Prevalence of dental caries and dental fluorosis among 6-12 years old school children in relation to fluoride concentration in an endemic fluoride belt of Mahabubnagar district, Telangana state, India : Journal of Dr. NTR University of Health Sciences

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Prevalence of dental caries and dental fluorosis among 6-12 years old school children in relation to fluoride concentration in an endemic fluoride belt of Mahabubnagar district, Telangana state, India

Kola, Srikanth Reddy; Mallela, Manoj Kumar1; Puppala, Ravindar1; Kethenaeni, Balaji1; Tharasingh, P1; Reddy, Venumbaka Sivakalyan2

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Journal of Dr. NTR University of Health Sciences 8(1):p 29-36, Jan–Mar 2019. | DOI: 10.4103/JDRNTRUHS.JDRNTRUHS_54_17
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The aim of the study is to evaluate the prevalence of dental caries and dental fluorosis among the school going children in Mahabubnagar district, and also to assess F- levels in drinking water from different areas of Mahabubnagar district.

Materials and Methods: 

The study was carried out in 2,000 children of age group 6–12 years. The dental caries status was assessed by Decayed/missed filled tooth (DMFT)/deft index using WHO criteria 1997 and dental fluorosis status using Modified Dean's fluorosis index. Alizarin visual method was used to estimate F levels in water.

Statistical Analysis: 

All data entered to an SPSS (18) program (IBM Corporation, Chicago, USA); both descriptive and analytic approaches were used in the data analysis. The correlation of deft with different F- levels using ANOVA test. The P < 0.005 was considered statistically significant.


The prevalence of dental caries in primary teeth and permanent dentition was 64.2% and 26.6%, respectively. Indicating that dental caries was more among 7–8 years old children and less in 11–12 years old children (P > 0.005). Dental fluorosis in primary dentition was 15% and 70.3% in the permanent dentition; it was more in 9–10-year-old children and less in 6-year-old children.


The dental caries and dental fluorosis were more in Northern, Eastern region of Mahabubnagar district, whereas dental caries and dental fluorosis were less in local villages of Mahabubnagar district. The F- content in Northern, Eastern zone of Mahabubnagar district was about 2 mg/l, whereas in local villages of Mahabubnagar is 1.2 mg/l.


Fluoride (F-) is one of the very few chemicals that can leave significant effects on human health through drinking water.[12] Different forms of F exposure have shown to affect systemic F content, thus increasing the risk of F-prone diseases.[3] At low concentrations (<1.0 mg/L), drinking water F has positive effects on teeth such as preventing or decreasing the risk of dental caries[3456], which is one of the main concerns of dentists. This ion might prevent the occurrence of new caries and even might allow recovery of some small cavities. F influences the process of dental caries formation through three ways: Improvement of the enamel chemical structure during its development and making it more resistant to acid attack; facilitation of mineralization with an improved quality of enamel crystals; and reduction of the ability of plaque microorganisms to produce acid.[135] However, too much F (higher than 1.5–2 mg/l) ingested for longer durations can cause dental fluorosis.[124567] The results pertaining to the effect of F on caries prevention are controversial,[891011121314] possibly because the effect of F can be altered by some factors. These include climate, total dissolved solids, the chemical composition and porosity of the rocks, temperature, pH, availability and solubility of F minerals, velocity of flowing water, concentration of calcium and bicarbonate ions in water, lack of calcium/vitamins/proteins, and consumed foods.[151617] Both dental caries and fluorosis are public health problems world-wide.[5679] Endemic fluorosis resulting from high F concentration in water can be a major public health issue,[9] to the extent that many western European countries have halted fluoridation of water supplies to prevent exacerbating it.[6] Because no cure exists, prevention is the only available treatment.[5] Monitoring the concentration of F in different areas might help to establish proper preventive measures.

Because of the effects of F on health, F levels in water supplies have been the subject of various recent studies.[4] High levels of F in drinking water have been observed in India, Turkey, Pakistan, and China.[19]

Mahabubnagar district is a geographical area located in Telangana state at the border between Telangana and Karnataka. Majority of the people staying here belong to lower socio-economic status. Telangana state has many areas which have high F levels in drinking water, and Mahabubnagar district is one among them, where people are affected with dental and skeletal fluorosis. No study showing the prevalence of dental caries and dental fluorosis has been conducted so far in this region.

