Sociodemographic, biological, and timing characteristics of dental caries and fluorosis using mixed-type cluster analysis on 12-year-olds in Ho Chi Minh city, 1989-2019.

Objectives: In 1990, Ho Chi Minh City started Community water fluoridation (CWF) at 0.7 ppm F, and in 2000, it was adjusted to 0.5 ppm F. Here, we analyzed dental caries and fluorosis data in Ho Chi Minh City to explore commonalities associated with CWF among 12-year-old children Methods: Dental caries and fluorosis data were collected in 1989, 2003, 2012, and 2019 (N = 4773). Trained dentists scored dental caries using the WHO detection criteria and fluorosis using Dean's Fluorosis Index. We used these data and the k-prototypes method by the R package to identify clusters of participants with shared clinical and water fluoride levels. Results: We used datasets 1 (4773 participants) and 2 (4194 participants, missing fluorosis data in 1989). K-prototypes analysis identified three clusters in each dataset. Cluster 1, with 80 % of the sample at 0.5 ppm F area characterized by low caries and fluorosis scores. Cluster 2 with 60 % of the sample non-fluoridated area had high caries and low fluorosis scores. Cluster 3, with 75 % of the sample in 0.7 ppm area, had low caries but borderline high fluorosis scores. Conclusion: Identifying three clusters based on clinical and environmental scores supports the decision to fluoridate the water to prevent caries (0-0.7 ppm) and the shift from 0.7 to 0.5 ppm to keep the caries preventive effect while reducing the risk of fluorosis. Clinical significance: Our results support the effectiveness of CWF in preventing dental caries and the appropriateness of changing the F concentration to reduce the risk of fluorosis while maintaining its effectiveness.