Mandibular Anesthesia, Endodontic Anesthesia, Intraosseous ...



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).

Aggarwal and co-authors73a found the Gow-Gates technique was better (52%) than the inferior alveolar nerve block (36%) in patients with irreversible pulpitis. However, the numbers in Aggarwal’s study were small which may have affected the results.

Recently, Click and co-authors73b studied patients presenting with symptomatic irreversible pulpitis and found subjective lip numbness was obtained 92% of the time with the Gow-Gates technique and 63% of the time with the Vazirani-Akinosi technique. The difference was statistically significant (P=.0001). For the patients achieving lip numbness, successful pulpal anesthesia was obtained 35% of the time with the Gow-Gates technique and 16% of the time with the Vazirani-Akinosi technique. The difference was statistically significant (P=.0381). They concluded for patients who achieved lip numbness, neither the Gow-Gates or Vazirani-Akinosi techniques provided adequate pulpal anesthesia for mandibular posterior teeth in patients presenting with symptomatic irreversible pulpitis. Both injections would require supplemental anesthesia. Though this study demonstrated that the Vazirani-Akinosi technique may not be indicated for routine endodontic treatment, it certainly has a useful indication clinically. If a patient experiencing trismus is in need of endodontic treatment, the Vazirani-Akinosi injection may be a valuable primary anesthetic technique. Because the muscles of mastication protectively guard painful mouth opening in patients, the Vazirani-Akinosi technique can result in facilitated mouth opening due to anesthesia of the ipsilateral muscles of mastication or anesthesia of the inflamed/infected tissue. Once an increased opening is achieved, a conventional inferior alveolar nerve block may be administered to the trismus patient if needed.

Incisive Nerve Block at the Mental Foramen Nist and co-authors,74 Joyce and Donnelly,75 Whitworth and co-authors,75a and Dressman and co-authors75b demonstrated the incisive nerve block alone (or an infiltration at the apex of the second molar) was moderately successful in anesthetizing the premolar teeth – but pulpal anesthesia declined after 20-25 minutes. Nist et al.74 and Dressman et al.75b showed that the technique did not anesthetize the central and lateral incisors.

Mandibular Infiltration of a Lidocaine Solution

Labial or lingual infiltrations of a lidocaine solution alone are not very effective for pulpal anesthesia in mandibular teeth.45, 46, 76 A combination of a labial and lingual infiltration will significantly increase success in anterior teeth over either a labial or lingual infiltration alone.77

Meechan et al.78 using 1.8 mL of 2% lidocaine with 1:100,000 epinephrine for either a buccal or buccal plus lingual infiltration of the mandibular first molar resulted in a 32 to 39% success rate (no response to pulp testing).

Mandibular Infiltration of a Lidocaine Solution Following an Inferior Alveolar Nerve Block

Adding a labial infiltration (1.8ml of 2% lidocaine with 1:100,000 epinephrine) to a conventional inferior alveolar injection increases the success of anterior pulpal anesthesia.79

Foster et al.80 found that adding a labial or lingual infiltration injection, using 1.8 mL of 2% lidocaine with 1:100,000 epinephrine, after an inferior alveolar nerve block did not significantly result in more profound anesthesia in the first molar.

Mandibular First Molar Infiltration of an Articaine Solution

One study81 showed articaine was significantly better than lidocaine for a primary buccal infiltration of the mandibular first molar. Articaine only had a 64% success rate (two consecutive 80 readings with the electric pulp tester). Jung et al.82 and Corbett et al.82a also used a primary first molar buccal infiltration of an articaine formulation and found a 54% and 64 to 70% success rate respectively. Another study83 found an 87% success rate (two consecutive 80 readings with the electric pulp tester) for a primary articaine buccal infiltration of the mandibular first molar versus a 57% success rate for a lidocaine solution. The duration of pulpal anesthesia declined over 60 minutes for both anesthetic solutions. Nydegger and co-authors83d found that a 4% articaine formulation was statistically better than both 4% lidocaine and 4% prilocaine formulations for buccal infiltration of the mandibular first molar in asymptomatic mandibular first molars. Rather than a 4% concentration, it is likely the chemical structure of articaine results in better anesthesia for mandibular buccal infiltrations. However, the success rate of 55% was not high enough to support its use as a primary buccal infiltration technique in the mandibular first molar. Therefore, the superiority of articaine over lidocaine may be related to the intramolecular hydrogen bonding allowing better bone penetration.83a

Mandibular Incisor Infiltration of an Articaine Solution

Jaber et al.83b found 4% articaine was more effective than 2% lidocaine (both with 1:100,000 epinephrine) in anesthetizing mandibular incisor teeth after labial or labial plus lingual infiltrations. However, neither solution sustained anesthesia for 45 minutes. Nuzum and co-authors83c found the labial infiltration of a cartridge of 4% articaine with 1:100,000 epinephrine plus a supplemental lingual infiltration of a cartridge of 4% articaine with 1:100,000 epinephrine significantly improved the success rate (no response to two consecutive 80 readings with the pulp tester) to 98% when compared to a labial infiltration of a cartridge of the same articaine formulation (76% success). The combination labial and lingual infiltrations did not provide pulpal anesthesia for an hour. An option would be to administer an inferior alveolar nerve block and then add articaine infiltrations in the anterior teeth to increase success.

Mandibular First Molar Infiltration of an Articaine Solution Following an Inferior Alveolar Nerve Block in Asymptomatic Subjects

Haase et al.84 in a prospective, randomized, double-blind, crossover study comparing the degree of pulpal anesthesia achieved by means of mandibular first molar buccal infiltrations of two anesthetic solutions: 4% articaine with 1:100,000 epinephrine and 2% lidocaine with 1:100,000 epinephrine following an inferior alveolar nerve block found 4% articaine with 1:100,000 epinephrine, resulted in a higher success rate (88%) than 2% lidocaine with 1:100,000 epinephrine (71% success rate). Success was defined as achieving two consecutive 80 readings within 10 minutes following the inferior alveolar nerve block plus infiltration injections and the 80 reading was continuously sustained through the 60th minute.

Kanaa et al.84a found a 91% success rate (two consecutive 80 readings with a pulp tester) of the mandibular first molar when 4% articaine with 1:100,000 epinephrine was added as a supplemental buccal infiltration after an inferior alveolar nerve block.

Methods That Have Tried to Increase Success of the Inferior Alveolar Nerve Block for Restorative Dentistry

Increasing the Anesthetic Volume

One potential method to increase anesthetic success is to double the injection volume of local anesthetic solution. However, increasing the volume of 2% lidocaine with epinephrine to 3.6 ml (two cartridges) does not increase the incidence of pulpal anesthesia with the inferior alveolar nerve block1, 24, 87-89.

Increasing the Epinephrine Concentration

A second approach for increasing the success of inferior alveolar nerve blocks is to increase the concentration of epinephrine. However, when evaluated in clinically normal teeth, there was no advantage to using a higher concentration (1:50,000) of epinephrine in an inferior alveolar nerve block.21, 90

Does the combination of 3% mepivacaine plain (Carbocaine) plus 2% lidocaine with epinephrine improve anesthesia and reduce the pain of anesthetic injection for the inferior alveolar nerve block? Three percent mepivacaine plain has a higher pH and concentration than 2% lidocaine with epinephrine. In theory, using 3% mepivacaine initially for an inferior alveolar nerve (IAN) block would decrease the pain of injection, provide faster onset, increase success, and possibly potentiate the effect of a second cartridge of 2% lidocaine with epinephrine. Lammers and co-authors90a found The combination of 3% mepivacaine plus 2% lidocaine with 1:100,000 epinephrine was equivalent to the combination of two cartridges of 2% lidocaine with 1:100,000 epinephrine in terms of injection pain, onset time, and pulpal anesthetic success for the IAN block.

