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Rotten luck ... baby teeth are especially vulnerable to tooth decay. Photo: Domino Postiglione

Sugary foods and over-processed carbs take much of the rap for chronic disease and overweight, but here's another casualty that makes fewer headlines – baby teeth. We might live in the age of fluoride and flash cosmetic dentistry, but the latest report card on children's dental health showed a surprising number of little kids with holes in their first teeth. Almost 50 per cent of  six-year olds attending school dental services had one or more teeth that was either decayed, missing or had been filled, the Australian Institute of Health and Welfare's Child Dental Health Survey revealed this year.

So what makes little teeth decay so quickly?

This thinner enamel is no match for the acid attack that happens when an overload of sugar and refined carbohydrates change the environment in the mouth to favour the bacteria that cause tooth decay. 

Baby teeth begin with a disadvantage – because their enamel is less robust than that of the permanent teeth that replace them, they're less decay resistant, explains Associate Professor Wendell Evans of the University of Sydney's Faculty of Dentistry.

This thinner enamel is no match for the acid attack that happens when an overload of sugar and refined carbohydrates change the environment in the mouth to favour the bacteria that cause tooth decay, he says.

"Plaque is the film of bacteria that builds up on the teeth but it's not plaque that causes decay – it's the acid produced when bacteria ferment sugar and refined carbohydrates. This acid dissolves the tooth enamel – and the more sugar and refined carbohydrates there are in the mouth the more dominant these bacteria become," he explains. The mouth does have its own brilliant anti-cavity repellent – it's called saliva and it works in two ways. One is by rinsing away the acid and the other is by helping to reverse the early stages of tooth decay - saliva also contains calcium that can help remineralise damaged enamel.

"But if there's too much sugar in the mouth too often the saliva can't keep up. If the mouth has three or four hour breaks in between eating sugary food the natural repair process can take place, but when babies have bottles filled with cordial, soft drink or sweetened milk, or children graze on lollies, biscuits and cakes or snacks made from refined carbohydrates through the day, there's no opportunity for periods of remineralisation to take place," Evans says.

"Another contributor to this early  decay may be  that children are also drinking more flavoured drinks rather than tap water containing fluoride."

Decay is also surprisingly swift, he adds. In research from a Danish dental school in the 1960s, a group of students rinsed their mouths frequently with a sugar solution but didn't brush their teeth – and within three weeks their teeth showed little white spots, the early signs that demineralisation had begun dissolving the enamel.

"Teeth can be decimated in weeks, but the good news is that demineralisation can be reversed by regular brushing with fluoride toothpaste," Evans says.

Does it really matter if baby teeth come to grief if they're replaced by permanent teeth?

Well, yes. Not only can decayed baby teeth hurt, but losing them too early can cause problems with the alignment of the second teeth – one of the jobs of the first teeth is to hold the position for the permanent teeth. However, if first teeth are lost prematurely, dentists can use stainless steel or plastic space maintainers to help prevent alignment problems.

Besides regular brushing and avoiding over-grazing on sugary foods and refined carbohydrates, how else can parents keep tiny teeth decay free?

Teaching them to drink from a cup by the age of one is good, says Evans – with a bottle children are  more  likely to suck on a drink for longer, exposing teeth to any sugary fluids such as juice for longer periods. And look out for the arrival of more teeth in need of brushing - the permanent molars that can sneak in unnoticed at the back of the mouth sometimes as early as four and half or five years of age.

What's your approach to rationing sugar in your children's diet?