Cavities/Tooth Decay


The black area in the two front teeth is decay (adult.)

The black area in the two front teeth is decay (adult.)

Tooth decay is one of the most common diseases in the world. In the U.S. alone, more than 90% of all individuals will be affected by tooth decay at one time or another during their lifetime. It should be noted that tooth decay is also one of the most easily preventable diseases.

Tooth decay is the process by which bacteria in your mouth convert carbohydrates (such as sugar) to acid, which demineralizes, or dissolves tooth structure. There are two major bacteria that cause tooth demineralization: Streptococcus mutans and Lactobacilli. The demineralization happens in stages and, given time, creates holes in your teeth.


Plaque: the Primary Agent in Tooth Decay

Tooth decay in a child.

Tooth decay in a child.

Plaque is a highly organized colony of bacteria that forms on teeth, tongues, fillings, crowns, dentures, partials, and anything you place in your mouth for any period of time. This bacteria produces a glue-like substance that helps it to stick to everything and can only be removed by the mechanical action of brushing and flossing, and/or the use of a waterpik. If you are not flossing and/or the using a waterpik, you are only doing half the job of plaque removal. If you are not brushing correctly, you are only doing about a quarter of the job of plaque removal, which can lead to tooth decay and gum disease.

Plaque takes about 24 hours to fully mature in your mouth to a point where it can harm you. It will form on anything, even dentures. For example, if you take out all of your teeth and place a sterile penny on your tongue for 24 hours, when you remove the penny it will be coated with mature, highly organized bacterial plaque.

How does tooth decay occur?

This tooth decay has gone untreated and has invaded the nerve, artery and vein inside the tooth (pulp chamber.)

This tooth decay has gone untreated and has invaded the nerve, artery and vein inside the tooth (pulp chamber.)

Tooth decay occurs when four factors come together:

  • Plaque- or acid-producing bacteria
  • Sugar or any other readily fermentable carbohydrate
  • Tooth structure (any part of the tooth)
  • Time

Once sugar is taken into your mouth and dissolved, it takes about 20 seconds for bacteria to begin acid production. Given time, undisturbed bacteria can produce enough acid to dissolve any part of the tooth. There are progressive stages of tooth decay, and a complete breakdown of tooth structure does not happen immediately. The activity of the bacteria can be interrupted (by properly cleaning your teeth) and the decay is then stopped or “arrested.”

Fortunately, our body has a built-in protection that helps: your saliva contains natural biological agents that help neutralize acid and re-mineralize enamel (see Parts of a Tooth). This was discovered in the late 1970s, when radiation therapy to treat Hodgkin’s Lymphoma  shut down the salivary glands, causing the incidence of cavities to go up. This can also be seen in patients who take medications that decrease the production of saliva.

To compound the problem there is sugar in just about every processed food in the United States. Sugar is consumed in enormous quantities in this country. This is evident not just from the mouths of patients but by the nationwide obesity and diabetes statistics.

Tooth decay in early adolescence with both adult and "baby" teeth (mixed dentition.)

Tooth decay in early adolescence with both adult and “baby” teeth (mixed dentition.)

Children and teens are more cavity-prone because they may not have the knowledge, attention span, or the necessary coordination  to effectively remove plaque from their teeth. Children, especially boys, need help on a daily basis to completely remove bacteria from their teeth. As people age (65+ years), they re-enter a cavity-prone state because they naturally produce less saliva. Remember, saliva buffers acid and re-mineralizes enamel. There are thousands of medications that cause saliva production to decrease; as use of these medications increase so does the incidence of tooth decay.

How to Prevent Tooth Decay


Ineffective brushing, regardless of its frequency, does little to prevent the process of tooth decay. Unless you are effectively removing plaque, every time you consume sugar, the acid produced by plaque will begin work to dissolve your teeth, creating cavities.

