the common problems they have with pulpal anesthesia in asymptomatic patients. The following information may be helpful to you and your referring dentists.
IMPORTANT CLINICAL FACTORS RELATED TO LOCAL ANESTHESIA
Before reviewing the specifics of local anesthesia, we would like to provide an overview of some factors that are important to clinical anesthesia.
How do we traditionally confirm anesthesia clinically? Traditional methods to confirm anesthesia usually involve questioning the patient (“Is your lip numb?"), soft tissue testing (e.g., lack of mucosal responsiveness to a sharp explorer), or simply commencing with treatment. The problem with these approaches is they may not be effective for determining pulpal anesthesia.1-4
Objective means of determining pulpal anesthesia in non-painful, vital teeth. A more objective measurement of anesthesia, in non-painful vital teeth, is obtained with an application of a cold refrigerant, or by using an electric pulp tester (EPT). Clinically, application of cold or the electric pulp tester can be used to test the tooth under treatment for pulpal anesthesia prior to beginning a clinical procedure.5-10
Determining pulpal anesthesia in painful, vital teeth. Clinically, after administration of local anesthesia, the cold or electric pulp tester can be used to test painful, vital teeth for pulpal anesthesia prior to beginning the endodontic procedure.5-12 If the patient responds positively to the stimulus, then pulpal anesthesia has not been obtained and supplemental anesthesia should be administered. However, in painful, vital teeth (eg., irreversible pulpitis), the lack of response to pulp testing may not guarantee pulpal anesthesia even if there is vital tissue present in the pulp chamber.5, 9, 10 Therefore, if a patient experiences pain when the endodontic procedure is started, after negative pulp testing, supplemental anesthesia is indicated.
Naturally, if the chamber is necrotic and the canals are vital, no objective test can predict the level of clinical anesthesia. However, as suggested by Hsiao-Wu, et al.10, cold testing adjacent teeth for anesthesia may provide evidence of anesthesia in the working area.
Previous Difficulty with Anesthesia. Patients who report a history of previous difficulty with anesthesia are more likely to experience unsuccessful anesthesia.13 These patients will generally identify themselves with comments such as "Novocaine doesn’t work on me" or "A lot of shots are needed to get my teeth numb." A good clinical practice is to ask the patient if they have had previous difficulty achieving clinical anesthesia. If they have had these experiences, supplemental injections should be considered.
Red Haired Patients. Red hair is a phenotype for melanocortin-1 receptor gene, which is associated with red hair, fair skin, and freckles. There is evidence in medicine that these patients may be more resistant to anesthetic agents.13a,b However in dentistry, red hair was unrelated to success rates of the inferior alveolar nerve block.13c Red hair was associated with higher levels of dental anxiety.13c
MANDIBULAR ANESTHESIA – Restorative Dentistry
Conventional Inferior Alveolar Nerve Block
As a frame of reference, we will review the expected outcomes following administration of a conventional inferior alveolar nerve block, to asymptomatic patients, using 1.8 mL of 2% lidocaine with 1:100,000 epinephrine. While anesthesia requirements vary between dental procedures, the following discussion will concentrate on pulpal anesthesia.
Anesthetic Success
One way to define anesthetic success is the percentage of subjects who achieve two consecutive 80 readings (EPT) within 15 minutes and continuously sustain this lack of responsiveness for 60 minutes.1-4, 20-24 In other words, the objective is to achieve anesthesia within 15 minutes and have anesthesia that lasts 1 hour. This objective is equally important to restorative dentistry as it is for endodontic treatment. What then is the percentage of anesthetic success? For the first molar it was 53%, for the first premolar it was 61%, and for the lateral incisor it was 35%.1-4, 20-24 Therefore, success occurs most often in the molar and premolar teeth. It is important to realize that 100% of the subjects in these studies1-4, 20-24 had profound lip numbness.
Anesthetic Failure
Anesthetic failure has been defined as the percentage of subjects who never achieved two consecutive 80 EPT readings at any time during a 60-minute period. These patients have the highest potential for pain during a dental procedure. How often does failure occur? For the first molar it was 17%, for the first premolar it was 11%, and for the lateral incisor it was 32%.1-4, 20-24 Again, 100% of these subjects had profound lip numbness.
Slow Onset
In most cases following the conventional inferior alveolar nerve block injection, the onset of pulpal anesthesia usually occurs within 15-16 minutes.1-4, 20-25 However, in some patients onset will be delayed. Slow onset is defined as the percentage of subjects who achieved an 80 EPT reading after 15 minutes. Slow onset occurs about 19-27% of the time in mandibular teeth; about 8% of patients have onset after 30 minutes.1-4, 20-25 In contrast to the onset of pulpal anesthesia, the onset of lip numbness occurs usually within 5-9 minutes.1-4
Duration
Duration of pulpal anesthesia in the mandible is very good.1-4, 20-24 Therefore, if patients are anesthetized initially, anesthesia usually persists for approximately 2 1/2 hours with 2% lidocaine with 1:100,000 epinphrine.23
What Does Lip Numbness Mean?
