Exposure to chemicals found in common household objects such as refillable drinking bottles and plastic food containers may irreversibly weaken children's teeth, a new study has found.

Such chemicals cause teeth to degrade by interfering with hormones that initiate the development of teeth enamel, which is the outer layer of each tooth. Dental enamel is recognized as the hardest and most mineralized part of the body.

One condition that affects the dental enamel is called molar incisor hypermineralization (MIH), which is experienced by about 18 percent of children between 6 and 9 years old.

MIH is characterized by the growth of permanent first molars and incisors that have sensitive spots, which are prone to pain and cavities. As enamel does not regrow like bones, the damage brought about by MIH is irreversible.

Hormone Disruptors

There are some chemicals that disrupt the function of hormones, which are responsible for multiple mechanisms in the body. One example is bisphenol A (BPA), which is the most common disruptor of all. Objects being used every day such as drinking bottles and food containers made of plastic usually contain BPA.

Another disruptor is vinclozolin, which is typically used as fungi destroyer in vineyards, orchards and golf courses.

Animal Studies

In the past, scientists found that MIH may be due to BPA exposure. In rat experiments where they induced BPA levels equivalent to human BPA exposures, the enamel of the animals sustained the same damage.

In the recent study, scientists gave rats either BPA or BPA and vinclozolin every day upon birth until the 30th day of life. After the experiment, they obtained cells from the subjects' teeth and discovered that the chemicals altered the expression of two genes in charge of tooth enamel mineralization.

The scientists also cultured and analyzed the cells that leave enamel during teeth development. They discovered that sex hormones such as testosterone and estrogen enhance the expression of genes that make the tooth enamel. Because the hormone disruptors are recognized to hinder the effects of the male sex hormone, the findings suggest that the chemicals reduce the strength of teeth.

"Tooth enamel starts at the third trimester of pregnancy and ends at the age of 5, so minimizing exposure to endocrine disruptors at this stage in life as a precautionary measure would be one way of reducing the risk of enamel weakening," said lead investigator Katia Jedeon of the French National Institute of Health and Medical Research.

Details of the research were presented at the European Congress of Endocrinology on May 30.

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