Diphenhydramine as a Local Anesthetic Agent

DIPHENHYDRAMINE (BENADRYL) HAS BEEN ADVOCATED FOR PATIENTS WHO ARE ALLERGIC TO COMMONLY USED LOCAL ANESTHETICS. TWO STUDIES91, 92 FOUND DIPHENHYDRAMINE WAS LESS EFFECTIVE THAN LIDOCAINE FOR EXTRACTIONS. WILLETT AND CO-AUTHORS93 FOUND THE COMBINATION OF LIDOCAINE/DIPHENHYDRAMINE WITH EPINEPHRINE AND DIPHENHYDRAMINE WITH EPINEPHRINE WERE SIGNIFICANTLY LESS EFFECTIVE FOR PULPAL ANESTHESIA THAN LIDOCAINE WITH EPINEPHRINE FOR INFERIOR ALVEOLAR NERVE BLOCKS. THEY ALSO FOUND THAT THE DIPHENHYDRAMINE SOLUTIONS WERE MORE PAINFUL UPON INJECTION AND HAD A HIGH INCIDENCE OF MODERATE POSTOPERATIVE PAIN.

ADDING HYALURONIDASE TO A LOCAL ANESTHETIC

HYALURONIDASE DECREASES THE VISCOSITY OF THE INJECTED TISSUE PERMITTING A WIDER SPREAD OF INJECTED FLUIDS. RIDENOUR AND CO-AUTHORS93A FOUND THAT ADDING HYALURONIDASE TO A LIDOCAINE SOLUTION WITH EPINEPHRINE DID NOT STATISTICALLY INCREASE THE INCIDENCE OF PULPAL ANESTHESIA IN INFERIOR ALVEOLAR NERVE BLOCKS. ANOTHER PROBLEM WE FOUND WAS THE COMBINED LIDOCAINE/HYALURONIDASE SOLUTION RESULTED IN A SIGNIFICANT INCREASE IN POSTOPERATIVE PAIN AND TRISMUS.

Adding Demerol to a Local Anesthetic

INVESTIGATIONAL AND CLINICAL STUDIES IN MEDICINE HAVE SHOWN MEPERIDINE (DEMEROL) HAS A LOCAL ANESTHETIC EFFECTS AND MAY NOT COMPETE FOR THE SAME BINDING SITE AS LIDOCAINE. THEREFORE, THERE IS A POTENTIAL FOR ENHANCEMENT OF A LOCAL ANESTHETIC EFFECT IF LIDOCAINE IS COMBINED WITH MEPERIDINE. HOWEVER, GOODMAN AND CO-AUTHORS93B FOUND THAT A MEPERIDINE/LIDOCAINE COMBINATION WAS INFERIOR TO THE USE OF A LIDOCAINE SOLUTION ALONE IN INFERIOR ALVEOLAR NERVE BLOCKS.

How about Carbonating a Local Anesthetic?

EXPERIMENTALLY, HYDROCARBONATED ANESTHETIC SOLUTIONS ARE SUPPOSEDLY MORE EFFECTIVE DUE TO THE TRAPPING OF THE ANESTHETIC WITHIN THE NERVE. ADDITIONALLY, CO2 HAS A SYNERGISTIC RELATIONSHIP TO LOCAL ANESTHETICS AND A DIRECT DEPRESSANT ACTION ON NERVES. HOWEVER, CHANEY AND CO-AUTHORS93C WERE NOT ABLE TO DEMONSTRATE A SUPERIOR EFFECT OF LIDOCAINE HYDROCARBONATE IN INFERIOR ALVEOLAR NERVE BLOCKS. A HYDROCARBONATED SOLUTION HAS A HIGHER CONCENTRATION OF CARBON DIOXIDE THAN A SOLUTION BUFFERED WITH SODIUM BICARBONATE.

Buffering a Local Anesthetic

THERE ARE A NUMBER OF STUDIES IN MEDICINE THAT HAVE FOUND A FASTER ONSET OF ANESTHESIA AND LESS PAIN WITH BUFFERED ANESTHETIC SOLUTION. WHITCOMB AND CO-AUTHORS93D COMPARED THE DEGREE OF PULPAL ANESTHESIA OBTAINED WITH 2% LIDOCAINE WITH 1:100,000 EPINEPHRINE/SODIUM BICARBONATE (8.4%) VERSUS 2% LIDOCAINE WITH 1:100,000 EPINEPHRINE IN AN INFERIOR ALVEOLAR NERVE BLOCK. THEY REPORTED THAT BUFFERING 2% LIDOCAINE (WITH 1:100,000 EPINEPHRINE) WITH SODIUM BICARBONATE DID NOT STATISTICALLY INCREASE ANESTHETIC SUCCESS, PROVIDE A FASTER ONSET, OR DECREASE PAIN OF INJECTION WHEN COMPARED TO UNBUFFERED 2% LIDOCAINE WITH 1:100,000 EPINEPHRINE FOR AN INFERIOR ALVEOLAR NERVE BLOCK.

OnPharma has introduced a new system that buffers a local anesthetic solution using a unique dispensing system. A recent study170a using the Onpharma system for IAN blocks found a quicker onset time and less pain with injection for a buffered lidocaine formulation – which is completely different than Whitcomb’s study.93d Hobeich and co-authors170b found buffering did not result in faster onset times or decreased pain of injection for maxillary infiltration.

Studies Evaluating Mechanisms of Failure with the Inferior Alveolar Nerve Block

Accessory Innervation

Judging from clinical and anatomical studies,94, 95 the mylohyoid nerve is the accessory nerve most often cited as a cause for failure with mandibular anesthesia. Clark et al.88 compared the inferior alveolar nerve block alone to a combination injection of the inferior alveolar nerve block plus the mylohyoid nerve block, which was aided by the use of a peripheral nerve stimulator. The investigators found that the mylohyoid injection did not significantly enhance pulpal anesthesia of the inferior alveolar nerve block. Therefore, the result of the study does not lend much credibility to the notion that the mylohyoid nerve is a major factor in failure with the inferior alveolar nerve block.

Accuracy of the injection

It has been theorized that an inaccurate injection contributes to inadequate mandibular anesthesia. Hannan and co-authors 20 used a medical ultrasound unit to guide needle placement for inferior alveolar nerve blocks. While they found that the nerve block administered with ultrasound was accurate, it did not result in more successful pulpal anesthesia. Another study used a peripheral nerve stimulator to locate the inferior alveolar nerve but it was not any more successful than a standard block.22 Therefore, accuracy of needle placement is not the primary reason for anesthetic failure with this block. Two studies performed thirty years ago reached similar conclusions. Berns and Sadove,96 and Galbreath97 used radiographs to locate the mandibular foramen and found that accurate needle location did not guarantee successful anesthesia. Twenty-five percent of accurate blocks resulted in anesthetic failure. The authors speculated that migration of the anesthetic solution followed the path of least resistance and this was determined by fascial planes and structures encountered in the pterygomandibular space. These studies provide an important clinical point – the lack of pulpal anesthesia is not necessarily due to an inaccurate injection.

Needle Deflection.

Needle deflection has been theorized as a cause for failure with the inferior alveolar nerve block.98-100 Various authors,98-103 using in vitro methods, have reported that beveled needles, when passed through substances of varying densities, will deflect toward the non-beveled side. That is, the needle will deflect away from the bevel. Recently, Hochman and Friedman100 developed a bi-directional needle rotation technique using the computer-assisted Wand (CompuDent, Milestone Scientific Inc., Deerfield, IL). The bi-directional technique rotates the Wand handpiece assembly and needle in a manner similar to rotation of an endodontic hand file. The technique was found to reduce needle deflection during needle insertion. Kennedy et al.104 compared the anesthetic efficacy of the conventional inferior alveolar nerve block, administered with the needle bevel oriented away from the mandibular ramus (so the needle would deflect toward the mandibular foramen), to the bi-directional needle rotation technique, administered using the computer-assisted Wand anesthesia system, in patients diagnosed with irreversible pulpitis. There were no significant differences between the success rates (50% for the conventional and 56% for the bi-directional technique) of the two techniques. Neither technique resulted in an acceptable rate of anesthetic success in patients with irreversible pulpitis.

