Toothpaste Abrasivity

Q: My teeth are sensitive and they hurt at the gum line. Could it be my toothpaste?

A: Most assuredly it could be toothpaste. Your complaint is becoming a very common one that dentists hear. Other factors also cause tooth sensitivity, but let’s just address what is called “toothpaste abrasion” first. Toothpaste makers regularly measure their product’s abrasivity. It’s necessary for FDA approval and usually is not included in marketing. Abrasivity measurements are given in what’s known as an RDA value, which stands for the relative dentin abrasivity.

So how hard is a tooth? A Mohs unit is how you rate the hardness of a crystalline structure (this includes teeth). For instance, the Mohs hardness of a diamond is 10, while the Mohs hardness of glass is 5. The Mohs hardness of tooth enamel is also 5, while Mohs hardness of dentin is 2.5. Sodium bicarbonate (baking soda) has a Mohs hardness value of 2.5 and an RDA value of 7. It is the dentin or root of the tooth that is most effected by toothpaste abrasion.

This means that any toothpaste with a higher RDA value than 7 has the potential to cut dentin.

Research shows that 50% of toothpaste abrasion occurs in the first 20 seconds of brushing. So the spot that your toothbrush-toothpaste hits first will receive the most abrasion damage. Big toothbrushes and lots of highly abrasive toothpaste, such as whitening toothpastes and Crest Pro-Health, have the potential to do an incredible amount of damage. The Crest Pro-health RDA value is 189!

But there are also many other modifying factors that can enhance toothpaste abrasivity, such as amount of toothpaste, size of brush, bristle size and texture, frequency of brushing, length of brushing time, force of brushing, brushing speed or strokes per minute, recent soda consumption, recent bleaching, dryness of mouth, and many more factors.

It would follow that a motorized toothbrush either circular or ultrasonic shoving toothpaste against the tooth, would greatly increase the abrasivity of the toothpaste. The same would be said of the excessive use of force with a manual toothbrush.

A toothbrush should last at least 6 months, or even longer. If the bristles bend within a few weeks, then the brushing force is excessive. The smaller the head of the toothbrush the better.

Below is a list of frequently used toothpaste products and their corresponding RDA values. See if you can find your favorite brand of toothpaste. If your toothpaste RDA exceeds 7 and you’re experiencing sensitivity, a simple test would be to change toothpastes to a lesser RDA toothpaste for a short while. If the sensitivity goes away, Bingo! You just diagnosed the problem! Just take some time to think this thru.


(Relative Dentin Abrasivity) – Tooth Cutting Ability

Toothpaste makers regularly measure their product’s abrasivity. It’s necessary for FDA approval, and usually is not included in marketing. Abrasivity measurements are given by what’s known as an RDA value which stands for radioactive dentin abrasion or relative dentin abrasivity.

These are RDA values for common toothpaste: 0-70= low abrasive, 70-100= medium abrasive, 100-150= highly abrasive, 150-250= regarded as harmful limit.

The Mohs hardness of dentin is 2.5, the Mohs hardness of baking soda (sodium bicarbonate) is 2.5. The RDA value of baking soda is 7. That means any toothpaste that has an RDA value higher than 7 has the potential to cut dentin. The Mohs hardness of toothbrush bristles is 2.5. Also, research shows that 50% of damage occurs in the first 20 seconds of brushing.

