Injection Techniques to Anesthetize the Difficult Tooth
by Christine L. Quinn, DDSCopyright 1998 Journal of the California Dental Association
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Failure to achieve anesthesia can be a significant problem in the day-to-day practice of dentistry.
The usual strategy following an anesthetic failure is to reinject. Therefore, a good understanding
of conventional anesthetic techniques is important. But the practitioner also needs to have a
broad armamentarium of injection strategies available for the "difficult-to-anesthetize cases".
These strategies include the use of 5 percent lidocaine, intrapulpal injection, periodontal
ligament injection and intraosseous injection. This paper will be a brief discussion of those
techniques with an emphasis on the intraosseous injection. |
Article copyright 1998 Journal of the California Dental Association.
Photographs copyright of the authors.
Failure to achieve anesthesia can be a significant problem in the day to day practice of dentistry. In a survey conducted by Kaufman1 it was concluded that about five anesthetic failures occur each week in a general practice, with the inferior alveolar nerve block being identified as the injection with the greatest number of failures. Eleven percent of the dentists responding to the survey reported that they had an anesthetic failure (within the survey week) that resulted in uncompleted treatment. These patients may eventually lose confidence in the dentist, questioning if they will ever be able to provide them with adequate pain control.
The usual strategy following an anesthetic failure is to reinject. Therefore, a good understanding of conventional anesthetic techniques is important. But the practitioner also needs to have a broad armamentarium of injection strategies available for the "difficult to anesthetize cases". There are several causes for failure of anesthesia: incorrect needle placement, anatomic variation, presence of inflammation, and patient anxiety. This discussion will focus on the difficult-to-anesthetize tooth and some ways in which to improve anesthetic success.
It is difficult to achieve anesthesia in the presence of acute inflammation. It was thought that because the inflamed tissue has a low pH (5 to 6), relative to nonimflamed tissue (pH 7.3), the local anesthetic was acidified. This would decrease the amount of nonionized anesthetic that would be available to cross into the nerve. Inflammation also leads to increased blood flow in the tissue. This would speed the removal of the anesthetic from the injection site. Conventional wisdom has traditionally suggested to provide nerve block anesthesia at a site distant to the inflammation to avoid the decrease in pH. This, in fact, does not always guarantee anesthesia. One of the most difficult situations to achieve profound anesthesia is in the mandibular molar with acute pulpitis in which the local anesthetic is delivered some distance away from the inflammation. Rood2 conducted clinical trials comparing buffered 2 percent lidocaine with epinephrine with commercially available lidocaine with epinephrine. He demonstrated that there was no difference in effectiveness between the two solutions when used for maxillary infiltration on inflamed teeth. Rood concluded that pH is not the major factor causing anesthesia failure in the presence of inflamed tissue.
It has been shown that morphological changes occur along the nerve some distance away from the inflammation..3 There is also interest in the mediators of inflammation in terms of how they may affect nerve transmission and local anesthetics.4,5
Concentrated local anesthetic solutions may be one way to anesthetize the acutely inflamed tooth. Eldridge6 demonstrated, in a double blind study, that 5 percent lidocaine with epinephrine was able to successfully anesthetize teeth with acute pulpits. There was a 93 percent success rate with 5 percent lidocaine when used for inferior alveolar block anesthesia versus a 22 percent success rate with 2 percent lidocaine. It should be noted, however, that a concentrated anesthetic solution is more toxic than standard formulations.
Another approach to the difficult-to-anesthetize tooth is the incorporation of supplemental injection techniques into the anesthesia armamentarium. These techniques include the intrapupal injection, periodontal ligament injection and the intraosseous injection.
Intrapulpal Injection
This technique is a supplemental injection technique that may be used when trying to achieve pulpal anesthesia for root canal treatment. The technique is as follows: A small opening is made in the pulp chamber. The needle is wedged against the pulp canal walls and a small amount of local anesthetic is injected with considerable back-pressure. Anesthesia will occur immediately allowing for instrumentation of the canal. The pressure effect has been shown to produce the anesthesia rather than the local anesthetic itself. VanGheluwe7 found that saline was as effective in providing anesthesia, when given intrapulpally, as 2 percent lidocaine (1:100,00 epinephrine). A disadvantage to this technique is that the patient will initially experience some pain during the injection. It may be possible to decrease this pain by placing a cotton pledget soaked in the local anesthetic solution on the exposure site prior to the intrapulpal injection.
