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Dental Myths

Pregnant Women and Fluoride Supplements

Fifty years ago you could have walked into a pharmacy and seen fluoride drops that were specifically targeted toward pregnant women. The packages claimed that fluoride drops, when taken during pregnancy would help keep their children cavity-free.

That all changed on October 20, 1966 when the FDA cracked down on the fluoride supplement makers.  They banned them from making claims that fluoride would benefit unborn babies’ teeth due to a lack of clinical evidence to substantiate that claim.

Source: Food and Drug Administration: Statements of general policy or interpretation, oral prenatal drugs containing fluorides for human use. Fed Regist Oct. 20, 1966

You may be wondering what we’ve figured out in the past 50 years about taking fluoride supplements during pregnancy.

Should Women Take Fluoride Supplements During Pregnancy?

Pregnant Women and Fluoride SupplementsThe answer is no — there is no evidence that taking fluoride supplements during pregnancy helps improve the baby’s chances of having healthier teeth.

Since fluoride supplements taken by the mother can cross the placenta, there is a chance that the well-meaning mother-to-be could actually cause their baby to get dental fluorosis.

The Evidence Against Taking Fluoride Supplements During Pregnancy

Here’s three different credible sources that all agree that there is no benefit derived from taking fluoride supplements during pregnancy.

A Clinical Trial

This clinical trial took 1400 pregnant women and divided them into two groups.  One group received 1 mg of fluoride per day during the last six months of their pregnancy while the other group received a placebo.  The kids were followed until age 5.  No noticeable difference in the amount of cavities was noted between the two groups.

A Scholarly Article

This scholarly article from the journal Pediatric Dentistry states, “Although fluoride crosses the placenta, prescribing fluoride supplements to pregnant women is not recommended because there is little evidence that fluoride provided to the mother during pregnancy reduces caries prevalence in their offspring.

A Statement from the American Academy of Pediatric Dentistry

This guideline from the American Academy of Pediatric Dentistry states, “The AAPD does not support the use of prenatal fluoride supplements to benefit the fetus.”


Although 50 years ago many people thought that taking fluoride supplements during pregnancy was good for their baby’s teeth, it turns out that modern science has debunked that myth.

There is no reason to take fluoride supplements during pregnancy.  And there’s actually a good reason not to: dental fluorosis.

Do you have any questions or thoughts regarding fluoride supplements and pregnancy?  I’d love to hear what you have to say in the comments section below.  Thanks for reading!

Fluoride in Water and Toothpaste

Jake (whom I assume is a dentist) left an interesting comment about fluoride on Sunday.  He said:

I had an anti-fluoride patient the other day that was saying he read somewhere that a pea-sized amount of toothpaste contains the same amount of fluoride in 1 liter of tap water (1 ppm). His argument was that the toothpaste labels says to call poison control if more than a pea-sized amount is swallowed (which it doesn’t), and the same amount is in 1 liter of water. So he was wondering if he should call poison control every time he drinks more than a liter of water. It sounded ludicrous, but how much fluoride is actually in a pea-sized amount of toothpaste in comparison to 1 liter of water?

Fluoride Warnings On Toothpaste
Fluoride Warnings on Toothpaste (Click to enlarge)

I enjoy talking about water fluoridation.  Looking back, I’ve actually written 15 different posts about fluoride!

Jake’s comment really got me wondering about how the fluoride levels compare between fluoridated water and toothpaste.

Do Toothpastes Contain a Warning Telling You to Call Poison Control?

First, let’s take a look at the common anti-fluoride claim that fluoride is poison.  I took a picture of the back of three different brands of toothpastes: Colgate, Aquafresh, and Crest.  If you click on the picture, you can view a large size that will let you read the warning.  Each tube has a similar warning.  The back of the Colgate Total toothpaste box states:

If more than used for brushing is accidentally swallowed, get medical help or contact a Poison Control Center right away.

