Original
©2012 Dustri-Vertag Dr. K. Feistle ISSN 0946-2104DOI 10.5414/TEX01186 e-pub: Deœmber28, 2011
Urine and saliva iodine levels in patients with
dental caries and normal healthy volunteers
Mine Gulaboglu\ Hayati MuratAkguP, Nilgün AkguP and Meltem Cetin''
^Department of Biochemistry, Faculty of Pharmacy, ^Department of Oral Diagnosis and Oral Radiology, ^Department of Restorative Dentistry, Faculty of Dentistry, and ''Department of Pharmaceutical Technology, Faculty of Pharmacy, Ataturk
University, Erzurum, Turkey
Key words
dental caries iodine -saliva - urine
Accepted for publication March 11,2011 Correspondence to Mine Gulaboglu, PhD Department of Bio-chemistry, Faculty of Pharmacy, Ataturk University, 25240 Erzurum, Turkey gulaboglumine(g yahoo.com
Abstract. The aim of this study was to
in-vestigate the iodine concentration in the urine and saliva of patients with dental caries and of healthy volunteers in Erzurum, Turkey. Urine and saliva specimens were obtained from 29 patients, who have dental caries and from 26 healthy volunteers. The iodine concentration in the urine of patient's with dental caries was found to be 7.50 ± 2.68 jig/ dl, which was lower than the urinary iodine level of healthy persons, which was found to be 12.02 ±3.16 |ag/dl (p < 0.0001). Simi-larly, the saliva iodine level of patients with dental caries was lower than that of healthy volunteers, beeing 4.42 ± 2.21 jig/dl, 8.28 ± 2.78 ng/dl, respectively (p < 0.0001). There was a positive correlation between urinary iodine level and saliva iodine level in both groups (r = 0.750, p < 0.001; r = 0.519, p < 0.001). There was, however, no significant difference in iodine levels of urine and saliva between males and females for both groups of subjects. A positive correlation between iodine levels in urine and saliva of patients and healthy volunteers was also observed. Our results suggest that iodine concentration in urine and saliva might be an indication for dental cavity, where iodine supplementation could be considered as a way of prophylaxis.
Introduction
Dental caries is a highly prevalent diet-related disease and a major public health problem. Saliva is produced in and secreted from salivary glands. The basic secretory units of salivary glands are clusters of cells called acini. These cells secrete a fluid that contains water, electrolytes, mucus and en-zymes, all of which flow out of the acinus into collecting ducts. Small collecting ducts within salivary glands lead into larger ducts, eventually forming a single large duct that empties into- the oral cavity. In fact, some
important functions of saliva are: cleansing of the oral cavity, solubilization of food sub-stances, bolus formation, facilitation of mas-tication and swallowing, food and bacterial clearance, dilution of detritus and lubrication of mucosa [1].
Entering the cells as iodide (I~), iodine (I) is the richest in electrons of the required ele-ments in the animal diet. Iodide is necessary for all living animal cells, but only the verte-brates have the thyroid gland and its iodin-ated hormones. In humans, the total amount of iodine is about 25 50 mg. Around 50 -70% of total iodine is non-hormonal, which is concentrated in extra-thyroidal tissues, where its biological role is still unknown [2]. Venturi et al. [3] and Kupper et al. [4] reported that iodine has an ancestral anti-oxidant function in all I"concentrating cells from primitive marine algae to more recent terrestrial vertebrates. In these cells iodide acts as an electron donor in the presence of H2O2 and peroxidases. The remaining iodine atom readily iodinates tyrosine, histidine or certain specific lipids, and so, neutralizes its own oxidant power [5].
The primitive tongue and the formation, from I-concentrating ectodermic and endo-dermic cells of oral mucosa, of the primitive salivary glands, which maintain I-concen-trating ability, and are able to solubilizating food substances. In anuran amphibian meta-morphosis iodides and thyroxine are the most important factors inducing the spectacular apoptosis of cells of tail, gills, fins and lar-val gut. Sodium iodide symporter (NIS) is a molecule involved in active accumulation of iodine in tyroid gland for the biosynthesis of thyroid hormone. The thyroid gland shares its capacity to accumulate iodine activity with several other tissues like salivary gland.
stomach and lactating mammary gland, where (NIS) expression has been documented [6].