Periodontal Ligament Injection
The periodontal ligament injection is useful in situations of incomplete anesthesia. This technique relies on intraosseous spread of the local anesthetic.8 A 27-gauge (or 30-gauge) short needle is placed between the periodontal ligament and the tooth to be anesthetized on either the mesial or distal aspect of the tooth. A small volume of anesthetic, 0.2 ml, is deposited under pressure. A separate injection is required for each root of a multirooted tooth. The onset of anesthesia is immediate and the duration is unpredictable. Patients may experience some sensitivity postoperatively in the area of the injection. Periodontal ligament damage and bone resorption does occur at the site of needle insertion but these changes are transient. Care should be taken when using a local anesthetic with epinephrine in patients who may be sensitive to the vasoconstrictor effects. Anesthetic solutions given intraosseously will enter the blood system rapidly.9
Success of the periodontal ligament injection is dependent on the anesthetic being delivered under pressure into the periodontal ligament space. There are specialized syringes available to give the dentist a mechanical advantage and a metered dose when injecting, but most dentists are capable of administering a periodontal ligament injection with the traditional syringe.
Intraosseous Injection
The intraosseous injection is not a new technique. The original technique required surgical exposure of the cortical bone and drilling a hole with a small round bur. A new technique has been developed in which an introducer device prepares a small hole in the cortical bone. A 27-gauge ultrashort needle is then placed in the perforator hole and local anesthetic is injected into the cancellous bone. There are two systems currently on the market: Stabident and Cyberdent. The Stabident system uses a perforator that fits on a contra-angle slow-speed handpiece. The injection needle is the same length and diameter as the perforator. Cyberdent is a unit in which the perforator and needle are mounted on a specially designed slow-speed handpiece.
The first step in the intraosseous injection is to locate the perforation site. The perforation site is typically distal to the tooth of interest at an equal distance from the adjacent tooth; 2 mm below a line connecting the gingival margins of the teeth. Once the perforation site is located it is necessary to deposit a small amount of local anesthetic for soft tissue anesthesia, if the patient is not already anesthetized. Perforation may be approached in one of two ways. One approach is to hold the introducer tip perpendicular to the injection site and penetrate the soft tissues and buccal plate in a series of short bursts. Cancellous bone is reached when there is a sudden loss of resistance. The other approach is to angle the perforator so that the needle is directed apically. A 35-degree angle is used for all maxillary injections. In an anterior mandible a very acute angle is used (10 degrees). This angle will gradually increase for the posterior mandible (60 degrees for the molars). The soft tissues and buccal plate are penetrated until the collar of the perforator touches the gingiva. Once perforation is complete the perforator is removed and the needle is introduced into the hole, following the same path of entry. Single tooth anesthesia may be achieved through the slow deposition of a third of a cartridge of local anesthetic. A full cartridge of local anesthetic will provide anesthesia for multiple teeth. It is not recommended to use this injection near the mental foramen, near the midline, nor close to the maxillary sinus if sinus penetration is likely. It is also not recommended for use when the adjacent teeth are very close together and introduction of the perforator may penetrate the periodontal ligament.
Many patients will experience an increase in heart rate with the intraosseous injection of epinephrine-containing local anesthetics. This effect lasts about 2-3 minutes and is seen in approximately 60 percent-80 percent of individuals receiving the injection. 10-13 Patients should be informed of this effect to decrease their anxiety, should it happen. If the patient is sensitive to epinephrine or cardiovascularly compromised it may be a better choice to use 3 percent mepivacaine plain for the intraosseous injection. 3 percent mepivacaine plain has been shown to be effective when used as a supplemental intraosseous injection in teeth with irreversible pulpitis.14
The intraosseous injection may be used as a primary anesthetic technique.11,15 Replogle11 evaluated, in a clinical study, the efficacy of an intraosseous injection of either 2 percent lidocaine (1:1000,000 epinephrine) or 3 percent mepivacaine plain in mandibular first molars. Anesthetic success was achieved in 74 percent of the first molars injected with the lidocaine solution and only 45 percent of the first molars injected with the mepivacaine solution. The duration of anesthesia decreased over 60 minutes with the lidocaine solution having a longer duration of action.
