This review evaluates the relationship between second-hand smoke (SHS) and dental caries in epidemiological studies. Only Medline and reference lists of identified articles were searched. The review included 14 studies, one cohort and 14 case-controls. Quality was assessed using the modified Newcastle–Ottawa Scale.

They found, 11 studies examined early childhood caries, with a significant independent association of SHS in 10 studies, the strength being mostly weak to moderate.  One study did not select SHS as a significant variable. Three studies reported decreases in the risk of previous exposure, and the association was not significant. Dose-response relationships were evident in five studies. Permanent teeth were examined in seven studies, with five studies reporting significant associations, which were mostly weak. The risk of previous exposure remained similar to that of current exposure, and a dose-response relationship was not evident in one study.

They concluded that:

The overall evidence for the causal association in early childhood caries is possible regarding epidemiological studies, and the evidence of permanent teeth and the effect of maternal smoking during pregnancy were insufficient.

The results warrant further studies of deciduous teeth using a cohort format and basic studies regarding the underlying mechanism.

Hanioka T, Ojima M, Tanaka K, Yamamoto M. Does second-hand smoke affect the development of dental caries in children? A systematic review. Int J Environ Res Public Health. 2011 May;8(5):1503-19. Epub 2011 May 12. PubMed PMID: 21655133