Some Teeth Whiteners Weaken Tooth Enamel

teeth whiteners

Go to any drugstore or supermarket and you will find numerous teeth whiteners on the shelves. Many ask whether they are healthy for the teeth or gums. And certainly a dentist will tell anyone with sensitive teeth to be careful of teeth whiteners: Because they can increase teeth sensitivity.

But there is another issue to be concerned about when it comes to chemical teeth whiteners. The subject is microhardness.

What is Microhardness?

What is it and why is microhardness important?

Microhardness is the hardness of the surface of the enamel. When the teeth enamel softens, it exposes more of the internal tooth to invasion by bacteria or their byproducts, creating more dental decay.

Whiteners reduce microhardness

Dental researchers from South Africa’s University of the Western Cape have confirmed that some commercial teeth whiteners will significantly reduce the microhardness of the enamel of the teeth.

The researchers tested four commercially available, over-the-counter teeth-whiteners. They prepared fifty enamel blocks from molars that had been extracted from human dental patients.

They then applied each of the four whitening products to 10 of the molar blocks, and one block of ten was kept in a solution that matched saliva as a control.

The whiteners were tested for one day, seven days and 14 days, and at each interval, the molar blocks were tested with a digital hardness testing machine combined with a Vickers diamond indenter.

The data was then analyzed with a standardized comparison model. The researchers found that two of the products tested (“Rapid White” and “Absolute White”) significantly reduced microhardness of the enamel, while another had no effect (along with the saliva) and one (“White Glo”) slightly increased enamel microhardness.

The data supported the researchers cautionary conclusion:

“Over-the-counter tooth-whitening products might decrease enamel microhardness depending on the type of product.”

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Other studies confirm reduced microhardness with whiteners

A similar study from the University of the Western Cape in 2009 tested ten different commercially available tooth whitener products. All of them contained carbamide peroxide or hydrogen peroxide.

This study focused upon results only after 14 days of treatment. Again an artificial saliva sample provided the control.

In this study, nine of the ten whiteners caused a decrease in enamel microhardness. Furthermore, five of the whitener products resulted in “significant” decreases in enamel microhardness according to the research.



Majeed A, Grobler SR, Moola MH, Oberholzer TG. Effect of four over-the-counter ooth-whitening products on enamel microhardness. SADJ. 2011 Oct;66(9):412-5.

Grobler SR, Majeed A, Moola MH. Effect of various tooth-whitening products on enamel microhardness. SADJ. 2009 Nov;64(10):474-9.

Case Adams is a California Naturopath with a PhD in Natural Health Sciences, and Board Certified Alternative Medicine Practitioner. He has authored 26 books on natural healing strategies. “My journey into writing about alternative medicine began about 9:30 one evening after I finished with a patient at the clinic I practiced at over a decade ago. I had just spent the last two hours explaining how diet, sleep and other lifestyle choices create health problems and how changes in these, along with certain herbal medicines and other natural strategies can radically yet safely turn ones health around. As I drove home that night, I realized I needed to get this knowledge out to more people. So I began writing about health with a mission to reach those who desperately need this information. The strategies in my books and articles are backed by scientific evidence along with wisdom handed down through traditional medicines for thousands of years.” Case connects with the elements by surfing, hiking and being a beach bum.

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