Secondhand Smoke Linked to Tooth Decay in Kids

Image courtesy of stockimages at


Image courtesy of stockimages at

Smoking around children is a bad idea due to the potential for respiratory illnesses. But researchers at Kyoto University in Japan also have linked it to tooth decay in deciduous teeth.

Their study assessed 76,920 children born between 2004 and 2010 in Kobe City, Japan, who received periodic municipal health checkups from the age of 4 months to 3 years. According to the researchers, 55.3% of the children came from households where smoking was prevalent, and another 6.8% had evidence of exposure to smoke.

The data showed a total of 12,729 incidents of dental caries, defined as at least one decayed, missing, or filled tooth assessed by qualified dentists without radiographs. Most of these caries were decayed teeth.

The risk of caries at the age of 3 was 14.0% for kids with no smoker in the family, 20.0% for kids who showed no evidence of exposure to tobacco smoke but still came from households where there was smoking, and 27.6% for kids who were exposed to tobacco smoke.

The risk of caries, then, was increased by a factor of 1.5 for children who were exposed to household smoking. In particular, children exposed to tobacco smoke at the age of 4 months showed an approximately twofold increased risk of caries. The effect of maternal smoking during pregnancy on caries, however, was not statistically significant.

Secondhand smoke can inflame the oral membrane, impair salivary gland function, decrease serum vitamin C levels, and cause immune dysfunction. Children exposed to it also have lower levels of salivary immunoglobulin A (IgA) and higher levels of salic acid with higher activity. Furthermore, the offspring of rats exposed to passive smoking show inhibited morphology and mineralization of dental hard tissue.

With 40% of children worldwide exposed to secondhand smoke, the researchers say, public health and clinical interventions should be extended to reduce its risks. Yet they also note that further investigation is necessary to conclude whether a smoking prevention program would reduce the risks of caries since the size of the effects of secondhand smoke was not large.

The study, “Secondhand Smoke and Incidence of Dental Caries in Deciduous Teeth Among Children in Japan: Population Based Retrospective Cohort Study,” was published by the BMJ.

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