Advances in Human Biology

ORIGINAL ARTICLE
Year
: 2021  |  Volume : 11  |  Issue : 4  |  Page : 18--21

Salivary zinc levels in mixed unstimulated saliva of children and its correlation with dental caries


Anmol Mathur1, Aditi Mathur2, Vikram Pal Aggarwal3, Ridam Jain4,  
1 Department of Public Health Dentistry, Dr. DY Patil Vidyapeeth, Pune, Maharashtra, India
2 Department of Pedodontics and Preventive Dentistry, Dr. DY Patil Vidyapeeth, Pune, Maharashtra, India
3 Department of Public Health Dentistry, Surendera Dental College and Hospital, Sri Ganganagar, Rajasthan, India
4 Department of Orthodontics, Rishiraj College of Dental Sciences, Bhopal, Madhya Pradesh, India

Correspondence Address:
Anmol Mathur
Department of Public Health Dentistry, Dr D.Y Patil Vidyapeeth, Pune - 411 018, Maharashtra
India

Abstract

Introduction: Zinc is the second most abundant trace element in human and animals. It is essential for the growth and development in humans and has diverse roles. While the effects of zinc on calculus and plaque growth have been reviewed extensively, its interaction with dental caries has received less attention. Materials and Methods: This was a cross-sectional study done on 60 children belonging to 4–6 and 12–14 years of age groups (30 children in each age group). After intraoral examination, the patients were categorised into low caries (deft <2) and high caries category (deft more than 5), with 15 children in each group. Saliva samples were collected, and the estimation of salivary zinc was done by Atomic Absorption Spectrophotometer. Statistical analysis used was Student's t-test, applied to test the association between high and low caries group. Results: The mean values of salivary zinc levels are significantly higher in the low caries category of both groups. The difference in mean salivary zinc values computed for Student's t-test among high and low caries category is found to be highly significant for both the age groups. Conclusion: Salivary zinc levels are negatively correlated with dental caries experience in both the dentition. The authors conclude that zinc can be used in toothpaste to reduce the caries prevalence.



How to cite this article:
Mathur A, Mathur A, Aggarwal VP, Jain R. Salivary zinc levels in mixed unstimulated saliva of children and its correlation with dental caries.Adv Hum Biol 2021;11:18-21


How to cite this URL:
Mathur A, Mathur A, Aggarwal VP, Jain R. Salivary zinc levels in mixed unstimulated saliva of children and its correlation with dental caries. Adv Hum Biol [serial online] 2021 [cited 2021 Dec 7 ];11:18-21
Available from: https://www.aihbonline.com/text.asp?2021/11/4/18/328388


Full Text



 Introduction



Zinc is the second most abundant trace element in human and animals.[1] Despite its abundance, zinc was not established as an essential nutrient for animals until 1934.[2] It is essential for the growth and development in humans and has diverse roles, being a critical component of several hundred enzymes and proteins.[2] In the human body, zinc is present in muscles (60%), bones (30%), and skin (5%).[3] Zinc is required for many bodily functions, including being involved in the activation of various enzymes and proteins,[4] and zinc are also required for the absorption of Vitamin A, E and folate.[5] Low levels of zinc are found to be associated with an increased chance of developing infections and degenerative pathologies.[6] Zinc also plays a vital role in the psychosocial functioning of human behavior.[5]

While the effects of zinc on calculus and plaque growth have been reviewed extensively, its interaction with the dental hard tissues and possible role in de- and remineralisation has received less attention.[3] Salivary zinc plays many roles and affects numerous metabolic processes.[7] Activation of many enzymes is dependent on the presence of zinc.[8] The impact and the amount of Zn in the tooth enamel are more in the outer layer (200–900 ppm) as compared to the inner layer (up to 200 ppm).[3],[9],[10] Large amounts of zinc are incorporated into the enamel pre-eruptively, and zinc concentration increases on the surface post-eruptively suggesting that incorporation does occur onto the tooth surface from oral fluids.[11] Various studies have proposed that zinc can easily replace calcium ions in the crystal structure, and its incorporation is proposed to decrease enamel solubility.[12] Zinc in dental plaque and oral fluids has been described as an important factor in reducing bacterial counts.[13]

Although studies have been conducted correlating zinc and dental caries, studies in children are very limited. There is even more scarcity of data regarding salivary zinc levels in very young children and their correlation with dental caries in primary dentition. This study was undertaken to estimate the zinc levels in the saliva of 12–14 and 4–6 years old children and to evaluate the correlation, if any, with dental caries in permanent and primary dentition, respectively.

 Materials and Methods



This was a cross-sectional, in vivo analytical study done on 60 children belonging to 4–6 and 12–14 years of age groups (30 children in each age group), selected from the outpatient Department of Pedodontics and Preventive Dentistry of our hospital. Approval from the Institutional Ethics Committee was obtained before commencing with the study (RAH/2019/3452). Parents of the patients were explained the procedures in detail, and written consent was obtained. Patients with no underlying medical conditions and no history of medications, which can alter the salivary flow rate, were selected for the study. One factor which has been proposed as a confounding influence in estimating salivary zinc is that zinc is a common component of dental restorations, leading to contamination in participants who are or have been, by definition, caries-prone. Therefore, in our study, we have excluded participants with restorations to avoid changes in salivary concentrations of elements due to the leaching of ions from the restorative materials.