Instructions for brushing with a manual toothbrush:

  1. The toothbrush should not be dragged back and forth over the tooth surfaces; the focus should be on removal of bacterial plaque.
  2. You need to take your time: three to five minutes.
  3. Use a mirror and watch what you are doing.
  4. When brushing the upper back teeth on the cheek side, shift your jaw towards the side you are brushing, as it will give you more room to get behind the last tooth.
  5. Develop a system whereby you will reach all areas (e.g., start at the upper right and work your way around the upper arch, then move to the inside until you finish on the upper inside. Repeat on the lower teeth).
  6. Place the brush at a 45-degree angle; make sure your brush handle is parallel to the teeth you are cleaning and the tip of the handle is on the opposite side of your nose.
  7. To effectively brush your teeth on the inside, in the front, place the brush upright and parallel to the teeth, push either the head or heel of the brush against the teeth, and jiggle it in tiny up-and-down movements. Overlap each area you are cleaning with the previous area to avoid missing any teeth. Use a “jiggling” motion; circles tend to get too big, and rolling downward or upward does not clean under the gum tissue.

Instructions for brushing with a mechanical toothbrush:

There are three points that need to be stated about using a mechanical toothbrush versus a manual toothbrush:

  1. The mechanical vibration of this type of brush does all of the “jiggling” for you.
  2. It will clean your teeth better than a manual brush can.
  3. The instructions above still need to be followed, as the toothbrush is only as good as the technique of the person holding.


Flossing is perhaps the issue least understood by patients. If you are not flossing, live, gooey bacteria are growing between your teeth and under your gums, causing odor, tooth decay, periodontal disease (gum disease), staining, and bleeding. Why? Cleansing foods such as apples, salads, and meat have the capability to remove and interrupt the activity of bacterial plaque when you eat; however, these foods do not get to the bacteria between your teeth and below the gum line. Dental floss is required to remove plaque effectively between your teeth.

If you find flossing difficult, there are many different types of floss and flossing aids that will assist you in thorough cleansing between your teeth.

If you thoroughly brush your teeth every day, removing all the bacterial plaque that your brush can reach, but you choose not to floss, you are leaving bacteria on 40% of your tooth surfaces.

Instructions for flossing:

  1. Wrap the floss around your middle fingers; do not tie up your index (pointing) fingers. You need your index fingers to control and manipulate the floss.
  2. Seesaw the floss only to get it between your teeth.
  3. Wrap the floss around one of the two teeth it is between in a C shape and rub the side of the tooth two or three times, gently bumping into the gum tissue. Then wrap the adjacent tooth and repeat the process. Do not “seesaw” on the gum tissue.
  4. Do not forget to floss behind the last tooth in your mouth; there is a good chance that your brush did not reach there.
  5. Flossing is nothing more than cleaning between your teeth where the brush cannot reach. You are washing the sides of the teeth, much like you wash your arm or leg in the shower.


If used properly, the waterpik (sometimes called a water brush or water flosser) can effectively remove the bacteria between the teeth.  Adding an antibacterial mouthwash to the water reservoir increases bacterial removal.


Although many patients feel fluoride is “bad” for human use, fluoride is undoubtedly one  of the most highly qualified, public successes in prevention of dental disease. Is it poisonous?  Yes, as is chlorine, medication, alcohol and even water if too much is consumed all at one time. Fluoridated water contains approximately .7-1.0 parts per million and when consumed while teeth are forming reduces tooth decay by as much as 60%.

Systemic Fluoride

Systemic fluoride is the dietary consumption of fluoride so that it gets into the body’s bloodstream. The fluoride ion is laid down as enamel forms within the tooth bud (the sack where the tooth forms within the jaw). This incorporation of fluoride into the enamel prevents tooth decay and/or makes it more difficult for the bacteria to dissolve the enamel.

