ABSTRACT
Drinking water can contain fluoride which is effective in preventing dental caries at
concentration of ≤1.5 mg/L however at concentrations ≥1.5 mg/L, it could lead to
dental fluorosis. Dental fluorosis is a disorder that occurs due to excessive fluoride
intake during the mineralization of the teeth, resulting in an uneven distribution of
brown and yellow coloration. I assessed fluoride levels in 19 samples of natural
water sources (such as boreholes, streams, and wells) and commercial drinking water
sources (such as sachet and bottled water products) in Zing Local Government Area,
Taraba State, northeastern Nigeria, I then determined the prevalence of dental
fluorosis in 135 children, aged 10 to 17 years, who were born in Zing. Using cross
tabulations and logistic regression modelling, I evaluated factors that might influence
whether a child had dental fluorosis, such as dental care habits and drinking water
source. Fluorosis occurred in 111 respondents. Fluoride levels exceeded the World
Health Organization permissible limit of 1.0mg/L for tropical environments in most
borehole samples, while most stream and well samples did not exceed this limit. The
regression model showed that odds of a child having dental fluorosis were higher for
vii
those children who drank borehole water compared to those who do not (OR =
8.522), while the odds of having fluorosis decreases for children who drink from
stream water (OR = 0.203). Consequently, community boreholes may need to be defluoridated and there should be community awareness about the sources of water
with high fluoride concentrations.
Keywords: Boreholes, dental fluorosis, drinking water, fluoride, Nigeria, streams,
wells
viii
TABLE OF CONTENTS
CERTIFICATION PAGE ……………………………………………………………………………..ii
APPROVAL PAGE …………………………………………………………………………………….iii
DEDICATION…………………………………………………………………………………………….iv
ACKNOWLEDGEMENTS …………………………………………………………………………..v
ABSTRACT……………………………………………………………………………………………….vi
TABLE OF CONTENTS …………………………………………………………………………..viii
LIST OF TABLES ……………………………………………………………………………………….x
LIST OF FIGURES …………………………………………………………………………………….xi
LIST OF ABBREVIATIONS………………………………………………………………………xii
CHAPTER 1 ………………………………………………………………………………………………..1
INTRODUCTION…………………………………………………………………………………………1
Signs of Dental Fluorosis……………………………………………………………………11
Sources of Fluoride in the Environment and Human Body …………………….11
Stages of Dental Fluorosis…………………………………………………………….21
Dental Fluorosis Correction………………………………………………………………..22
Methods of Water De-fluoridation….…….…………….…………………..23
HYPOTHESES………..………….…………………………….………………….25
AIMS AND OBJECTIVES…………………………………………………………………………..25
CHAPTER 2……………………………………………………………………………………………….26
MATERIALS AND METHODS ………………………………………………………………….26
Study Area ………………………………………………………………………………………26
Data Collection and Analysis ……………………………………………………………..26
Ethical Guidelines……………………………………………………………………….……31
CHAPTER 3 ……………………………………………………………………………………………….32
RESULTS…………………………………………………………………………………………………..32
CHAPTER 4 ……………………………………………………………………………………………….39
DISCUSSION………………………………………………………………………………………………39
Limitations of Study ………………………………………………………………………….42
Challenges………………………………………………………………………………………..43
Recommendations …………………………………………………………………………….43
CHAPTER 5 ………………………………………………………………………………………………44
ix
CONCLUSION …………………………………………………………………………………………..44
APPENDIX I ………………………………………………………………………………………………45
APPENDIX II………………………………………………………………………46
REFERENCES…………….……………………………………………………….48
x
LIST OF TABLES
Table 1. Prevalence of dental fluorosis in Estonia in respect to different concentrations
of fluoride in drinking water………………………………………………………….7
Table 2. Fluoride concentration is several water sources studied across different
countries……………………………………………………………………..….…….8
Table 3. Fluoride content and percentage of fluoride extracted in tea plants (extraction
time)…………………………………………………………………………………..17
Table 4. Level of fluorosis according to Dean’s dental fluorosis index………………..21
Table 5. Number of water samples collected from different sources of water in
each ward…………………………………………………………………………….28
Table 6. Frequencies of drinking water sources used by children in Zing LGA……..33
Table 7. Fluoride concentration in various water sources tested across different
wards…………………………………………………………………..……………34
Table 8. Relationship between predictor variables measured in this study and the
presence of dental fluorosis in children in Zing LGA…………………………….…35
Table 9. Frequencies of cases of dental fluorosis in relation to the ward where a child
was born.…………………………………………………………………………… 36
Table 10. Likelihood-ratio estimates of logistic-regression parameters for the best-fit
model……………………………………………………………………………..….37
xi
LIST OF FIGURES
