A Tale of Two Sisters
by Amy Joughin
Why do some people seem to get away with consuming a lot of sugar, yet have no cavities? For example, say you have two sisters. They’re both given a bag of sweets once a week as a treat. One sister, Mary, is a bit greedy, so she eats them all straight after her dinner, and goes to bed feeling slightly sick. She’s also prone to laziness, and although her parents have told her to rinse her mouth with water after brushing, she can’t be bothered and just spits out the toothpaste.
The other sister, Anne, is very good at restraining herself. She snacks on the sweets having just one every half hour or so, and they last her all week. She’s also very diligent and rinses her mouth out after brushing, just like her parents told her to.
At the dentist, their parents are shocked to find that Anne, the seemingly ‘good’ sister, has a cavity and needs a filling. ‘But it doesn’t make any sense!’ they say. ‘It’s her sister that’s got the sweet tooth, she gobbles her sweets down, and she doesn’t rinse her mouth like we tell her to. It must be genetics, poor Anne must have inherited weak teeth.’
So does Anne have weak teeth? Was Mary just born lucky? The answer lies in the science behind tooth decay, so it would be helpful to revisit this.
The Science Behind Tooth Decay
We naturally have a plaque of bacteria on our teeth. When we consume sugar-containing food or drinks, bacteria within this plaque feed on these sugars and produce organic acids. The plaque therefore becomes acidic, and because of this, any enamel adjacent to the plaque starts to lose calcium and phosphate minerals. Acids can dissolve away the enamel hydroxyapatite crystal, and eventually lead to a visible breakdown in tooth structure; a cavity.
Fighting Tooth Decay
However, we do have some fantastic weapons in our arsenal to fight this process. Indeed the best weapon is our own saliva. Saliva is rich in calcium and phosphate ions, and given time (approximately two hours) it can neutralise the plaque acids and remineralise enamel. The other weapon is fluoride. When fluoride is present the enamel remineralises faster, and with a different structure, fluorapatite, which is more acid-resistant that the original hydroxyapatite structure.
Lifestyle or Genetics?
If we look at the underlying science, we can see why Anne has a cavity. As she is eating sweets every half hour, her saliva never gets a chance to buffer the plaque acids and remineralise the tooth. Each half hour more sugar comes, and the bacteria produce more acid. Eventually the enamel structure is so weakened, a cavity appears. To add insult to injury, by rinsing away the fluoride toothpaste each time, Anne has limited the formation of fluorapatite crystals which would make her enamel more resistant to the acid.
Mary on the other hand eats her sweets straight after a meal, so she already has extra saliva swimming around ready to buffer the plaque acid. As she eats all her sweets in one go, this only counts as one acid ‘attack’ on her enamel that her saliva can easily remineralise. She also has stronger teeth from leaving the fluoride toothpaste in her mouth for longer.
Conclusion
So if you like a sugary treat, but want fewer cavities, use the underlying science to your advantage. Eat sweet things with a meal, and in one go; avoid snacking. The same goes for sweet drinks, it doesn’t matter how many sugars you put in your tea or coffee, the important thing is how often you sip on it throughout the day. The key is to reduce the frequency of acid attacks on your teeth. Don’t forget to brush twice a day with a fluoride toothpaste to strengthen the enamel, and remember the advice from your dentist nowadays is ‘spit, don’t rinse’!
