Impact of Secondhand Smoke from Conventional Cigarettes, IQOS, and E-Cigarettes on Children's Oral Health: A Cross-Sectional Study.

Secondhand smoke (SHS) is a major public health concern, especially for children, who are particularly vulnerable to its harmful effects. Although alternative smoking devices like IQOS and e-cigarettes are marketed as harm reduction tools, their impact on paediatric oral health remains underexplored. This study evaluates the effects of SHS from conventional cigarettes, IQOS, and e-cigarettes on cotinine levels in gingival crevicular fluid and the risk of dental caries in children. A cross-sectional study was conducted involving 160 children aged 3 to 14 years, categorised into four groups based on exposure: SHS from conventional cigarettes, SHA (secondhand aerosol) from IQOS, e-cigarettes, and a no-smoking control group. Each group included 40 participants, ensuring an equal distribution across exposure conditions. Children in the SHS/SHA groups were exclusively exposed to emissions from a single product type (cigarettes, IQOS, or e-cigarettes) to isolate product-specific effects. Cotinine levels were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and dental caries were assessed via the Decayed-Missing-Filled Teeth (DMFT) index. Parental smoking habits, oral health behaviours, and environmental factors were recorded through a questionnaire. Statistical analyses included one-way ANOVA, Kruskal-Wallis tests, and Spearman's correlation. SHS exposure from all sources negatively impacts children's oral health, with conventional cigarettes posing the greatest risk. While IQOS and e-cigarettes reduce SHS exposure compared to conventional cigarettes, they still result in measurable nicotine absorption and increased caries risk. Public health strategies and clinical interventions should prioritise creating smoke-free environments and raising awareness about the risks of SHS/SHA from all nicotine-containing products on paediatric health.