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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 18  |  Issue : 2  |  Page : 72-77

Metal ions release in children with stainless steel crowns and banded space maintainers


1 Department of Pediatric Dentistry, Faculty of Medicine, Tanta University, Tanta, Egypt
2 Department of Medical Biochemistry, Faculty of Medicine, Tanta University, Tanta, Egypt

Date of Submission16-Jul-2020
Date of Decision26-Sep-2020
Date of Acceptance12-Jul-2021
Date of Web Publication15-Sep-2021

Correspondence Address:
MSC Nora M M. Aboshanady
Al-Ghofran Neighborhood, Kohafa, Al-Gharbia, 31111, Tanta
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tdj.tdj_24_20

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  Abstract 


Aims
This work aimed to assess the salivary and urinary levels of nickel and chromium ions in children with stainless steel crowns and band and loop space maintainers.
Settings and design
The study was conducted as a clinical trial. The clinical part was carried out at Pediatric Dentistry Department, Faculty of Dentistry, Tanta University and the laboratory work was carried out at Biochemistry Department, Faculty of Medicine, Tanta University.
Patients and methods
Sixty children of both sexes aged between 5 and 8 years old were included in the study. The selected children were divided into two groups; group 1 included 30 children received stainless steel crowns and group 2 included 30 children received band and loop space maintainers. Salivary and urinary samples were collected from the participating children at the beginning of the study and then after 1 week, 2 weeks, 1 month, 3 months, 6 months and 9 months of receiving the appliances. The samples were prepared and analyzed for measuring nickel and chromium ions release using inductively coupled plasma optical emission spectrometry.
Statistical analysis used
All test statistics were performed using the SPSS software statistical package and the significance was set at P value less than or equal to 0.001.
Results
Salivary metal ions release reached its peak on the first week then diminished with time and urinary release increased on the first week, nearly remained stable till the first month then it decreased with time. Ions levels were higher in urine than in saliva with statistically significant differences. The release is slightly higher in group 2 but without statistically significant differences between both groups.
Conclusions
The maximum levels of released ions were significantly below their average dietary intake levels and did not reach their upper tolerable intake levels.

Keywords: ions release, space maintainers, stainless steel crowns


How to cite this article:
M. Aboshanady NM, El-Hosary AM, El Horany HE. Metal ions release in children with stainless steel crowns and banded space maintainers. Tanta Dent J 2021;18:72-7

How to cite this URL:
M. Aboshanady NM, El-Hosary AM, El Horany HE. Metal ions release in children with stainless steel crowns and banded space maintainers. Tanta Dent J [serial online] 2021 [cited 2021 Oct 19];18:72-7. Available from: http://www.tmj.eg.net/text.asp?2021/18/2/72/326036




  Introduction Top


Primary teeth exfoliation and permanent teeth eruption is a normal physiological process that occur in a harmonious sequence. Disruption of this process due to factors like premature loss of primary teeth, proximal carious lesions or extensive tooth decay may lead to malocclusion in permanent dentition [1]. So, preservation of the primary teeth or their space after premature extraction is of great importance in maintaining arch length integrity, orofacial development of the child and prevention of malocclusions [2].

In pediatric dentistry, stainless steel crowns (SSCs) and space maintainers (SMs) are widely used, they are fabricated from stainless steel alloys with nickel (Ni) and chromium (Cr) are main components [3]. Ni is added to the alloy to stabilize the austenitic phase, decreases the ductility, increases the strength and enhances corrosion resistance of the alloy. While, Cr is the main element that significantly increases the corrosion resistance of the alloy by facilitating protective anticorrosive passive oxide layer formation on the surface of the alloy [4].

Corrosion is an electrochemical process which results in loss of the essential metallic properties of a metal, it leads to release of metal ions either directly into solution or by progressive biodegradation of the surface oxide layer [5]. The oral cavity is considered an ideal environment for the biodegradation of metals; the warm and moist oral aerobic condition offers an aggressive environment for electrolytic and electrochemical activity that facilitates corrosion process [6].

When the released metal ions and corrosion products are introduced into the human body, they may lead to systemic and local adverse biological effects such as allergy, toxicity, mutagenicity or even carcinogenicity [7]. Biocompatibility of the alloy is related to its corrosion, it depends mainly on the quantity of the released metal ions, the pathogenicity and the reaction products of these ions [7],[8].

The assessment of biocompatibility of the alloy is of great concern nowadays. It might be determined by identifying and quantifying the amount of metal ions released during the process of biodegradation as the consequence of corrosion [9]. The major released metal ions from stainless steel dental appliances are iron (Fe), Cr, and Ni. Among these ions, Ni and Cr have received the most attention because of their reported adverse biological effects on human health [10].