Needle Bevel and Success

In asymptomatic subjects, Steinkruger and co-authors105 found the orientation of the needle bevel (away or toward the mandibular ramus) for an inferior alveolar nerve block did not affect anesthetic success or failure. Therefore, the use of commercial needles with markers to indicate needle bevel is not necessary.

Cross Innervation

Cross innervation from the contralateral inferior alveolar nerve has been implicated in failure to achieve anesthesia in anterior teeth after an inferior alveolar injection. Experimentally, cross innervation occurs in incisors89, 106 but plays a very small role in failure with the inferior alveolar nerve block.

Why don't asymptomatic patients achieve pulpal anesthesia with the inferior alveolar nerve block?

The central core theory 107, 108 may be our best explanation. The theory states that nerves on the outside of the nerve bundle supply molar teeth while nerves on the inside supply anterior teeth. The anesthetic solution may not diffuse into the nerve trunk to reach all nerves to produce an adequate block, even if deposited at the correct site. The theory may explain the higher experimental failure rates in anterior teeth with the inferior alveolar nerve block. 1-4, 20-25

Studies That Have Increased the Success of Mandibular Anesthesia in Restorative Dentistry

Use of a Supplemental Articaine Infiltration of the Mandibular First Molar Following an Inferior Alveolar Nerve Block

As discussed previously, Haase and Kanna and co-authors84, 84a found increased success. This approach would be the best for restorative dentistry in the first molar, premolars, and anterior teeth. However, the second molar may require a supplemental intraosseous injection.

Use of the Supplemental Intraosseous Injection

Dunbar,110 Guglielmo,27 Stabile111 and co-authors studied the contribution of the supplemental intraosseous injection after an inferior alveolar nerve block. Using common local anesthetic agents with vasoconstrictors and the Stabident intraosseous system, anesthetic success (no response to pulp testing) was significantly increased for 60 minutes in the first molar. The intraosseous injection was more successful than the periodontal ligament injection109 due to the greater amount of anesthetic solution delivered with the intraosseous injection. Additionally, the intraosseous injection significantly decreased the incidence of slow onset of pulpal anesthesia to 0% when compared to the inferior alveolar nerve block alone (18% incidence).110 Therefore, when pulpal anesthesia is required in asymptomatic teeth, the addition of the intraosseous injection to the inferior alveolar nerve block, in the first molar, will provide a quick onset and a high incidence of pulpal anesthesia for 60 minutes.

Gallatin and co-authors112 found that the use of 3% mepivacaine as a supplemental intraosseous injection following an inferior alveolar nerve block resulted in statistically increased pulpal anesthesia for 30 minutes. The shorter duration of the 3% mepivacaine, when compared to 2% lidocaine with 1:100,000 epinephrine,110 was related to the lack of a vasoconstrictor.

Use of the Supplemental Intraligamentary Injection

Childers and co-authors109 studied the contribution of the supplemental intraligamantary injection after an inferior alveolar nerve block. Using 2% lidocaine with 1:100,000 epinephrine and a high-pressure syringe, anesthetic success (no response to pulp testing) was significantly increased for 23 minutes in the first molar. The short incidence of anesthesia was related to the small amount of anesthetic solution administered.

Speed of Injection and Success

Kanaa and co-authors113 found a slow inferior alveolar nerve block injection (60 seconds) resulted in higher success rates (electric pulp testing) than a rapid injection (15 seconds). However, this was not true for patients diagnosed with irreversible pulpitis.113a

ENDODONTIC ANESTHESIA

Success of the Inferior Alveolar Nerve Block

Clinical studies in endodontics,9, 11, 12, 19, 50, 86, 131, 151, 153, 155 in patients with symptomatic irreversible pulpitis, have found success (mild or no pain upon endodontic access or initial instrumentation) with the inferior alveolar nerve block occurred between 19% and 56% of the time. These studies would indicate that anesthesia is often difficult to achieve in irreversible pulpitis with only the inferior alveolar nerve block. In patients presenting with asymptomatic irreversible pulpitis – that is, patients who have no spontaneous pain at the emergency visit, Argueta-Figueroa and co-authors167 found success rates were higher in these asymptomatic patients.

Why does anesthesia fail in patients with painful teeth? One explanation, as we discussed previously, is that conventional anesthetic techniques do not always provide profound pulpal anesthesia. One explanation, as we will discuss soon, is that conventional anesthetic techniques do not always provide profound pulpal anesthesia. Another explanation relates to the theory that the lowered pH of inflamed tissue reduces the amount of the base form of anesthetic to penetrate the nerve membrane. Consequently, there is less of the ionized form within the nerve to achieve anesthesia. However, this explanation of local influences on the anesthetic solution does not explain the mandibular molar with pulpitis, which is not readily blocked by an inferior alveolar injection administered at some distance from the area of inflammation. Therefore, it is difficult to correlate local influences with failure of the inferior alveolar nerve block. Another explanation for failure is that nerves arising from inflamed tissue have altered resting potentials and decreased excitability thresholds.14, 15 Modaresi, Wallace and co-authors 14,14a demonstrated that local anesthetic agents were not sufficient to prevent impulse transmission due to these lowered excitability thresholds. Another factor would be the tetrodotoxin-resistant (TTXr) class of sodium channels that have been shown to be resistant to the action of local anesthetics.16 A related factor is the increased expression of sodium channels in pulps diagnosed with irreversible pulpitis.17 And finally, patients in pain are often apprehensive, which lowers their pain threshold. Therefore, practitioners should consider supplemental techniques - such as intraosseous9, 11, 18, 19 or periodontal ligament injections12 when an inferior alveolar nerve block fails to provide pulpal anesthesia for patients with irreversible pulpitis.

It is not your fault! If there is one important fact that you need to remember, it is that patients DO NOT always achieve pulpal anesthesia in endodontics, but it is not your fault.

Success of Maxillary Molar Infiltration in Patients with Irreversible Pulpitis.

Endodontic clinical studies of maxillary, posterior buccal infiltrations in patients presenting with irreversible pulpitis have shown success occurs from 54% to 88% of the time.9,157,158 Srinivasan et al.85b found articaine was superior to a lidocaine formulation for maxillary buccal infiltrations in patients with irreversible pulpitis. However, the numbers were small in this study. Rosenberg, et al.85 and Sherman et al.85a found no significant differences between an articaine solution and a lidocaine solution when used as a maxillary infiltration, supplemental infiltration after inferior alveolar nerve blocks, or Gow-Gates injection in patients with irreversible pulpitis. However, the numbers were small in these studies. While some authors have found a difference between articaine and lidocaine,159 others have not.160,161

Kanaa and co-authors158 found no significant difference in success (no pain on access) between articaine (76% success) and lidocaine (70% success).

Success with Articaine for Inferior Alveolar Nerve Blocks in Patients With Irreversible Pulpitis. Success rates for the inferior alveolar nerve block using 4% articaine with epinephrine have ranged from 26% to 87%50b-i. Claffey and co-authors50 found an articaine solution had a success rate of 24% and a lidocaine solution had a success rate of 26%, with no significant difference between the solutions. Neither solution resulted in an acceptable rate of anesthetic success in patients with irreversible pulpitis. Tortamano and co-authors50a found similar results in patients with irreversible pulpitis.

Primary Infiltrations for Mandibular Anesthesia in Patients with Irreversible Pulpitis

Aggarwal and co-authors73a found a primary buccal plus lingual infiltration of articaine had only a 27% success rate in mandibular first and second molars for patients presenting with irreversible pulpitis.

