Strategies for Successful Local Anesthesia in Endodontics

Part 1 of this series was published in the September 2005 issue of Woman Dentist Journal.

Supplementing with alternative techniques ...

WRITTEN BY Pamela S. Stein, DMD, and Jennifer K. Brueckner, PhD

In his text “Endodontic Therapy,” F.S. Weine writes, “Being able to extirpate a pulp from a mandibular first molar tender to percussion and sensitive to hot in a painless manner is the most demanding anesthetic test in dentistry.”

Research has shown that the traditional inferior alveolar nerve block is effective in only 25 percent of mandibular molars with irreversible pulpitis. This data clearly indicates the need for supplemental local anesthesia techniques.

Another author suggests the following for pulpitic mandibular molars: begin with two inferior alveolar blocks, followed by infiltration both buccal and lingual, and if necessary, administer the intraligamentary injection.

Intraligamentary injection technique

The term intraligamentary injection or periodontal ligament (PDL) injection may be a misnomer, as the injection is actually intraosseous. This means it uses the periodontal ligament to administer the local anesthetic solution, which reaches the pulp via natural perforations of the bony socket. This is a popular supplementary injection when conventional anesthesia fails. “The periodontal ligament (PDL) injection is the technique of choice and should be used first if the conventional injection is unsuccessful,”writes R.E. Walton.

Using the intraligamentary injection to supplement the IAN block in the mandibular first molar has proven to significantly increase pulpal anesthesia for the first 23 minutes.Research also indicates the intraligamentary injection is effective as a primary anesthetic technique for endodontics. In a study by Kim, this injection provided successful anesthesia (no discomfort during endodontic procedures) in 81 percent of the 96 inflamed mandibular molars receiving treatment. Another study reported only 60 percent success when using this technique as a primary means of anesthesia in endodontic procedures.

A clinical trial by Malamed indicated that nearly all dental patients prefer this technique over conventional blocks in the mandible, primarily due to the lack of anesthesia in the lower lip and tongue.However, patients report “a sharp pain” upon injection, and clinicians agree nearly unanimously that this technique is painful and may result in postoperative discomfort.

Following are tips for enhancing success when using the intraligamentary technique:

Use of a local anesthetic with a vasoconstrictor significantly increases efficacy. However it is recommended that a local anesthetic with greater than 1:100,000 epinephrine not be used because the anesthetic is rapidly absorbed intravenously, predisposing to tachycardia.

Disinfect gingival sulcus prior to injection.

Use a 27-gauge short or 30-gauge ultrashort needle.

Slip the needle into the gingival sulcus at a 30-degree angle to the long axis of the tooth, advance to the depth of the gingival sulcus, and wedge the needle between the root and the alveolar bone. Bevel orientation is a point of contention, with some authors supporting the bevel toward the root for ease of insertionand others advocating inserting the bevel away from the tooth. Kim felt bevel orientation toward the alveolar bone was an important criterion for success of the technique, because it prevented backflow of the anesthetic into the gingival sulcus.

Injections should be given interproximally, beginning with the distal and then the mesial.

Special syringes can be used but are not necessary.

Slowly express only a few drops (0.2 ml) of anesthesia under pressure.Malamed advocates allowing at least 20 seconds to give 0.2 ml of anesthetic to decrease pain during injection.

Pressure in this injection could break the glass cartridge, although this is not frequently reported. To reduce pressure, express two-thirds of the anesthetic in the cartridge before injecting. When using a conventional syringe, a piece of tape may be placed over the exposed area of the glass cartridge to contain the glass in the event of breakage. This is not necessary when using special PDL syringes, because these provide a protective covering over the glass cartridge.

Do not use in areas of marginal periodontal disease or in patients with symptomatic periapical pathology (cellulitis or abscess).

Onset occurs within 30 seconds to two minutes, and duration may be as short as eight minutes but is usually 30 minutes.

Patients may experience postop pain and the tooth may be in hyperocclusion following this injection. To counter this complication, inject slowly, use a small volume of anesthesia, and limit the number of penetrations by the needle. This condition usually resolves within two to three days with saltwater rinses and mild analgesics. Occlusion should be checked carefully on temporary restorations after injections.

Avoid this injection in patients predisposed to bacterial endocarditis or patients with cardiovascular disease.

Intraosseous injection technique

Some authors advocate intraosseous anesthesia as the first choice when conventional local anesthesia fails in endodontics.In this technique, the anesthetic is placed directly into the cancellous bone near the tooth requiring anesthesia. A perforator in a slow-speed handpiece creates an opening through the cortical plate, which allows a 27-gauge ultra-short needle to be placed within the opening to deposit anesthetic solution into the cancellous bone.

The Stabident injection system, marketed by Fairfax Dental, and the X-tip system, marketed by X-tip Technologies, are the two intraosseous systems currently available to dentists. The X-tip differs from its predecessor by offering a guide sleeve for the anesthetic needle that is placed in the perforation step. In 2003, Gallatin and colleagues compared the two systems in mandibular posterior teeth and reported no significant differences in the anesthetic success rates (Table 2) or degree of difficulty in technique.

In a study by Leonard in 1995, the Stabident system was compared to traditional injection techniques regarding efficacy in exodontia. He found that the intraosseous technique was successful as a primary local anesthesia technique for extractions and provided several advantages including a faster onset - he could typically begin the extraction in 3.5 minutes including the time for the injection; no anesthesia of the lips or tongue; decreased amount of anesthetic solution required - usually less than one cartridge; no palatal injection required; and patient acceptance.