Urinary iodine excretion is a good mark-er of the dietary intake of iodine, and is the index for evaluating the degree of iodine deficiency, correction and toxicity. Recom-mendations by the International Council for the Control of Iodine Deficiency Disorders, WHO, and UNICEF [7] set the minimal uri-nary iodine concentration (UIC) for iodine sufficiency as 100 mg/1, which corresponds roughly to a daily intake of 150 mg iodine. The recommended amount is 150 mg/day for adults, 200 mg for pregnant or lactating women, and lower amounts for children [8]. In previous study, the incidences of den-tal caries for three groups of prehistoric hu-man skeletons from different regions of the Cape Province, South Africa were examined and the results of this examination showed the importance of (I-rich) marine foods in the diet and they varied through time, aeross space, and according to sex. The incidence of dental caries ranges from 0% among heav-ily marine-dependent individuals from the south-western Cape eoast, to 17.7% among skeletons from an archaeological site on the south coast. Also, overall cancer incidenee in I-rich marine fishes is lower than in fresh-water fishes [9, 10]. In an anthropological investigation of the Ngaraangbal Aboriginal Tribe's (Broadbeach, Australia), a hunter-gatherer population, determined that the caries prevalence (0.8%) was very low. The results of this study support the proposal that the Ngaraangbal tribe had a diet that includ-ed marine foods. In fact, it is rare to find oral diseases, as well as malignant tumors, in I-rich marine fish [10, 11]. Hardgrove [12] re-ported that in his community (Fond du Lac, WI, USA), since the beginning of adminis-tration of iodine to prevent goiter, children have less caries. Iodine seems to increase re-sistance to caries, retarding the process and reducing its incidence. Recently Abnet et al. showed a statistical correlation between I-deficient goiter and gastric cancer [13] and between gastric cancer and tooth loss in a Chinese cohort of the Linxian general popu-lation nutrition intervention trial [14, 15]. Another researcher reported that, in adoles-cence, immunodeficiency and malnutrition and iodine deficiency and dental caries are associated [10].
Akarsu et al. [16] have reported the prev-alence of goiter in Erzurum, a city in North-eastern Anatolia of Turkey, as 5.6% and the frequency of people with urinary iodine con-centration lower than 5 |xg/dl as 37.6%, indi-cating that this region is an endemic region in terms of iodine deficieney [7, 16].
However, there is no study reporting iodine levels in saliva and urine in patients with dental caries. The aim of this study was, therefore, to examine a possible relationship between dental caries and healthy volunteer the iodine levels in urine and saliva of these subjects.
Patients and methods
A total of 29 patients (12 female and 17 male, ranging in age between 17 and 26 years; average: 21.8 years) with dental ear-ies and 26 healthy volunteers (12 female and 14 male, ranging in age between 18 and 26 years; average: 20.9 years) were included in the study (in Department Restorat Dent & Endodontthe Dental of Faculty of Atatürk University Erzurum, Turkey). They were not allowed to take any medication which might affect the composition of their saliva and urine. The study protocol was approved by the local ethical committee and the subjects gave their informed consent.
Following WHO criteria, the state of den-tition and the level of dental caries in all indi-viduals were determined by the same person using the decayed, missing and filled teeth (DMFT) index. In this study, we studied with dental caries at advanced level (> 5).
The subjects were instructed to refrain from eating, drinking or using breath fresh-eners for a minimum of 2 h before the saliva and plaque samples were collected following breakfast. Approximately 1.5 ml of unstimu-lated whole saliva was eolleeted by having subjects salivate into sterile tubes; at the same, time urine sample was also collected into sterile tubes. Urine and saliva samples were stored at -80 °C until the time of analy-sis.
All ehemieals used in this study were ob-tained from Sigma-Aldrich Co., St. Louis, MO, USA.
16 -j
14 -¡ 12 10
> Heatty volunteers s Patientswith dental caries
É.I..
Urine Saliva
Figure 1. Iodine concentration in the urine and saliva of patients with dental caries and of healthy volunteers (*p < 0.0001 ).
Determination of iodine levels in
urine and saliva
In a previous study it is reported that there was no significant difference in the concen-tration between the 24-h urine sample and the morning spot urine sample [17]. Therefore, morning spot urine samples were used to determine urine iodine concentration (UIC). Urine samples were stored at -80 °C until analysis. The UIC was determined using the Sandell-Kolthoff reaction [18]. The urine was first digested with chloric acid in a heat-ing block and iodine was determined from its catalytic reduction of eerie ammonium sulfate in the presence of arsenious acid. The iodine concentration in saliva was determined by the Sandell-Kolthoff reaction, following the ho-mogenization of saliva [18], where the same protocol as urine iodine level was applied.