SUPPLEMENTAL INJECTIONS

Supplemental injections are essential when, as frequently occurs, anesthesia from conventional injections is inadequate and the pain is too severe for the endodontist or dentist to proceed. There are four such supplemental techniques – infiltration of 4% articaine for mandibular posterior teeth, the intraligamentary injection, the intraosseous injection, and the intrapulpal injection.

If the patient has profound lip numbness and experiences pain upon endodontic access, repeating the inferior alveolar nerve block does not solve the problem.156 Kanaa and co-authors156 found only a 32% sucess rate for a repeat inferior alveolar nerve block. Clinicians may think that another injection is helpful because the patient sometimes achieves pulpal anesthesia after the second injection. However, the patient may just be experiencing slow onset of pulpal anesthesia. That is, the second injection does not provide additional anesthesia – the first injection is just “catching up” due to the slow onset of pulpal anesthesia.

Supplemental Infiltrations of Articaine for Mandibular Anesthesia in Patients with Irreversible Pulpitis

Supplemental Buccal, Lingual, or Buccal Plus Lingual Infiltrations of Articaine

While the infiltration of articaine is effective in restorative dentistry as a supplemental technique (following the inferior alveolar nerve block),84,84a its use in endodontically involved teeth will not result in predictable pulpal anesthesia.86,151,153 Success rates in studies have ranged from 38% to 84%,50b,50e,86,86b,151,152,153,156,162,162a with the majority of studies reporting success rates less than 60%.50b,86b,167,151,152,153,162 The reason for the higher success rates in some studies is related to not using patients with failed inferior alveolar nerve blocks. Therefore, it was not known how many of the patients would have been successfully anesthetized with the inferior alveolar nerve block alone. This omission in study design could have affected the results. There will be no difference between 1.8 mL and 3.6 mL of 4% articaine for supplemental buccal infiltrations.50d

Buccal infiltration alone, buccal plus lingual infiltrations alone (or following an inferior alveolar nerve block) will not result in complete pulpal anesthesia.86a,86b,86c,152,157,162,163

Therefore, the intraosseous and intraligamentary injections are the preferred techniques for supplemental anesthesia, with the intrapulpal injection being indicated when the intraosseous or intraligamentary injections are not successful.

Intraligamentary Injection

Success as a Primary Injection

For use as a primary injection, good success rates have been reported for restorative procedures. However, when compared to the inferior alveolar nerve block, the primary intraligamentary injection resulted in higher pain scores during treatment.114 There is more difficulty in achieving adequate pain control in extractions and endodontic treatment.115, 116 Malamed116 reported a 50% success rate in endodontics when the intraligamentary injection was used as a primary technique. Kaufman et al.,117 using a high-pressure syringe, found a 79% success rate in performing vital pulpectomies. Higher success rates have been shown in posterior teeth than anterior teeth.77, 118

Success as a Supplemental Injection in Endodontics

The success of supplemental intraligamentary injections in achieving pulpal anesthesia for endodontic procedures has been reported to be 50 to 96%.12, 119, 120 Walton and Abbott119 reported a 63% success rate of the supplemental intraligamentary injection during endodontic and restorative procedures. Re-injection, if the first intraligamentary injection failed, was shown to be successful in 71% of the patients for an overall success rate of 92%. Smith et al.120 reported similar results. Cohen et al.12 studied endodontic patients with irreversible pulpitis and found that a supplemental intraligamentary injection was 74% successful. Re-injection increased success to 96%. The intraligamentary injection will not be successful in mandibular anterior teeth.77, 118

Fan and co-authors86a found a 83% success rate with a supplemental intraligamentary injection of articaine in patients with irreversible pulpitis. However, Fan’s study did not use patients with failed inferior alveolar nerve blocks. Therefore, it was not known how many of the patients would have been successfully anesthetized with the inferior alveolar nerve block alone. This omission in study design could have affected the results. Kanaa and co-authors158 and Zarei and co-authors164 found a 48% and 70% success rate, respectively, for the intraligamentary injection after a failed inferior alveolar nerve block in patients with irreversible pulpitis.

Recently, Bangerter and co-authors,120a in a survey of endodontists (response rate of only 33%), found the intraligamentary injection was used more often than other intraosseous techniques – with older endodontists using the intraligamentary injection more often. The reported finding may be because many endodontists have not been taught the newer intraosseous systems.

Technology for the Intraligamentary Injection – The CCLAD

Recently, a computer controlled local anesthetic delivery system (CCLAD) has been introduced which can be used to administer an intraligamentary injection. The Wand, CompuDent, STA (CompuDent, Milestone Scientific Inc., Deerfield, IL) local anesthesia computer-controlled injection system accommodates a standard local anesthetic cartridge that is linked by sterile micro tubing to a disposable, pen-like handpiece with a Leur-Lok needle attached to the end. The device is activated by a foot control, which automates the infusion of local anesthetic solution at a controlled rate. A slow or fast flow rate is initiated and maintained by a foot pedal control. The fast rate delivers 1.4 ml of solution in 45 seconds. The slow rate delivers 1.4 ml of solution in approximately 4 minutes and 45 seconds. The slow rate is used for the intraligamentary injection.

Success of the Primary Intraligamentary Injection, Using the CCLAD, in Asymptomatic Vital Teeth

An experimental study121 compared the anesthetic efficacy of the primary intraligamentary injection of 1.4 mL of 4% articaine with 1:100,000 epinephrine and 1.4 mL of 2% lidocaine with 1:100,000 epinephrine, administered with computer-controlled local anesthetic delivery system, in the mandibular first molar. Successful pulpal anesthesia (two consecutive 80 readings with an electric pulp tester) was obtained 86% of the time with the articaine solution and 74% of the time with the lidocaine solution. There was no significant difference between the articaine and lidocaine solutions. The duration of pulpal anesthesia for the first molar ranged from 31 to 34 minutes – which is longer than the 10 minutes recorded in a similar study using a pressure syringe and 0.4 ml of a lidocaine solution.118 Therefore, there is an advantage to using the computer-controlled local anesthetic delivery system to increase the duration of pulpal anesthesia. However, the clinician must be aware that anesthesia does decrease slowly over the hour.

Success of the Intraligamentary Injection, Using the Wand (CCLAD), in Symptomatic Vital Teeth

Nusstein et al.122 determined the anesthetic effectiveness of the supplemental intraligamentary injection, administered with a computer-controlled anesthetic delivery system, in mandibular posterior teeth diagnosed with irreversible pulpitis when the conventional inferior alveolar nerve block failed. Success of the intraligamentary injection (none or mild pain upon endodontic access or initial instrumentation) was obtained in 56% (30 of 54) of the patients. The results were somewhat disappointing because the computer-controlled anesthetic delivery system should have been capable of delivering approximately 1.4 mL of anesthetic solution via of the intraligamentary injection by consistently maintaining a precise flow rate.

Intraligamentary Injection, Using STA (Single Tooth Anesthesia) Technology

The STA device uses dynamic pressure-sensing (DPS) technology which allows continuous feedback during the intraligamentary injection.123 Lights on the STA unit give audible and visual indicators which indicate the correct pressures involved to deliver the anesthetic solution by intraligamentary injection. Therefore, it transforms a “blind” intraliamentary injection with a syringe into an accurate pressure-sensing injection with the STA unit. However, no studies have been performed to evaluate this new technology.

INTRAOSSEOUS ANESTHESIA

Intraosseous Anesthesia with the Stabident and X-Tip Systems

The intraosseous injection allows placement of a local anesthetic solution directly into the cancellous bone adjacent to the tooth to be anesthetized. Because primary infiltration injections with lidocaine or articaine solutions are not effective for anesthesia of the mandibular molar teeth, endodontists do not use infiltration anesthesia to achieve pulpal anesthesia in patients presenting with irreversible pulpitis. The intraosseous injection overcomes this problem by allowing direct access to the cancellous bone. How similar is an infiltration and intraosseous injection? Nusstein et al.124 compared these two injection techniques, using 1.8 ml of 2% lidocaine with 1:100,000 epinephrine, in the maxillary lateral incisor. The two techniques were similar except the intraosseous technique had a quicker onset and a shorter duration of anesthesia.

