Tooth Decay page

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The steps in filling cavities


The first step in restoring a tooth is to determine the extent of decay. We do this with an x-ray. Above you see a large area of decay in the bottom tooth, second from the right. The bright areas in the teeth are all old amalgam fillings. The decay is seen as the dark area to the left of the amalgam in that tooth. The dark area in the center of the teeth are where the nerves are located. You can see that the decay has gotten very close to the nerve. (Learn about X-rays; click here.)

CariesBeforeThe image above shows what the tooth looks like before it is restored. The hole to the back of the tooth, just behind the amalgam is apparent to the naked eye. The X-ray above shows the actual extent of the decay.

Caries_excavatedAfter the patient has been made numb, the tooth is prepared with a high speed handpiece removing all the old fillings, and all the decayed areas in the tooth.

CariesRestoredAfter the tooth is completely clean, all the holes are filled with light cured composite, and the tooth is carved to resemble the form it had before the decay occurred. This tooth looks wonderful now, but it is important to remember that the original decay was very close to the nerve, and it is not possible to guarantee that the nerve will not become inflamed and start to swell causing a toothache later. (See my explanation of Root Canals).

How decay progresses inside a tooth

toothcrosssectionThe image on the right is a simplified diagram of a cross section of a tooth.  The white covering on the tooth is called enamel.  It really is white in color, but somewhat translucent and allows the color of the underlying structures to shine through.   It is also very hard and quite resistant to acid attack.  The brownish yellow material underlying the enamel is called dentin, and it too is hard, but it is much less hard than enamel.  The dentin has a density like that of hard bone.  It is much less resistant to acid attack.  Underlying the dentin is the nerve of the tooth.  The nerve is actually a complex organ.  In a healthy state, it is pink and soft, like the lining of your mouth, and is composed of blood vessels, connective tissue and, of course, nerve fibers.  The dentin is permeated with thousands of tiny tubules which run perpendicularly from the nerve to the enamel/dentin interface, and also to the outer surface of the root in areas which are not covered by enamel.  These tubules are filled with fluid.  The fluid is actually contained within tiny projections from cells that line the inside of the nerve space.  These cells are part of the nerve complex and are called odontoblasts.    Touching the living dentin produces movement of the fluid in the tubules which transmits impulses back to the nerve making the dentin sensitive to any type of direct stimulus.  Because of the presence of these tubules, the dentin is actually quite permeable to fluids.

caries_cross_sectionThe image above is a picture of an actual tooth which has been attacked by decay.  It has been stained to better show the structures within the tooth.  Originally, the tooth was adjacent to two other teeth which made contact with this one at the positions shown by the yellow arrows. Since teeth can move slightly when pressure is applied to them, such as when a person chews or clenches his teeth, the teeth move slightly in their sockets, and they can rub together at the places where they contact their neighboring teeth.  The combination of acid attack from sugar soaked plaque, plus the friction of the constant rubbing of the teeth at the contact points produces tiny holes in the enamel.  The contact on the left side of the tooth shows how acid plus friction can produce a hole in the enamel.  This one has not yet penetrated through to the dentin.  The contact on the right shows what happens when the enamel has been breached allowing the decay to penetrate into the dentin.  Note that while the hole in the enamel is relatively small, the decay has rapidly progressed within the dentin to a much larger extent due to the relative softness and permeability of the dentin as compared with the enamel.   The decay has a tendency to spread along the dentinal tubules from the enamel surface toward the nerve from which the tubules arise.

Q. Do drugs cause tooth decay? 

In general only drugs that contain sugar that comes into prolonged contact with the teeth have the potential to cause tooth decay on their own.  The type of drugs I am referring to here include sweetened liquid suspensions and chewable forms.  Drugs in pill (or injectable) form do not directly cause decay.

Unfortunately, some prescription and over-the-counter drugs can cause dry mouth.  The drugs which are most likely to produce dry mouth are the older style antihistamines, and antidepressants, as well as diet drugs, blood pressure medications, decongestants and cancer treatment drugs.  Patients with chronically dry mouths experience a shift in the normal balance of bacterial flora present in the mouth.  The type of germs that come to predominate in patients with dry mouth are also the ones which produce the most acid when the patient eats sugar, so even normal amounts of sugar at mealtimes may cause serious decay.

Unfortunately, chronic users of most illegal recreational drugs also suffer from lifestyle issues that are associated with their drugs of choice, as well as dry mouth and side effects from some of the drugs themselves which make the user cravesugar.

The metabolic depressants

Heroin addicts (as well as addicts of other narcotic drugs such as Percodan and Percocet, (oxycodone), Vicodin (hydorcodon) and codeine) experience serious decay in their teeth due to a relentless sweet tooth.  Note that this is not a direct effect of the drug itself, but rather a lifestyle tendency stimulated by the drug.  In effect, these drugs stimulate a simultaneous addiction to sugary soft drinks and candy which is the proximate (most direct) cause of their tooth decay.  Addicts of all stripes are more likely to eat and drink sugary items because they are always easily available, inexpensive, and require no preparation.

