Pro- and Antifluoride Use Messages on YouTube in Japan: Content Analysis.

Background: Dental caries is one of the most prevalent chronic conditions globally. In Japan, fluoride application-mainly via toothpaste, mouth rinses, and professional treatments-is a key preventive measure, as community water fluoridation is not implemented. Despite its proven effectiveness, fluoride use faces opposition from certain groups citing potential health risks. Social media platforms, especially YouTube, have become major sources of health information, but also facilitate the spread of misinformation, which may influence public perceptions and behaviors toward fluoride use. Objective: This study aimed to analyze YouTube videos addressing fluoride use for caries prevention, focusing on the types of information presented and comparing the messages shared by proponents and opponents of fluoride use. Methods: A comprehensive search was conducted on YouTube using fluoride-related keywords in Japanese. The top 50 videos for each keyword were screened, and after excluding irrelevant or duplicate content, 86 videos were analyzed. Videos were categorized as proponent ("pro"), opponent ("anti"), or others. The sources, intended audiences, and content themes were assessed. Interrater reliability was confirmed using the Cohen κ coefficient. Results: Of the 86 analyzed videos, 58% (n=50) were categorized as "pro," 22% (n=19) as "anti," and 20% (n=17) as others. Proponent videos, mainly produced by dental professionals, emphasized scientific evidence, such as the mechanism of fluoride in preventing caries and guideline-based recommendations. Opponent videos, largely uploaded by laypersons, highlighted potential dangers of fluoride, including health risks and additives, and frequently promoted fluoride-free products. Opponent videos had higher daily viewership and engagement than proponent videos. Conclusions: Anti-fluoride content on YouTube appears to reach broader audiences than expert-generated profluoride videos. Opponent messages tend to use emotionally charged communication, whereas proponents focus on scientific information. These differences in style may influence public perceptions of fluoride use. Public health professionals should develop engaging and accessible communication strategies to counter misinformation and promote evidence-based practices.