Background: Fluoride is an ionic form of fluorine by the ionization process occurring in the earth crust (Kapp, 2014). It is also high in natural water bodies such as the ocean, river, and lakes (World Health Organization, n.d.). The addition of fluoride into the main water supply system has been practiced since the 1930s; it helps prevent dental caries, especially among young children (Engineering Services Division, Ministry of Health, 2010). This study aimed to review the human health risk and benefit of fluoridation in drinking water.
Subjects and Method: This systematic review searched articles related to fluoride in drinking water from various sources of World Wide Web such as Google Scholar, Scopus, PubMed, Science Direct, and Mendeley. A total of 31 articles were included in this syste-matic review. The dependent variables were the risk and benefit. The independent variable was the fluoride in drinking water.
Result: A sufficient amount of fluoride intake is necessary to maintain and support the mineralization of bones and teeth in the human body based on previous scientific studies (Everett, 2010). However, if fluoride intake exceeds the safe limit (0.4-0.6 mg/L), it may lead to various kinds of health effects on teeth, skeletal, thyroid gland and may also influence insulin secretion and neural development (U.S. Public Health Service, 2015).
Conclusion: Fluoride intake from drinking water may lead to different health effects that may either benefit or harm the health of consumers.

Keywords: fluoride, dental health, skeletal fluorosis, thyroid gland, neural development.

Correspondence:
Shaharuddin Mohd Sham. Universiti Putra Malaysia. Department of Environmental and Occupational Health, Faculty of Medicine and Health Sciences, UPM, 43400 Serdang, Selangor, Malaysia. Email: shaha@upm.edu.my. Mobile: +6012338¬7305