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.
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.
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.
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.