But how much do people really use for brushing?  There’s the ultra-conservative pea size, and then there’s the large stripe that toothpaste manufacturers want us to use so that we buy lots of toothpaste!

I decided to find out how much toothpaste is in a large stripe by conducting a two-part experiment.

My Toothpaste Experiment

On the back of the toothpaste tube, it states that you should call the poison control center if you swallow more than is used for brushing.  This is what the toothpaste manufacturers write.  I took the liberty of assuming that a normal amount of toothpaste for them is a thick stripe on a manual toothbrush (like they show in their commercials).

I decided to find out exactly how much toothpaste is in a big stripe so that I could figure out how much fluoride it has.  I got carried away and tried two different brands.

Here’s the large stripe of Colgate Total that I put on my wife’s toothbrush (are your toothbrush bristles as straight as hers?  If not, it may be time to get a new toothbrush):

A Large Stripe of Colgate on a Brush

I measured the toothpaste and found that it filled the 1/4 teaspoon – giving us 1.25 ml of toothpaste:

Colgate Toothpaste Measured

Out of curiosity (and because it seemed like a fun idea after taking two finals over the past 36 hours), I measured the Crest Toothpaste as well.  I was able to get a slightly bigger stripe on the brush this time.  Unfortunately, the stripe I created just wasn’t as good looking as it is on the toothpaste commercials!  However, if you want to practice making a beautiful stripe of toothpaste on your brush, I have to recommend the Crest since it is much thicker.

Crest Stripe on Toothbrush

This large stripe of Crest ended up overflowing the 1/4 teaspoon, giving us about 1.75 ml of toothpaste:

Crest Toothpaste Measured

I decided to take the average of my two “large stripes” to use as the baseline amount of toothpaste you can swallow and still be safe (according to the toothpaste manufacturers) – which appears to be 1.5 ml from my unscientific experiment.

Contrast this with a peasize amount of toothpaste which is only 0.2 ml.  Who would’ve guessed that the average pea only takes up a volume of 0.2 ml?

Now that we know how much toothpaste we use, we can figure out how much fluoride we would ingest if we swallowed a large stripe of toothpaste.

How Much Fluoride is in Toothpaste?

A majority of toothpastes on the market contain about 0.15% fluoride ion, which comes out to 1500 ppm (parts per million.)

In 1.5 ml of toothpaste (the large stripe pictured above) you would find 2.25 mg of fluoride.

In a pea sized amount of toothpaste, you would only find 0.3 mg of fluoride.

How Much Fluoride is in Fluoridated Water?

Most fluoridated water contains about 1.0 ppm.  That means that in 1 liter of water, you would find about 1 mg of fluoride.

Not sure how much fluoride is in your water? Then find out how much fluoride is in your tap water!

Comparing the Amount of Fluoride In Water with the Amount of Fluoride in Toothpaste

As you can see, you would have to drink over 2 liters of water to get the same amount of fluoride that you would get by swallowing a large stripe of toothpaste.  You would only have to drink 300 ml of water (a little less than a 12 oz. can of soda) to get the same amount of fluoride you would get by swallowing a pea size amount of toothpaste.

You Don’t Need to Call Poison Control When You Drink Fluoridated Water!

I’m sure Jake’s patient was just trying to make a point.  Point taken!  However, according to the American Dental Association (Page 31 in their Fluoridation Facts PDF), it would take 5-10 grams of fluoride to cause fluoride toxicity in an average 155-pound man.  That means that a 155-pound man would need to drink 5,000 liters of water (over 1300 gallons!) in order to get a toxic dose of fluoride.

The water would kill you (as this tragic story illustrates) long before the fluoride would have any toxic effect.


Interestingly, there is more fluoride in a liter of water than in a pea-sized amount of toothpaste, but more fluoride in a large stripe of toothpaste than in a liter of water.  Here’s what I found:

  • In a pea size amount of toothpaste, there’s 0.3 mg of fluoride.
  • In a large stripe of toothpaste, there’s 2.25 mg of fluoride.
  • In one liter of fluoridated water, you’ll find 1 mg of fluoride.

