A previous review of studies had suggested that secondhand smoke could play a causal role in kids' cavities, and a new critical take on the evidence explores the link further.
A critical summary of a previous 2011 review of 15 studies that were published between 1990 and 2010 says the review shows there's "potential for a causal relationship -- not only a statistically significant association -- between SHS [secondhand smoke] and caries in primary teeth." (Caries is the term for cavities or tooth decay, and primary dentition is another term for baby teeth.) In the original review, the findings held true even after taking into account other potential factors, such as the children's socioeconomic status.
However, the evidence from the review was "insufficient" to demonstrate a similar causal relationship between secondhand smoke and cavities in permanent teeth.
But how could secondhand smoke affect risk for cavities? The commentary on the review, published in the Journal of the American Dental Association, explored some potential avenues:
Proposed mechanisms linking exposure to SHS with caries risk include influencing oral microbiota; influencing the mineralization of developing dentition; increasing environmental cadmium levels; decreasing vitamin C levels; decreasing immune function; decreasing the production and effectiveness of saliva by affecting the development and function of salivary glands; and by causing nasal congestion, which could increase mouth breathing.
Overall, the commentary said that more research is needed to establish that secondhand smoke does indeed cause cavities, but that secondhand smoke does carry other health risks.
Smoking is already known to lead to or increase risk of certain dental problems in actual smokers, including increased tooth plaque and tartar, tooth discoloration, gum disease, bone loss, delayed healing, and even oral cancer.
Correction: A previous version of this article incorrectly characterized the new JADA article as "new research"; it is a critical summary of a review published in 2011.