There are two intraosseous systems that have been studied clinically – the Stabident system (Fairfax Dental Inc., Miami, FL) and the X-tip system (Dentsply, York, PA – the X-tip system has recently been acquired by Dentsply International). Recently, three other anesthetic system have been introduced – the IntraFlow (Pro-Dex Inc., Santa Ana, CA), the Comfort Control Syringe (Dentsply International, York PA), and the Anesto system (Innovadontics, Camarillo, CA). Reemers et al.125 studied the IntraFlow system as a primary technique in 15 patients with irreversible pulpitis and found an 87% success rate (two consecutive 80 readings with a pulp tester – which is not reliable for measuring anesthesia in patients with irreversible pulpitis). They did show the needle/drill became clogged and resulted in leakage around the transfuser assembly and subsequent failure. The IntraFlow system is no longer marketed. The Comfort Control Syringe is an electronic delivery system for local anesthesia and has 5 different injection rates that are pre-programmed into the system. Anesto is a new system which consists of a handpiece which drills through the cortical bone and then the local anesthetic is delivered using the lever arm. No studies have evaluated the Comfort Control Syringe or Anesto systems in clinical dentistry.

The Stabident system is comprised of a slow-speed handpiece driven perforator, a solid 27-gauge wire with a beveled end, that, when activated, drills a small hole through the cortical plate. The anesthetic solution is delivered to cancellous bone through the 27-gauge ultra-short injector needle placed into the hole made by the perforator.

The X-tip anesthesia delivery system consists of an X-tip that separates into two parts: the drill and guide sleeve component. The drill (a special hollow needle) leads the guide sleeve through the cortical plate, whereupon it is separated and withdrawn. The remaining guide sleeve is designed to accept a 27-gauge needle to inject the anesthetic solution. The guide sleeve is removed after the intraosseous injection is complete.

The technique of intraosseous anesthesia, using the Stabident or X-tip system, can be reviewed in their respective instruction manuals and/or published papers.110, 126-130

Perforator Breakage with the Stabident and X-tip Systems

About 1% of perforators "separate" during use.19, 110, 126-130 That is, the metal perforator separates from the plastic shank. Each is easily removed with a hemostat. The "separation" usually occurs during a difficult perforation (e.g. dense cortical bone) and it is likely the metal is heated excessively, causing the plastic hub to melt. No perforator "breakage" (metal perforator breaking into parts) has been reported in numerous studies.19, 110, 126-130

Optimal Injection Site Location for Anesthesia

It is important to remember that a site DISTAL to the tooth to be anesthetized will result in the best anesthesia.19, 27, 110, 111, 126-130 An exception to this rule would be in maxillary and mandibular second molars - a MESIAL site should be selected.19, 27, 110, 111, 126-130

Onset of Anesthesia

Basically, the onset of anesthesia is immediate.19, 27, 110, 111, 126-131 Therefore, there is no "waiting period" for onset of anesthesia.

Site Selection- Attached Gingiva or Alveolar Mucosa?

Both the Stabident and X-tip intraosseous systems instruct the user to locate the perforation site in attached gingiva. The gingival site allows the perforation to be made through a minimal thickness of cortical bone and is generally equidistant between adjacent root structures. However, because the guide sleeve remains in place with the X-tip system, two studies19, 127 have successfully used it in alveolar mucosa at a more apical location. The X-tip system has a definite clinical advantage over the Stabident system because the X-tip perforation may be made at an apical location in unattached gingiva. That is, if the Stabident system is used apically in alveolar mucosa, it is almost impossible to find the hole to deliver the anesthetic solution. Therefore, the clinician may want to consider using the X-tip in an apical location in specific clinical situations. For example, when periodontal pocketing does not allow perforation into cancellous bone through the more coronal attached gingiva or there is a lack of interproximal space (roots are too close together), the X-tip system can be used to achieve pulpal anesthesia. Furthermore, if the Stabident system fails, the clinician may want to consider using the X-tip apically to achieve pulpal anesthesia.

Success of Supplemental Intraosseous Anesthesia in Patients with Irreversible Pulpitis

Stabident Success

Nusstein et al.9 ,in a clinical study, found a supplemental mandibular intraosseous injection of posterior teeth, using the Stabident system and 1.8 mL of 2% lidocaine with 1:100,000 epinephrine was 91% successful in gaining total pulpal anesthesia for posterior teeth diagnosed with irreversible pulpitis. Likewise, Oleson et al.151 and Simpson et al.153 found, in similar studies, a 94% and 86% success rate, respectively. Parente et al.18 used the Stabident intraosseous injection in patients with irreversible pulpitis when conventional local anesthetic techniques failed. They found an initial supplemental intraosseous injection, using 0.45 to 0.9 mL of 2% lidocaine with 1:100,000 epinephrine, was successful in 79% of posterior mandibular teeth. A second intraosseous injection increased success to 91%. Pereria and co-authors165 found there was no significant difference in success rates between the supplemental intraosseous injection of 4% articaine with 1:100,00 epinephrine (97% success) and 4% articaine with 1:200,000 epinephrine (93% success).

Reisman et al.11 reported the supplemental intraosseous injection of 1.8 mL of 3% mepivacaine increased success in mandibular teeth diagnosed with irreversible pulpitis to 80% when compared to the inferior alveolar nerve block alone (25% success). A repeated intraosseous injection of 3% mepivacaine increased success to 98%. Therefore, one cartridge of 3% mepivacaine plain is not as efficacious as one cartridge of 2% lidocaine with 1:100,000 epinephrine. But 3% mepivacaine does not have the heart rate increase seen with epinephrine-containing solutions.

Success of the Supplemental Intraosseous Anesthesia versus Intraligamentary Anesthesia in Patients with Irreversible Pulpitis

A recent study found that following an inferior alveolar nerve block, intraosseous anesthesia was more successful (100% success) than intraligamentary anesthesia (70%).164

Success of Supplemental Intraosseous Anesthesia Using Articaine in Patients with Irreversible Pulpitis. Bigby and co-authors131 found that for posterior teeth diagnosed with irreversible pulpitis, the supplemental intraosseous injection of 1.8 mL of 4% articaine with 1:100,000 epinephrine was 86% successful when the inferior alveolar nerve block failed. Therefore, the success rate of the articaine solution was similar to a solution of lidocaine.

X-Tip Success in Irreversible Pulpitis

Nusstein et al.19 used an X-tip supplemental intraosseous injection in patients with irreversible pulpitis when a conventional inferior alveolar nerve block failed. The X-tip injection site was 3-7 mm apical to the mucogingival junction of the mandibular molar or premolar tooth and 1.8 mL of 2% lidocaine with 1:100,000 epinephrine was administered. They found that 6 of the 33 (18%) X-tip injections resulted in backflow of the anesthetic solution into the oral cavity – none were successful in obtaining anesthesia. Twenty-seven of the remaining 33 X-tip injections (82%) were successful. They concluded that when the inferior alveolar nerve block fails to provide profound pulpal anesthesia, the X-tip system, when used in an apical location and when there was no backflow of the anesthetic solution into the oral cavity, is successful in achieving pulpal anesthesia in mandibular posterior teeth of patients presenting with irreversible pulpitis. Other studies of the X-tip supplemental IO injection recorded success rates of 100%19a, 87%50f, 83%165b,93%165a, and 97%165, using 1.8 mL of anesthetic solution and 68%158, using half a cartridge.

The Key to Success with an Intraosseous Injection

The key to success with the intraosseous injection is flow of the anesthetic into the cancellous space. If anesthetic solution flows out of the perforation site into the oral cavity - naturally, no anesthetic effect will be realized. Reperforation or choosing another perforation site would be a good choice to gain access to the cancellous bone.