The presence of soft tissue anesthesia (usually measured by “lip numbness” or lack of mucosal responsiveness to a sharp explorer) does not adequately indicate pulpal anesthesia.1-4, 20-24 This is in contradiction to the traditional view. However, the lack of soft tissue anesthesia is a useful indicator that the block injection was not administered accurately for that patient.
How often do missed blocks occur? A missed block is defined as not obtaining profound lip numbness within 15-20 minutes following an IAN block. Pulpal anesthesia will NOT be present with a missed block. We studied missed blocks in over 3,000 asymptomatic subjects and in emergency patients presenting with symptomatic irreversible pulpitis.25a What did we find? The incidence of missed blocks for asymptomatic subjects was 6% for the one-cartridge volume and 4% for the two-cartridge volume. For patients presenting with irreversible pulpitis, the incidence of missed blocks was 8% for the one-cartridge volume and 2% for the two-cartridge volume. In both asymptomatic subjects and patients with irreversible pulpitis, the two-cartridge volume was significantly better than the one-cartridge volume.
Alternate Anesthetic Solutions for the Inferior Alveolar Nerve Block
Plain Solutions: 3% Mepivacaine (Carbocaine®, Polocaine®, Scandonest®) and 4% Prilocaine (Citanest Plain®).
McLean and co-authors,2 in an experimental study, have shown that 3% mepivacaine plain and 4% prilocaine plain are as effective as 2% lidocaine with 1:100,000 in an inferior alveolar nerve block. Cohen et al.12 in a clinical study of patients with irreversible pulpitis, also found that 3% mepivacaine and 2% lidocaine with 1:100,000 epinephrine were equivalent for inferior alveolar nerve blocks. Clinically, this is an important finding because when medical conditions or drug therapies suggest caution in administering epinephrine-containing solutions, 3% mepivacaine can be used as an alternative.
4% Prilocaine with 1:200,000 epinephrine (Citanest Forte®) and 2% Mepivacaine with 1:20,000 Levonordefrin (Carbocaine with Neo-Cobefrin®)
Hinkley and co-authors 4 in an experimental study, have shown that 4% prilocaine with 1:200,000 epinephrine and 2% mepivacaine with 1:20,000 levonordefrin are equivalent to 2% lidocaine with 1:100,000 in an inferior alveolar nerve block in achieving pulpal anesthesia.
Levonordefrin has 75% α activity and only 25% β activity making it seemly more attractive than epinephrine (50% α activity and 50% β activity).26 However, levonordefrin is marketed as a 1:20,000 concentration in dental catridges.26 Clinically, the higher concentration of levonordefrin makes it equipotent to epinephrine in clinical and systemic effects.4, 27 Therefore, 1:20,000 levonordefrin offers no clinical advantage over 1:100,000 epinephrine.
Articaine with 1:100,000 epinephrine (Septocaine, Zorcaine, Articadent)
Articaine was approved for use in the United States in April 2000.28 The formulation is available as a 4% solution with 1:100,000 and 1:200,000 epinephrine. Articaine is classified as an amide and contains a thiophene ring instead of a benzene ring like other amide local anesthetics.28 A second molecular difference between articaine and other amide local anesthetics is the extra ester linkage incorporated into the articaine molecule,28 which results in hydrolysis of articaine by plasma esterases.
A number of studies28-36 have evaluated articaine and have concluded that it is safe when used in appropriate doses. Both lidocaine and articaine have the same maximum milligram dose of 500 mg (recommended dose of 6.6 to7 mg/kg) for the adult patient.26 Because articaine is marketed as a 4% solution, the maximum manufacturer’s recommended dose for a healthy 70 kg adult would be 7 cartridges of an articaine solution compared to 13 cartridges of a 2% lidocaine solution.26
Paresthesia and methemoglobinemia with articaine.
Articaine, like prilocaine, has the potential to cause methemoglobinemia and neuropathies.28 While the incidence of methemoglobinemia is rare, dentists should be aware of this complication in patients who are at an increased risk of developing this condition.37 Haas and Lennon38 and Miller and Lennon39 investigated the incidence of local anesthetic-induced neuropathies. The incidence of neuropathies (which involved the lip and or tongue) associated with articaine and prilocaine was approximately five times that found with either lidocaine or mepivacaine.39 In the Haas and Lennon retrospective study,38 the incidence of paresthesia was only 14 cases out of 11 million injections or approximately one in 785,000 injections. Therefore, according to these studies, the paresthesia incidence is higher for articaine and prilocaine, but it is still a clinically rare event. Pogrel40 evaluated patients referred with a diagnosis of damage to the inferior alveolar and/or lingual nerve which could only have resulted from an inferior alveolar nerve block. He found 35% were caused by a lidocaine formulation and 30% were caused by an articaine formulation. He concluded there was not a disproportionate nerve involvement from articaine. Therefore, fear of paresthesia should not limit the use of articaine clinically.
