Dental MythBuster #9 – You can’t get a cavity under a crown

This is one dental myth that I wish I did not have to see.  The myth typically plays out like this:

“Mrs. Jones, I can see both on the x-ray and upon clinical exam that there is decay on this particular tooth.”

She will typically respond by saying:

“How can I have a cavity on that tooth? It has a crown!”

After years of practicing dentistry, I can say that this happens about 98% of the time when there is decay on a tooth which already has a crown. So this dental myth definitely needs to be busted!

Photograph of a cavity under a crown

Seeing is believing, so let’s take a look at a photo I took of a patient in my dental office in Orange, CT.

Photo showing a cavity, also known as dental decay, under a dental crown

A cavity, known more formally as dental decay, evident underneath a crown on a lower molar on a patient of mine in Orange, CT.

The decay is visible in the above photo at the gum line. Treatment will most likely involve a new crown. Without treatment, this patient will lose his tooth eventually.

By looking at the photo, you can see that it is possible to get decay under a crown. So the myth is busted! But let’s look at how it happens.

What are dental cavities?

Dental decay photo showing a cavity on an upper canine tooth

Decay on an upper canine near the gum line.

Dental decay (known less formally as dental cavities) occurs when bacteria inside the mouth ingest certain foods and then attack the teeth. This leads to a weakening of the tooth and can ultimately lead to an actual hole (a.k.a cavity) in the tooth.

Decay can occur on any part of any tooth in the mouth. It can occur on teeth that have never had a filling before. Or the decay can start on teeth that have had fillings, crowns, or root canals.  It can start at age 2 or age 100! For a more detailed explanation, you can refer to a page I authored on my main practice website.

How teeth with dental crowns can develop decay

As stated earlier, decay can develop on any tooth. But cavities are more likely to occur in certain areas.

Dental x-ray radiograph showing decay or cavities under or below a dental crown

The red circles indicate the decay at the margin of two different crowns.

When it comes to teeth with crowns, the area most susceptible to developing decay is the margin. The margin, as you would guess, is where the crown meets the tooth. It is the weak spot. It is the Achilles Heel.

Food and other debris can collect right at the margin. A crown that was poorly made will collect even more food. If you combine this with a diet rich in sugar or acid, along with home hygiene that is not ideal, you have a perfect storm. That perfect storm affected the two crown to the upper right on the x-ray, resulting in decay.

Another Dental Myth Busted

The above photos, descriptions, and x-ray show that even with a crown, a tooth can still develop a cavity. So it bears repeating:

Crowns will protect an already weakened tooth but you still need to brush and floss sensibly. If you don’t, you can develop decay just like you would on any other tooth.


Dental MythBuster #2 – Diet Soda is Better for My Teeth?

Dental MythBuster #2 – Diet Soda is Better than Regular Soda for my Teeth.

Another common dental myth that I see nearly every day in practice in Orange, Connecticut is the notion that drinking diet soda is better for your teeth than non diet soda.  Frequently when I see a new patient with a lot of decay (a.k.a tooth cavities), both my dental hygienists and I discuss the dietary factors that influence decay.  While many people with cavities will admit to a sweet tooth or drinking lots of coffee with sugar, others will try to say “well I don’t understand why I have cavities because I only drink diet soda now.”  

The most accurate way to describe diet soda with respect to your oral health is as follows:

Diet soda is only marginally less destructive to your teeth than regular soda.  Frequent, daily consumption of either diet soda or regular soda will significantly increase the likelihood of dental cavities.

Soda vs. Regular Soda - both will cause tooth cavities for the dentist

In a previous blog post on Sports and Energy drinks, I wrote that dental decay was caused by sugary foods and acidic foods.  In the case of regular soda, you are ingesting sugar in an acidic liquid.  With diet sodas, there is no sugar, but the artificial sweetening is still being delivered in a very acidic mixture.  The acids in soda first weaken and then ultimately begin to wear away the tooth enamel.  Enamel is the hard outer layer of the tooth; without it, your teeth have little to no protection.

Differences between Diet Soda and Regular Soda on Teeth

As mentioned above, both acidic and sugary foods and drinks will cause dental decay.  We know that regular soda contains sugar.  I won’t bore you with the math, but on average, there are the equivalent of about 10 teaspoons of sugar in a typical 12 ounce can of soda.  Most sodas these days contain high fructose corn syrup but the distinction between high fructose corn syrup and sugar is not important for this blog post.  The key difference is that regular soda has large quantities of sugar while diet soda does not.  So when it comes to sugar content alone, diet soda is actually better for your teeth.

