Re: "Hot" tooth - Myths or Reality?


"Dr Steve" <nospam@xxxxxxxx> wrote in message
news:G5NHe.352$646.261@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Are the hydrogen ions added to change the pH or to change the polar
> charge? Or, does that question make any sense?

It changes the pH...which changes the polar charge.


> ~+--~+--~+--~+--~+--
> Stephen [What's a Temporary?], D.D.S.
> Michigan, USA
> ....................................................
>
> 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
>>
>
>


.

Relevant Pages

  • Re: "Hot" tooth - Myths or Reality?
    ... Are the hydrogen ions added to change the pH or to change the polar charge? ... > " Local anesthetics are weak bases with pKa in the range of 7.9. ... > order to keep the local anesthetic molecules in solution, ...
    (sci.med.dentistry)
  • Re: "Hot" tooth - Myths or Reality?
    ... > It changes the pH...which changes the polar charge. ... Local anesthetics have pH's of approximately ... But hydrogen ions are added to make them ... >>> order to keep the local anesthetic molecules in solution, ...
    (sci.med.dentistry)
  • Re: "Hot" tooth - Myths or Reality?
    ... Not too sure about the "as most junior high school students know" bit, ... But hydrogen ions are added to make them acidic: ... > " Local anesthetics are weak bases with pKa in the range of 7.9. ... > course means that at a pH of 7.9 a population of local anesthetic molecules ...
    (sci.med.dentistry)
  • Re: "Hot" tooth - Myths or Reality?
    ... 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. ... course means that at a pH of 7.9 a population of local anesthetic molecules ...
    (sci.med.dentistry)