Insurance Carrier Hysteria with Articaine
A letter was sent to thousands of U.S. dentists by Emery and Webb/ACE USA stating – “…we have noticed an increase in reversible and, in some cases, nonreversible paresthesias [with Septocaine]. …We are writing you to alert you to these events in hopes that you will not fall victim to one of these incidents.”.41 Knowledgeable dentists and educators communicated their concerns and a Notice of Retraction was issued – “Unfortunately, we at Emery & Webb discovered upon further review, and subsequent to the mailings, that both documents contained inaccuracies and an alarmist tone, which was not warranted.” “Emery and Webb has not noted an increase in malpractice claims or lawsuits in connection with articaine… It should be made clear that Emery and Webb has not conducted any scientific investigation, sampling, testing, or other investigation of the articaine anesthetic, and has no independent knowledge or data which would restrict the use of the product.” 41
We must also be very careful of Web chat sites and colleagues’ clinical endorsements because they may not accurately reflect the correct information regarding articaine.
Clinical effectiveness of articaine for Inferior Alveolar Nerve Blocks and Maxillary Infiltration
Articaine has a reputation of providing an improved local anesthetic effect.42 The available literature indicates that articaine is equally effective when statistically compared to other local anesthetics for nerve blocks.36, 43-50 When comparing the anesthetic efficacy of 4% articaine with 1:100,000 epinephrine to 2% lidocaine with 1:100,000 epinephrine for inferior alveolar nerve blocks, Mikesell and co-authors49 found that the two solutions were not significantly different. Tofoli et al.51 found that 4% articaine with 1:100,000 epinephrine was equivalent to 4% articaine with 1:200,000 epinephrine in inferior alveolar nerve blocks. Moore et al.52 found no difference in clinical efficacy between 4% articaine with 1:100,000 and 1:200,000 epinephrine in clinical studies. However, for maxillary periodontal surgery, Moore et al.53 found the 1:100,000 epinephrine concentration for 4% articaine provided better visualization of the surgical field and less bleeding. In summary, repeated clinical trials have failed to demonstrate any statistical superiority of articaine over lidocaine for nerve blocks.
Long-Acting Anesthetic Agents
Clinical trials with bupivacaine (Marcaine, Vivacaine) and etidocaine (Duranest) have been performed in oral surgery,54, 55 endodontics,56, 57 and periodontics.58, 59 Etidocaine has been withdrawn from the market by Dentsply Pharmaceuticals. Bupivacaine provides a prolonged analgesic period and is indicated when postoperative pain is anticipated. However, not all patients want lip numbness for extended periods of time55 and patients should be questioned regarding their preference. Bupivacaine, as compared to lidocaine, has been shown to have a somewhat slower onset but almost double the duration of pulpal anesthesia (approximately 4 hours), in the mandible.23
A relatively new long-acting local anesthetic is ropivacaine (Naropin®). It is a structural homologue of bupivacaine.60 A number of studies have demonstrated that ropivacaine has a lower potential for central nervous system and cardiovascular toxic effects than bupivacaine.60 Kennedy and co-authors60 concluded that 0.5% ropivacaine with 1:200,000 epinephrine was equivalent to 0.5% bupivacaine with 1:200,000 epinephrine in pharmacologic action. El-Sharrawy and Yagiela61 found that 0.5% and 0.75% concentrations of ropivacaine without epinephrine were effective for inferior alveolar nerve blocks. Another study62 evaluated levobupivacaine for inferior alveolar nerve blocks and found it was equivalent to bupivacaine. Therefore, ropivacaine and levobupivacaine have the potential to replace bupivacaine, in clinical dental practice, due to the decreased potential for cardiac and central nervous system toxicity.
Alternate Injection Locations
Gow-Gates and Vazirani-Akinosi techniques
The Gow-Gates technique63 has been reported to have a higher success rate than the conventional inferior alveolar nerve block.26, 64 However, experimental studies have failed to show that the Gow-Gates technique is superior.25, 65-67,68 The Vazirani-Akinosi26, 69 technique has not been found to be superior to the standard inferior alveolar injection.65, 70-72 Neither technique is better than the inferior alveolar nerve block in reducing the pain of injection.73 These techniques do not replace the conventional inferior alveolar nerve block. The Vazirani-Akinosi technique is indicated when there is limited mandibular opening (for example, trismus).