This makes Mahabubnagar district is an ideal place for the present study. The aim of the study is to assess the prevalence of dental caries and dental fluorosis among 6–12 years old school children of Mahabubnagar district, Telangana state. In addition, their correlation at different concentrations of F in drinking water. The objectives were to estimate the F level in drinking water in these respected areas.


A cross-sectional study was carried out in Mahabubnagar district to assess the prevalence of dental caries and dental fluorosis among school children in the age group of 6–12 years. It contains about four revenue divisions: 64 mandals; villages 1,541; municipalities four; and 4,689 schools of which 3,133 were primary schools, 889 were upper primary schools, 658 were high schools, and nine were higher secondary schools.[18] Before starting the study, ethical clearance was taken from the ethical committee of Institution, Mahabubnagar. An official permission was obtained from the district education officer (DEO) Mahabubnagar. An informed consent was obtained from the respective school head masters and parents of the children.

Training and recording procedures were standardized by repeated sections of calibration between the examiner and preventive Dentistry. iThe draft of the questionnaire used in the study was reviewed by a panel of experts, which included faculty members from Pedodontics and Preventive Dentistry, Public Health Dentistry, school teachers, and headmasters, and there after, the draft was finalized.

A pilot study was conducted on a convenient sample 50; the prevalence of dental fluorosis was assessed, and it was found to be 49.71%. On this, the sample size was decided with n = 1849 with consideration of 3% precision and 99% confidence level. The final sample was rounded to 2,000. Hence, a total of 2,000 school going children aged 6–12 years from rural areas were enrolled in this study. The sampling procedure involved multistage stratified sampling[19], where whole Mahabubnagar district is divided into five strata viz, Mahabubnagar Central, Southern, Northern, Eastern, and Western. In each strata, following areas were selected.

Mahabubnagar Central: Boyapalli, Jainallipur, Ramaiahbowli, Mettugadda.

Mahabubnagar Southern part: Kollapur, Utkoor, Bijinapalli, Wanaparthy.

Mahabubnagar Eastern part: Kalwakurthy, Thadoor, Uppununthala, Kollur.

Mahabubnagar Northern part: Kotthur, Badepalli, Balanagar, Nawabpeta.

Mahabubnagar Western part: Kosghi, Narayanpet, Bomaraspet, Makthal.

Fifteen of the 64 madals in the district of Mahabubnagar were selected by simple random sampling, lottery method, and then, three schools from each of these selected mandals were chosen at random. Eligible children were selected randomly from a list obtained from school records. Age eligibility requires that the subjects fall into the appropriate age at the time of sampling. All 6–12-year-old children were present on the clinical examination day. School children who were continuous residents in Mahabubnagar district and who were available on the day of examination were included in the study. Children without fluorosis stains and children with orthodontics brackets or crown are excluded from the study.

The clinical examination (American dental association type 111) was done by three dentists; they were assisted by three dental assistant over a period of 1 year for recording data. A questionnaire was used to fill out personal data such as name, age, gender, occupation and income status of the parent, permanent address, source of drinking water, oral hygiene methods, and diet chart. Standard infection control guidelines were applied. All the recordings were done in the daylight, and the child was made to sit in ordinary chair facing away from a direct sunlight.[20] The oral examination of study subject was conducted in respective schools using a plane mouth mirror under natural light. Dental caries was assessed using Decayed missing and filled tooth/dmft index[9] and dental fluorosis using Modified Dean's Fluorosis Index (1942).[21]

”The Collection of water samples was done from the methodology followed in National Oral Health Survey and Fluoride Mapping 2002–2003.[22] Sufficient numbers of plastic bottles were carried to the schools. Water was collected from drinking water source, which was used by children, and all the bottles were labeled. The water samples were sent to the laboratory of Rural water supply” Mahabubnagar to confirm the F levels in water before commencement of clinical examination. Water F analysis was done using Alizarin visual method.[23]

Statistical analysis

All data were entered into an SPSS (18) program (IBM corporation, Chicago, US). The quantitative data were expressed in terms of mean and standard devation. The categorical data were expressed in frequencies and percentages. ANOVA was used for comparing mean from more than two groups. Where ever ANOVA was found to be significant, post hoc Turkeys test was used for multiple pair wise comparisions. The categorical data were analyzed using Chi-square test. The Pearsons correlations co-efficient was used for correlation between F concentration and DMFT as well as dental fluorosis. The statistical significance was set at 0.005.