RDA ValuesToothpaste Brand and VarietySource
0non-alcoholic mouthrinse (Biotene PBF(*Green Label), Act II Anticavity, Crest Pro-Health Complete, Oasis, Listerine Zero, Peridex, Peroxyl and water)Church & Dwight
7straight baking soda (The Arm & Hammer Yellow Box) 
8Arm & Hammer Tooth PowderChurch & Dwight
23Biotene PBF Drymouth Toothpaste 
30KID’S TOOTH GEL STRAWBERRY-RASPBERRY (ph value: 7.0-7.5)Lavera
30Elmex Sensitive PlusElmex
42Arm & Hammer Peroxicare Tartar ControlChurch & Dwight
42Arm & Hammer Advance White Baking Soda PeroxideChurch & Dwight
42Arm & Hammer Peroxicare RegularChurch & Dwight
44-53Squigle Enamel Saver 
49Arm & Hammer Peroxicare Tartar ControlChurch & Dwight
49Tom’s of Maine Sensitive (given as 40’s)Tom’s
53Rembrandt Original (RDA)Rembrandt
57Tom’s of Maine Children’s, Wintermint (given as mid-50’s)Tom’s
60Boiron Homeodent Natural Toothpaste-Lemon Flavor 
62Clinpro 5000 Fluoride Toothpaste 
63Rembrandt Mint (‘Heffernan RDA’)Rembrandt
63Biotene Regular 
68Colgate RegularColgate-Palmolive
70Colgate TotalColgate-Palmolive
70Arm & Hammer Advance White SensitiveChurch & Dwight
70Colgate 2-in-1 Fresh Mint (given as 50-70)Colgate-Palmolive
70-76Squigle Tooth Builder 
83Colgate Sensitive Maximum StrengthColgate-Palmolive
85Biotene Sensitive 
91Aquafresh SensitiveColgate-Palmolive
93Tom’s of Maine Regular (given as high 80’s low 90’s)Squigle (Tom’s)
94Rembrandt PlusRembrandt
94Plus WhiteIndiana Study
95Kid’s Crest 
95Crest Regular (possibly 99)P&G (P&G)
101Natural WhiteIndiana Study
104Sensodyne Extra WhiteningColgate-Palmolive
104Sensodyne Repair and Protect with Novamin (Purchased on Pharmaceuticals
106Colgate PlatinumIndiana Study
106Arm & Hammer Advance White PasteChurch & Dwight
107Crest Sensitivity ProtectionColgate-Palmolive
110Colgate HerbalColgate-Palmolive
110Amway Glister (given as upper boundary)Patent US06174515
112Prevident 5000 Booster 
113Aquafresh WhiteningIndiana Study
117Arm & Hammer Advance White GelChurch & Dwight
120Close-Up with Baking Soda (canadian)Unilever
124Colgate WhiteningIndiana Study
130Crest Extra Whitening with ScopeIndiana Study
130Crest Pro-Health with Scope (Crest for Me)Burt’s Bees, Inc.
133Ultra brite (or 120-140)Colgate-Palmolive
144Crest MultiCare WhiteningP&G
145Ultra brite Advanced Whitening FormulaP&G
150Pepsodent (given as upper bound)Unilever
165Colgate Tartar Control (given as 155-165)Colgate-Palmolive
189Crest Pro-HealthP&G
200Colgate 2-in-1 Tartar Control/Whitening or Icy Blast/Whitening (given as 190-200)Colgate-Palmolive
200recommended limitFDA
250recommended limitADA

To measure RDA in the lab, the tester starts with extracted human or cow teeth. The teeth are irradiated in a neutron flux, mounted in methyl methacrylate (bone glue), stripped of enamel, inserted into a brushing-machine, brushed by ADA standards (reference toothbrush, 150g pressure, 1500 strokes, 4-to-1 water-toothpaste slurry). The radioactivity of the rinse water is then measured and recorded. For experimental control, the test is repeated with an ADA reference toothpaste made of calcium pyrophosphate, with this measurement given a value of 100 to calibrate the relative scale.

Consumer Reports reviewed toothpastes (August 1998). Unfortunately, they did not consider RDA, only stain removal. So, high-abrasivity toothpastes like Ultra brite got the best ratings. I think you should be skeptical of their rankings. Which toothpaste is the best? Almost every dentist I know swears by Colgate Total, because it has a long-lasting antimicrobial ingredient. But in reality maybe no toothpaste is best for some people, depending on the relationship of enamel to root to sulcus (i.e. root coverage).

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