But what about acidity? There is lots of research on this topic.  In a widely cited 2007 study by the Academy of General Dentistry, the pH of Regular Coca Cola is 2.52.  Compare that to Diet Coke which has a pH of 3.28.  I won’t bore readers with chemistry here, but pH is a logarithmic measure of how acidic a liquid is.  A lower pH means greater acidity. Stomach acid has a pH of approximately 1.5 to 3.5.  Tap water has a pH of 7.  A key point to remember when you’re drinking diet soda then is:

Both diet and regular sodas are only slightly less acidic than stomach acid!

That’s very acidic!  If you’ve ever experience heartburn (GERD) you know the acidity of the stomach.  But what about the difference in acidity between Coke and Diet Coke? That can be best be summed up in the graph below:

Alt Text

Graph showing the percent weight loss of tooth structure by type of Soda.  From the Academy of General Dentistry, March/April 2007

I included this graph from the same Academy of General Dentistry showing the percent weight loss of teeth immersed in different sodas for 48 hours.  A tooth immersed in Regular Coke for 48 hours would have 6% of its mass dissolved away, while that same tooth immersed in Diet Coke would lose “only” 1.5% of its mass.  Note that for 7 Up, the percent weight loss does not vary significantly between regular versus diet.

So what does this all mean? It is worth repeating what was stated in bold earlier in this post, which is:

Diet soda is only marginally less destructive to your teeth than regular soda.

Frequent consumption of diet soda will place you at increased risk for dental decay, resulting in the need for dental fillings. And if the decay is not treated in a timely fashion, you could end up needing crowns, root canals, or even having the tooth or teeth extracted, requiring dental implants!  Keep that in mind next time you reach for that Diet Coke or Diet Pepsi.

Thanks for reading, and stay tuned for the next Dental MythBuster in a couple of weeks.

Gatorade Versus Red Bull

Is Red Bull four times worse for your teeth than Gatorade?

Nearly every day, I get questions from patients in practice about the effects of diet on dental caries (a.k.a teeth cavities).  I can’t think of an instance in all my years as a dentist when a patient was not aware of the relationship between sugar intake and tooth decay.  Nearly all patients are aware of the harmful effects of regular soda on their teeth.  Many patients ask me if diet soda is better than regular soda (it is only marginally better and still very destructive – that will be addressed in another blog post).  But very few patients have ever asked me about sports drinks and energy drinks and the effects on their teeth.

Sports drinks like Gatorade cause tooth decay requiring fillings from the dentistSports drinks became first commercially available in the late 1960s after the University of Florida’s athletic teams achieved improved performance after consuming a beverage with high concentrations of carbohydrates and electrolytes.  The electrolytes include potassium, sodium, and others lost during rigorous physical exercise.  Not surprisingly, sports drinks such as Gatorade include large amounts of sugar designed to fuel the athlete.

Energy drinks like Red Bull cause tooth decay requiring fillings from the dentistEnergy drinks came to the United States in the late 1990s but did not become popular until approximately 10 years later when large marketing campaigns were launched around these beverages.  Energy drinks contain significant quantities of caffeine in addition to sugar.  They are being marketed not just for athletic performance but also for other uses including weight loss, stamina, and concentration.  Energy drinks are frequently associated with the “toxic jock identity” in adolescent males.  Like sports drinks, they are very acidic.

Like it or not, sports and energy drinks are very popular in the United States.  One study showed that 30% – 50% of adolescents and young adults in the U.S. consume energy drinks regularly.  Marketing for the various brands such as Gatorade, Red Bull, 5-Hour Energy, Powerade, and others ensure that the names are becoming nearly ubiquitous. Just recently, Red Bull sponsored Felix Baumgartner’s free fall record as chronicled in this article.  I routinely see patients in this age demographic consuming energy drinks.  I suspect many readers of this blog consume these drinks as well.

So what does all of this mean with respect to dental care, teeth and cavities? The short answer is that both sports and energy drinks have destructive effects similar to sugary soda (Coca Cola, Pepsi, Mountain Dew, etc.).  This is because of the high sugar content in the drinks as well as the acidity.  Acidic foods and drinks dissolve the protective enamel coating on all teeth, weakening them and making them susceptible to decay.  Sugars are used by specific bacteria (S. Mutans, as seen in this recent blog post) as food.  When these specific bacteria consume the sugar, they produce acids that cause cavities.

So this brings us to the big question, which is:

Energy drinks vs. Sports drinks: which are worse for your teeth?

Energy drinks are on average four times worse for your teeth than Sports drinks. This is based on a research paper by the Academy of General Dentistry. I won’t go into the fine details of how the researchers reached their conclusion.  But on average, energy drinks require four times the amount of “dilution” from saliva to get your mouth back to normal. Or stated another way, your oral cavity has to work four times harder and longer to neutralize the teeth destroying effects of an energy drink than it does for a sports drink!

