Clinical Outcomes Mandible: Buffered 1% vs. Non-Buffered 1% Lidocaine

Background:

Based on the discovery of its topical and locally injected anesthetic effects at the end of the 19th century, cocaine was rapidly adopted as a means of blocking painful sensory impulses from the periphery during surgical procedures.(1) In the last decade local anesthetics have been administered more often, alone or in combination with IV or inhalation anesthetics for most surgical procedures. For clinical procedures in the head and neck the local anesthetic drugs have been combined with a vasoconstrictor, usually epinephrine, to prolong the anesthetic effect at the locally injected anatomic site. To achieve pulpal and periosteal anesthesia by nerve or field block for procedures in dentistry, lidocaine at a 2% concentration has been preferred by clinicians for its reliable outcomes. To prolong the shelf life of the vasopressor, the drug combination must be formulated with a low pH, approximately pH 3.5 for lidocaine with 1/100k epinephrine (Epi).

With a better understanding of the pharmacology, new options for improving local anesthetic effectiveness including buffering the commercially supplied drugs to a neutral pH just prior to injection, continue to emerge.(2) When injected, the low pH causes the "sting" felt by patients on injection. Buffering to a neutral pH eliminates this discomfort and makes the maximum concentration of the non-ionized form of the anesthetic drug immediately available to the targeted nerve membrane.(3-7) Until recently, buffering local anesthetics containing Epi followed with bicarbonate just prior to injection was impractical for the quantities used in intraoral procedures. However, today we do have options to efficiently accomplish this buffering technique.(Anutra Medical, Research TrianglePark, NC).

Buffering local anesthetics just prior to use produces positive outcomes including less "sting" on injection, faster onset of the drug, and possibly added drug potency, ie the same positive clinical effect at lower dosage. In pilot studies with healthy adults as their own controls investigators have shown that Buffered 1% lidocaine with 1/100k Epi was as effective as Non-buffered 2% lidocaine with 1/100k Epi for pulpal anesthesia on a 1st molar or canine after nerve block in the mandible or field block in the maxilla-Phase one of this study.(8,9) These outcomes could be beneficial for performing multiple procedures in children whose lidocaine dosage is limited by body weight or others with chronic liver disease.

Rationale:

The recently reported results from the two clinical studies involving buffered lidocaine with Epi have led to clinicians questioning whether the Buffered 1% lidocaine with Epi might be as effective for achieving pulpal and periosteal anesthesia for dental procedures as Non-Buffered 1% lidocaine with Epi-Phase two of this study, outcomes not usually considered by most clinicians. This protocol addresses that question.

Specific Aims:

Compare clinical depths of pulpal anesthesia for maxillary(Phase one) and mandibular(Phase two) molar and canine teeth at 30min intervals Post-injection of lidocaine Assess pain levels during injection Assess time after injection to lower lip numb

Hypotheses:

No differences exist in anesthetic depth for pulpal anesthesia after intraoral injection mandibular nerve block between Buffered 1% lidocaine with 1/100k epinephrine as compared to Non-buffered 1% lidocaine with 1/100k epinephrine.

Subjects will serve as their own controls in a cross-over AB/BA study design which is uniform within sequences, uniform within periods, and balanced