May 2016
Volume 37, Issue 5


This in vitro study is the first to compare the pH buffering of seven commercially available local anesthetic preparations using a simple chairside hand-mixing technique with commercially available 8.4% sodium bicarbonate, versus the commercially available Onpharma mixing device with the Onset Sodium Bicarbonate Injection, 8.4% USP Neutralizing Additive. Both techniques were equally effective in raising the pH levels of all seven of the commercially available local anesthetics tested despite the Onpharma product having only been approved for buffering lidocaine.

While these results may have some significant clinical implications, additional clinical studies are needed to assess the safety and efficacy of 4% local anesthetic solutions. Additionally, the use of stored buffered solutions is not recommended and dentists should use alkalinized local anesthetic as close to mixing time as possible. Over time, the pH levels of the buffered solutions may continue to rise and, in some cases, a precipitate may form. Furthermore, the production of CO2 as a byproduct of the buffering reaction, while beneficial initially, may result in further instability of the mixture over time.


The authors would like to thank lab technician Vilma Torres for her help in testing and storing samples.


DENTSPLY Pharmaceutical, York, PA, donated the local anesthetics solutions used in this study. The authors received no financial assistance or remuneration for the completion of this study.

About the Authors

Jason H. Goodchild, DMD
Clinical Education Manager
Focus North America
Clinical Affairs, Dentsply Sirona Inc.
Milford, Delaware

Mark Donaldson, PharmD
Clinical Pharmacy Performance Services
Vizient Inc.
Whitefish, Montana
Clinical Professor
Department of Pharmacy
University of Montana
Missoula, Montana
Clinical Associate Professor
School of Dentistry
Oregon Health & Science University
Portland, Oregon


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