Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2011  |  Volume : 29  |  Issue : 3  |  Page : 205--215

A comparative study of pH modulation and trace elements of various fruit juices on enamel erosion: An in vitro study


S.V.S.G Nirmala1, VV Subba Reddy2,  
1 Department of Pedodontics and Preventive Dentistry, Narayana Dental College, Nellore, Andhra Pradesh, India
2 Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere, Karnataka, India

Correspondence Address:
S.V.S.G Nirmala
Department of Pedodontics and Preventive Dentistry, Narayana Dental College, Nellore, Andhra Pradesh - 524 002
India

Abstract

Fruit juices are popular worldwide with children of all ages as they are sweet and perceived to be healthful. This in vitro study was sought to measure pH of 10 different fruit juices, to find out possible erosive effects on human dental enamel of 40 extracted sound premolars and also to measure fluoride and trace elements of these juices. The estimation of pH of fruit juices was done by using Systronic upH 362 pH meter. The erosive effects of fruit juices were tested by using polarized light microscope. Orion electrode was used to measure fluoride. The trace elements were estimated by using Atomic Absorption Spectrophotometer No. 6501F. The pH values in different juices were observed at different levels, and pH values of these juices were more acidic than baseline after 24 hours. As the time increased, the erosion effect became more in pineapple; grape and sugarcane juices, and they had more cariogenic trace elements like selenium, iron and manganese. So, these juices were found to be cariogenic. To conclude, orange, mousambi, mango, pomegranate, apple, chikku and watermelon juices had no erosive effect on the human enamel, with the presence of highest amount of trace elements like fluoride and phosphorous which are considered as strongly cariostatic.



How to cite this article:
Nirmala S, Subba Reddy V V. A comparative study of pH modulation and trace elements of various fruit juices on enamel erosion: An in vitro study.J Indian Soc Pedod Prev Dent 2011;29:205-215


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Nirmala S, Subba Reddy V V. A comparative study of pH modulation and trace elements of various fruit juices on enamel erosion: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2011 [cited 2020 Dec 3 ];29:205-215
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Full Text

 Introduction



Changes in diet have included substantial increase in the consumption of fruit juices, carbonated beverages and acid drinks. Fruit juices are marketed aggressively and are promoted as a "health drink". Parents are aware of the deleterious effect of the various carbonated beverages on the teeth, so they prefer more natural and healthful products such as fresh fruit juices which are easy to prepare at home and provide a good source of vitamin C. The erosive effect of fruit juices has been recognized for a long time, with references dating as early as by Darby (1892) and WD Miller (1907) who reported tooth decalcification due to excessive fruit juice consumption. [1],[2] The frequent fruit juice consumption is directly proportional to erosion, abrasion, dental caries. [3] Trace elements are essential nutrients which are required for humans in very small amounts. They have a vital function to avoid deficiency diseases. The study was carried out to measure pH, to estimate trace element levels of 10 different fruit juices, to find out possible erosive effect on 40 extracted premolars.

 Materials and Methods



This study was performed in the Department of Pedodontics and Preventive Dentistry, Bapuji Dental College and Hospital, in collaboration with the Department of Oral Pathology, Vimta Labs and Environment Protection Training Research Centre, Hyderabad.

Storage, collection and grouping of teeth

The materials used are shown in [Figure 1].{Figure 1}

Measuring pH of fruit juices

pH meter Systronics upH system 362 was used [Figure 2].{Figure 2}

Test drinks

Pineapple juiceOrange juiceMousambi juiceMango juicePomegranate juiceApple juiceGrapes juiceChikku juiceWatermelon juiceSugarcane juice

Preparation of juice

250 g of each variety of fresh fruit was taken to which 100 ml of water and 4 g of sugar were added. Except for sugarcane juice which was supplied as such by stall, other juices were prepared in a mixer used for the study.

