Dr. Shnall's Dental Blog
By Dr. Jeff Shnall
“You have a cavity.” The four words none of us wants to hear when we go to the dentist. But what is a cavity? What causes them? How do you prevent them?
While all of us have been told since we were little kids that cavities are caused by sugar bugs and we will get cavities if we eat too much candy, there is far more to it.
I hate having to tell my patients they have a cavity or worse, cavities. No one likes being the bearer of bad news and even I can understand that there are many things you would rather be doing than having a cavity filled.
I do have some patients who never seem to get a cavity while I have others that unfortunately are cavity prone, that is, it will be more common than not that I find a cavity when they come in for their six month check up.
As a dentist one of my primary duties is to advise my patients on how to prevent cavities. In this article I will discuss some basic do's and don’t’s which will hopefully help keep you cavity free and will give you a better understanding of the cavity process.
What is a cavity
A cavity is a softening or destruction of a tooth caused by bacteria. We also use the term tooth decay to describe the cavity process as the tooth is decaying or literally rotting.
A cavity can take on many different appearances, for example:
How do you know if you have a cavity?
Interestingly, sometimes a tooth with a cavity will be sensitive and sometimes it won’t.
I have seen patients with a small cavity that is sensitive whenever they eat something sweet or have a cold drink while I have seen other patients with a huge cavity that has not given them the slightest trouble.
The latter can be a bigger problem as sometimes a painless cavity will get so deep that by the time it finally does become painful or sensitive the cavity has reached a point when the tooth will need a root canal treatment or removal.
Since cavities can be sometimes symptom-free even when they are fairly large or deep it is important that you get your teeth checked for cavities every six months, and for the typical patient the teeth at the back of the mouth should be x-rayed to check for cavities once per year.
The cavity process
If a cavity is going to develop you need two things: bacteria on the tooth and food for the bacteria, which is sugar in some form.
First, a few words about bacteria: At this moment there are between 100 to 200 different types of bacteria in your mouth, But only a few types of these bacteria are responsible for causing cavities.
As well, right now you have anywhere from 1,000 to 100,000 individual bacteria on each of your teeth, assuming you do a decent job when you brush and floss.
These bacteria are single celled creatures that cause cavities in the following way: when you eat or drink anything containing sugar, certain types of bacteria will ingest this sugar and produce acid. The acid is secreted on the tooth surface and can start to dissolve the enamel (or other parts of the tooth), a process called demineralization (the breakdown of the mineral content of the tooth).
To combat this acid attack, our saliva normally washes away the acid and sugar from the tooth surface and also delivers calcium, phosphate and fluoride to the tooth to rebuild the enamel that has been demineralized, a process called remineralization.
Therefore, there is a constant and delicate balancing act occurring constantly on our tooth surface wherever this bacteria or plaque exists, plaque being the name we give to clumps of bacteria.
If the bacteria or plaque has a ready supply of sugar this will result in more and more acid production on the tooth which will lead to the acid eating a hole in your tooth, and a cavity is born.
If you don’t brush or floss well or regularly, this will result in more bacteria on the tooth and will promote cavity formation.
So whether you get a cavity comes down to this fine balance between the dissolving of tooth structure by acid produced by bacteria and remineralization of the tooth from calcium delivered in your saliva.
If an area on your tooth that is being dissolved by acid can remineralize a cavity will not develop, however if the amount of acid present on the tooth overwhelms the ability of the saliva to remineralize the tooth a cavity will form.
The Tip of the Iceberg
The same way that ninety percent of an iceberg is below the surface of the water and be dangerous to a passing ship, a cavity that looks small and innocent on the surface can sometimes be large and troublesome. The reason for this has to do with way that some teeth form when you are very young.
While some people have very well formed and decay resistant teeth, other people have teeth that are more prone to developing cavities in the grooves and pits of their teeth.
The tooth pictured in Figure 1 is well formed and has shallow grooves. This means that bacteria is less likely to accumulate in the grooves of the tooth, as it is easily washed away by saliva or more easily scrubbed away by a toothbrush.
The other key point is that the entire groove is lined with enamel, a very hard tissue which is harder than bone and more resistant to acid attack than other materials that make up a tooth.
The tooth pictured in Figure 2 has deeper grooves that attract plaque/bacteria. The deep grooves provide a safe haven for the bacteria. As well the crucial thing is that there is no enamel lining the floor of the deep groove of the tooth in figure 2. Instead the floor of the groove is lined with dentin, which is softer than enamel and less able to withstand acid attack by the bacteria in the groove.
In a deeply grooved tooth, if there is a hint of decay in the grooves it is far better to clean out the decay and place a shallow filling than to watch and wait, as the deep cavity pictured in Figure 3 is the result.
What increases your cavity risk?
1) The frequency that you eat or drink food that contains sugar:
2) The duration of the exposure of your teeth to sugar:
3) Having a dry mouth.
4) Poor oral hygiene
5) Having deeply pitted or grooved teeth. This was discussed earlier in the article.
6) A tooth with poorly formed enamel.
6) Crowding: teeth that overlap one another can be bacteria or plaque traps and can be harder to keep clean.
Ways to Decrease your Cavity Risk
1. Switch to sugarless candies or mints.
2. If you like soft drinks try diet versions.
3. Reduce the frequency you eat sugary foods and drinks
4. Reduce the duration that sugar stays in your mouth.
5. Brush well and longer: aim for two minutes each time you brush. Brush two to three times each day.
6. Consider switching to an electric toothbrush to get more plaque off your teeth.
7. See your dentist regularly to catch cavities while they are small. Every six months is ideal.
8. Use a daily fluoride mouthwash and/or a high content Fluoride toothpaste if you are cavity
9. A paint-on fluoride varnish can be applied to your teeth if you are cavity prone
10. Sealants can be placed in teeth with deep grooves to seal out bacteria. I will place sealants on permanent molars when they are deeply grooved.
11. If you are on a medication that is causing dry mouth ask your doctor for an equally effective
drug that does not reduce saliva flow.
To conclude, your biology, tooth anatomy, diet and habits are unique and all combine to result in whether or not cavities will form on your teeth.
I hope this article has given you a few tips and better insight into how cavities form and how they can be prevented so that hopefully at your next dental visit you will be less likely to hear those four unpleasant words: “ you have a cavity.”
If you have any comments, questions or suggestions for future articles please feel to leave a comment below.
Jeff Shnall DDS BSc