In less than 10% of intraosseous injections, constricted cancellous spaces may limit the distribution of the anesthetic solution around the apices of the teeth.9, 11, 19, 27, 50, 110, 111, 126-131 Therefore, failure may result even when the anesthetic solution is delivered intraosseously.

What Do We Tell Patients When Administering Intraosseous Anesthesia?

An example would be - “Your tooth isn’t as numb as we would like – therefore, we are going to give additional numbing solution next to your tooth. You will feel some vibrations and possibly your heart may beat a little faster.” We should not say - “We are going to drill through your gum and bone and then give you a shot of the anesthetic”. Basically, for the inferior alveolar nerve block we do not give detailed instructions such as - “We are going to go through the mucosal surface, then some tissue and possible muscle and then hit the bone and nerve.” We simply say – “We are going to get you comfortable by numbing your tooth.” Regarding details, the intraosseous injection should be no different than what we say when administering other local anesthetic injections.

Success of Intraosseous Anesthesia Alone in Patients with Irreversible Pulpitis

Although some authors131a,165,73c have suggested an IO injection alone will successfully anesthetize patients presenting with irreversible pulpitis, it is very doubtful if this would be successful.9,19,86,131,151,153

Duration

With a primary IO injection, duration of pulpal anesthesia declines steadily over an hour.126, 127, 130 There is an even shorter duration with 3% mepivacaine or 1.5% etidocaine with 1:200,000 epinephrine compared with 2% lidocaine with 1:100,000 epinephrine.130, 132

With a supplemental IO injection after the inferior alveolar nerve block in patients without pain, duration of pulpal anesthesia is very good when using anesthetic solutions with vasoconstrictors.27, 110 A solution of 3% mepivacaine will result in a shorter anesthetic duration.112

In mandibular posterior teeth in patients with irreversible pulpitis, the supplemental intraosseous injection, using the Stabident or X-tip systems, provided anesthesia for the entire debridement appointment.9, 19, 131

Repeating the Intraosseous Injection

Jensen et al.133 found that repeating the intraosseous injection, using 1.4 mL of 2% lidocaine with 1:100,000 epinephrine, 30 minutes after the initial intraosseous injection provided an additional 15-20 minutes of pulpal anesthesia – which was similar to the duration of the initial intraosseous injection. Adding an additional intraosseous injection may be helpful if anesthesia starts to wear off near the end of an appointment.

When Should the Intraosseous Injection Be Given?

Considering the high failure rate of the initial inferior alveolar nerve block, it would be prudent to give all patients with irreversible pulpitis a supplemental intraosseous injection following an inferior alveolar nerve block. That is, once we have signs of lip numbness, we administer an intraosseous injection. An infiltration of 1.8 mL of 4% articaine with 1:100,000 epinephrine is first given over the site of the proposed intraosseous injection to help decrease the pain of the injection and supplement anesthesia. Wait a few minutes and administer the intraosseous injection. This procedure has significantly decreased patients’ pain and allowed a quicker onset of treatment.

Why don’t more dentists use this regimen? Basically, many clinicians do what they were taught in their initial clinical training and sometimes it is hard to change. For example, a 1998 study in the Journal of the American Medical Association134 urges the use of anesthesia during circumcision. Currently, up to 96% of babies don’t receive anesthesia. The physicians were taught in their residencies not to administer anesthesia and consequently it will probably be a slow process to change them over. This is a common problem in many health care disciplines and emphasizes the need to stay current with new advances.

Success in Painful Teeth with Totally Necrotic Pulps and Radiolucent Areas

No published study has investigated the success rate in these teeth. In a preliminary study we performed, anesthetic solution deposition intraosseously was very painful in these teeth and we had to terminate the study.

Success in Partially Vital Teeth

The intraosseous injection should work in teeth where the chamber is necrotic, the canals are vital or partially vital, and there is a widening of the periodontal ligament radiographically. A recent history of hot and cold sensitivity should differentiate this condition from one of a tooth with a necrotic pulp and periapical radioluceny experiencing an acute exacerbation (Phoenix abscess).

Systemic Effects with the Intraosseous Injection

Heart rate effects of intraosseous anesthesia

Various authors9, 19, 27, 110, 111, 126-129, 131, 135,165a have reported a transient increase in heart rate (46% to 93% of the time) with the Stabident or X-tip intraosseous injection of epinephrine- and levonordefrin-containing solutions. Replogle and co-authors135 reported 67% of their subjects objectively (electrocardiogram recordings) had an increased heart rate with the Stabident® intraosseous injection of 1.8 mL of 2% lidocaine with 1:100,000 epinephrine. The mean increase was 28 beats per minute. Chamberlain et al. 136 found the Stabident intraosseous injection of 2% lidocaine with 1:100,000 epinephrine resulted in a mean heart rate increase of 12 beats per minute. Guglielmo et al.27 reported that the supplemental Stabident® intraosseous injection of 1.8 mL of either 2% lidocaine with 1:100,000 epinephrine or 2% mepivacaine with 1:20,000 levonordefrin resulted in a mean increase in heart rate of 23-24 beats per minute (measured with a pulse oximeter) in 80% of the subjects. Stabile et al.111 found the supplemental intraosseous injection of 1.8 mL of 1.5% etidocaine with 1:200,000 epinephrine resulted in a mean increase in heart rate of 32 beats per minute (measured with a pulse oximeter) in 90% of the subjects. Bigby et al.131 found a pulse rate increase of 32 beats/minute using 4% articaine with 1:100,000 epinephrine. Wood et al.137 found that a transient heart rate increase (measured with a pulse oximeter) will occur with the intraosseous injection but not with the infiltration injection of 1.8 mL of 2% lidocaine with 1:100,000 epinephrine in the maxillary anterior region. Generally, all these studies showed that the heart rate returned to baseline readings within four minutes in most patients. Therefore, injection of anesthetic solutions containing vasoconstrictors, using either the Stabident or X-tip systems, would result in a transient heart rate increase. No significant change in diastolic, systolic or mean arterial blood pressure will be observed with the intraosseous injection of 2% lidocaine with 1:100,000 epinephrine.135, 136

Slowing the rate of the intraosseous solution deposition of 2% lidocaine with 1:100,000 epinephrine by utilizing the slow rate (4 minutes and 45 seconds) of a computer-assisted local anesthetic delivery system significantly lowered the heart rate (10 to 12 beats per minute) when compared to a fast rate (45 seconds) resulting in a heart rate increase of 25 beats per minute.138

Clinical significance of heart rate increase

While the heart rate increase with the Stabident® or X-tip® intraosseous injection of 2% lidocaine with 1:100,000 epinephrine would likely be noticed by the patient, it would not be clinically significant in most healthy patients.135 Replogle et al.135 discussed the clinical significance, cardiovascular effects and contraindications to the use of vasoconstrictors in intraosseous injections. The reader is referred to this article for review.

The lack of heart rate effect of 3% mepivacaine in intraosseous anesthesia

There will be no significant increase in heart rate when 3% mepivacaine is used for intraosseous anesthesia.112, 135 Importantly, in those patients whose medical condition (moderate-to-severe cardiovascular disease) or drug therapies (patients taking tricyclic antidepressants or nonselective ß-adrenergic blocking agents) suggest caution in administering epinephrine- or levonordefrin-containing solutions, 3% mepivacaine would be an excellent alternative for intraosseous injections.112, 135

Caution in the use of long-acting anesthetic agents for intraosseous anesthesia

In an attempt to increase the duration of pulpal anesthesia with intraosseous injections, some clinicians may use long-acting anesthetic agents. Bupivacaine (Marcaine) and etidocaine (Duranest) are long-acting anesthetic agents but only for inferior alveolar nerve blocks. Long-acting anesthetic agents are not long-acting agents for intraosseous and maxillary infiltration anesthesia.111, 132, 139, 140 It is important to realize that bupivacaine and etidocaine have cardiotoxic effects141 and are basically equivalent to 2% lidocaine with epinephrine in terms of efficacy, duration, and heart rate effects for intraosseous anesthesia. Therefore, bupivacaine and etidocaine offer no advantage clinically for intraosseous anesthesia.