Figure 1. Countries with endemic dental fluorosis due to excess fluoride in drinking
water……………………………………………………………………..………….…8
Figure 2. Sources of drinking water in Nigeria………………………………………..9
Figure 3. Different local governments across the geopolitical zones in Nigeria where
fluoride in drinking water exceeds 0.8ppm………………………………..…..….….10
Figure 4. Fluoride cycle……………………………………………….…………….12
Figure 5. Different stages of fluorosis…………………………….………….………22
Figure 6. Location of Taraba State in Nigeria and location of Zing LGA (far northeast)
in Taraba State………………………………………………………………..……….27
xii
LIST OF ABBREVIATIONS
WHO – World Health Organization
UNICEF – United Nations Children Fund
ppm – Parts per million
mg/L – Milligram per liter
mg/kg – Milligram per kilogram
km – Kilometer
F
+
– Fluorine ion
1
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
2
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
3
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
4
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
5
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).
Climatic conditions also play a role in the prevalence of dental fluorosis in some
regions. Although the WHO global recommendation for fluoride concentrations in
water is ≤ 1.5 mg/L, the organization advises that permissible level is ≤ 1 mg/L in
tropical regions (UNICEF, 1999). This is simply because in warmer climates, people
perspire more and tend to drink more water, hence consuming more fluoride
compared to people who live in temperate regions. In Africa, dental fluorosis has
been associated with fluoride levels in natural drinking water sources as low as 0.1–
0.4 mg/L (Akpata, 2014). In addition, research has shown that in southern parts of
Ukraine where the climate is warmer than other parts of the country, fluorosis is
evident at concentrations lower than 1.2 mg/L (Fordyce et al., 2007). Marya et al.
(2014) suggested that in warm parts of the United States, fluoride content in water
sources should range between 0.7 – 1.2 ppm.
Dental fluorosis is not a disease, but rather a defect hence various societies and
cultures perceive it differently. It is considered to be an aesthetic problem because it
changes the natural coloration of the teeth hence making individual with fluorosed
teeth feel embarrassed by this condition. The smile greatly affects people’s view on
attractiveness, it plays a role in a person’s confidence and self-esteem (Hassebrauck,
1998, as cited in Molina-Frechero, et al., 2017). In Brazil, there have been cases of
people reported to be stigmatized and discriminated as result of the color of their
teeth. These people were deprived of smiling and having a normal social life (SantaRosa et al., 2014). Brown (2012) conducted a study in order to determine the rate at
6
which individuals with fluorosed teeth perceive it as an aesthetic problem. The study
revealed that cases categorized as “mild” or more were identified by the affected
individuals as an aesthetic problem. Study conducted by Molina-Frechero et al
(2017) in Durango city of Colorado showed that 68% of adolescent with dental
fluorosis showed concern about the colour of their teeth. A study conducted in
Palestine revealed that 87.5% of the 350 children with fluorosis studied do not accept
the apearance of their teeth as a result of the colour, in addition, 99.7% of the
children believe that the appearance of the teeth affects personality and aesthethic
appearance (Abuhaloob & Abed, 2014).
Asides from dental fluorosis, high intake of fluoride leading into accumulation in
bones can also result into skeletal fluorosis. This condition is characterized by joint
pains and stiffness. Furthermore, much higher concentrations can cause
atherosclerosis and other bone deformities. These conditions are very evident in
communities such as the Rift Valley and in China where very high concentration of
fluoride exists naturally in groundwater (WHO, 2010). Dan (2008) highlighted that
the ability of fluoride to tamper with the crystalline structure of bone could lead to
increased risks of fractures. Though there are few studies on this, fluoride intake has
also been associated with hypersensitivity (Kaminsky, Mahoney, Leach, Melius, &
Miller, 1990). Few studies have raised fears that fluoride could lead to proliferation
of osteoblast cells (bone-building cells) and result into the formation of malignant
tumors (Fagin, 2008). Sutton et al. (2012) suspects that exposure to high naturally
occurring fluoride in water contributes to cardiovascular dysfunction. Animals who
ingest these fluoride toxic substances also prone to fluorosis; fluoride toxicity is not
7
just harmful to human health but also affect animal husbandry, agricultural crops and
plants in their natural habitat (Abugri & Pelig-Ba, 2011).