Table 1 shows that the age group of the population ranges from 6 to12 years with an mean age of 9.45 ± 2.0 years. Among total population of 2,000 children, 332 of them belonged to age group of 6–7 years, and 286 of them belonged to 9–10 years age group. Out of the population, 1,021 were males and 979 were females.

Table 1:
Sample Distribution According To Age And Gender

The distribution of sample size according to the region wise; the Mahabubnagar district had been divided into five regions: Central, Eastern, Western, and Northern. From each region 400 children were selected [Table 2].

Table 2:
Sample Distribution According To Region

Graph 1 shows that the correlation of deft with different F levels by using ANOVA test. According to the region, the values are not statistically significant.

Graph 2 shows that the correlation of DMFT and DMFS with different F levels by using ANOVA test. According to the region, the values are not statistically significant.

The highest water F level was found in Kalwakurthy, Nawabpet (2 ppm). The lowest water F level was found in Uppununthala, Balanagar, Kottur (0.6 ppm) [Graph 3].

Table 3 shows that there is a direct positive relationship between the prevalence and severity of dental fluorosis and increasing water F levels i.e. there was an increase in both prevalence and severity of dental fluorosis with increase in water F level.

Table 3:
Correlation Of Caries Prevalence, Dental Fluorosis, And Water Fluoride Concentration In Primary Dentition

Table 4 shows that there is a decrease in dental caries prevalence as water F level increase up to 1.8 ppm, and there after an increase in dental caries prevalence was observed with increasing water F level.

Table 4:
Correlation Of Caries Prevalence, Dental Fluorosis, And Water Fluoride Concentration In Permanent Dentition


F, the pivot of preventive dentistry, continues to be the cornerstone of caries prevention programs. The effect of drinking water F concentration on human health, particularly dental health has been a matter of debate since the works of McKay and Dean. Thus, the important milestone discovery was at last that at 1 ppm of F in drinking water, maximum reduction of caries experience, i.e., 60% was achieved and only sporadic instances of the mildest form of dental fluorosis of no practical or esthetic significance were observed (Dean et al. 1942).[24] The recommended level of water fluoridation for optimal dental caries reduction is 0.7–1.0 ppm, with 4.0 ppm being the maximum contaminant level allowed by the environmental protection agency.[25]

Many studies[926272829] have been conducted to identify the prevalence of caries and fluorosis in different parts of India. However, there has been relatively very few data reported in literature concerning the prevalence of fluorosis and dental caries among Mahabubnagar district, children particularly in mixed dentition period, so the present study was conducted in school children of 6–12 years. The school children were targeted because of the ease of accessibility and adequate representation of the target population.[30]

The literature on the relation between F concentration in drinking water with dental caries is conflicting. Some studies reveal an inverse relation,[31] whereas others found no relation[3233] or a positive association.[2634]

Caries prevalence in the study population was about 64.2%. This is higher than Andhra Pradesh average caries prevalence of 41.5% in permanent dentition as reported by National oral health survey and Fluoride Mapping 2002–2003.[22]

In the present study, it was seen the dental fluorosis in children has been found to be 85.3% at the range of 0.6–2.2 mg/l of F concentrations in drinking water. Similar observation was made in Nelakondapallimandal (65.4%) in Khammam district.[35] In addition, close to this findings in Sarada Tehsil (69.4%) in Udaipur district, Rajasthan[36] and Prakasham district (82.4%) of Andhra Pradesh, Naidu GM et al.[27] and Manji et al.[37] recorded 100% dental fluorosis among the children of 5–14 year-old-age groups in Nalgonda district of Telangana state and Kenya. This is in contrast to a study done in urban slum area of Nalgonda district, Telangana state, whereas low dental fluorosis rate, 30.6% was reported by Nirgude et al.[28] The study conducted by Dubey et al.[38] and Bhalla et al.[29] showed the prevalence of dental fluorosis as 54.5,18% which is less when compared to the present study.