Intraoral examination was done, and the patients in both the age groups were categorised into low caries category (deft <2) and high caries category (deft more than 5), with 15 children in each group. The scheduled date and time of saliva collection was intimated to the subjects as well as to their parents. Saliva collection was always scheduled between 9 am and 11 am to standardise saliva collection time and minimise the effect of the circadian rhythm. Within this stipulated time, it was scheduled to collect saliva from an average of six subjects per day.

On the day of saliva collection, the children were asked to perform regular oral hygiene procedure after breakfast (1.5 h before collection), and during this period, children were not allowed to eat or drink (except water). Children were seated on dental chairs, and five cc of unstimulated saliva were collected in special tubes using the method described by Colin Dawes.[14] (In this method, the child was asked to pool the saliva in the floor of the oral cavity and asked to spit intermittently). No exogenous stimulation was used, and every effort was made to obtain as nearly as possible the resting secretion of the salivary gland.

The salivary samples were transported within an hour in a thermal insulated box. Estimation of salivary zinc was done by atomic absorption spectrophotometer (model: analyst 200, Perkin Elmer) using the air acetylene flame.

 Results



The study sample, according to [Table 1] consisted of 60 children selected randomly from the outpatient department, according to the inclusion criteria. These children selected comprised of two age groups: 3–5 years and 12–14 years, which represented the two dentitions; they were further classified into two categories according to their caries status but in equal numbers (n = 15) to allow a valid comparison. The two groups were formulated as follows.{Table 1}

Group A: Consisted of samples with the age group of 3–5 years

Category (I): deft score < 2 and category (II): deft score more than 5Group B: Consisted of samples with the age group of 12–14 years

Category (I): DMFT score less than 2 and Category (II): DMFT scores more than 5.

The difference in mean salivary zinc values as computed for Student's t-test among high and low caries category is found to be highly significant for both the age groups, with a P = 0.00 in [Table 2]. The mean values of salivary zinc levels are significantly higher in the low caries category of both groups. In Group A, values for mean salivary zinc levels are 0.77 ± 0.02 mg/l for high caries and 0.84 ± 0.03 mg/l for low caries category. In Group B, the mean salivary zinc is 0.85 ± 0.03 mg/l and 0.78 ± 0.02 mg/l for the low and high dental caries category, respectively [Figure 1].{Figure 1}{Table 2}

 Discussion



In the oral cavity, zinc is present naturally in plaque, saliva, and enamel.[3] Concentration of Zinc in human mixed saliva varies greatly, ranging from 88 mg/l to 0.135 mg/l.[15] This variation may reflect the difference between saliva collection or analytical procedures. However, in studies by Greger and Sickles, 1979[16] and Freeland-Graves, 1981[17] comparable results were found with mean salivary zinc levels being 0.266 mg/l. In addition, zinc concentration in human saliva showed circadian variations, decreasing upon rising in the morning, followed by an increase in the late morning and eventually decreasing again in the late afternoon and evening.[17] Relatively large amounts of zinc are incorporated into enamel prior to the eruption, but after the eruption, zinc concentration at the surface of the teeth apparently increases further.[3]

In our study, we found a mean salivary zinc level of 0.84 mg/l and 0.77 mg/l in the low and high caries categories, respectively, in 4–6 year age group children. Among the 12–14 years' age group, mean salivary zinc level was 0.85 mg/l for low caries and 0.78 for high caries category children. A strong negative correlation was observed between the salivary zinc levels and caries index in both age groups. Our results are in coordination with the study conducted by Hussein et al 2013.[18] They studied the correlation between salivary zinc content and dental caries in a group of children in Ismailia. Mean salivary zinc level was found to be 0.1 mg/l in caries free and 0.05 mg/l in caries affected group. They found a significant negative correlation between salivary zinc levels and dental caries. The present study is also in correlation with a study conducted by Borella et al.,[19] who studied the relation of trace elements in saliva with dental caries in young adults. They compared salivary zinc levels with recent caries experience and found that there was a tendency for a decrease in levels of zinc with an increasing number of caries.

The negative correlation of zinc with dental caries found in our results is also supported by a study conducted by Uçkardeş et al.[20] in 2009. They studied the effect of systemic zinc supplementation on oral health in low socioeconomic level children. After supplementation, oral health factors were found to be improved in their study. They concluded in their study that zinc supplementation may contribute to the prevention of caries. On the other hand, in a study conducted by Duggal et al.[21] no relationship of salivary zinc concentration with dental caries was found. Contradictory results were obtained in a study conducted by Hussein et al.[18] They found a positive correlation of salivary zinc and dental caries in children suggesting a possible role of zinc in the formation of dental decay.

The reductive caries effect of salivary zinc observed in the present study could be explained by the fact that zinc can reduce the enamel solubility and also modify the crystal-growth of the calcium phosphates implicated in remineralization.[3] Further zinc is known to have an antibacterial effect. In vitro tests, where S mutans was grown in chemically defined media of known trace element composition containing either 0.5, 5, or 16 ppm Zn, showed depressed Streptococcus mutans growth, initial plaque formation, and inhibition of acid production.[22] It was suggested that zinc might inhibit the growth by interfering with cysteine metabolism.

 Conclusion



Zinc is an essential trace element for maintaining oral health. It is a component of many dental materials, mouth rinses, and toothpaste. Zinc is effective in the treatment of oral mucosa diseases, especially aphthous ulcer and is useful in the prevention and treatment of plaque-related diseases. However, the role of zinc in dental caries prevention is still not fully established. Within the limitation of this study, it can be concluded that salivary zinc levels are negatively correlated with dental caries experience in the primary dentition.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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