Exposure to chemicals in plastic and fungicides may irreversibly weaken children’s teeth

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.

Pot-Smokers Harm Gums; Other Physical Effects Slight

Long-term study finds no differences in metabolism, lung function, inflammation

A long-term study of nearly 1,000 New Zealanders from birth to age 38 has found that people who smoked marijuana for up to 20 years have more gum disease, but otherwise do not show worse physical health than non-smokers.

The international research team assessed a dozen measures of physical health, including lung function, systemic inflammation and several measures of metabolic syndrome, including waist circumference, HDL cholesterol, triglycerides, blood pressure, glucose control and body mass index.
Tobacco users in the study, which appears online the week of June 1 in JAMA Psychiatry, were found to have gum disease as well as reduced lung function, systemic inflammation and indicators of poorer metabolic health.

“We can see the physical health effects of tobacco smoking in this study, but we don’t see similar effects for cannabis smoking,” said Madeline Meier, an assistant professor of psychology at Arizona State University who conducted the study with colleagues at Duke University, King’s College in the UK and the University of Otago in New Zealand.

While study participants who had used marijuana to some degree over the last 20 years showed an increase in periodontal disease from age 26 to 38, they did not differ from non-users on any of the other physical health measures. To measure cannabis use, they asked study subjects to self-report their use at ages 18, 21, 26, 32 and 38.

The study’s statistical analysis found that the decline in periodontal health in pot smokers was not explained by tobacco smoking, alcohol abuse or less tooth brushing and flossing. The lack of physical health problems among cannabis users also was not attributable to their having had better health to begin with or to living healthier lifestyles.

“We don’t want people to think, ‘Hey, marijuana can’t hurt me,’ because other studies on this same sample of New Zealanders have shown that marijuana use is associated with increased risk of psychotic illness, IQ decline and downward socioeconomic mobility,” Meier said.

“What we’re seeing is that cannabis may be harmful in some respects, but possibly not in every way,” said study co-author Avshalom Caspi, the Edward M. Arnett Professor of psychology and neuroscience at Duke. “We need to recognize that heavy recreational cannabis use does have some adverse consequences, but overall damage to physical health is not apparent in this study.”

“Physicians should certainly explain to their patients that long-term marijuana use can put them at risk for losing some teeth,” said Terrie Moffitt, the Nannerl O. Keohane University Professor of psychology and neuroscience at Duke and co-director of the Dunedin Multidisciplinary Health and Development Study, from which these data were gathered.