CHAPTER 1 INTRODUCTION
Water is a very important basic requirement for human life and that is why water quality is an important factor and a key area of concentration in public health.
Fluoride, is an important element considered to be beneficial at low concentrations and toxic at high concentrations when present in water. Fluoride is toxic as a result of its strong affinity for calcium, this gives it the ability to react with structures that are made of calcium such as teeth and bones. The World Health Organization (WHO) guideline for permissible fluoride concentration in drinking water is set at 1.5 mg/L (WHO, 2011). However, the WHO has emphasized the need for national authorities to set national fluoride standards taking into consideration climatic condition, fluoride intake from alternative sources, and daily water intake (Lennon, Whelton, O’Mullane, & Ekstrand, 2005).
Common techniques used to detect fluoride levels include fluoride ion selective electrode method, calorimetric methods, ion chromatography methods, and use of photometer (Agency for Toxic Substances and Disease Registry, 2001).
For many years, there has been a global public health debate about both the beneficial and adverse effects of fluoride in water sources (UNICEF, 1999). This debate first came about in the 1930s and 1940s when a study revealed that fluoride concentrations below 1.5 mg/L in water is effective in preventing tooth decay, otherwise known as dental caries (Dean & Brandt Jr, 1974). According to jones et al. (2005), dental caries affects approximately 60-90% of school children in most
developed countries. In addition, Jones et al. (2005) also identified Latin American and Asia as the continents with the highest prevalence of dental caries.
According to Gussy et al. (2008), fluoride provides protection to the teeth in two ways; pre and post eruption. The pre-tooth eruption occurs while the tooth is still developing. Dental tissues, especially the enamel, are incorporated with fluoride giving them the ability to resist de-mineralization. The post-eruptive stage occurs when there is topical contact between the fluoride and erupted teeth enhances the ability of the teeth to replace surface minerals on the teeth. In addition, jones et al. (2005) highlighted that fluoride improves the chemical structure of the dental enamel and it also reduces the acid formation ability of plaque bacteria. All these properties further emphasized by gussy et al. (2008), makes fluoride an effective agent in preventing dental caries.
Despite the effectiveness of fluoride in combating dental caries, in high concentrations, fluoride could lead to a condition called dental fluorosis (Dean, 1934). Dental fluorosis, also referred to as Colorado brown stain, is a disorder that occurs during the mineralization of the teeth, resulting in an uneven distribution of brown and yellow coloration. McKay (1952) refers to dental fluorosis as the mottling of the enamel. The teeth appear opaque, disfigured, and discolored (Soto-Rojas et al., 2004). This defect occurs in children between the ages of 0 and 8 when the teeth is still developing (Beltran-Aguilar, Barker, & Dye, 2010).
Dean and Brandt Jr. (1974) were one of the first researchers to show the relationship between dental caries and dental fluorosis in respect to fluoride concentration in
community water. Their study showed that 4-5% of the 114 children in their study who drank from community water that had fluoride concentration of 0.6 – 1.5 ppm were dental caries free while 22-27% of the children who drank from community water of concentrations above 1.5 ppm were caries free and showed dental fluorosis. More studies have also shown the inverse relationship between dental fluorosis and dental caries. Marya et al. (2004) showed that in Haryana, India, as the level of fluoride rose from 0.5 – 1.13 ppm, the prevalence of dental caries reduced from 48.02% to 28.07% without very significant increase in prevalence of dental fluorosis. However, as fluoride concentrations continued to increase to 1.51 ppm, the prevalence of dental fluorosis increased as well (Marya et al., 2004).
In the last two decades, there has been a considerable reduction in the incidence of dental caries on the other hand, there has been reasonable increases in the number of cases of dental fluorosis (Buzalaf, Cury, & Whitford, 2001). These changes in the patterns of dental health are mainly due to the increased fluoridation of community water evident in countries like the United States, Australia (Fagin, 2008; Gussy et al., 2008). Research conducted in Australia showed that since the introduction of community water fluoridation, 90% of children (12 years of age) had experienced dental fluorosis. This number however, in 1994 had reduced to 42.5% and in 1999, it reduced to 35.5% (Gussy et al., 2008).
During the process of tooth formation, amelogenins: proteins that the build-up of hydroxyapatite crystals, are broken down and eliminated from the matured enamel after tooth development. When fluoride is ingested at higher concentrations than the normal, it interferes with tooth development causing amelogenins to remain in the
developing tooth longer than normal causing the crystalline structure of the enamel to be tampered with. When the enamel finally develops and erupts, the teeth is seen to have unevenly distribution of lines and color. At more severe situations, the teeth are pitted with brown or yellow coloration (Fagin, 2008). This is why dental fluorosis usually occurs in children (0-8 years) whose teeth are in the process of still developing. This results in an increased risk of having an aesthetic change or fluorosis in the permanent teeth when children are exposed to high levels of fluoride during this period (Alvarez, et al., 2009).
Dental fluorosis is a public health concern in places where the concentration of fluoride in water exceeds the prescribed levels (Soto-Rojas et al., 2004). Brown (2012) reports that 38% of children (15 years of age) in fluoridated Irish communities have shown signs of having dental fluorosis. Despite that dental fluorosis is mainly caused by naturally occurring fluoride in natural drinking water sources, it is also associated with wide use of fluoridated products, such as toothpaste, supplements, and nutrition (Akpata, Danfillo, Otoh, & Mafeni, 2009).
Many fluoridation programs have been implemented in several countries worldwide so as promote a decrease in dental caries. In some Latin American Countries, fluoridation of salt and water have been largely introduced (Jones et al., 2005). The total amount of fluoride obtained from other sources of consumption during tooth development contributes to the risk of having dental fluorosis (Buzalaf et al., 2001). The severity of dental fluorosis depends on the length of exposure to fluoride, response of the individual, nutritional factors, and physical activities. Some
researchers have also shown that living at high altitudes and climatic conditions also play a role in the prevalence of dental fluorosis (Soto-Rojas et al., 2004).
