|Year : 2020 | Volume
| Issue : 4 | Page : 332-337
Relationship between dental fluorosis and I.Q of school going children aged 10-12 years in and around Nalgonda district-A cross-sectional study
R Kranthi Kumar1, Kola Srikanth Reddy1, N Venugopal Reddy2, Toviti Karthik2, M Ajay Reddy1, Nagakishore1
1 Department of Pedodontics and Preventive Dentistry, Mallareddy Dental College for Women's and Hospital, Hyderabad, Telangana, India
2 Department of Pedodontics and Preventive Dentistry, Mamata Dental College and Hospital, Khammam, Telangana, India
|Date of Submission||02-Apr-2020|
|Date of Decision||08-Aug-2020|
|Date of Acceptance||01-Dec-2020|
|Date of Web Publication||5-Jan-2021|
Dr. Kola Srikanth Reddy
Department of Pedodontics and Preventive Dentistry, Mallareddy Dental College for Women's and Hospital, Hyderabad, Telangana
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: The fluoride ion toxicity has been associated with both dental fluorosis and neurotoxicity; dental fluorosis has tended to be considered with respect to tooth appearance and function rather than as a marker for neurotoxicity. Aims and Objectives: This study assessed the intelligence quotient (IQ) of school-going children aged 10–12 years in villages of Nalgonda district with different fluoride levels. Materials and Methods: A cross-sectional study was conducted among the permanent residents of Nalgonda district of Telangana state, India. A total of 480 government schoolchildren aged 10–12 years were selected by stratified random sampling from three different areas with different levels of naturally occurring fluoride in drinking water. Intelligence levels were assessed by conducting the Ravens standard progressive matrices test (1991 edition). Statistical Analysis: The data were subjected to analysis of variance (ANOVA), Student's t-test, and Krustal–Wallis ANOVA. A logistic regression model was performed (SPSS version; 21(IBM corporation, Chicago,IL, USA)). Results: The mean IQ levels were more in the villages with low fluoride concentration in drinking water (15.26) compared to villages with medium fluoride content (12.91) and high fluoride content (9.1). A significant statistical association was found (P < 0.001). Conclusion: The overall IQ levels in children exposed to high fluoride level significantly lower than the low fluoride areas. Thus, children intelligence can be affected by high water fluoride levels.
|How to cite this article:|
Kumar R K, Reddy KS, Reddy N V, Karthik T, Reddy M A, Nagakishore. Relationship between dental fluorosis and I.Q of school going children aged 10-12 years in and around Nalgonda district-A cross-sectional study. J Indian Soc Pedod Prev Dent 2020;38:332-7
|How to cite this URL:|
Kumar R K, Reddy KS, Reddy N V, Karthik T, Reddy M A, Nagakishore. Relationship between dental fluorosis and I.Q of school going children aged 10-12 years in and around Nalgonda district-A cross-sectional study. J Indian Soc Pedod Prev Dent [serial online] 2020 [cited 2021 Jun 17];38:332-7. Available from: https://www.jisppd.com/text.asp?2020/38/4/332/306213
| Introduction|| |
The concentration of fluoride level in most of the Asian countries including India is more than the WHO Guidelines values. Sixty million Indians are residing in approximately 200 districts of twenty states categorized as the endemic areas of fluorosis, and about 66 million people in India suffer from dental and skeletal fluorosis, out of the these six million are children below the age of 14 years.
Nalgonda district is a geographical area located in Telangana state; the district is bounded by Khammam and Krishna distinct on the East, Hyderabad, Rangareddy district, Mahabubnagar districts on the West, Medak and Warangal district on the North, and by river Krishna and Guntur on south. The majority of the people staying here belong to lower socioeconomic status. Nalgonda district consists of various levels of fluoride in drinking water starting from below optimal to optimum and above optimal levels.
