Excessive fluoride intake during tooth development causes dental fluorosis.


This study aimed to (1) determine the prevalence of dental fluorosis in association with fluoride concentrations in drinking water, (2) explore the effects of altitude on the severity of fluorosis in two towns with high fluoride levels in the drinking water, and (3) assess decayed, missing, and filled teeth (DMFT) and oral hygiene practices among participants.

Material and methods

The sample consisted of 100 and 141 schoolchildren, aged 15.3 ± 1.4 and 16.1 ± 1.3 years, living in Ruwaished and Kuraymah, respectively. Oral examinations were carried out, and dental fluorosis was assessed using the Dean’s index. The DMFT index was also used for assessment. Samples of drinking water were analyzed using a fluoride-ion selective electrode. SPSS was used to analyze the data.


Two-thirds (68.8%) of adults from Kuraymah had moderate to severe fluorosis, with only 7% being unaffected. In Ruwaished, 50% of the sample had severe fluorosis, 22% showed moderate fluorosis, and none were unaffected. The average DMFT scores were 3.18 ± 1.81 and 3.81 ± 1.41 for Kuraymah and Ruwaished, respectively. In both towns, males had significantly higher caries scores than females. Oral hygiene was poor, as 64% and 57% of the participants from Kuraymah and Ruwaished, respectively, did not brush their teeth. A significant correlation was found between poor oral hygiene and increased DMFT scores.


This study concluded that higher fluorosis incidence and severity were present in the higher-altitude location (Ruwaished). Moreover, this study also indicated that fluorosed teeth are not immune to caries, and the preventive management of dental fluorosis should be directed to de-fluoridation of drinking water in endemic areas.


Dental fluorosis
Dean’s index
DMFT index
Oral hygiene

1. Introduction

Fluoride (F) in drinking water remains the cornerstone of public caries prevention programs. Other F sources, including dietary F supplements (tablets, lozenges, and drops), self-used fluoridated toothpaste and mouthrinse, and professionally-applied topical F agents (solutions, gels, foams, varnishes) significantly contribute to caries prevention (Murray, 1986, Marinho, 2009, Twetman and Keller, 2016). However, these sources of F may cause dental fluorosis if their applications are not well controlled. Excessive F intake during tooth development causes dental fluorosis, which is characterized by defective enamel matrix formation and subsequent hypomineralization. After the enamel is completely formed, dental fluorosis cannot develop even if excessive F is ingested. It has been observed that the pitting and staining of moderate to severely fluorosed enamel is induced by prolonged excessive F ingestion from drinking water supplies containing 2 ppm F and higher. The optimal intake of F in children has been widely accepted as being between 0.05 and 0.07 mg F/kg of body weight (Wei and Hattab, 1988, Burt and Eklund, 2005) (see Fig. 1).

Fig. 1. Examples of fluorosis severity in Ruwaished and Kuraymah. A. normal. B. very mild. C. mild. D. moderate. E. severe.

Epidemiological studies in the Western world indicate that dental caries among children and young adults has declined by 50% since the early 1980s (Glass, 1986, Marthaler, 2004). The reason behind this decline is the availability of F from multiple sources, particularly dentifrices. However, there has been an increase in the incidence of dental fluorosis. According to the United Nations’ Environment Programme/World Health Organization (UNEP/WHO, 1992), dental fluorosis is endemic in at least 25 countries across the world, with millions of people affected, particularly in tropical regions. The World Health Organization (WHO, 2019) recommends that F levels in drinking water should not exceed 1.5 ppm F. Reports from Africa, southeast Asia, Jordan, and Saudi Arabia revealed a prevalence of dental fluorosis among residents in areas with drinking water containing 1 ppm F or more (Hattab et al., 1997a, Akpata et al., 1997). Furthermore, the consumption of dietary F supplements during the first years of life has been associated with an increased risk of fluorosis (Ismail and Hasson, 2008).

Evidence indicates that F levels in the drinking water differ between countries and within the same country, depending on the geology of the area. The long-term ingestion of excess F, mostly from drinking water, can cause fluorosis, which affects the teeth and bones (Wei and Hattab, 1988, WHO, 1994. Atmospheric temperature and altitude are additional factors that contribute to the severity of fluorosis (Galagan and Vermillion, 1957). Furthermore, despite a sub-optimal F concentration in drinking water, an increased incidence of dental fluorosis was found among inhabitants of high altitudes in Kenya (Manji et al., 1986), Nigeria (Akosu and Zoakah, 2008), and Mexico (Pontigo-Loyola et al., 2008).

Jordan has a combination of Mediterranean and subtropical arid climates and is usually warm, with dry summers and relatively cold winters. The annual average temperature ranges from 10 to 35 °C, with relative humidity ranging from 35% in summer to 70% in winter. Jordan also has both the highest and lowest points relative to sea level. For example, Jebal Rum is 1734 m above sea level, while the surface and shores of the Dead Sea are about 430 m below sea level—Earth’s lowest elevation on land (Royal Jordanian Geographic Center, 2012). However, it is noteworthy that the summit of Jebal Rum is not inhabited and that the inhabited surrounding the desert plain is about 900 m above sea level (Royal Jordanian Geographic Center, 2012).

Moreover, few studies have reported the prevalence rate of dental fluorosis among Jordanians. Hamdan (2003) found that 18.5% of the 12-year-old school children in the southern region of Jordan presented with dental fluorosis. Furthermore, F concentrations in the drinking water of eleven Jordanian provinces varied considerably, ranging from 0.10 to 2.15 ppm. Higher F concentrations in drinking water were found in the northeast (Mafraq), far north (Irbid), and central (Madaba) regions of Jordan (Hattab et al., 1997a). Fluoride in bottled water ranged from 0.08 to 0.23 ppm and beverages from 0.16 to 0.67 ppm (Hattab et al., 1997b).

For infants, powdered milk formulas were the main source of F when prepared with fluoridated water. When infant powder formulas (contained 0.12–1.08 µg/g) were diluted in a ratio of 1:1, with water containing 0.7 or 1 ppm F, the dose of F was about 55- and 70-times more than that obtained from cow’s milk (Hattab and Wei, 1988). No studies were carried out in Jordan to explore the influence of altitude on the prevalence of dental fluorosis in areas with high fluoride levels in the drinking water.

The main aims of the present study were (1) to determine the prevalence of dental fluorosis in association with F concentrations in drinking water, (2) to explore the effects of altitude on the severity of dental fluorosis in two towns with high fluoride levels in the drinking water, and (3) to assess decayed, missing, and filled teeth (DMFT) scores and oral hygiene practices in individuals living in both towns.

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