Enhance Patient Comfort With Buffering

Comfort is key to providing compassionate and effective dental care. While advances have been made in the pharmacology of local anesthetic (LA) drugs, buffering improves safety, efficacy, and comfort.

LA drug solutions are acidified during manufacturing to enhance solubility and increase stability. In addition, solutions with vasoconstrictors are more acidic because they include sulfite antioxidants to improve vasoconstrictor shelf life, which further lowers pH levels. Throughout the useful shelf life of vasoconstrictor-formulated LA drugs, these preservatives continue to lower pH levels.

At these levels, the percentage of charged molecules (RNH+) initially deposited into tissues is increased, which can delay onset and increase burning and stinging sensations. Studies comparing nonbuffered to buffered intraoral injections have noted significant improvements in comfort using buffered solutions.^1-5 Physiologic (natural carbonate) buffering in human tissues quickly raises the pH of LA drugs after injection, offsetting initially low pH levels. For example, the pH of 2% lidocaine with a vasoconstrictor ranges from 2.9 to 4.4.^4,6 In this pH range, the percentage of nonpolar molecules (RN) that are available to cross nerve membranes is significantly less than in typical extracellular tissue (7.2 to 7.4). It’s helpful to appreciate that an LA drug with a pH of 6.4 is 10x more acidic than physiological pH (7.4). And a pH of 5.4 is 100x more acidic than 6.4. A pH of 4.4 is 1,000x more acidic than 7.4. According to Malamed,^5,7,8 at a pH of 3.5, only 0.004% of RN anesthetic molecules are available to cross the nerve membrane initially (99.996% are not). When LA drugs are buffered to a pH of 7.2, 50% of the RN molecules are available to cross nerve membranes.

Catchlove⁹ describes mechanisms by which CO₂ — generated when actively buffering LA drugs — is thought to enhance LA efficacy. It is known to have a rapid direct depressant effect on the nerve membrane (fast onset and comfort); it decreases the axoplasmic pH by forming carbonic acid, which concentrates RNH+ ions; and it results in an additional trapped surplus of RNH+ in the axoplasm. CO₂’s rapid actions have been suggested as an explanation for active buffering’s enhanced anesthetic effectiveness.^4,5,9

Evidence confirms that buffered anesthetics have faster onsets and are more effective than their nonbuffered counterparts.^1,3,4,5,7,9 LA solutions are slightly diluted when 0.1 mL of buffering agent is added. Even if only marginally less concentrated, compared to nonbuffered LA, buffered anesthetics are effective in smaller doses, which can also enhance safety.

Buffering LA solutions are shown to improve patient comfort by reducing the initial discomfort associated with low pH levels, enhancing clinical time management with the rapid development of anesthesia, decreasing doses administered, and improving safety and efficacy. Ultimately, the use of buffering agents leads to more efficient and pleasant dental experiences. As such, it is reasonable to consider that buffering may become the standard of care.

References

1. Bassett KB, DiMarco AC, Naughton DK. Dental local anesthetic drugs, articaine. In: Local Anesthesia for Dental Professionals. 2nd ed. Upper Saddle River, New Jersey: Pearson Education; 2015:55–58.
2. Goodchild JH, Donaldson M. Novel direct injection chairside buffering technique for local anesthetic use in dentistry. Compend Contin Educ Dent. 2019:40:1–10.
3. Kattan S, Lee S-M, Hersh EV, Karabucak B. Do buffered local anesthetics provide more successful anesthesia than nonbuffered solutions in patients with pulpally involved teeth requiring dental therapy? A systematic review. J Am Dent Assoc. 2019;150:165–177.
4. Donaldson M, Goodchild JH. Taking local anesthesia to the next level: Four strategies clinicians may consider. Compend Contin Educ Dent. 2022:43:20–24.
5. Malamed SF, Tavana S, Falkel M. Faster onset and more comfortable injection with alkalinized 2% lidocaine with epinephrine 1:100,000. Compend Contin Educ Dent. 2013;34:10–20.
6. Frank SG, Lalonde DH. How acidic is the lidocaine we are injecting, and how much bicarbonate should we add? CaJ J Plast Surg. 2012;20:71–73.
7. Malamed SF. Buffering local anesthetics in dentistry. Pulse. 2011;44:8–9.
8. Malamed SF. Articaine 30 Years Later. Available at: oralhealthgroup.c/​m/​features/搰/​. Accessed March 13, 2025.
9. Catchlove RF. The influence of CO₂ and pH on local anesthetic action. J Pharmacol Exp Ther. 1972;181:298-309.

From Decisions in Dentistry. March/April 2025;11(2):46.