Plasma levels of lidocaine after intraosseous injection

Some authors142 have cautioned that administration of an overly large volume of local anesthetic with an intraosseous injection could lead to overdose reactions. Wood and co-authors,137 using human subjects and 1.8 mL of 2% lidocaine with 1:100,000 epinephrine, found that the venous plasma levels of lidocaine were the same for maxillary anterior intraosseous and infiltration injections. While there is a short-lived effect on the heart rate due to the vasoconstrictor, the plasma concentration of lidocaine delivered with the intraosseous injection is no more than that delivered with an infiltration. Therefore, the intraosseous technique should not be considered an intravascular injection. Additionally, if it were an intravascular injection, little or no anesthetic effect would be demonstrated. That is, all the local anesthetic solution would be carried into the vascular system with none left for pulpal anesthesia. Obviously, clinical and experimental studies9, 19, 27, 110, 111, 126-129, 131, 135 have demonstrated clinical anesthesia with intraosseous techniques. In conclusion, the same precautions for the maximum amount of lidocaine given for an infiltration injection would seem to also apply to an intraosseous injection.

Postoperative Problems

For the Stabident system, less than 5% of patients will develop swelling and/or exudate at the site of perforations.27, 126, 128, 129, 135 Gallatin et al.143 found that the X-tip system may have a higher incidence of postoperative swelling clinically. With both systems, the swelling/exudate may be present for weeks after the injection but all resolve with time.27, 126, 128, 129, 135, 143 These slow healing perforation sites may be due to overheating of the bone caused by pressure during perforation.

Woodmansey et al.143a, in a case report, reported osteonecrosis supposedly occurred due to intraosseous anesthesia. Unfortunately, this case report did not confirm that intraosseous anesthesia caused osteonecrosis. Basically, an inexperienced undergraduate student performed the intraosseous injection and separated a portion of an X-tip perforator. Judging from the photographs, the intraosseous site was coronal to the ideal site. Following separation, gingival surgery with bone removal was performed. Follow-up appointments were poor and eventually the first and second molars were extracted. The patient also was HIV positive and was on medications for the condition - this may have contributed to poor bone healing. Basically, a number of well controlled studies using experienced operators have not reported osteonecrosis resulting in tooth loss.27, 126, 128, 129, 135, 143

With both the Stabident and X-tip systems, approximately 4% to 15% of patients will report that their tooth "feels high" when chewing for a few days.27, 126, 128, 129, 135, 143 This feeling is most likely an increased awareness to biting that results from soreness in the area caused by damage from perforation or inflammation of the bone. The incidence with the intraosseous injection is lower than reported with the periodontal ligament injection (36% to 49%).144, 145

INTRAPULPAL INJECTION

In about 5 to 10% of mandibular posterior teeth with irreversible pulpitis, supplemental injections, even when repeated, do not produce profound anesthesia; pain persists when the pulp is entered. This is an indication for an intrapulpal injection.

The major drawback of the technique is that needle placement and injection are directly into a vital and very sensitive pulp; the injection may be moderately to severely painful.9 In the Journal of Endodontics,146 Miles a dentally trained neurophysiologist needing endodontic treatment, reported intense pain when the intrapulpal injection was administered. While he reported it was successful – success was achieved at a price. Miles stated that there was decreased confidence in the endodontist and increased apprehension. Because we currently have more successful methods of supplemental anesthesia, the intrapulpal injection should only be given after all other supplemental techniques have failed. Another disadvantage of the technique is the duration of pulpal anesthesia may be short (15 to 20 minutes). Therefore, the bulk of the pulpal tissue must be removed quickly, at the correct working length, to prevent reoccurrence of pain during instrumentation. Another disadvantage is that, obviously, the pulp must be exposed to permit direct injection; frequently anesthetic problems occur prior to exposure while still in dentin.9, 11, 19, 122, 131

The advantage of the intrapulpal injection is that it works well for profound anesthesia if given under back-pressure.147, 148 Onset will be immediate and no special syringes or needles are required. The methods for this technique can be found in many excellent endodontic textbooks. Strong-back pressure has been shown to be a major factor in producing anesthesia.147, 148 Depositing anesthetic passively into the chamber is not adequate; the solution will not diffuse throughout the pulp.

Preemptive Strategies to Try and Improve the Success of the Inferior Alveolar Nerve Block in Patients with Irreversible Pulpitis

A preemptive approach is to give NSAIDs one hour before anesthetic administration. Modaresi et al.149 recommended the use of ibuprofen for this purpose. However, they evaluated success (the assumption of profound anesthesia) using “tooth sensitivity level” evaluated by an electric pulp tester. Using a lowered stimulus reading or no response from a pulp tester in patients with irreversible pulpitis will NOT ensure profound anesthesia.5 Ianiro et al.150 used either preoperative acetaminophen or a combination of acetaminophen and ibuprofen and found a trend toward higher success rates (no pain on access) of 71% to 76% respectively when compared to the placebo group (46%). However, the differences were not significant. Jena and co-authors150a administered preoperative ketorolac, ibuprofen, and aceclofenac with paracetamol and found it increased success of the IAN block but not significantly. In a small study, Noguera-Gonzalez150b found 600 mg ibuprofen improved IAN block success.

Oleson et al.151 evaluated the effect of preoperative ibuprofen (800 mg) on the success (no or mild pain on access or initial instrumentation) of the inferior alveolar nerve block in patients presenting with symptomatic irreversible pulpitis. They found no significant difference between a placebo (35% success) and ibuprofen (41% success). Aggarwal et al.152 evaluated the effect of preoperative ibuprofen (600 mg), or ketorolac (20 mg), on the success (no or mild pain on access or initial instrumentation) of the inferior alveolar nerve block in patients presenting with symptomatic irreversible pulpitis. They found no significant difference between a placebo (29% success), ibuprofen (27% success), and ketorolac (39% success). Simpson et al.153 evaluated the effect of a preoperative combination of ibuprofen (800 mg)/acetaminophen (1000 mg) on the success (no or mild pain on access or initial instrumentation) of the inferior alveolar nerve block in patients presenting with symptomatic irreversible pulpitis. They found no significant difference between a placebo (24% success) and a combination of ibuprofen/acetaminophen (32% success). Therefore, preemptive NSAIDs will not improve the success of the inferior alveolar nerve block in patients with symptomatic irreversible pulpitis.

Fullmer and co-authors153a evaluated the effect of preoperative 1000 mg acetaminophen/10 hydrocodone on the success (no or mild pain on access or initial instrumentation) of the inferior alveolar nerve block in patients presenting with symptomatic irreversible pulpitis. The success rate for the IAN block was 32% for the combination dose of 1000 mg acetaminophen/10 hydrocodone and 28% for the placebo dose, with no statistically significant difference between the two groups (p=0.662). Therefore, a combination dose of 1000 mg of acetaminophen/10 mg of hydrocodone, given 60 minutes before administration of the IAN block, did not result in a statistically significant increase in anesthetic success for mandibular posterior teeth in patients experiencing symptomatic irreversible pulpitis.

In patients presenting with no spontaneous pain at the endodontic appointment (asymptomatic irreversible pulpitis), a preoperative administration of 600 mg ibuprofen or 75 mg indomethacin increased the success of the IAN block (78% and 62% respectively) over a placebo (32%).154 Another recent study found 400 mg ibuprofen, 0.5 mg dexamethasone, and a placebo resulted in success rates, in patients presenting with asymptomatic irreversible pulpitis, of 25%, 38%, and 13%, respectively.166 However, the success rates with either ibuprofen or dexamethasone would not ensure profound pulpal anesthesia. However, as shown by Argueta-Figueroa et al.,167 success rates are higher in patients with asymptomatic irreversible pulpitis.