Fluoride is a protoplasmic poison; in excess amounts, it has definite toxic effects on the cells of animals including humans. It enters the cells of various organ systems and binds with protoplasm inside, ultimately causing damage to protoplasm. Fluoride, after entering a nerve cell, can damage the protoplasmic structure and its function, leading to a disruption of normal brain function. Under normal circumstances, fluoride ions maintain equilibrium within the body, a matter of primary importance for the normal physiological function of the organism.
Fluoride poisoning in humans can affect the activation of the central nervous system (CNS), typical sufferers of fluoride poisoning present with symptoms such as headache, dizziness, memory deficits, lethargy, fatigue, insomnia, upper respiratory inflammation, stomach pain, joint pain, rhinitis, dermatitis, and gingivitis. Animal studies have observed shedding of the myelin sheath and a decrease in the number of Purkinje cells, with irregularities in the Nissl bodies.
Since a review of scientific literature indicated a scarcity of such studies in Nalgonda district, the current study was conducted to assess the intelligence quotient (IQ) of school going children aged 10–12 years in villages of Nalgonda district with different fluoride levels.
| Materials and Methods|| |
A cross-sectional analytical study was conducted among 10–12-year-old schoolchildren of Nalgonda district, Telangana state.
Nalgonda district is located at latitude–Northern between 16.25 and 17.60 longitudes–Eastern 78.40 and 80.05. The district covers spread over 1,424,000 hectares. It lies at an average 91–103 m above from the sea level with a population of 34,83,648, the annual average temperature is 37.1 c. It contains about six revenue divisions, 90 mandals, 320 villages, 1230 panchayts, primary schools 3031, upper primary schools 528, high schools 1117, and higher secondary schools were 2.
Sampling technique/selection of sample/sample size
The sampling procedure involved multistage stratified sampling was used, where the entire Nalgonda district is divided into three strata based on different levels of naturally occurring fluoride in drinking water supply. Fluoride levels in the drinking water for stratifying the district were obtained from the documented records of district rural water supply department, Nalgonda. Fluoride level 1.5 PPM low (Mushampally), fluoride level 3 PPM medium (yellareddy gudem), and Fluoride levels >5 PPM high (Marriguda). In each area, one school was selected by simple random sampling (lottery) method, and the whole about twenty government schools were selected from the abovementioned areas. The eligible 480 children were selected randomly from a list obtained from school records. Age eligibility requires that the subjects fall in to the appropriate age at the time of sampling. All 10–12-year-old children present on the day of clinical examination.
- All participants were long life residents of the villages under study, with their mothers having lived in the area during their pregnancies.
- Children suffering from any developmental disorders related to psychiatric illness and children with defective audio, speech or visual activity, systemic disease, brain trauma
- Children who had migrated from some other place or who were not permanent residents of that particular area were excluded
- Children with severe extrinsic stains on their teeth, ion whom assessing is not possible, are excluded
- Children with orthodontic brackets.
Collection and water sample analysis
Collection of water sample was done on methodology followed in National oral health survey and fluoride mapping 2002–2003. Sufficient number of plastic bottles carried to the schools. Data and time of water collection and the location of water source (nearest postal address with pin code) were noted. The type of water source (e.g., open well/bore well/tube well) was also noted. The water fluoride levels were measured using a Orion 720 A fluoride meter analysis center, Panikal, Nalgonda.
Data collection: Ethical clearance and informed consent
Before start of the study, an ethical clearance was obtained from the Ethical Committee of Mamatha dental college and hospital Khammam. An official permission was obtained from the District Educational officer, Nalgonda.
Informed consent was obtained from the school headmaster on behalf of the students before the onset of study.
The study was conducted between the months of 15 August 2018-31 st October 2018.
Data were collected using a self-administered questionnaire and clinical examination. Self-administered questionnaire consisted of information on demographic data, permanent residential address, information on source of drinking water, duration of use of a present source of drinking water, staple food, liquids routinely consumed, and aids used for oral hygiene maintenance (fluoridated or nonfluoridated).