  Patients and methods Top


The study was conducted as a clinical trial. The clinical part was carried out at Pediatric Dentistry Department, Faculty of Dentistry, Tanta University and the laboratory work was carried out at Biochemistry Department, Faculty of Medicine, Tanta University. Approval for this study was obtained from Research Ethics Committee, Faculty of Dentistry, Tanta University.

Sixty children of both sexes aged from 5 to 8 years old were selected from patients attending outpatient clinic of Pediatric Dentistry Department. They were divided into two groups as follow:

  1. Group 1: 30 children were received 1, 2, 3 or 4 SSCs [Figure 1].
  2. Group 2: 30 children were received 1, 2, 3 or 4 band and loop SMs [Figure 2].
Figure 1: A case received four stainless steel crowns.

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Figure 2: A case received two space maintainers.

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The selected children should not have had any amalgam fillings, previous SSCs, SMs or orthodontic treatment. They also should have been in good health without any systemic disease or prolonged use of any medication to not affect salivation and/or systemic absorption of metal ions [10].

Salivary and urinary samples were collected in the morning. The samples collection was performed at the beginning of the study before any appliance application then after 1 week, 2 weeks, 1 month, 3 months, 6 months and 9 months of the treatment.

A 2.5 ml sample of unstimulated saliva was collected from the floor of the mouth with the child seated in a dental chair using a sterile disposable syringe and transferred into an identified polyethylene Eppendorf tube. No food or beverage ingestion was permitted an hour prior to the clinical appointment but without any restrictions regarding food consumption at any other time. No previous mechanical cleaning and/or mouth washing was accomplished right before samples collection [11].

Urinary samples were collected in an identified sterile container, then an amount of a 2.5 ml of urine was transferred into an identified polyethylene Eppendorf tube [12]. Both salivary and urinary samples were transported within 1 h to the laboratory, and stored in a freezer (−20°C) up to the time the chemical analysis were performed.

Each sample was defrosted at room temperature, dissolved in 10 ml of nitric acid to remove the organic particulates and digested using Microwave Digestion System (Milestone, Ethos Easy model: ACT 36, Italy). After that, it was diluted with deionized water until reaching a volume of 25 ml to maintain the original concentration proportional to the volume for all the samples. The analysis of Ni and Cr ions was carried out using an inductively coupled plasma optical emission spectrometry (ICP/OES) (Perkin Elmer Model: Optima 7000 DV, Germany) [13].

Descriptive statistics of salivary and urinary metal ions release amount in both groups were expressed as means and SDs. The data were analyzed by analysis of variance (f) test and t test. All test statistics were performed using the SPSS software statistical package and the significance was set at P value less than or equal to 0.001.


  Results Top


In the present study, total number of 74 SSCs were performed on primary molars of 30 children in group 1 and total number of 71 band and loop SMs were applied to 30 children in group 2.

Group 1 evaluation

The release of Ni and Cr in saliva reached its peak on the first week then it diminished with time. While, their release in urine increased on the first week, nearly remained stable till the first month then it diminished with time as shown in [Figure 3].
Figure 3: The released ions over the follow-up periods in saliva and urine in group 1.

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Mean differences between salivary and urinary levels of Ni and Cr at different follow-up periods in group 1 are presented in [Table 1] and [Table 2]. The urinary levels of Ni were higher than their levels in saliva at all evaluation times with statistically significant differences. Whereas, urinary Cr levels were higher than their levels in saliva at all evaluation times with statistically significant differences at all evaluation times except at 1-week follow-up period.
Table 1 Mean differences between salivary and urinary levels of nickel (ppm) at different follow-up periods in group 1

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Table 2 Mean differences between salivary and urinary levels of chromium (ppm) at different follow-up periods in group 1

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Group 2 evaluation

The salivary and urinary Ni and Cr in this group showed the same pattern of release as group 1. The average differences between salivary and urinary levels of Ni and Cr at different follow-up periods in group 2 are shown in [Table 3] and [Table 4]. The levels of Ni in urine were higher than those levels in saliva at all evaluation times with statistically significant differences at all evaluation times except at 1-week follow-up period. Whereas, urinary Cr levels were higher than their levels in saliva at all evaluation times with statistically significant differences.
Table 3 Mean differences between salivary and urinary levels of nickel (ppm) at different follow-up periods in group 2

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Table 4 Mean differences between salivary and urinary levels of chromium (ppm) at different follow-up periods in group 2

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Groups 1 and 2 comparison

Salivary and urinary ion level differences between groups 1 and 2 according to the number of received appliances are shown in [Table 5] and [Table 6]. There were no statistically significant differences between both groups. However, salivary and urinary levels of Ni and Cr were higher in SMs group (group 2) than SSCs group regardless of the number of received appliances.
Table 5 Salivary ions level comparison between groups 1 and 2 according to the number of received appliances

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Table 6 Urinary ions level comparison between groups 1 and 2 according to the number of received appliances

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  Discussion Top


Metallic alloys have extensive uses in dentistry, they are applied in a variety of fields and in pediatric dentistry, there are also broadly used metallic appliances like SSCs and SMs [14]. There is a growing attention among dental professionals about the biocompatibility of these alloys as a result of real increase in frequency of their related allergic reactions and increase in awareness of their other adverse side effects especially Ni and Cr [15]. So, the present study was directed to measure the level of these elements in children with metallic appliances.