Although fluoride is great for your teeth, too much of it during development of the teeth can cause dental fluorosis.

Do you have any questions about toothpaste fluoride content or water fluoride content?  I’d love to hear what you have to say in the comments section below.  Thanks for reading!

Replace Toothbrush After Being Sick?

Have you ever heard that you should replace your toothbrush after you are sick?  I had heard that you should, but I never understood why.  After you get sick, your body figures out how to fight the illness and then makes you healthy again.

Once your body knows how to fight off the illness, you usually won’t ever get that exact same illness again.  Because of this, I wondered why some people recommend changing your toothbrush after you get sick.

The Case For Replacing Your Toothbrush After You’ve Been Sick

Should You Change Your Toothbrush After You Get Sick?The book Primary Preventive Dentistry says, “In addition to regular [toothbrush] replacement, replacement after contagious illness is imperative.”

…and that’s all.

The authors don’t say why you should replace your toothbrush after you get sick, and they don’t even bother to cite any studies that support their recommendation.

Colgate mentions on their oral health care website that you should replace your toothbrush after you’ve been sick:

It is also important to change toothbrushes after you’ve had a cold, the flu, a mouth infection or a sore throat. That’s because germs can hide in toothbrush bristles and lead to reinfection.

Again, they don’t give any references.  Let’s look more closely at the case against replacing your toothbrush after you’ve been sick to determine the strength of their argument.

The Case Against Replacing Your Toothbrush After You’ve Been Sick

Now don’t get too excited, but the American Dental Association has a whole page dedicated to their policy on toothbrush care — don’t worry, I read it so that you don’t have to!

The ADA never states on that page that you should replace your toothbrush after you get sick.  In fact, they even acknowledge that bacteria is almost always on your toothbrush and that your toothbrush can even be contaminated before you buy it because toothbrushes aren’t required to be sold in sterile packaging.

Ultimately, the ADA has this to say:

Although studies have shown that various microorganisms can grow on toothbrushes after use, and other studies have examined various methods to reduce the level of these bacteria, there is insufficient clinical evidence to support that bacterial growth on toothbrushes will lead to specific adverse oral or systemic health effects.

Basically, the ADA is at a loss when it comes to finding evidence linking bacteria on your toothbrush to any bad health effects.

About a year ago, I asked one of the dentists at my school what she thought about changing your toothbrush after you’re sick.  She told me that there is no scientific evidence that says that you should.  She also brought up the point that it would be hard to know exactly when to change your toothbrush since you can’t really tell when you’re very first infected and when your body has finally eliminated all of the bacteria/virus that caused the illness.


Although I don’t think it’s necessary to change your toothbrush after you get sick, I do believe that it’s a good idea to replace your toothbrush every 3 to 4 months because your brush can become a nice home for all of the bacteria that live in your mouth.  There may be exceptions if you have a compromised immune system or if you have other health issues that affect your ability to fight off infection.

What are your thoughts? Do you replace your toothbrush after you’re sick?  I’d love to hear about your views in the comments section below!

Is Water Fluoridated with Toxic Waste Fluoride
©Olivier Le Queinec/Shutterstock.com

Not too long ago I was talking with my mom about water fluoridation.  She said that she isn’t a big fan of it.  When I asked her why, she said that although she thinks it is good for teeth, she doesn’t like that they use toxic waste fluoride to fluoridate our public water supplies.  I was pretty skeptical, but I figured it wouldn’t hurt to look into this claim.

Here’s what I found.