According to the region wise distribution of dental fluorosis in primary dention, the Northern part of Mahabubnagar is mostly affected (28.4%) when compared with other parts of Mahabubnagar district as F concentration in drinking water was between 0.6 and 2.0 ppm. Mahabubnagar Central region was least affected (9.7%) in primary dentition where the F concentration was between 0.8 and 1.2 ppm. In permanent dentition, both Eastern and Northern part of Mahabubnagar district was mostly affected (58%), whereas least affected was Mahabubnagar Central (50.6%). This is because of high F content in the drinking water ranging from 0.6 to2 ppm in Eastern and Northern part, whereas in Mahabubnagar Central the F content was 0.8–1.2 ppm. A step wise increase in the prevalence of dental fluorosis with the corresponding increase in water F content was seen by Sebastian ST and Soman RR.[39]

Various studies have shown a positive relationship between dental caries reduction and water F levels such relationship was correct in this study because findings of this study suggest there is a gradual increase in mean DMFS scores up to 1.8 ppm, and there onward there is a gradual increase in mean DMFS scores of the study population which is statistically significant. These findings are similar to other studies viz; Shanthi M et al.[35] and Wondwossen F et al.[40]

In a similar study, DMFT was found to increase when the severity of dental fluorosis was up to grade 3 and found to decrease when the severity of dental fluorosis was between grade 3 and grade 5[41] In another study, a decline in DFS and DMFS was associated with water F levels between 0 and 0.7 ppm, with little additional decline between 0.7 and 1.2 ppm of F.[42]

The study conducted by Kotecha et al.[9] showed no correlation between the occurrences of dental caries and dental fluorosis. It has been reported that the risk of dental caries was less when the F content in drinking water was more.

The study conducted by Ramesh M et al.[43] in Salem, which has been done in 5,000 school children, and there was no correlation was found between the occurrence of dental caries and dental fluorosis.

The possible reasons for this phenomenon were explained by many authors. According to VV Subbareddy et al. (1992),[44] the mutilated morphology of the fluorotic teeth facilitates plaque accumulation and food lodgment that leads to initiation of dental caries. Once the initial lesion occurred in severely fluorotic tooth, it progresses very fast, leading to total destruction of the tooth structure.

However, the actual prevalence of dental fluorosis especially in permanent dentition was higher (70.3%) than in primary dentition (15%) similar to other studies like in a study done by Salman F D et al.[45]

Mineralization of primary teeth occurs in intrauterine phase only. During this phase, only placental barrier exits that prevents transfer of F to the developing primary teeth. Hence, fluorosis is less prevalent in primary dentition.[46] Moreover, the duration of exposure to F of the enamel during the formation of primary teeth is shorter.[47] Other reasons are the thinner enamel of primary teeth as compared to permanent teeth,[47] and the rapid F absorption in growing fetus, making it less available for primary teeth.[48] On the contratary, the greater physical size, activity, and kind of nutrients intake lead to higher intake of water, and hence, a higher prevalence in older age groups.[49]


Hence, there is a need for further epidemiological studies with wider geographical base and greater number of study subjects. Further studies are also required to analyze the association of other oral health disorders affecting childhood and the quality of life of the children affected with both dental caries and fluorosis.


Adequate health education measures should be taken to inform the school children about the prevention of common oral diseases by suitable education materials and by engaging school children in health promotion activities.

The dental public health professionals should interact with them in a mutually beneficial manner, and there is a great need for inclusion of oral health promotion in the curriculum of the school children.


The following conclusions were drawn from this study:

  1. There is a direct positive relationship between the prevalence and severity of dental fluorosis and increasing water F levels, i.e., there was an increase in both prevalence and severity of dental fluorosis with increase in water F level
  2. There is a decrease in dental caries prevalence as water F level increases up to 1.8 ppm, and thereafter an increase in dental caries prevalence was observed with increasing water F level
  3. There is positive relation between severity of dental fluorosis and dental caries prevalence.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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Dental caries; dental fluorosis; children; school; water

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