The Metabolic stimulants


Ecstasy (E), methamphetamines  (Speed) cocaine and its younger brother, crack are all biological stimulants and tend to cause serious bruxing (tooth grinding) habits which can result in very seriously abraded ( ground down) teeth.  The bruxing, in turn, stimulates the headaches, neck aches and ear aches associated with TMJ syndrome.  For a while, it became fashionable for Ravers to carry and use pacifiers in order to avoid the worst effects of the tooth grinding stimulated by Ecstasy.  (Raves are all night parties where there are lots of young people, lots of loud music and other entertainment, and generally lots of drugs.)  Ecstasy is popular at raves since it makes people feel wired, or more awake and active at these events.  Ecstasy is a bit like a combination of methamphetamine and a hallucinatory drug like LSD.  It’s main effect is to temporarily increase the supply of serotonin and dopamine in the brain, which causes an increase in empathy (feelings of love and sympathy) and the desire for repetitive, vigorous physical exercise (dancing).  Serious bruxing is only one of the unfortunate side effects of ecstasy and the other stimulant drugs mentioned above.  These drugs also cause hyperthermia (abnormally high body temperature) which leads to dry mouth and ravenous thirst.  Since sweet soft drinks are cheap and readily available, they are popular among ravers and addicts for quenching thirst.  The combination of large amounts of sugar and a dry mouth causes particularly virulent tooth decay among many of these people.

Meth mouth. Note tooth decay, gum disease and broken teeth
Meth mouth. Note tooth decay, gum disease and broken teeth

Meth Mouth–Due to its importance, I have devoted an entire page to this subject.  Click on the image above.

Methamphetamine deserves a category of its own.  (In fact, it has a page of its own.)  Meth addicts have a combination of drug induced symptoms and behavior patterns that cause severe tooth decay and gum disease.  The drug induced symptoms are dry mouth, muscular hyperactivity, excessive sweating, diarrhea and violent, self destructive behavior patterns.  The loss of fluid from the excessive sweating and diarrhea produces a ferocious thirst and dry mouth.  The increased muscle hyperactivity produces a physical need for quick energy and a huge appetite for sugar.  Soda and other soft drinks including Gatorade and sweet ice teas are cheap, ever-present sources of both fluid and sugar and many meth addicts eat and drink little else.  The dry mouth produced by the methamphetamine exacerbates the severity of the decay, and the drug induced increase in muscular activity produces relentless bruxing (grinding and clenching) which causes the decay weakened teeth to break.  Meth also produces violent and self destructive behavior which directs the addict’s attention away from looking after his or her own well-being.  Consequently, little attention is paid to personal hygiene, including oral hygiene.


Dilantin  (phenytoin)

DilantinDilantin is a drug used to treat seizures in epileptics–can cause swelling of the gums (gingival hyperplasia), especially in persons who do not brush their teeth regularly.  The image to the right shows what the combination of poor oral hygiene and Dilantin can do to a patient’s gums.  Better oral hygiene would have reduced the enlargement of the gingiva.  A limited number of other types of drugs can also cause this problem, although to a lesser extent.  They include blood pressure medications in the calcium channel blocker category (Cardizem), birth control and hormone replacement drugs (Progestogen) and immunosuppressive agents such as cyclosporine. 

In general, this type of gingival enlargement can be prevented by good hygiene, but once it occurs, the only way to eliminate it is through surgical removal of the excess tissue, a procedure called gingivectomyOne lady wrote to me asking me if the manufacturer Dilantin could be sued for causing this complication.  I told her that I doubted that the manufacturers of any of these drugs could be held responsible since gingival hyperplasia is controllable with good hygiene and the benefits of these drugs far outweigh the risks.  Dilantin was approved by the FDA in 1953, and thus has been on the market for over 5o years.  It was approved in spite of the well known fact that it can cause gingival hyperplasia.

Q. Does sugarless gum prevent decay?

A. Yes!  Clinical studies have shown that chewing sugarless gum for 20 minutes following meals can help prevent tooth decay, especially in children.   If you chew after eating, the increased salivary flow can help neutralize and wash away the acids that are produced when food is broken down by the bacteria in plaque on your teeth.   Sugarless gum also prevents tooth decay because the gum base itself has a detersive effect which means that the mechanical action of chewing gum tends to remove some plaque from teeth.  Even sugared gums have detersive qualities and increase salivary flow.  However, sugarless gum sweetened with sorbitol, manitol or other non sugar sweeteners will not promote decay, and will reduce the incidence of tooth decay, especially if the patient does not use too much sugar between meals.

Unfortunately, this does not substitute for brushing, flossing and avoiding between-meal exposures to sugar.  Plaque is made of bacteria, and it adheres to the teeth with a seriously sticky mucous-like material called dextrans.  Thus plaque resists removal or dilution during normal chewing and eating.

Large amounts of plaque left on the teeth, as well as multiple exposure to sugar between meals (usually eaten as a result of one of the sugar habits) can easily overcome the benefits of the increased saliva production and detersive effects of gum chewing.