Socioeconomic status was considered as one of the confounding. Variable so, Modified Kuppa Swamy socioeconomic status scale was used to assess socioeconomic status of the each children. It consisted of questionnaire, with eight closed-ended questions related to parental education, family income, fathers occupation, etc.
All the children were asked to fill the form, and the answers obtained were scored using Modified kuppaswamy socioeconomic status scoring keys, finally all the children were divided into five group's, i.e., upper, upper middle, lower middle, upper lower, and lower class.
ADA specified Type III dental examinations were carried out by the investigator itself according to the WHO 1997 recommended Modified Dean's index. Calibrations were done on every twenty patients who were examined twice using diagnostic criteria on successive days. All the teeth were examined for the fluorosis; the severity of fluorosis was recorded taking into consideration the degree of fluorosis of the central incisors. If the two central incisors differ in the degree of fluorosis, the one with the lowest degree was considered, and then the results were compared to know the diagnostic variability.
Assessment of intelligence
Intelligence level was assessed by conducting the Raven's Standard Progressive Matrices test. Raven's test consists of sets A, B, C, D, and E each set having s multiple choice questions, and was asked to answer all the questions in a separately designed answer paper which were arranged in the order of difficulty. This test was initially developed by John C. Raven in 1936. Each test item consists of a missing element, which the student has to identify and complete the pattern from the options. There were allotted a time limit of 30 min according to the specification of the test manual.
The total scores were transformed into percentile and specific grades were given as follows.
- Grade I: Intellectually superior (IQ score ≥ 95%)
- Grade II: Definitely above average (IQ score > 75%)
- Grade III: Intellectually average (IQ score 75%–25%)
- Grade IV: Definitely below average in intellectual capacity (IQ score ≤ 25%)
- Grade V: Intellectually impaired (IQ score ≤ 5%).
| Results|| |
[Table 1] shows the children analyzed according to the different levels of fluoride. The mean IQ levels were more in the village with low fluoride concentration in drinking water (15.26) compared to villages with medium fluoride concentration (12.91) and high fluoride concentration (9.1).
|Table 1: Children analyzed according to the different levels of fluoride|
Click here to view
When the mean IQ levels of boys were combined, it was more in the village with low fluoride concentration (16.23) compared to villages with medium fluoride concentration (13.60) and high fluoride concentration (9.43) [Table 2] and [Graph 1].
The mean IQ levels of girls were based on fluoride concentrations. The mean IQ levels of girls were more in the village with low fluoride concentration (14.25) compared to villages with medium fluoride concentration (12.17) and high fluoride concentration (8.91) [Table 3] and [Graph 2].
[Table 4] and [Graph 3] shows the mean IQ levels of girls were compared based on fluoride concentration, a significant statistical association was found (P < 0.001).
| Discussion|| |
The mean IQ levels of children in low, medium, and high fluoride villages are 15.26, 12.91, and 9.18, respectively, with P < 0.001, which is statistically significant. The mean IQ levels of boys in low, medium, and high fluoride villages are 16.23, 13.6, and 9.43, respectively, and when mean IQ levels of girls were combined in low, medium, and high fluoride villages, it was 14.25, 12.17, and 8.91, respectively.
The correlation between boys and girls in low, medium, and high fluoride villages is not significant with P = 0.138, 0.268, and 0.612, respectively. The percentage of children with Grade I and V scores in all the three villages is zero. The percentages of children with Grade II score in low, medium, and high fluoride villages are 6.25, 3.75, and 1.875, respectively.
The percentages of children with Grade III score in low, medium, and high fluoride villages are 61.25, 56.87, and 36.25, respectively. The percentages of children with Grade IV score in low medium and high fluoride villages are 32.5, 39.37, and 6.87, respectively.