Estimation of erosion

40 extracted premolars, polarized light microscope (Leica), acetone, glass slides and cover, Polarised Light Microscope (Leica Microsystems GMbH, Germany) model trimmer (Buffalo, NY, USA) , waterproof fine silicon grid paper (no. 400, 240), Arkansas stone no. 4, Canada balsam [Figure 3],[Figure 4],[Figure 5]{Figure 3}{Figure 4}{Figure 5}

Determination of trace elements

Juices of 10 different fruits, Atomic Absorption Spectrophotometer (AAS) (No. 6501F) [Figure 6].{Figure 6}

Determination of fluoride

Beaker, fluoride ion-specific electrode, pipette, (Orion model 901), 0.5 M sodium citrate, total ionic strength adjustment buffer (TISAB) II

Determination of pH of fruit juices

The pH values of 10 different juices were assessed at different time intervals (10 a.m., 4 p.m., 10 p.m., 4 a.m. and 10 a.m.) for 24 hours by using Systronics upH 362 pH meter and the values were tabulated [Table 1].{Table 1}

Estimation of trace elements in fruit juices

Estimation of trace elements in 10 different fruit juices was done by using AAS and the values were tabulated [Table 2],[Table 3],[Table 4],[Table 5],[Table 6].{Table 2}{Table 3}{Table 4}{Table 5}{Table 6}

Estimation of fluorides

10 ml of juice was added to 2 ml of TISAB II solution, Orion microprocessor model was used for the analysis [Figure 7]. This instrument was calibrated each day with different standards prepared. The digital reading of meter should show actual concentration of the known standard. After every use of sample, electrode should be rinsed and blotted with clean tissue paper carefully. Wait for the correct concentration to be displayed. The final results were given in a computer printout. Thus, the samples were analyzed.{Figure 7}

Use of TISAB II

To provide a constant background ion strengthDecomplex fluoride from aluminum, iron, etc.To adjust the pH between 5 and 5.5 to render the solution fit for estimation and free from interference.

Preparation of TISAB II

Glacial acetic acid (57 ml), 58 g of sodium chloride, and 4 g of 1,2-diamino cyclohexane N, N, N', N' tetra acetic acid (DCTA) were added to 500 ml of deionized water. The mixture was thoroughly mixed and kept in a water bath for cooling. 5 M NaOH solution was added by constant magnetic stirring until the pH was adjusted to 5.2 on a calibrated pH electrode. Deionized water was added gradually to make the solution one litre and it was shifted to a container.

Preparation of standards

Deionized water (100 ml) was taken to which 22.1 mg of desiccated sodium fluoride analytical reagent was dissolved to obtain a standard sodium fluoride solution of 100 ppm strength. Further dilution of 10 ml of 100 ppm standard was done with deionized water to obtain 10 ppm standard. A number of serial dilutions were made from 10 standards to obtain 0, 0.5, 1.0, 2.0, 3.0, 5.0 and 8.0 ppm standard solutions.

Use of standards

To check electrode potentials' efficiency.To plot potentials on linear axis against their concentrations on long axis to obtain a calibration curve and thus to obtain exact fluoride concentration.

Collection and grouping of teeth

A total number of 40 healthy premolars extracted for orthodontic reasons were used for study. Teeth were divided into 10 groups with 4 teeth in each group. Selected teeth were free of caries and cracks in enamel. Each of the 40 teeth was carefully held with wet gauze in between thumb, index and middle fingers, washed to remove any saliva, blood and tissue debris.

All the teeth were completely coated with nail varnish, except a window on enamel which is approximately 4 × 4 mm [Figure 8]. Among these 40 teeth, 20 were placed in 10 samples of different juices for 15 hours and the other 20 teeth for 24 hours at room temperature. Teeth were removed from the juices, rinsed with water, and dried; nail varnish was removed with acetone. Window area on enamel was examined macroscopically for any change in the appearance of surface enamel prior to preparation of 100 μm undemineralized sections. Each tooth was sectioned into two equal halves longitudinally in a buccolingual direction under slow speed with a carborandum disk along with water coolant. Sections were mounted on a glass slide with Canada balsam and viewed under polarized light.{Figure 8}

Scoring criteria followed in the study (stereomicroscopic evaluation)

No visible change.Surface of enamel is mildly altered, suggested by a roughening or loss of luster in few continuous or discontinuous patches within study boundary. Margins of boundary may not be clearly demarcated.Large areas within study boundary showing opacification, boundary clearly demarcated.Entire area within study boundary showing opacification uniformly, boundary clearly defined throughout [Figure 3].

