Reader Question: Why Doesn't My Whitening Toothpaste Whiten Anymore?

Teeth whitening has always been super interesting to me. (Did you guys check out the last line I test drove?) Like, why can some people get sparkling white smiles despite sipping red wine every night, and then some people can whiten their teeth monthly and only have a so-so smile? So, when a friend recently asked me why her whitening toothpaste didn't whiten her teeth anymore, I had to investigate.

First, a little background. There are three layers of your teeth that affect their color: the inner dentin layer, the outer enamel layer and a layer called pellicle that forms a film over your teeth just seconds after you clean 'em; pellicle's job is to protect your pearlies from acidic compounds and continuous deposition of calcium phosphate. Phew, got it? 

So, when you brush with whitening toothpaste, you're just scrubbing away that surface stain layer -- the pellicle film -- that sits on top. That's the whitening you see from whitening paste.

Anyway, if that surface stain layer hangs on teeth too long (i.e. you're not brushing regularly), the film starts to seep into your enamel, which is porous. So, trying to get deep stains out with a whitening toothpaste is essentially a waste of time, since those toothpastes JUST remove the outer film, not anything that's seeped into the enamel. Instead, you need to use a whitening treatment or hit up the dentist for a quality job. These treatments do actually seep into the enamel and cause an oxidation reaction to break down deep stains. (You know that foamy weirdness that happens with white strips? That's the oxidation.)

So, question answered. Interesting, right?

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Image Credit: Devon Jarvis

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