What impact does a lower tissue pH have on dental anesthesia?

A lower tissue pH has a significant impact on the effectiveness of dental anesthesia, specifically making anesthesia more difficult to achieve. Local anesthetics are weak bases that exist in a balance between their ionized and non-ionized forms. At a lower pH, as commonly found in infected or inflamed tissue, the proportion of the ionized form increases. This ionized form is less able to cross cell membranes to reach the nerve cells and exert its anesthetic effects.

Consequently, when the tissue pH is low, the local anesthetic's ability to diffuse through tissues and bind to its receptors in the nerve fibers is compromised. This leads to a reduced effectiveness of the anesthetic, requiring either higher doses or alternative techniques to achieve adequate anesthesia. Thus, a lower tissue pH indeed makes the delivery of local anesthesia more challenging.