Principle of polarized light microscopy

Light is a transverse wave, i.e. it travels in a direction perpendicular to the source of propagation of light. When a crystal is placed in front of a light beam, then only that plane of light would be able to pass through it which has its plane parallel to the plane of crystal. In other words, all other planes of light would be inhibited. Hence, light is being channelled in single plane. Such a phenomenon is called as polarization and the resultant flame of light is called as polarized light.

Principle of AAS

When a solution containing a metallic salt (some other metallic compound) is aspirated into a flame (e.g. acetylene burning in air), a vapor which contains atoms of metal is formed. However, a much larger number of gaseous metal atoms will normally remain at the ground state. These ground-state atoms are capable of absorbing radiant energy of their own specific resonance wavelength which, in general, is the wavelength of radiation that atoms would emit if excited from the ground state. Hence, if light of resonance wavelength is passed through a flame containing atoms in question, then part of light will be absorbed, with the extent of absorption being proportional to the number of ground-state atoms present in flame. The amount of absorption of light energy by a particular element is measured through AAS.

 Results



Analysis of variance (2-way classification) revealed that pH level was different in different fruit juices. It also showed that reduction observed in pH levels in different juices in 24 hours was also significant (P < 0.01) [Table 7] and [Table 8].{Table 7}{Table 8}

pH values

Results of pH values of 10 different fruit juices are tabulated [Table 1]. pH levels in different juices were observed at different time intervals. Analysis of variance (2-way classification technique) [Table 7] and [Table 9] was used. It was observed that the pH values of all juices were more acidic than baseline after 24 hours. F test (variance ratio) revealed that the pH levels in different juices were significantly different (P < 0.01) and also reduction in pH values assessed at different time intervals was statistically significant [Table 8].{Table 9}

Trace elements

Trace elements were estimated in 10 varieties of juices by using AAS and the results were tabulated [Table 2],[Table 3],[Table 4],[Table 5],[Table 6]. According to literature, caries promoting trace elements are selenium, magnesium, cadmium, platinum, lead, and silicon [Table 2]; caries inert trace elements are barium, aluminum, nickel, iron, palladium, and titanium [Table 3]; trace elements with doubtful effect on caries are beryllium, cobalt, manganese, tin, zinc, bromine, and iodine [Table 4]; mildly cariostatic trace elements are molybdenum, vanadium, strontium, calcium, boron, and lithium [Table 5]; and strongly cariostatic trace elements are fluoride and phosphorus [Table 6].

Erosion

Two teeth were immersed in each of the 10 fruit juices for 15 and 24 hours, and then erosion was observed by using polarized light microscope. The results were tabulated according to the criteria [Table 10]. Orange, mousambi, mango, pomegranate, apple, watermelon, and chikku juices did not show any erosion after 15 and 24 hours [Table 10],[Figure 9] and [Figure 10].{Table 10}{Figure 9}{Figure 10}

At the end of 15 and 24 hours, pineapple, grape, and sugarcane juices showed erosion scores of 1, 2 and 2, 3 and 3, 3, respectively [Table 10],[Figure 11],[Figure 12],[Figure 13],[Figure 14],[Figure 15].{Figure 11}{Figure 12}{Figure 13}{Figure 14}{Figure 15}

Sections under polarized light indicated appreciable destruction of enamel. Complete loss of surface enamel had taken place with irregular surface. Beneath this surface, there was a zone of enamel which had a translucent appearance, reminiscent of translucent zone seen in early enamel caries [Figure 16],[Figure 17],[Figure 18],[Figure 19],[Figure 20].{Figure 16}{Figure 17}{Figure 18}{Figure 19}{Figure 20}

 Discussion



Results of this study were discussed under the following headings



pH of various fruit juices, their erosive effect.Levels of various trace elements in 10 different fruit juices.

In modern societies, the extrinsic factor, i.e. "dietary" factor is becoming more important as in order to avoid gaining weight, some people eat lots of fruit salads or vegetables. With the increase in urbanization of civilization, consumption of various fruit juices and soft drinks has become a common custom in Indian population. Mothers prefer to give fruit juices for their children because of lack of lactation or otherwise. Mothers involved in domestic work usually give sweetened water or fruit juices to their children in bottle so that they are not disturbed. These juices maintain homeostasis during prolonged physical activity. [4]

Almost all juices contain acids; ingestion of these may initiate demineralization of enamel and initiation of caries. Investigators [5],[6] have described erosion having a dietary origin. Elsbury (1952) [7] and Eccles (1982) [8] reported the destructive effect of citric acid on enamel as a result of complex calcium citrate which forms when citric ions come in contact with enamel, causing dissolution.