Recent research has shown that one sugar substitute, xylitol (Google search) actually helps to prevent tooth decay.  Xylitol interferes with the metabolic processes of Strep mutans, the major bacterial contributor to tooth decay.  Xylitol is currently used to sweeten toothpastes and some brands of sugarless gum and sugarless candy.  It is likely that it will be found in more and more sugarless products now that research has shown that it has the added benefit of helping to prevent tooth decay.  Xylitol has been shown to have the following qualities:

  • Xylitol blocks bacteria from producing the acids that cause tooth decay.
  • Xylitol decreases the level of bacteria known to ferment sugars which produce acid.
  • Chewing Xylitol gum three times a day is said to eliminate Strep mutans, which is one of the major decay producing organisms in the mouth.
  • Xylitol sweetened mints and candies also have the same effect, but gum is probably more effective due to its detersive (cleaning) action.
  • Xylitol decreases plaque formation.
  • Xylitol helps promote remineralization of previously decayed tooth    structure.

Epic® Xylitol Gum, Xponent® gum, Zapp®, and Spry® Xylitol Gum are all considered to be good xylitol delivery systems. These brands contain approximately 1 gram of xylitol per stick, which is the concentration you should be looking for in xylitol gum brands.

While Trident® gum contains xylitol, the concentration is too low. It contains approximately .17 grams of xylitol per stick. There is no evidence that it is effective in preventing tooth decay.

A number of years ago, the US Navy kicked off research into the cariostatic effects of xylitol. Now all three branches of the military are quite impressed with the cavity fighting qualities of xylitol and have recommended the following regimen to help keep their soldiers’, sailors’ and airmen’s teeth in good shape:

  • Chew 1.5 – 2 grams of xylitol gum for 5 minutes, 3 to 5 times a day
  • Chew xylitol gum after meals or as a snack
  • Xylitol-sweetened mints can be used by people who can’t or prefer not to chew gum.
  • You can purchase xylitol candy and gum online at various sites.  Click here for a Google search. has a rather interesting website that may be of interest to some readers with doubts about xylitol’s safety and effectiveness.

  A note on artificial sweeteners


Unlike sugar, artificial sweeteners do not cause tooth decay.  The major artificial sweeteners used today are aspartame  (Equal® and Nutrasweet®), saccharine(Sweet ‘n Low® is the largest selling brand), and sucralose (Splenda®).  All three of these have been lambasted by various health groups who claim that they are toxic and cause untold misery in anyone foolhardy enough to use them.   Let me set the record straight.  Saccharine was invented in 1879 and has been in constant use in the United States since the early 1960s.  During that time  no evidence that it has caused an increase in any human disease, including cancer has come to light .  Likewise aspartame (Nutrasweet®) was invented in 1965.  It also has been in use for more  than 40 years and there has been no evidence of toxicity.

There are hundreds of websites articles accusing aspartame (Nutrasweet) of causing blindness and brain or peripheral nerve damage.  No matter what authorities these sources invoke, THERE IS NO PEER REVIEWED SCIENCE THAT SHOWS THESE CLAIMS HAVE ANY VALIDITY!  All peer reviewed science done to date confirms the safety of aspartame.  The following is from a Wikipedia article which references a few of the studies proving this:

The safety of aspartame has been studied extensively since its discovery with research that includes animal studies, clinical and epidemiological research, and post-marketing surveillance, with aspartame being one of the most rigorously tested food ingredients to date. Multiple peer-reviewed comprehensive review articles and independent reviews by governmental regulatory bodies have analyzed the published research on the safety of aspartame and have found aspartame is safe for consumption at current levels. Aspartame has been deemed safe for human consumption by over 100 regulatory agencies in their respective countries, including the UK Food Standards Agency, the European Food Safety Authority (EFSA) and Canada’s Health Canada

Sucralose (Splenda®) was discovered in 1976 by researchers working under the auspices of Tate & Lyle Ltd., a large British sugar refiner.  In 1980, Tate & Lyle arranged with Johnson & Johnson, the world’s largest health care company, to develop sucralose.  Johnson & Johnson formed McNeil Specialty Products Company in 1980 to commercialize sucralose.  Sucralose has been in use commercially in Canada since 1991 and was approved for consumption in the United States in 1998.  It has been in use in the US since that time, and has been approved for use in 50 other countries.  It is derived from sugar and has the advantage of sweetening with few calories and no negative effect on the teeth.  It has the added advantage of being useful in cooking, unlike aspartame which breaks down in heat.  A small percentage of people note a bitter aftertaste while eating foods prepared with sucralose.  Most find that it tastes just like sugar.

I get quite a few e-mails condemning me for suggesting that these sugar substitutes are safe and don’t cause brain tumors and other forms of cancer.  The following link is an official government document.  You can satisfy yourself that the link is actually to government websites by looking at the .gov domain in the link bar at the top of your browser when you click on them.  The United States government Food and Drug Administration (The FDA) has evaluated the safety of aspartame, sucralose and saccharine and have found them to be safe. An FDA paper on the safety of saccharine and aspartame (which also addresses the purported “brain tumor” allegations associated with aspartame) can be found by clicking here.

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