Other research has shown intraosseous injections, when used as the primary anesthetic technique, to be 75 percent effective in obtaining pulpal anesthesia in noninflamed mandibular molars, and 93 percent effective in noninflamed maxillary molars. When used in combination with the inferior alveolar nerve block, the intraosseous injection had a 95 percent rate of anesthetic success on noninflamed mandibular first molars, and 91 percent success rate in mandibular posterior teeth with irreversible pulpitis.

Malamed recommends using a nonvasopressor containing anesthetic due to the incidence of palpitations.Using 3 percent mepivicaine in the intraosseous technique to supplement the inferior alveolar nerve block has been shown to increase the anesthetic efficacy in mandibular molars with irreversible pulpitis from 25 percent with the IAN block alone to 80 percent after the first supplemental intraosseous injection, and 98 percent after a second intraosseous injection. However, when using the intraosseous injection as the primary anesthetic technique, elimination of a vasopressor may decrease the efficacy. In a study by Repogle utilizing intraosseous injections as the primary anesthetic technique, 2 percent lidocaine (1:100,000 epinephrine) provided successful anesthesia in 74 percent of mandibular first molars, while the success rate for 3 percent mepivacaine was 45 percent in mandibular first molars.

It has been recommended that intraosseous injections not be administered in patients with heart disease or in those who take tricyclic antidepressants or ß-adrenergic blockers.

Intrapulpal injectin technique

The intrapulpal injection supplements conventional local anesthesia by placing the anesthetic solution directly into the pulp chamber. While most texts and practitioners list the intrapulpal injection as a last resort, it is a technique that warrants discussion because there are occasions when it may be necessary. The following are tips for enhancing success when utilizing the intrapulpal injection technique:

Avoid this injection in the very anxious patient as it is associated with a brief period of pain.

Explain to patient that it will be necessary to give a bit more anesthetic to provide maximum comfort and that there may be a “brief moment of sensitivity.” Nitrous oxide may be used.

Anesthetize dentin to be removed by placing a cotton pellet saturated with anesthetic agent to the pulpal floor, waiting 30 seconds and then pressing the pellet into the dentinal tubules for two to three minutes. This may be repeated if necessary.

Using a slow-speed drill, make a small perforation through the anesthetized dentin into the pulp to allow for a snug fit of the anesthetic needle.

Use a 25-, 27-, or 30-gauge needle, depending upon the size of the access opening (it may be necessary to bend the needle), and inject a small amount such as 0.2 ml of anesthetic into the pulp chamber slowly (at least 20 seconds) under pressure.A recent study showed that success of this injection depends on pressure and not on the delivery of anesthetic solution.

In molars, the solution should be deposited in the largest canal, distal for mandibular molars and palatal for maxillary molars.

Consider use of a topical anesthetic intrapulpally. DeNunzio describes using Hurricane brand topical to coat a No. 10 or No. 15 file, and then pushing the topical down the canal using an alternating pumping and watch-winding motion, copiously irrigating after the canals are anesthetized. In a six-year period, he reports only one patient in more than 1,000 did not become anesthetized using this technique.

There are rare instances when none of the supplemental techniques outlined above will be successful in achieving anesthesia for the endodontic patient. In these cases, sedation may be employed, provided the patient is not medically compromised. Referral to an endodontist should be considered.■

References(full list for Parts 1 and 2 of this series)

¹ Weine FS. Endodontic therapy, 6th ed; St. Louis: Mosby 2004.
2 Walton RE, Torabinejad M. Principles and practice of endodontics, 2nd ed; Philadelphia: W.B. Saunders 1996.
3 Clark K, Reader A, Beck M, Meyers W. Anesthetic efficacy of an infiltration in mandibular anterior teeth following an inferior alveolar nerve block. Anesth Prog 2002; 49:49-55.
4 Mikesell A, Reader A, Beck M, Meyers W. Analgesic efficacy of volumes of lidocaine in human maxillary infiltration (Abstract) J of Endod 1987; 13:128.
5 Vreeland D, Reader A, Beck M et al. An evaluation of volumes and concentrations of lidocaine in human inferior alveolar nerve block. J of Endod 1989; 15:6.
6 Chaney M, Kerby R, Reader A et al. An evaluation of lidocaine hydrocarbonate compared with lidocaine hydrochloride for inferior alveolar nerve block. Anesth Prog 1992; 38:212.
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8 McLean C, Reader A, Beck M, Meyers W. An evaluation of 4% prilocaine and 3% mepivacaine compared with 2% lidocaine (1:100,000 epinephrine) for inferior alveolar nerve block. J of Endod 1993; 19:146.
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Pamela S. Stein, DMD
Dr. Stein is an assistant professor of anatomy and neurobiology at the University of Kentucky College of Medicine. A board-certified lecturer on the topic of local anesthesia, she recently co-authored “The Anatomy of Local Anesthesia,” a multimedia tutorial software program to be distributed to dental students nationwide. Contact her at [email protected].

Jennifer K. Brueckner, PhD
Dr. Brueckner is an assistant professor of anatomy and neurobiology at the University of Kentucky College of Medicine, where she directs the dental gross anatomy course. With a strong interest in dental education, she currently serves as councilor in the anatomical sciences section of the American Dental Education Association. Contact her at [email protected].