The intraosseous injection has been very successful as a supplemental technique. Reisman14, in a clinical study, gave patients with a symptomatic mandibular molars an inferior alveolar nerve block with 2 percent lidocaine (1:100,000 epinephrine). Anesthesia was successfully achieved 25 percent of the time. By adding a supplemental intraosseous injection of 3 percent mepivacaine plain, there was an overall success rate of 80 percent. If an additional intraosseous injection was given (with 3 percent mepivacaine plain) the overall success rate was boosted to 98 percent.
Finally, no matter how successful different injection techniques are reported to be, if the patient is anxious they will be very difficult to anesthetize. Anxiety lowers the pain threshold. When this occurs the patient will experience non-painful stimuli as being painful. Decreasing patient anxiety is as important as the local anesthesia. Ways to manage patient anxiety may be through the use of nitrous oxide and oxygen inhalation sedation, oral sedation, or intravenous anesthesia.
Author
Christine L. Quinn, DDS, is currently an adjunct associate professor at the UCLA School of
Dentistry in the Division of Diagnostic and Surgical Sciences. She also has a private practice in
dental anesthesiology.
References/ 1. Kaufman E., Weinstein P, Milgrom P. Difficulties in achieving local anesthesia. JADA,
108:205-208, 1984.
2. Rood JP, Some anatomical and physiological causes of failure to achieve mandibular
analgesia. Brit. J. Oral Surg, 15:75-82, 1977.
3. Najjar TA, Why can't you achieve adequate regional anesthesia in the presence of infection?
Oral Surg Oral Med Oral Path, 44:7-13, 1977.
4. Horrobin, DF, Durand, LG, Manku, MS, Prostaglandin E1 modifies nerve conduction and
interferes with local anaesthetic action. Prostaglandins, 14:103-108, 1977.
5. Brown RD, The failure of local anaesthesia in acute inflammation. Brit Dent J, 151:47-51,
1981.
6. Eldridge DJ, Rood JP, A double-blind trial of 5 percent lignocaine solution. Brit Dent J,
142:129-130, 1977.
7. VanGheluwe J, Walton R, Intrapulpal injection-factors related to effectiveness. Oral Surg
Oral Med Oral Path Oral Radiol.Endod, 83:38-40, 1997.
8. Cannell H, Kerawala C, Webster K, Whelpton R, Are intraligamentary injections
intravascular? Brit Dent J, 175:281-284, 1993.
9. Jastak JT, Yageila JA, Donaldson D, Local Anesthesia of the Oral Cavity, Philadelphia, WB Saunders Co, 1995.
10. Replogle K, Reader A, Nist R, Beck M, Meyers W, Weaver J, Anesthetic efficacy and
cardiovascular effects of the intraosseous injection. J Endodon, 21:227,1995 (abstract)
11. Replogle K, Reader A, Nist R, Beck M, Weaver J, Anesthetic efficacy of the intraosseous
injection of 2 percent lidocaine (1:100,000 epinephrine) and 3 percent mepivacaine in
mandibular first molars. Oral Surg Oral Med.Oral Path Oral Radio l Endod, 83: 30-37, 1997.
12. Coggins R., Reader A., Nist R., Beck M., Meyers WJ, Anesthetic efficacy of the
intraosseous injection in maxillary and mandibular teeth. Oral Surg Oral Med Oral Path Oral
Radiol Endod, 81: 634-641, 1996.
13. Dunbar D, Reader A., Nist R, Beck M., Meyers WJ, Anesthetic efficacy of the intraosseous
injection after an inferior alveolar nerve block. J Endodon, 22(9):481-486, 1996.
14. Reisman D, Reader A., Nist R, Beck M, Weaver J. Anesthetic efficacy of the supplemental
intraosseous injection of 3 percent mepivacaine in irreversible pulpitis. Oral Surg Oral Med Oral
Path Oral Radiol Endod, 84:676-682, 1997.
15. Leonard MS, The efficacy of an intraosseous injection system of delivering local anesthetic.
JADA, 126:81-86, 1995.
To request printed copies of this article please contact: Dr. Christina L. Quinn, UCLA School of
Dentistry, Room 3-050, Box 951668, Los Angeles, CA 90095-1668.