The Three Types of Fluoride That Are Used in Water Fluoridation

Is Fluoride Toxic Waste?There are three main types of fluoride used to fluoridate public water supplies in the United States: sodium fluoride, sodium fluorosilicate, and fluorosilicic acid.  Here’s a quick overview of each of those materials:

Sodium fluoride is a white powder or crystal.  It is easy to transport and is  the “gold standard” of water fluoridation.  When artificial water fluoridation began, sodium fluoride was the powder that was used.  Unfortunately, sodium fluoride is relatively expensive, so some utility companies use other fluoride-containing compounds.  It is made up of the elements sodium and fluorine.

Fluorosilicic acid is a liquid by-product formed when phosphate fertilizers are made.  It is a liquid that has varying concentrations.  Due to the liquid form, it is expensive to ship.  It is made up of the elements hydrogen, silicon, and fluorine.

Sodium fluorosilicate is similar to fluorosilicic acid, but it is in powder form.  It is much less expensive to ship and has thus found widespread usage in many cities throughout the United States.  It is made up of the elements sodium, silicon, and fluorine.

Just to clarify above, fluorine is an element whose ion is known as fluoride.

Fluoride Used in Water Fluoridation Must Meet Rigorous Standards

The American Water Works Association has set rigorous standards that fluoride must meet in order to be used in public water supplies.  Here is how they describe each set of guidelines:

“The purpose of this standard is to provide purchasers, manufacturers, and suppliers with the minimum requirements for [the particular type of fluoride], including physical, chemical, packaging, shipping, and testing requirements.”

Here are their guidelines for the three types of fluoride used to fluoridate public water supplies:

Is Water Really Fluoridated With Toxic Waste Fluoride?

Is Fluoride an Air Pollutant?

Water is fluoridated with the above three fluoride-containing chemicals.  Many times, these fluoride chemicals are by-products of fertilizer production or other industrial by-products.  Calling them “toxic waste” may be a bit of a stretch.

Before the fluoride “waste products” can find their way into our water, they must be purified and have any contaminants removed so that when they are added to water, the water can still meet the minimum water quality guidelines.

If you’re interested in learning more about the water quality guidelines in the United States, here’s a good resource put out by the Environmental Protection Agency of all the chemical contaminants that are regulated in the public water supply.


If pure toxic waste were added to our drinking water, it wouldn’t be safe to drink.  Fluoride, when added to water has been found to make teeth more resistant to cavities.  On the flip side of the coin, fluoride also causes dental fluorosis.

If you have any questions, comments, or opinions to share on the chemicals we use to fluoridate our water supplies, please leave them in the comments section below.  Thanks for reading!

Is Blue Dental Light Harmful?
©Nejron Photo/Shutterstock.com

Recently, Christopher, a thirteen-year-old reader from Michigan wanted to know if the blue light that dentists use to cure fillings and sealants can hurt your teeth when used for a long period of time.

Blue Dental Curing LightHe told me that when he was at the dentist’s office getting sealants placed on his back teeth, they shined a light in his mouth.  After the sealants were put on, the dental assistant hardened (cured) the sealants by shining a blue light on them.  He noticed that after the blue light had shut off automatically, the dental assistant would press the button to get it to turn on again and continue curing the sealants.

Christopher wanted to know if the blue light can burn, irradiate or otherwise hurt someone’s teeth when used longer than it should be.

About the Blue Dental Curing Light

Before I answer Christopher’s question, here’s a little background information for those who aren’t familiar with the blue dental curing light.  When a dentist puts a white filling (or a sealant, or a light-cured filling material) in your mouth, it is in a liquid or semi-solid state so that the dentist can put it exactly where it needs to go and shape it correctly.  In order for the material to harden so that it can withstand the forces of chewing, it needs to be cured.

Curing the material is accomplished by shining a blue light on it.  Not just any blue light will do.  It has to be a certain shade of blue.

The blue dental curing light emits light at a wavelength of around 450 to 490 nm, a blue light.  You can read more about the visible light spectrum here.

The very first light-activated filling materials used ultraviolet light.  Fortunately, today dentists only use materials that are cured by visible light as the use of UV cured materials has pretty much died out due to the dangers posed by ultraviolet light.