Oral Conscious Sedation with Triazolam (Halcion) and Xanax (Alprazolam)

Patients who are anxious have reduced pain tolerance155 and may be harder to anesthetize. Oral conscious sedation is beneficial in reducing patient’s anxiety. However, as shown by two studies, Triazolam and Xanax are not a way to reduce pain during endodontic or dental treatment.155,168 Profound local anesthesia is still required to control the patient’s pain.

Conscious Sedation with Nitrous Oxide

Nitrous oxide provides conscious sedation for apprehensive dental patients. Moreover, nitrous oxide provides a mild analgesic effect. A recent study showed administration of 30%-50% nitrous oxide resulted in a statistically significant increase in the success of the IAN block in patients presenting with symptomatic irreversible pulpitis.169 This is a significant finding because …

Use of Buffered Lidocaine for IAN block in Patients Presenting with Symptomatic Irreversible Pulpitis

Saatchi et al.171 evaluated a buffered 2% lidocaine with 1:80,000 epinephrine formulation for IAN blocks in patients presenting with irreversible pulpitis and found buffering did not statistically increase success.. Recently, Schellenberg and co-authors172 studied a 4% buffered lidocaine formulation for inferior alveolar nerve block in patients presenting with irreversible pulpitis. They found the success rate for the IAN block was 32% for the buffered group and 40% for the non-buffered group, with no significant difference (P = .4047) between the groups. Injection pain ratings for the IAN block were not significantly (P=.9080) different between the two formulations.

Incision and Drainage with Buffered Lidocaine

One explanation for the failure of local anesthetics is the low pH associated with inflamed/infected tissues, particularly in acute apical abscesses. The presence of acute inflammation/infection may limit the formation of the non-ionized base form of the local anesthetic. If a local anesthetic solution is buffered to a pH that is closer to its pKa, more of the free base form will be available upon injection to enter the nerve sheath.

In a recent study by Balasco and co-authors170, 81 adult emergency patients with pulpal necrosis and an associated acute facial swellings were randomly divided into two treatment groups who received two infiltration injections (mesial and distal to the swelling) of either 2% lidocaine with 1:100,000 epinephrine buffered with 0.18 mL 8.4% sodium bicarbonate (Onpharma System) or 2% lidocaine with 1:100,000 epinephrine. An incision and drainage procedure was performed and the pain of incision, drainage, and dissection were recorded.

Pain ratings for the mesial and distal solution deposition phase of the infiltrations for both solutions resulted in a 34% to 51% incidence of moderate to severe pain with no significant difference between the two anesthetic solutions

Moderate to severe pain occurred in 56% to 88% of patients during the incision and drainage procedure using both solutions and there was no significant difference between the two solutions. Therefore, I & D is a very painful procedure.

We concluded that while the theory of buffering local anesthetics is logical, in reality the presence of a buffer in the local anesthetic may not be enough to overcome the lowered excitability thresholds and peripheral sensitization associated with such significant inflammatory and infectious conditions of an acute apical abscess.170

Satisfaction with Endodontic Treatment

In our studies73b,153a,155,169,170 we have shown that patients were moderately or completely satisfied with endodontic treatment even though moderate to severe pain was experienced. Patient satisfaction may be related to the bedside manner of the dentist or satisfaction with the completion of the emergency procedure in the hope that their discomfort will be abated. This is an important clinical finding because it helps explain why patients accept painful dental and medical procedures.

Postoperative Pain

Wells and co-authors170c studied ibuprofen versus ibuprofen/acetaminophen usage for postoperative endodontic pain in symptomatic patients with a pulpal diagnosis of necrosis experiencing moderate to severe preoperative pain. They found the combination ibuprofen/acetaminophen was not more effective for postoperative pain control than just the ibuprofen. Because approximately 20% of patients in both groups required escape medication to control pain, the combination ibuprofen/acetaminophen or ibuprofen was not completely effective at controlling postoperative pain in symptomatic patients with necrotic pulps and associated periapical radiolucencies.

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159Srinivasan N, Kavitha M, Loganathan CS, Padmini G.: Comparison of anesthetic efficacy of 4% articaine and 2% lidocaine for maxillary buccal infiltration in patients with irreversible pulpitis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 107:133, 2009.

160Rosenberg PA, Amin KG, Zibari Y, Lin LM: Comparison of 4% articaine with 1:100,000 epinephrine and 2% lidocaine with 1:100,000 epinephrine when used as a supplemental anesthetic. J Endod 33:403, 2007.

161Sherman MG, Flax M, Namerow K, Murray PE: Anesthetic efficacy of the Gow-Gates injection and maxillary infiltration with articaine and lidocaine for irreversible pulpitis. J Endod 34:656, 2008.

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163 Poorni S, Veniashok B, Senthilkumar AD, Indira R, Ramachandran S.: Anesthetic efficacy of four percent articaine for pulpal anesthesia by using inferior alveolar nerve block and buccal infiltration techniques in patients with irreversible pulpitis: a prospective randomized double-blind clinical trial. J Endod 37:1603,2011.

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165aVerma PK, Srivastava R, Ramesh KM. Anesthetic efficacy of X-tip intraosseous injection using 2% lidocaine with 1:80,000 epinephrine in patients with irreversible pulpitis after inferior alveolar nerve block: A clinical study. J Conserv Dent. 2013 Mar;16(2):162-6. doi: 10.4103/0972-0707.108202.

165bBhuyan AC, Latha SS, Jain S, Kataki R. Anesthetic efficacy of the supplemental X-tip intraosseous injection using 4% articaine with 1:100,000 adrenaline in patients with irreversible pulpitis: An in vivo study. J Conserv Dent. 2014 Nov;17(6):522-5. doi: 10.4103/0972-0707.144578.

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169 Stanley W, Drum M, Nusstein J, Reader A, Beck M.: Effect of nitrous oxide on the efficacy of the inferior alveolar nerve block in patients with symptomatic irreversible pulpitis. J Endod 38:565, 2012.

170 Balasco M, Drum M, Reader A, Nusstein J, Beck M. Incision and drainage pain using buffered lidocaine: A prospective, randomized double-blind study. J Endod, Nov;39(11):1329-34, 2013.

170a Malamed S, Tavana S, Falkel M. Faster onset and more comfortable injection with alkalinized 2% lidocaine with epinephrine 1:100,000 epinephrine. Compendium Feb;34 Spec No 1:10-20, 2013.

170bHobeich P, Simon S, Schneiderman E, He J. A prospective, randomized, double-blind comparison of the injection pain and anesthetic onset of 2% lidocaine with 1:100,000 epinephrine buffered with 5% and 10% sodium bicarbonate in maxillary infiltrations. J Endod. 2013 May;39(5):597-9. doi: 10.1016/j.joen.2013.01.008. Epub 2013 Mar 20.

170cWells LK, Drum M, Nusstein J, Reader A, Beck M. See comment in PubMed Commons belowEfficacy of Ibuprofen and ibuprofen/acetaminophen on postoperative pain in symptomatic patients with a pulpal diagnosis of necrosis. J Endod. 2011 Dec;37(12):1608-12. doi: 10.1016/j.joen.2011.08.026. Epub 2011 Oct 1.

171 Saatchi M, Khademi A, Baghaei B, Noormohammadi H. See comment in PubMed Commons belowEffect of sodium bicarbonate-buffered lidocaine on the success of inferior alveolar nerve block for teeth with symptomatic irreversible pulpitis: a prospective, randomized double-blind study. J Endod. 2015 Jan;41(1):33-5. doi: 10.1016/j.joen.2014.09.011. Epub 2014 Oct 31

172Schellenberg J, Drum M, Reader A, Nusstein J, Fowler S, Beck M. Effect of buffered 4% lidocaine on the success of the inferior alveolar nerve block in patients with irreversible pulpitis: a prospective, randomized, double-blind study. J Endod 2015: in press.

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