Pineapple juice

Wynn and Haldi [9] concluded that pineapple juice was midway on scale of erosive ability. This study showed erosion scores of 1 and 2 and the erosive effect was directly proportional to time.

Orange juice

Citrus fruits are found to contain 7-8% sugars. Shallenberger [10] and Duke et al.[11] reported acidogenic potentiality of orange juice. This study did not show any erosive effect on both samples kept at 15 and 24 hours, which could be attributed to pH 3.75. Even though it contains citric acid, it did not show any erosive effect due to the sugar content and concentration of juice.

Mousambi juice

It did not show any erosive effect after 15 and 24 hours due to its pH 3.93. Even though it contains citric acid, it did not show any erosive effect which may be due to its sugar content.

Mango juice

Trask and Zeigler [12] stated that acid foods with pH of 4 and less were important factors in decalcification, but in this study the pH was 4.60 which was mildly acidic and did not show any erosion.

Pomegranate juice

The pH was 3.51 and did not show any erosive effect after 15 and 24 hours.

Apple juice

Mistry and Greenby [13] tested the erosive effect of apple juice on rats' teeth and concluded that there was no erosive effect. In this study, the pH was 5.64 and the juice did not show any erosive effect after 15 and 24 hours. These results are comparable with those of the above study, even though it was conducted on rats.

Grape juice

Wynn and Hardly [9] and Lussy et al.[14] reported that grape juice has got the greatest erosive effect. In the present study, the pH was 3.47 and the erosion scores were 2 and 3. These findings are almost similar with the above findings. This may be because of more viscous nature of the juice. The erosive effect was directly proportional to time.

Chikku juice

The pH was 5.20, and the juice did not show any erosive effect because Baseline pH was second highest towards alkalinity of all juices.

Sugarcane juice

The pH was 4.60 and the juice showed an erosion score of 3. As it contains natural sugars and citric acid, its erosive effect can be attributed to the same. There may be intense erosion with time intervals, which can be shown only by assessment of its depth of erosion. But this parameter was not assessed in this study.

Watermelon juice

The pH was 4.24 and the juice did not show any erosive effect due to the baseline surface microhardness or iodide permeability of enamel.

Trace elements like selenium, fluoride, and phosphorous can modify chemical and physical composition of teeth, especially surface layer of enamel. They may alter the size of enamel crystals available to acid exposure, influencing the solubility of enamel. They may also influence microbial ecology of plaque to either inhibit or prolong the growth of caries producing bacteria.

In infancy, main sources of trace elements like fluoride and phosphorous are thought to be the commercial beverages and foods used during weaning, as this period coincides with calcification stages of developing permanent tooth germs. [15]

Investigators suggested that trace elements may be cariogenic, [16],[17],[18],[19],[20] mildly cariostatic, [21],[22],[23],[24] caries inert, [20] having doubtful effect on caries, [20] or strongly cariostatic. [20],[25],[26],[27] Hadjimarkos, [19] Tank and Storvick, [24] Bonherst and Hadjimarkos, [17] Navia and Barmes, [16] and Gauba [18] reported that selenium is cariogenic; in the present study, selenium concentrations in pineapple, grape, sugarcane juices were 0.018, 0.021, and 0.029 ppm, respectively, and the erosion scores were 1, 2 and 2, 3 and 3, 3, respectively, after 15 and 24 hours.

Hewat and Eastcott, [28] Navia, [20] Rothaman, [23] and Gauba [18] concluded that iron was cariogenic, whereas in the present study, the iron concentrations in pineapple, grape, and sugarcane juices were 0.021, 0.029, and 0.026 ppm, respectively, and its erosive scores were 1, 2 and 2, 3 and 3, 3, respectively, after 15 and 24 hours. These findings are similar to the above findings.

