I’ve receive several questions from patients about the use of baking soda

(sodium bicarbonate) as an alternative to commercial toothpaste, and especially regarding its claimed ability to whiten teeth.

Searching the Internet regarding brushing your teeth or whitening your teeth with baking soda, you’ll routinely see the claim that baking soda is VERY abrasive to use on your teeth – so if you use it, don’t use it every day. Baking soda is NOT abrasive.

Baking soda (the stuff in the box in the super market) is, by far, the lowest abrasiveness of anything you would ever brush your teeth with.

Here’s the problem – non-scientists writing articles based on assumption, and not proven fact. And once ONE person writes something, others quote him or her. Then when you have several people saying that same [false] thing, people state it and believe it as fact.

Why do so many people “assume” baking soda is extremely abrasive? It’s because the particles are large and have sharp edges, so it “feels” gritty when you touch it.

Below on the left you see a microscopic photo of baking soda particles. Notice how they have edges and corners. Below on the right you see silica particles, which would be the most common abrasive in toothpastes. Notice how rounded and smooth the silica particles are. But also realize that the baking soda particles are much, much larger than the silica particles.

Baking soda particles can be as much as 15 times larger than silica particles in toothpaste.

So what’s the difference? Silica particles are much, much harder than baking soda particles.

When you forcefully rub two hard objects against each other, the harder object will have almost zero damage, and the softer object will be greatly scratched and damaged. For example, a diamond is a hardness of 10 on the Mohs Hardness Scale, and glass is rated at 5. So diamond is much harder than glass. When diamond is firmly rubbed against glass, it will scratch the glass, but the diamond will not be damaged.

Mohs Hardness of materials (remember this is an ordinal scale, so there is no mathematical formula of consistent distance between each number):

• Tooth enamel = 5
• Tooth dentin/root = 3
• Baking soda = 2.5
• Hydrated silica in toothpaste = 5-7

Baking soda “feels” much more gritty than regular toothpaste (which usually has hydrated silica as the abrasive) because the particles are larger, and the edges are rough. Whereas silica particles are more round, smooth, and many times smaller. So baking soda “feels” more abrasive – but it’s not.

The fact is that Baking Soda, being much softer than tooth enamel, and very slightly softer than even tooth dentin, will not create much damage (abrasion) to the tooth.

The American Dental Association has published their RDA (Relative Dentin Abrasivity) to measure the abrasiveness of various toothpastes. The RDA abrasiveness categories are:

• Low 4-70 (plain water is 4. Baking soda is 7.)
• Medium 70-100
• High 100-150
• Harmful 150-250

The FDA limits abrasiveness to a maximum of RDA 200.

The RDA of Arm & Hammer baking soda is only 7. Whereas the most typical tooth paste will be in the 70-100 range with many far above that. THAT is how gentle baking soda is, as far as abrasion to your teeth.

Of course, keep in mind that commercial toothpastes that claim to be baking soda toothpastes also contain other abrasives. So using baking soda in the commercial toothpaste may be thought of as somewhat of a marketing gimmick to get you to buy the toothpaste.

This means you can brush your teeth with more paste and for a longer time if you’re using straight baking soda mixed to a paste with only water. That alone will help physically remove more bacteria and more stain. Why? Stain will typically be softer than baking soda, so, though

baking soda will not cause much abrasion of your teeth, it’s still hard enough to scrape off many types of stain from your teeth.

The main problem with using straight baking soda/water paste? No fluoride.