Statistical analysis
The results are given as the mean ± stan-dard deviation (SD), where SPSS 16.0 for Windows was used for the evaluation. The Student's T-test was carried out to compare the group means of the patients with the con-trol group. In order to compare saliva and urine iodine levels between male and female subjects, Mann-Whitney U-test was applied and the Pearson correlation coefficient was used for assessing the relationships.
Results
The urinary iodine level for patients with dental caries was 7.50 ± 2.68 |ag/dl (range
2.2 - 12), lower than that for healthy subjects which was 12.02 ± 3.16 i^g/dl (range 7.4 - 18) (p< 0.0001) (Figure 1).
On the other hand, the saliva iodine level for patients with dental caries was 4.42 ± 2.21 i^g/dl (range 2 - 9.5), lower than that for . healthy subjects which was 8.28 ± 2.78 |ag/dl
(range 5 - 16) (p < 0.0001) (Figure 1). There was no significant difference in io-dine levels (urine and saliva) for patients with dental caries and healthy subjects, as well as between males and females (data not shown).
There was a positive correlation between the iodine levels in saliva and urine for both, for healthy people chosen and for patients with dental caries (r = 0.519, p < 0.001; r = 0.750, p < 0.001, respectively).
Discussion
The hypothesis of nutritional and ben-eficial role of iodine in dental health is sup-ported by studies carried out by Bartelstone [19] and Bartelstone et al. [20] that showed an important direct radio-iodine penetration through intact dental enamel, dentin and the pulp, and an important uptake by the peri-odontal tissues. To the best of our knowledge, lower iodine levels in the urine and saliva of patients with dental caries compared to the urine and saliva of healthy persons, are being reported for the first time in this study. Uri-nary iodine excretion is a good marker of the dietary intake of iodine, and is the index for evaluating the degree of iodine deficiency. In this study, a possible relationship between the iodine levels in urine and saliva was ex-amined and showed that there was a positive correlation between iodine levels in urine and in saliva for subjects with and without dental caries. Therefore, this positive corre-lation may be a good demonstrate for evalu-ating the degree of saliva iodine deficiency.
Dental caries is a complex disease pro-cess that affiicts a large proportion of the world's population, regardless of gender, age and ethnicity, although it does tend to affect more individuals with a low socioeco-nomic status to a greater extent. The process of dental earies is dependent from biologi-cal factors that are present within the saliva and plaque. There are many different agents within saliva and plaque that serve to protect
the tooth surface against caries development. Salivary flow rate, buffering capacity, anti-microbial activity, microorganism aggrega-tion and clearance from the oral cavity, im-mune surveillance and calcium phosphate binding proteins all interact to inhibit or re-verse demineralization of exposed tooth sur-faces [21, 22].
Antioxidants are found in all biological species and protect against the potentially harmfiil effects of processes or reactions that cause excessive oxidations. Therefore, bio-logical antioxidants form an important part of our diet and together with intracellular antiox-idants and antioxidant enzyme systems may prevent various pathological diseases [23].
In recent studies, dietary supplementation of some of the most known antioxidants: beta-carotene, vitamin A and vitamin E, and fiiiit and vegetable intake seem not have any ben-efit for some chronic diseases [24, 25, 26, 27, 28]. For this reason, the research of new dietary protective trace element against some chronic diseases, as dental caries, might be important.
Winkler et al. [29] have shown that the addition of Nal increased the human serum total antioxidant status. As an antioxidant, it competes with free radicals for mem-brane lipids, protein and DNA to stabilize the cells. This antioxidant action can be ex-erted through oxidized iodine species (I) ob-tained by the diet or by local deiodination. It may induce antiproliferative and apop-totic mechanisms through the formation of iodolactones, and finally, it is a constitutive part of thyroid hormones [30]. We found that there was a decrease in iodine levels in the urine and saliva of patients with dental caries compared to the urine and saliva of healthy volunteers. Decreased iodine levels, may increase reactive oxygen species (ROS). One of the most important functions of sa-liva peroxidase is the control of oral bacteria that form dental plaque, which lead to dental caries and chronic inflammatory periodontal diseases [31].
