Chemicals commonly found in plastics and fungicides may be weakening children's teeth by disrupting hormones that stimulate the growth of dental enamel, according to a new study presented today at the European Congress of Endocrinology.
Endocrine disruptors are chemicals that interfere with mammalian hormones. Bisphenol A (BPA) is one of the most prevalent, found in every-day items including refillable drink bottles and food storage containers. Vinclozolin is another endocrine disruptor that was commonly used as a fungicide in vineyards, golf courses and orchards.
Molar incisor hypermineralisation (MIH) is a pathology affecting up to 18% of children aged 6-9, in which the permanent first molars and incisors teeth that erupt have sensitive spots that become painful and are prone to cavities. These spots are found on dental enamel, the tough outer covering of teeth that protects it from physical and chemical damage. Unlike bone, enamel does not regrow and so any damage is irreversible. Previous rat studies have shown that MIH may result from exposure to BPA after finding similar damage to the enamel of rats that received a daily dose of BPA equivalent to normal human BPA exposure, though the exact mechanism of action remains unclear.
In this study, researchers from the French National Institute of Health and Medical Research (INSERM) gave rats daily doses of BPA alone or in combination with vinclozolin, equivalent to an average dose a human would experience daily, from birth till they were thirty days old. They then collected cells from the rats' teeth surface and found that BPA and vinclozolin changed the expression of two genes controlling the mineralisation of tooth enamel.
In part two of their experiment, the team cultured and studied rat ameloblast cells, which deposit enamel during the development of teeth. They found that the presence of sex hormones like oestrogen and testosterone boosted the expression of genes making tooth enamel, especially male sex hormones. As BPA and vinclozolin are known to block the effect of male sex hormones, the findings reveal a potential mechanism by which endocrine disruptors are weakening teeth.
"Tooth enamel starts at the third trimester of pregnancy and ends at the age of 5, so minimising 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 Dr Katia Jedeon, lead author of the study.
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