Can the Blue Dental Curing Light Hurt Your Teeth?

Blue Dental Curing LightFortunately, the blue dental curing light normally won’t hurt your teeth.  Most of the modern curing lights use a blue LED light for curing.  In some of the old models, the tip could get really hot.  This heat could cause damage to the dental pulp — the innermost tissue composed of nerves and blood vessels inside of your tooth.

A good test to see if the curing light is too hot is to hold your finger 2-3 mm away from the curing light for 20 seconds.  If your finger gets too hot, then the curing light could do damage to the teeth.

The Blue Dental Curing Light Can Hurt Your Eyes!

One of the major dangers of the blue dental curing light is that it can hurt your eyes!  When we were learning how to do white fillings, our professors always advised us to never look at the blue light.

Here’s what the book Craig’s Restorative Dental Materials says about this:

Although there is minimal potential for radiation damage to surrounding soft tissue inadvertently exposed to visible light, caution should be used to prevent retinal damage to the eyes.  Because of the high intensity of the light, the operator should not look directly at the tip or the reflected light from the teeth.

The orange filter that you can see on the curing light above filters out the visible light, allowing the dentist or assistant to see what they are doing without looking directly at the light.


To answer Christopher’s question, there could be some harm in holding the light on your teeth for too long if it heated up your teeth.  Since you probably weren’t numb when the sealants were placed, you would have felt pain if your teeth had gotten too hot.  Other than that, as long as they didn’t shine the light in your eyes, no damage was done, since they used visible light rather than ultraviolet light.

The dental assistant probably just wanted to make sure that the sealant was hardened all the way, and didn’t want to leave any room for doubt.

Do you have any questions or comments about the blue dental curing light used in dentistry?  If so, feel free to leave them in the comments section below.  Thanks for reading!

By the way, I really enjoyed researching for this article.  If you have any dental questions, no matter how odd you think they are, feel free to contact me and I’ll either answer your question via email or in an article here at Oral Answers.

Do Fibrous Foods Clean Teeth?
©Mama Mia/Shutterstock.com

The internet is filled with what I like to call “Dental Pollution.” There are a lot of half-truths and myths about oral health. One of the reasons that I started Oral Answers was to provide facts and truths about dentistry to those that have unanswered questions about their oral and dental health.

Apples - Can they Clean Your Teeth?To dispel these myths, I have created a tag on this blog called Dental Myths.  Every time I set the record straight on a dental myth, I will apply the Dental Myths tag so you can easily find these myth-busting articles.

A common dental myth is that fibrous foods like apples, celery, carrots, lettuce, peppers, and many other raw foods can clean your teeth.

This belief has caused more than a few people, I’m sure, to rationalize their lack of oral hygiene, saying that they can simply “eat their way to cleaner teeth.”

The truth of the matter is that fibrous foods do not clean teeth.

Fibrous Foods Do Not Clean Teeth

In the book, Essentials of Dental Caries by Kidd it states the following about the effect fibrous foods have on teeth:

Health foods are very fashionable nowadays; it has been suggested that fibrous foods such as apples and carrots ‘clean’ teeth, thus removing plaque and preventing caries.  Although fibrous foods are preferable to a sucrose snack, there is no evidence that they can ‘clean’ the teeth.

Fibrous foods simply can’t do the same hard work that the bristles on your toothbrush do every day.

Fibrous Foods Are Good for You

This doesn’t mean that fibrous foods aren’t good for you.  They are great for your body (especially your digestive system), and good for your teeth.  Think about it — if your choice is between an apple, or an apple-flavored Jolly Rancher,  then definitely pick the apple!


As beneficial as fibrous foods are for you, they cannot actually clean your teeth; the only thing at your house that can do that is your toothbrush and some dental floss!

Are there other facts or claims you have heard about oral health that make you wonder or seem unclear?  Leave them below in the comments and I will clear them up for you.

Thanks for reading!