Dental decay,dental caries and cavities all mean the same thing; that certain decay-causing (cariogenic) bacteria, such as the mutans streptococci and the lactobacilli, have overgrown on certain parts of the tooth surface and have produced so much acid that the tooth mineral has dissolved or decayed, forming a cavity. This is a relatively slow process and does not hurt until the decay has extended near the pulp, at which time the nerves in the pulp are excited or irritated by products produced by the bacteria, and/or by hot or cold temperatures. Your dentist can detect cavities long before this, by either a visual exam, (he or she can see the cavity, or detect it by touch with a dental instrument), or by radiographs which give an estimate of how deep the decay has spread. At this stage the dentist recommends removing the decayed part of the tooth and replacing it with a dental restoration usually called an amalgam, but it could be made of gold, porcelain or polymers. This is a necessary and traditional way to treat dental decay.

But, if you want to prevent the recurrence of decay, one should determine what risk factors are present and then seek to eliminate or to control them. One risk factor is newly erupting teeth, as these teeth will have surfaces that could initially become colonized by the cariogenic bacteria. Accordingly, infants between 1 to 3, children from 6 to 7, and teenagers from 12 to 14 are most at risk to decay. If these age groups already have decay, then added effort should be made to control for a bacterial infection usually due to the mutans streptococci and lactobacilli. The mutans streptococci, in the germ world, are world class athletes when it comes to grabbing any sugar that enters the mouth in the form of candies, gums, or other sweetened snack-type foods. They don't need much sugar in order to lower the pH (form acid) on the teeth, causing the tooth to dissolve (decay). For example a few grams of sugar a day (only 8 to 10 calories), taken between meals can cause decay. This is because the millions upon millions of bacteria that normally live on your teeth are in a famine situation when there is no food in the mouth. But when a snack comes along containing soluble sugar, these bacteria are ready to gorge themselves. This is what the mutans streptococci are best at, taking into their cells all the sugar that comes their way. Sugar (sucrose) is the most cariogenic foodstuff because it is bioavailable to the plaque bacteria (its small size and solubility allows it to diffuse into the plaque where it is immediately converted to acid and biodegradable polymers by the mutans streptococci).

Mutans streptococci are also very good at surviving in the acid environment which they create. Many other bacteria cannot live at these low pHs and their numbers gradually decrease in the plaque. At the same time mutans streptococci increase, and this increase can be detected by bacteriological tests which look at the saliva, or at the plaque itself. If an individual has more than two decayed teeth (this number is chosen, so that one wouldn't be using the test every time that a single tooth is decayed, unless this person has other risk factors, such as newly erupting teeth), then it makes sense to determine how many mutans streptococci this individual has in his or her saliva. Also, at the same time one could look for the lactobacilli, the other group of bacteria implicated in dental decay. The lactobacilli are important because they are even better survivors than the mutans streptococci in an acid environment. If both these germs are present in high numbers in the saliva, using tests that are commercially available, then one has identified bacterial risk factors for the development of decay.

What can you do when there are bacterial risk factors? First the dentist can check for frequent between-meal eating of soluble sucrose (sugar) containing products. If that is the case, the dentist can suggest that the person switch to products containing xylitol as a sweetening agent. Xylitol is an amazing sucrose substitute in that it tastes as good as sucrose, and several studies have shown that it is anti cariogenic, i.e., it prevents decay. The mutans streptococci cannot use xylitol, and all the enzymes needed to use sucrose become excess baggage, when they are being exposed to xylitol between meals. In a crowded and competitive environment such as the dental plaque, any enzymes that are not useful will make a germ noncompetitive. As a result the levels of the mutans streptococci decrease in the plaque. Xylitol is hard to find in the supermarkets, but should be for sale in most health food stores. The price will be higher, because it is more expensive than sugar to produce, but given its ability to prevent decay (anti-cariogenic activity) it is well worth the added cost.

Another treatment, that can reduce decay in children is the placing of sealants on the tops of newly-erupting molar teeth, if there is a fair amount of decay in the primary dentition (baby teeth). Thus, for children aged 6 to 7, the first molars could be sealed, and for teenagers, the second molars and possibly the premolars could be sealed. This would not be done on everyone, but certainly would make sense in someone who has prior caries activity.

Everyone should be using a fluoridated toothpaste, as this is essential for caries control. Fluoride does so many good things for the tooth, like helping the saliva to restore, or remineralize the beginning decayed lesion, known as a white spot. And fluoride, at a low pH of the type that is often found in the plaque after eating sugar-containing products, can also inhibit the mutans streptococci. So fluoride can protect against decay by both promoting remineralization and by inhibiting the mutans streptococci. There are, of course, fluoride treatments of the type given by the dentist that should be applied when an individual has several decayed teeth. This fluoride treatment would necessarily come after all the dental restorations or fillings are placed, and would both replenish the tooth surface with fluoride and provide an additional reduction in the levels of the mutans streptococci.

Another treatment that is available is the use of an antimicrobial agent named chlorhexidine. Chlorhexidine has been used as a skin disinfectant for almost 40 years, but recently a prescription mouthrinse has been approved for gum disease. This mouthrinse has not been approved for the treatment of dental decay, but studies performed in Europe, mostly in Sweden, have shown that chlorhexidine, delivered in gels or mouth rinses, is very effective against the mutans streptococci. The chlorhexidine is taken for short periods of time. But chlorhexidine has a bitter taste which may turn some people off, and probably would not be very popular with children. But for the adult with recurrent decay, it may be an excellent way to control a mutans streptococci infection. Several groups are making a varnish which contains chlorhexidine, so that one may need only one application of the varnish every 3 or 6 months. Again this treatment should be reserved for individuals with one or more risk factors for dental decay. This is not a preventative treatment.