Research conducted by Indermitte et al. (2009) compared Estonia’s population
exposure to different natural water sources with different fluoride concentrations and
risk of dental fluorosis and the findings showed the increased risk of fluorosis in
populations where the people were exposed to water with fluoride concentration
higher than the WHO accepted value of 1.5 mg/L (Table 1).
Table 1. The prevalence of dental fluorosis in Estonia in respect to different concentrations
of fluoride in natural drinking water sources. (Source: Indermitte, Saava, & Karro, 2009).
According to UNICEF (1999), dental fluorosis is endemic in more than 25 countries
globally (Fig. 1), some of these countries affected globally include China, Japan,
India, Kenya, Uganda and Mexico amongst others. In addition, UNICEF (1999) adds
that dental fluorosis is endemic in 15 out of 32 states in India. Studies on dental
fluorosis in relation to different concentrations of fluoride in drinking water have
been conducted in various countries (Table 2).
8
Fig. 1. Countries with endemic dental fluorosis due to excess fluoride in drinking water
(Source: UNICEF, 1999).
Table 2. Fluoride concentration is several water sources studied across different countries
(Source: Lorna, Start, Dave, & Jamie, 2006).
9
Research conducted in Ghana and Tanzania showed that a good number of sources
of water exceeded fluoride concentration of 20 ppm in central parts of Tanzania and
4 ppm in parts of Ghana. The water samples analyzed (23% and 57% in Ghana and
Tanzania respectively) were all in excess of WHO permissible levels. Dental
fluorosis is prevalent in these areas (Smedley et al., 2002).
In Nigeria, only a few studies have been conducted to determine the relationship
between fluoride exposure and dental fluorosis. Akpata et al. (2009) conducted
research so as to map out fluoride concentration in water sources that cut across
Nigeria. From their findings, 62% of the 109 local governments had fluoride
concentration of 0.3 ppm or less. Some water samples showed high fluoride content
that exceeded 1.5 ppm and a certain well in their studies had maximum fluoride
concentration of 6.7 ppm (Akpata et al., 2009).
Fig. 2. Sources of drinking water in Nigeria (Source: Akpata et al., 2009).
10
Fig. 3. Different local governments across the geopolitical zones in Nigeria where fluoride in
drinking water exceeds 0.8 ppm (Source: Akpata et al., 2009).
Dental fluorosis has been identified in many Nigerian cities, some of which include
Abeokuta, Katsina, Maiduguri, and Yola (El Nadeef & Honkala, 1998). Water
samples collected over different zones of Nigeria showed variations in fluoride
content of water. In western Nigeria, water samples had between 0.0-0.4 ppm
fluoride content. While in northern Nigeria, water samples tested between 0.0-1.2
ppm fluoride content (El Nadeef & Honkala, 1998). One of those researches
conducted by El Nadeef and Honkala (1998) showed that in central Nigeria
particularly Bauchi and Plateau states showed that fluoride concentrations detected
were between 0.0-0.4 ppm and 51% of the subjects had dental fluorosis. Nigeria has
a humid tropical climate where temperature ranges between 28-32ºC, this suggests in
the results that temperature played a role (Akpata et al., 2009). Tropical regions
where there is more daily water consumption often show dental fluorosis even at low
concentrations of fluoride in drinking water. Despite that the WHO have set a
11
guideline of 1.5 ppm fluoride concentration in water, Brouwer et al. (2009)
recommended a limit of 0.6 ppm fluoride concentration in drinking water in Senegal.
In addition, Akpata et al. (2009) recommended a range of 0.3 – 0.6 ppm fluoride
concentration in drinking water for a warm country like Nigeria. Drinking water in
Nigeria is supervised by the Ministry of Health and it is responsible for ensuring that
water consumed via different sources are up to required quality (Standard
Organization of Nigeria, 2007)
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