Re: "Hot" tooth - Myths or Reality?

Are the hydrogen ions added to change the pH or to change the polar charge?
Or, does that question make any sense?

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Stephen [What's a Temporary?], D.D.S.
Michigan, USA
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This posting is intended for informational or conversational purposes only.
Always seek the opinion of a licensed dental professional before acting on
the advice or opinion expressed here. Only a dentist who has examined you
in person can diagnose your problems and make decisions which will affect
your health.
.......................
"NOYB" <noyb@xxxxxxxx> wrote in message
news:OVMHe.12782$oZ.3617@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> "Dr Steve" <nospam@xxxxxxxx> wrote in message
> news:BKJHe.230$646.52@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> Are you sure?
>
> Yes...sort of. Local anesthetics have pH's of approximately 7.9...making
> them a weak base. But hydrogen ions are added to make them acidic:
>
> " Local anesthetics are weak bases with pKa in the range of 7.9. This of
> course means that at a pH of 7.9 a population of local anesthetic
> molecules is equally divided between a charged and uncharged state. In
> order to keep the local anesthetic molecules in solution, hydrogen ions
> are added (that is, the solution is made acidic) or said another way, the
> pH of the solution is lowered. If the local anesthetic solution is made
> with epinephrine, the pH is made even lower.
>
> Lets turn our discussion now to a consideration of nerves. As most junior
> high school students know, nerve membranes are a lipid bilayer with
> protein channels. Local anesthetics act in the sodium channel, entering
> from the internal aspect. Now you may have noticed a bit of a problem.
> Positively charged local anesthetic molecules soluble in an aqueous
> solution will have trouble passing through a lipid membrane. This problem
> is overcome when the tissue surrounding the nerve accepts (or buffers) the
> hydrogen ion and the uncharged molecules are then free to pass through the
> axonal membrane. Once in the cell, the molecules must be recharged before
> they can effect a block of the sodium channel.
>
> OK, so what? What difference does this make clinically? Local anesthetics
> will not work in tissue that is unable to buffer the excess hydrogen ions.
> This is why local anesthetics injected into the acidic environment of an
> abscess will not cause numbness. Occasionally anesthesiologists will add
> NaHCO3 to local anesthetic to speed the onset of the drug effect. This
> additive is not a powerful enough base to overcome the acidity in
> abscessed tissue, however. "
>
> http://www.anesthesia.wisc.edu/med3/localanes/localhandout.html
>


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Relevant Pages

  • Re: "Hot" tooth - Myths or Reality?
    ... It changes the pH...which changes the polar charge. ... But hydrogen ions are added to make them acidic: ... >> " Local anesthetics are weak bases with pKa in the range of 7.9. ... >> order to keep the local anesthetic molecules in solution, ...
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  • Re: "Hot" tooth - Myths or Reality?
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  • Re: "Hot" tooth - Myths or Reality?
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