In this study, salivary and urinary samples were collected from children with SSCs and SMs to assess the administration and elimination pathways of the released elements; it is considered a principal approach in understanding the possible reactions to such elements [16].

The selected children had no amalgam restorations as the presence of dissimilar metals or alloys in oral cavity may result in triggering galvanic corrosion that could increase the ion release rate [17]. Also, they had no previous SSCs, SMs or orthodontic treatment so as not to influence the base line or the follow-up levels of the measured ions due to the probability of Ni, Cr and their compounds existence in saliva or urine [18].

The children were evaluated longitudinally to serve as their self-controls as far as it could eliminate interindividual variations and results interpretation [6]. Salivary and urinary samples were at both short and long term intervals; metal release was reported to be higher during the first month after insertion of metallic appliances, but they are used for extended period in the oral cavity and it is also necessary to evaluate the release at longer intervals during the different stages of treatment [13].

All the samples were taken 1 h after breakfast to standardize the sampling and rule out the effect of food consumption. Salivary ion release instantly reaches its peak after having meals, when salivary pH shifts to the acidic end enhancing corrosion and not returns to normal until 30–60 min after meal intake [19].

In the current study, salivary metal release reached its peak on the first week then it diminished with time that agree with Bhaskar and Reddy [3], Anand et al. [4], Kulkarni et al. [14], Evette Natasha et al.[20] and Basir et al.[21] in spite of their limited evaluation periods. This could be due to quick initial release of metal ions from the appliance surface then it is slowed down by protective oxide layer formation that stabilizes the appliance surface and reduces the corrosion process [22].

While, salivary results are not in accordance with Ramazani et al.[23] who reported that in vitro Ni release from SSCs on the 1st day then the rate decreased with time; these variations may be due to the differences between in vitro and in vivo composition of artificial/natural saliva, evaluated follow-up periods and the method of taking and analyzing the samples. They also disagree with Menek et al.[24] who reported that Ni release from SSCs increased over the different evaluation times and this is probably due to the acidic environment they used in their study that may disrupt formation and stability of the protective passive oxide layer, leading to continuous increase in Ni discharge.

Urinary ions release in this study increased on the first week, nearly remained stable till the first month then it decreased with time that is not in agreement with Morán Martínez et al.[25] who stated that Ni urinary levels increased with time. Complete comparison of urinary results of the current study with it is not logical due to methodological differences such as different evaluation periods, samples collection and analytical methods.

In addition, Ni and Cr release in SMs group was higher than that of SSCs group but without significant differences between both groups which are similar to the results reported by Kulkarni et al. [14]. This may be due to wires and solders used in SMs application as well as the heat used in soldering process.

The maximum levels of Ni and Cr in current study were 1.988 and 1.282 ppm respectively which are significantly below the average dietary intake levels of these metals (200–300 μg/day for Ni and 50–200 μg/day for Cr [26],[27]) and did not reach their upper tolerable intake levels (0.06–0.2 mg/day for Ni and 0.0001–0.001 mg/kg/day for Cr [28],[29]) that are in agreement with all previous studies concerned with metals release from dental metallic appliances.

These low levels of released Ni and Cr ions showed that the probability of their systemic toxic effects are so far. However, this can be a deceptive assurance of safety; such these low levels can be able to induce allergic reactions or biological effects in the nearby oral mucosal cells [15].

Pediatric patients (young children) are more active in terms of cell turnover and are much lighter in weight than adolescents or adults as those in orthodontic samples of metal ion release studies, so such small amounts of metal ions release in relation to children weight might matter more for them.


  Conclusion Top


Metal ions release in saliva reached its peak on the first week and in urine increased on the first week, nearly remained stable till the first month then it diminished with time. Ions levels were higher in urine than in saliva and in SMs group than SSCs group. However, their maximum levels were significantly below their average dietary intake levels and did not reach their upper tolerable intake levels.


  Acknowledgements Top


The authors thank all participants who helped during this study.

The manuscript has been read and approved by all the authors and each author believes that the manuscript represents honest work.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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Introduction
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Acknowledgements
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