Various extra thyroidal tissues, such as the gastric mucosa, salivary glands, lacrimal gland and human NIS may act as a target antigen for T cells and cross-reacting auto-antibodies, thus perhaps providing a link between autoimmune thyroid diseases and associated autoimmune diseases of other or-gans systems, such as autoimmune gastritis
[6]. The thyroid gland shares its capacity to concentrate iodine activity with several other tissues like salivary gland, stomach and lac-tating mammary gland. It has recently been hypothesized that iodide might have an an-cestral antioxidant function in all iodide-con-centrating cells [5]. In these cells, iodide acts as an electron donor in the presence of H2O2 and peroxidase, and the remaining iodine atoiii readily iodinates tyrosine or certain specific lipids. Iodine can add to the double bonds of some polyunsaturated fatty acids of cellular membranes, making them less reac-tive to free oxygen radicals [32].
Venturi et al. [5] have shown the atro-phie action of iodine on the gastric mucosa, a regulating action similar to the one exerted on the thyroid, and have found relationships among iodine deficiency, goiter and atrophie gastritis. These authors found that the gas-tric mucosa contains more iodine when it is healthy than when it is affected with atrophie gastritis, and in their study the prevalence of atrophie gastritis was correlated to the de-gree of iodine deficiency and goiter [5]. Sim-ilarly, the authors of the present study have previously shown that iodine levels were decreased in gastric cancer tissue compared with surrounding healthy tissue [33].
Kilbane et al. [34] demonstrated that io-dide content was significantly lower in the tissue of breast carcinomas than in healthy tissue from the tumor-bearing breast or in fi-broadenomas [34]. It has therefore been pro-posed that an iodide uptake disorder may be involved in the development of breast cancer, which might also involve the inhibition of so-dium iodide symporter (NIS) antibodies [6].
Another study have shown that a diet supplemented with seaweed (Laminaria) significantly delayed the occurrence of tu-mors in animals treated with the chemical carcinogen7,12-dimethylbenzanthracene [35]. The enhancement of iodine uptake by progesterone has been observed in other hor-mone-dependent tissues, including the uterus and ovary [36]. The trophic, antioxidant and apoptosis-inductor actions and the presumed anti-tumour activity of iodide might also be important for prevention of diseases of the oral and salivary glands [37].
Simratviset al. [38] evaluated the effec-tiveness of povidone iodine. The results of this study showed that application of 10%
Providone iodine caused a significant de-crease in the oral load of the organisms. Hence, oral rehabilitation coupled with this solution application can be a good alternative to control dental caries in children affected with Early Childhood Caries (ECC). Iodine with antibacterial agent that is effective and also acceptable to young children can help to establish a favorable oral environment and halt the caries process [38]. Variations in tooth number may represent an important factor for mammalian diversification. The evolutionary pathway from fish to reptiles to mammals is characterized by a reduction in the number of teeth and of their generations as well as an increase in morphological com-plexity of the teeth [39].
We demonstrated that there was a de-crease in iodine levels in the urine and sa-liva of patients with dental caries compared to the urine and saliva of healthy volunteers. Urinary iodine excretion is currently the laboratory marker of iodine deficiency. We showed that there was a positive correlation between iodine levels in urine and saliva of patients and those of healthy volunteers. Sa-liva iodine level may be a laboratory marker of dental caries. The methods are useñil for the rapid and low-cost assessment of iodine deficiency. One of the method for protection of population from deficiency is iodization of the tablet salts consumed. In some circum-stances such as in gestational hypertension, hyperemesis, etc. salt intake is restricted. However, iodinized salt is not a stable food and can be decreased if boiled or exposed to direct light. The WHO suggests that these patients can get iodine from foods rich in iodine such as marine vegetables, yogurt, cow's milk, eggs, strawberries and mozza-rella cheese [40]. As expected, the UIC and Saliva iodine concentration in patients with dental caries may be dependent on the di-etary intake of iodine.
In the first stage, we have planned to investigate the relationship between dental caries and iodine concentration in saliva and urine, therefore, dental caries at advanced level (> 5) was considered. In the study to be made in the future, we might investigate the relationship between the stages of dental earies and iodine concentration.
The iodine deficiency in our region may be one of the factors in dental cavity. Iodine
supplementation should be considered in dental caries prophylaxis. As a continuation of this study, dental drug delivery systems containing iodine or iodine/active substances might be prepared and evaluated in vivo.
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