Local anesthetics were first introduced in the 1880s by William Halsted, MD, when he found injectable cocaine to be useful for surgeries. Local anesthetics are now used for dental treatment on a daily basis. Previously, patients were given ester medications (remember Novocaine?). In today’s dental offices, amides such as lidocaine, mepivacaine, bupivacaine, articaine or prilocaine are likely used.
Adverse effects from dental injections can range from mild, such as prolonged anesthesia, hematoma or soreness in the injection site, to moderate/severe effects such as an allergic response (rare with amides) or overdosage, which could lead to respiratory arrest and death.
With proper precautions, it is difficult to overdose an adult patient. The toxic level of anesthetic is figured by a patient’s weight. The smaller the patient, the less anesthetic is needed to reach toxic levels. (See tables on page 48.)
To calculate the maximum amount of lidocaine 2 percent with 1:100,000 epinephrine and the number of carpules that can be safely administered to a 30-pound patient, the clinician would perform the following calculations.
The type of dental procedure may dictate the duration of local anesthetic needed. Vasoconstrictors such as epinephrine are added to anesthetics to increase duration by concentrating the solution in the injection site.
Healthy patients undergoing dental treatment are less apt to suffer from complications from the anesthetic. Contraindications to the use of vasoconstrictors or dental anesthetics include:
Before administering local anesthetics, it is recommended to get a thorough medical history, including blood pressure readings. Frequently this screening will uncover high blood pressure that will need to be monitored and treated by the patient’s physician. We will refer our patients to their PCP if their BP readings are too high.
- Recent heart attack (<1 month)
- Uncontrolled hypertension
- Uncontrolled diabetes mellitus
- Uncontrolled hyperthyroidism
- Documented allergy
- Recent drug abuse
A variety of injections are used for anesthetizing a patient for dental treatment. The areas anesthetized for the most common dental injections are shown:
Recent improvements in the administration of local anesthetics include buffering of the anesthetic solution with sodium bicarbonate, which raises the pH, allowing a more comfortable injection and hastening the onset of profound anesthesia. Because the buffered solution becomes unstable quickly, it must be mixed minutes before administering the anesthetic to the patient. The effectiveness of the buffered anesthetic allows a decrease in the amount of carpules used, due to fewer missed blocks (Onpharma, Anutra Medical).
An injectable solution of phentolamine mesylate can be given to reverse the effects of local anesthesia (OraVerse). It is not recommended for children under the age of 6, or who weigh less than 33 pounds. It may be most helpful in older children, geriatric patients and special-needs patients.
For the needle-phobes, intranasal local anesthetic is being tested and may be released soon (St Renatus, LLC). It provides anesthesia bilaterally in the maxilla from first molar to first molar, with 100 percent success occurring from bicuspid to bicuspid #4-#13. On maxillary first molars there were mixed results, so injections on these teeth may be needed for profound anesthesia when using this technique.
Delivery systems such as The Wand or STA are computer-
controlled local anesthetic delivery systems (C-CLAD), which allow more predictable single-tooth anesthesia. In tests on children there was a measurable decrease in reactions to C-CLAD anesthesia administration compared to the standard syringe, making it useful in pediatric dentistry.
Whether you are a recent graduate or an experienced dentist, periodically reviewing the dosages, contraindications and new developments in local anesthetics will be helpful to you and your patients. For more information, consult the Handbook of Local Anesthesia (6th Ed.) by Dr. Stanley Malamed.
- Malamed, SF. Handbook of Local Anesthesia, 6th Ed. St. Louis, Missouri: Elsevier Mosby; 2013.