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Caries and Cavities

Many people believe that sugar is the main cause of cavities. They are unnerved when I explain the shocking myth buster: Sugar itself does not harm teeth. It is helpful to understand exactly how tooth decay happens; then you will see how easy it is to control. Teeth are damaged only when sugar energizes a damaging kind of bacteria in your mouth. Sugar gives energy to this particular kind of bacteria and they, in turn, produce tooth-corrosive acids. Acids weaken teeth and cause cavities. Let me restate this simply: Without the harmful acid-producing bacteria, sugar will not harm your teeth.
The interaction between bacteria and sugar was discovered and explored during the 1950s and 1960s. Testing was done on germ-free rats raised in a laboratory. The animals were bred without bacteria in their mouths, and although they were fed sugar and water for long periods of time, not one of them developed cavities. Different types of bacteria were introduced into each rat’s mouth, and dental changes began to occur. Researchers found that one kind of bacteria in particular caused the most cavities to form in the animals. An antibiotic was used to eradicate these bacteria, and the tooth decay stopped. In other words, it was only when the specific bacteria were present in the animals’ mouths that cavities formed.1
These experiments showed how mouth bacteria can use sugar from the diet to multiply, produce acidic liquids, and damage teeth. They also showed how the bacteria were transferred from mothers to their pups. Some bacteria were found to be more aggressive than others and produced more corrosive acids, causing the most cavities in teeth.2 The damage we believed was from sugar was really damage from harmful mouth bacteria fed by sugar.
Whenever harmful mouth bacteria are energized and multiply, they damage tooth surfaces that are underneath or alongside them. The greatest damage will always occur where there is the most acidity. This is usually on the tooth surface in contact with the bacteria. When harmful bacteria continue to produce acids, over time these acids mix with saliva in the mouth and weaken teeth everywhere, even at a distance from the bacteria. Generalized mouth acidity is particularly dangerous because it encourages the growth of more acid-loving bacteria and the progression of this destructive, cavity-forming disease we know as tooth decay.
The 1960s studies illustrated the interaction between bacteria and sugar, yet even today most dentists and hygienists learn about sugar damage from the Vipeholm study, undertaken twenty years earlier. For decades dental students have been shown graphs that depict the results of this study, drawn by Dr. R. M. Stephan and carried out in a home for psychiatric patients in Sweden.3
The patients in this Vipeholm study lived in closed community conditions where harmful mouth bacteria would certainly have been present, and as a result, the bacteria of dental disease would have spread easily among them. These patients were obviously at high risk for dental disease. Their mouths would have been full of aggressive, acid-producing bacteria. We now understand how aggressive bacteria produce acids every time sugar is eaten. Something that is rarely explained to students is that in a mouth without harmful bacteria, acidity will not be produced and sugar will not harm teeth.
In the Vipeholm study, sugar was given to the residents and mouth acidity measurements were taken and related to measurements of tooth damage. Graphs were used to explain how sugar causes an acidic drop in the mouth and how this results in damaged teeth.4 Stephan’s diagrams are still used to illustrate how eating sugar makes the mouth acidic, too acidic for tooth safety. These diagrams are also used to show the time it takes for the dangerous acids to be diluted by saliva and for the mouth to return to a safe state. While the mouth is acidic, teeth are being damaged and cavities are developing.
Stephan’s diagrams show that it takes about thirty minutes for saliva to balance the acidity and return the mouth to a safe state for teeth.5 What is rarely explained is that this kind of balancing can occur only in a mouth with plenty of healthy nonacidic saliva. Obviously this balance cannot occur in a dry mouth without saliva or in a mouth where the saliva itself is acidic. This fact alone makes mouth acidity of extreme importance to everyone, especially for women in situations of hormonal imbalance, people who are taking medications, or people living under stress.

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