The present study involved almost equal number of male and female children which showed that there was no significant association between the mean IQ levels and gender. These results were similar to the studies done by Poureslami et al. Seraj et al.
In the present study, the percentage of children with below average IQ, i.e., Grade IV was larger (61.87%) in high fluoride village compared to low fluoride village (32.5%) and medium fluoride village (39.37%). The proportion of children with IQ Grades II and III was larger in village with low fluoride concentration level in drinking water (6.25%, 61.25%) compared to village with medium fluoride concentration in drinking water (3.75%, 56.87%) and to high fluoride village (1.87% and 36.25%) and the difference was statistically significant (P < 0.001).
These results are in accordance with results of Aravind et al. in high fluoride areas, percentage of children with below average IQ, i.e., Grade IV was larger (59.37%) compared to low fluoride areas (15.6%) and medium fluoride areas (0%). The proportion of children with IQ Grades II and III was larger in regions with low fluoride concentration level in drinking water (3.12%, 81.25%) and regions with medium fluoride concentration in drinking water (8.3%, 81.25%) compared to high fluoride areas (0%, 40.62%), and the difference was statistically significant (P < 0.001) the difference in percentages is due to variation in sample size and variation in concentration of fluoride levels in these studies.
According to Blaylock, this association was attributed to high levels of fluoride absorbed in the blood forms lipid-soluble complexes, which cross the blood–brain barrier and accumulate in the cerebral tissues. The penetrated fluoride complexes adversely affect the CNS development by different neurotoxic and excitotoxic mechanisms such as free radical generation, inhibition of antioxidant and mitochondrial energy enzymes, and inhibition of glutamate transporters. The structural and functional alterations in CNS, specifically in the fetal period and the first 8 years of life may lead to learning and intellectual deficits and cognitive dysfunctions.
The present study results were not in agreement with the study results of Broadbent et al. where there was no apparent difference in IQ because of fluoride exposure, as certain factors such as exposure to school environment and freedom from physical trauma; the possible effects of the confounding factors including the parental education and difference in socioeconomic status between the villages are considered. Therefore, it is not possible to explain the IQ of children based on the effects of exposure to high or low fluoride water alone.
According to Eswar et al. lack of IQ in children exposed to high levels of fluoride is mainly due to functional and biochemical harm to the nervous system during the prenatal and development periods of infancy and childhood because fluoride can cross the blood–brain barrier.
Aborted human fetuses collected from the endemic fluorosis area were found that accumulation of fluoride in the brain tissue causes disruption of certain neurotransmitters and receptors in nerve cells and also increased numerical density of volume of neurons and undifferentiated neuroblasts.,
Possible mechanisms for such a relationship have been suggested that ability of fluoride to enter the brain is enhanced by its ability to form a lipid soluble complex with aluminum. Aluminofluoride complexes are able to stimulate guanine nucleotide-binding protein (G proteins) and can produce pharmacological and toxicological effects in animal and human cells, tissues, and organs.
Higher concentration of fluoride has been found in embryonic brain tissue obtained from termination of pregnancy operations in areas where fluorosis due to coal burning was prevalent.
Stereological and ultramicroscopic study of this tissue showed the differentiation of brain nerve cells was poor, and brain development was delayed. This suggests that developing brain tissues are sensitive to the toxic effects of fluoride.
The main limitation of this study
The limitation of the study was the nature of the cross-sectional design and limited sample size. As fluoride compounds are not biodegradable, they gradually accumulate in the environment, in the food chain, soil, plants, and in bones and teeth of human beings. The findings of the present study highlight the consumption of fluoride-containing water in endemically fluorosed areas can be considered as possible risk factor affecting the IQ levels of children.
| Conclusion|| |
Although fluoride is widely recommended for the prevention of dental caries, its overconsumption may lead to dental and skeletal fluorosis and other adverse effects. Based on the present study findings, the chronic exposure to high levels of fluoride can be one of the factors that influence intellectual development.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]