Tips on reducing teeth cavities from Sports and Energy Drinks:

  • Minimize your consumption of them.
  • Do not brush your teeth directly after consuming one as your brushing action will wear away the weakened enamel.
  • Attempt to either rinse your mouth out with water or drink milk directly after.  The milk will help to neutralize the acidic effects of the drink.
  • Do not sip one throughout the day.  You will be bathing your teeth in a constant supply of acid and sugar. If you are going to drink sports and energy drinks it is best to drink them more rapidly.  However, consumption of highly-caffeinated energy drinks quickly can lead to very high blood levels of caffeine with possible fatal side effects.  Just another reason to avoid them!
So which is the worst energy drink?  The answer is Rockstar which is almost five times worse for your teeth than Propel Grape, a popular Sports Drink.

Like it or not, sports and energy drinks are here to stay.  Whether you are a dentist in Orange, CT like me or work in another health profession or are a frequent consumer of these beverages, you should be aware of the risks to not only your teeth but also your overall health.  With proper knowledge, you can consume them sensibly and safely.


Tooth Tattoo

Small Sensor May Help Dentists Assess Dental and Overall Health.

As a dentist in Orange, Connecticut, one of the things I enjoy most is watching and following all the exciting research developments in the dental field. It is amazing the creativity and ingenuity that goes in to developing these innovations.  The research spans all areas, from better local anesthetic delivery systems, stronger crowns, new surgical techniques, more esthetic restorative materials, etc.  Some products are still many years away from market release.  Other dental innovations are “cool” but will never be feasible as commercial products.  Some products are ready to be released and placed into the hands of dentists today!

To stay abreast of these dental developments, I subscribe to different email lists and participate in various online forums about dentistry.  I do this so that I can incorporate newer technologies into my daily practice.  I came across the following article just a couple of days ago. The article describes a device that can attach to a tooth and provide information about the types of bacteria present in the mouth.

Tooth Tatoo Diagram

Tooth Tatoo – The Sensor (A) attached to the tooth (B) binds with bacteria (D) and sends radio signals (C). Image courtesy of Manu Manoor/Nature Communications.

Researchers at Tufts University have developed this technology.  In the prototype, there is a sensor with a width less than a piece of paper that attaches to a tooth.  Outside the mouth there is a receiver that continuously “pings” the sensor providing it with power as well as allowing the sensor to send data back to the receiver.  The sensor will send back different types of data based upon the presence or lack of bacteria as well as the types of bacteria that are adhering to the sensor.

Strep Mutuans, the cocci bacteria found on teeth that cause cavities or dental decay

Strep Mutans – the bacteria responsible for cavities

Dental caries (also known as dental decay or dental cavities) are caused by specific bacteria, aided or hindered by certain dietary habits.  Periodontal disease (which includes periodontitis and gingivitis) is caused by specific bacteria as well and is affected by numerous other factors (smoking, certain systemic diseases, etc).  The presence/absence as well as the amount of these different types of bacteria are directly linked to the current disease process as well as the future possibility of disease.  So a device such as this would be beneficial in diagnosing both current and future cases of cavities and periodontal disease.

Dr. Gerard Kugel from Tufts University School of Dental Medicine mentions in the article examples of how this technology could be used in an everyday dental practice.  If a patient is experiencing a spike in bacterial loads associated with dental caries, the patient could be given a prescription for high strength fluoride and be instructed to chew xylitol gum multiple times throughout the day.  Or if the sensor is detecting a surge in one of the 3 main bacterial species associated with periodontitis, the patient could be notified and be recommended to have a cleaning soon or to start on a mouth rinse containing chlorhexidine.

Beyond assessing a patient for dental caries or periodontal disease, I see many other applications of this future tool.  There are many biological markers in saliva that could be monitored and tracked. For example, proteins from the HIV virus can be found in saliva.  In addition, biological markers associated with Type II Diabetes, breast cancer, Alzheimer’s Disease, Sjogren’s Syndrome, and many other diseases can be found in saliva.  A great summary of the different markers can be found here.

This development is still many years away from being commercially available and viable. However, there are many possibilities beyond what has been described in this blog post.  But perhaps the greatest finding with this research is the further solidification that the mouth is a gateway to the body and that dentists and physicians should work together closely to manage their patients’ health.

Disclosure: I completed my undergraduate studies at Tufts University and I routinely take continuing education classes at Tufts University School of Dental Medicine. But I have no connection with this product or the research in practice in Orange, CT.