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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Assembler on August 15, 2007, 12:16:17 AM

Title: Why doesn't the flouride in toothepaste form HF and corrode your mouth?
Post by: Assembler on August 15, 2007, 12:16:17 AM
After reading an ACS lab safety manual on how bad HF is, I got to thinking this question.  Toothpaste is effective because it has flouride (F-) and the bacteria in your mouth produces acid.  Wouldn't this form HF in your mouth?  If so, is it because it's formed in such dilute concentrations that it isn't harmful?  Thanks for looking.
Title: Re: Why doesn't the flouride in toothepaste form HF and corrode your mouth?
Post by: Mitch on August 15, 2007, 02:55:42 AM
Why not make the same argument for Table Salt? NaCl
Title: Re: Why doesn't the flouride in toothepaste form HF and corrode your mouth?
Post by: mir on August 15, 2007, 04:51:05 AM
You are correct about that high conc of fluoride is harmful. Fluoride in toothpaste is in the parts per billion area, very dilute. But you have to consider that you re exposed to fluor everyday in your food, in your drinking water etc. Fluor is a common element in the solar system. So why dont we get poisoned you ask? Some elements (or all?) is acting like poison in too high concentrations and is also killing you if you get too little of it. Your body needs a constant supply of iron for your blood, but too much iron might kill you. So goes for the fluoride, but in ultratrace amounts. We all need up to 12 elements in correct dose for an healthy life.

Read about the Bertrand rule.
Title: Re: Why doesn't the flouride in toothepaste form HF and corrode your mouth?
Post by: profmsg on August 15, 2007, 08:31:24 AM
you know the saying" even poison acts as a medicine in limited dose."
so F which is a poison to all microbes and kills off...they are in tiny amount present in tootpast so they dont affect multicellular animals however they are enought to kill single celled mircobes. F may effect in future if it collected in body for long term.
Title: Re: Why doesn't the flouride in toothepaste form HF and corrode your mouth?
Post by: Assembler on August 15, 2007, 08:08:08 PM
Thanks for the responses.  I understand.
Title: Re: Why doesn't the flouride in toothepaste form HF and corrode your mouth?
Post by: Sam (NG) on August 17, 2007, 05:01:51 PM
Quote from: profmsg on August 15, 2007, 08:31:24 AM
you know the saying" even poison acts as a medicine in limited dose."
so F which is a poison to all microbes and kills off...they are in tiny amount present in tootpast so they dont affect multicellular animals however they are enought to kill single celled mircobes. F may effect in future if it collected in body for long term.

Actually it works to strengthen remineralised tooth enamel by changing the structure of the apatite laid down from hydroxylapatite to fluoroapatite (Ca10(PO4)6(OH)2 to Ca10(PO4)6F2).  hydroxylapatite is much more acid sensitive than fluoroapatite.