If the water supply where you live does not contain fluoride, your doctor should prescribe the proper supplementation of fluoride for infants and toddlers. Once your child is old enough to start seeing a dentist, usually at about the age of two, your dentist will monitor your child’s fluoride intake. The supplementation of fluoride must be monitored by your dentist to prevent enamel fluorosis (the discoloration of enamel due to a higher than recommended intake of fluoride).

Topical Fluoride

Topical application of fluoride in a gel, foam, or varnish is used to soak the teeth. Use of topical fluoride should continue as long as you have teeth. Topical fluoride “soaks” into your enamel, microscopic cracks in your teeth, and exposed root surfaces, further protecting against tooth decay. This is most important in childhood (when brushing skills are immature) and later years, (when there is a decline in saliva production.) Topical application of fluoride does not cause enamel fluorosis. Once the enamel is calcified and the tooth has grown into the mouth, the topical application of fluoride cannot harm the tooth, it can only help.


Toothpaste is not a necessary ingredient to home tooth care. In other words, the thorough removal of plaque is not dependent on having toothpaste. Although toothpaste creates a more pleasant experience while removing plaque, the most important ingredient in toothpaste is the topical fluoride it provides.


Mouthwash, whether prescribed or over-the-counter, is not a substitute for brushing and flossing. There are mouthwashes that kill bacteria and improve gum (gingival) health; however, alone mouthwash does not do the whole job of cleaning teeth. It is a supplemental option designed to help kill or temporarily reduce the number of bacteria.


Sealants are a composite material that is bonded to the enamel of the tooth, predominately on the biting surfaces of back teeth. They are designed to seal deep grooves, pits, and fissures, helping in the prevention of tooth decay. If you could see these grooves microscopically, you would be able to see that a toothbrush bristle cannot reach to the very base of the groove or pit where bacteria can thrive and create decay.

Sealants close the groove, thereby eliminating areas where the bacteria can gather and do  damage, undisturbed. The re-mineralizing properties of saliva cannot reach the base of these grooves as readily as it does the remainder of the tooth; therefore, the placement of sealants in childhood is encouraged as a preventive measure.


Products containing Xylitol will decrease the number of damaging bacteria.  Xylitol, interferes with bacterial metabolism, temporarily decreasing bacteria reproduction.


Antibiotics control the overgrowth of, or infections caused by bacteria in the teeth and gums. They do not permanently kill the bacteria that each of us has acquired over the years since infancy. As an infant you acquire bacteria passing through the birth canal. When adults test a baby’s food for temperature, they pass on their bacteria. Kissing either people or pets, or when you share drinks, you share bacteria. These bacteria come to live in our mouths and number some 10 billion strong, by far more bacteria than on any other area on the body.

Tooth decay on the root surface (left) and on the biting surface (right.) There is a very high probability of decay under the silver filling as the margins of the filling are defective (lifting).

Tooth decay on the root surface (left) and on the biting surface (right.) There is a very high probability of decay under the silver filling as the margins of the filling are defective (lifting).

In short, antibiotics cannot rid your mouth of the bacteria you have acquired over time. However, antibiotics used for mouth infections or other systemic problems may alter your oral bacteria, in some cases, cause fungus to take over. Once the fungal infection is cured and medication discontinued, your acquired oral bacteria will return to their desired level.

Conversely, when antibiotics are taken for oral infections, fungus can grow out of control in other areas of the body i.e. antibiotics taken for tooth infections can cause vaginal yeast infections.

Fluoride Centers for Disease Control and Prevention. Recommendations for using fluoride to prevent and control dental caries in the United States. MMWR Recomm Rep. 2001;50 (RR-14):1–42. PMID 11521913. Lay summary: CDC, 2007-08-09.Up to 42% caries reduction

Fluoridation Basics
Water fluoridation prevents tooth decay mainly by providing teeth with frequent contact with low levels of fluoride throughout each day and throughout life. Even today, with other available sources of fluoride, studies show that water fluoridation reduces tooth decay by about 25 percent over a person’s lifetime.