Manganese was reported to be cariogenic by Hewat and Eastcott, [28] Ludwig, [29] Adkins and Losee, [30] Navia, [20] Glass, [31] Curzon and Losee, [25] and Gauba. [18] In the present study, the manganese concentrations in pineapple, grape, and sugarcane juices were 0.031, 0.041, and 0.021 ppm, respectively, and the erosive scores were 1, 2 and 2, 3 and 3, 3, respectively, after 15 and 24 hours. These findings are similar with the above reports.

Adler and Straub [21] stated that molybdenum was cariostatic, Tank and Storvick [24] concluded that vanadium was cariostatic. Rothman [23] and Curzon and Losee [25] reported strontium to be cariostatic, and Gauba [18] concluded lithium to be cariostatic. In the present study, molybdenum concentrations in orange, mousambi, mango, pomegranate, apple, chikku, and watermelon juices were 0.24, 0.023, 0.22, 0.21, 0.22, 0.23, and 0.23 ppm, respectively. Vanadium concentrations in these seven juices were 0.12, 0.11, 0.12, 0.13, 0.14, 0.13, and 0.12 ppm, respectively; strontium concentrations were 0.021, 0.031, 0.011, 0.011, 0.021, 0.021, and 0.023 ppm, respectively; lithium concentrations were 0.031, 0.021, 0.022, 0.012, 0.032, 0.012, and 0.011 ppm, respectively. All these juices did not show any erosion, and these findings are similar to the above reports.

Lennox, [26] Osborn and Noriskin, [27] Navia, [20] and Curzon and Losee [25] concluded phosphorous and fluoride to be strongly cariostatic. In this study, the fluoride concentrations in the above seven juices were 0.31, 0.33, 0.51, 0.44, 0.41, 0.4, and 0.35 ppm, respectively; phosphorous concentrations were 0.14, 0.13, 0.14, 0.12, 0.11, 0.10, and 0.13 ppm, respectively, and did not show any erosive effect. These findings are similar to the above reports. Baseline pH values of pineapple, grape, and sugarcane juices were 3.70, 3.47, and 4.60, respectively. Erosion scores of these juices were 1, 2 and 2, 3 and 3, 3, respectively. Concentrations of cariogenic trace elements like selenium, iron, and manganese in pineapple, grape and sugarcane juices were 0.018, 0.021, and 0.031; 0.021, 0.029, and 0.041; and 0.029, 0.026, and 0.021 ppm, respectively.

While comparing these three juices, erosion scores were more in grape than in pineapple juice due to reduced pH of grape when compared to pineapple juice and presence of increased concentration of selenium, iron, manganese in grape juice. Erosion scores were more in sugarcane than pineapple juice, which can be attributed to increased concentrations of selenium and iron in the sugarcane juice. When erosion scores of grape and sugarcane juices were compared, sugarcane was found to be more erosive than grape even though pH, iron, manganese concentrations were high, due to increased concentration of selenium. It was found that sugarcane juice was more cariogenic, followed by grape and pineapple juice. In spite of the presence of fluoride and phosphorous, erosion effect was more and this can be attributed to the presence of selenium, iron, manganese.

In this study, most of the known trace elements levels were estimated in all the fruit juices studied. Magnesium, cadmium, platinum, lead, silicon, barium, aluminum, nickel, palladium, titanium, beryllium, cobalt, tin, zinc, bromine, iodine, calcium, boron, and gold, present in varying concentrations (tabulated in results) in all the fruit juices, did not show any erosive effect, thus are assumed to be cariostatic.

 Summary and Conclusion





Pineapple, grape, sugarcane juices are considered to be cariogenic. The erosion effect increased with time.Even though orange, mousambi, mango, pomegranate, apple, chikku, watermelon juices had very small amount of cariogenic trace elements like selenium, iron and manganese, the erosive effect was not observed. Fluoride and phosphorous concentrations were high, and did not show any erosion effect on enamel. So, these juices are considered to be strongly cariostatic, and recommended for consumption.Even though pineapple, grape, sugarcane juices were found to be cariogenic, they can be consumed cautiously because juices come in contact with teeth only for a few seconds.Especially, mothers should be instructed that children should not be made to retain bottle in their mouth for a longer time, and after consumption, the child should be instructed to rinse mouth. Parents should be advised on mechanical cleansing like using wet cloth and children should be advised to brush at bed time. These fruit juices have less erosive effect and can be consumed safely in between meals.

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