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Journal of Indian Society of Pedodontics and Preventive Dentistry Official publication of Indian Society of Pedodontics and Preventive Dentistry
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ORIGINAL ARTICLE
Year : 2019  |  Volume : 37  |  Issue : 1  |  Page : 31-38
 

An in vitro evaluation of nickel and chromium release from different commercially available stainless steel crowns


1 Department of Paedodontics and Preventive Dentistry, Srinivas Institute of Dental Sciences, Mangalore, Karnataka, India
2 Department of Paedodontics and Preventive Dentistry, Yenepoya Dental College, Mangalore, Karnataka, India

Date of Web Publication25-Feb-2019

Correspondence Address:
Dr. Sham S Bhat
Department of Paedodontics, Yenepoya Dental College, Mangalore - 575 018, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JISPPD.JISPPD_176_17

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   Abstract 


Aim: The aim of the present study was to estimate nickel and chromium release from commercially available stainless steel crowns (SSCs) in artificial saliva. Materials and Methods: Ten crowns from three manufacturers were immersed in 10 ml of artificial saliva and stored in separate tubes in an incubator at 37°C for 28 days. The crowns were removed from each tube on every 7th day, and placed in other tubes with fresh artificial saliva. Flame type atomic absorption spectrophotometer was used to check for the release of metal ions in the solution inside each tube at the end of 1, 7, 14, 21, and 28 days and the control samples. Results and Statistical Analysis: Two-way analysis of variance and pairwise comparison using Bonferroni test was used for statistical analysis. There was statistically verified difference in the release of nickel and chromium on different days in each of the group of SSCs tested. However, no significant difference was seen in the release of both metals among the groups. Conclusion: In all the SSCs tested, there was the release of nickel and chromium, but the total release of both the metals even at a period of 28 days was below the critical level to cause any toxic effects. Hence, the release of metal ions should not be an alarming concern for the use of any of the group of commercially available SSCs.


Keywords: Artificial saliva, atomic absorption spectrophotometry, chromium, nickel, stainless steel crowns


How to cite this article:
Amanna EN, Bhat SS, Hegde SK. An in vitro evaluation of nickel and chromium release from different commercially available stainless steel crowns. J Indian Soc Pedod Prev Dent 2019;37:31-8

How to cite this URL:
Amanna EN, Bhat SS, Hegde SK. An in vitro evaluation of nickel and chromium release from different commercially available stainless steel crowns. J Indian Soc Pedod Prev Dent [serial online] 2019 [cited 2019 Mar 23];37:31-8. Available from: http://www.jisppd.com/text.asp?2019/37/1/31/252849





   Introduction Top


Stainless steel crowns (SSCs) generally called as preformed metal crowns, were first described by Engel followed by Humphery in 1950. Since then, these preformed metal crowns have become an invaluable rehabilitative technique for the treatment of severely broken down primary teeth and have been recognized as superior to other multisurface cavity restorations based on the durability and longevity of the restoration.[1] SSCs (18-8) Austenitic type of alloy contains17%–19% chromium, 10%–13% nickel, 67% iron, and 4% minor elements.[2]

Nickel is a known contact allergen and exposure to metal ions such as nickel and chromium and their hazardous effects have been examined for >100 years, and it was recognized that these metal ions could cause dermatitis, allergy, and asthma.[3] Nickel hypersensitivity has still been a major concern as seen in the case report of a delayed hypersensitivity to SSC in a 13-year-old Caucasian girl.[4] The hypersensitivity reaction caused by the use of stainless steel dental appliances may be due to metal ion release induced by saliva in the oral cavity.[4] The extensive use of SSCs in pediatric dentistry has led to an increase in the number of companies manufacturing the crowns and therefore, there is a need to estimate the amount of release of these metal ions from different commercially available SSCs.

Aim

The aim of this study was to estimate the release of nickel and chromium from commercially available SSCs in artificial saliva.

Objectives

  • To estimate the release of nickel and chromium from three commercially available SSCs over a period of 28 days
  • To compare the release of nickel and chromium among the three commercially available SSCs
  • To compare the release of nickel and chromium over a period of 1 day, 7 days, 14 days, 21 days, and 28 days in each of the three commercially available SSCs.



   Materials and Methods Top


A total of 30 samples of second primary lower molar SSCs were used.

SSCs used in this study were divided into three groups.

  • GROUP 1-DNTO SSCs (Taiwan)-10 crowns
  • GROUP 2-Kids crown (Korea)-10 crowns
  • GROUP 3-3M™ ESPE™ SSCs (USA)-10 crowns.


Preparation of simulated saliva medium

  • 0.14 g of NaCl (Sodium chloride)
  • 0.42 g of KCl (Potassium chloride)
  • 0.26 g NaH2 PO42 H2O (Disodium anhydrous phosphate)
  • 0.017 g Na2S,9H2O (Sodium sulphide)
  • 0.35 g (CO (NH2)2) (Urea)
  • 350 ml distilled deionised water
  • Albumin (albumin bovine fraction V).[5]


Methodology

The pH of artificial saliva was measured using the pH meter and by adding an increment of 1N sodium hydroxide or 1 N hydrochloric acid as required it was adjusted to 6.75 ± 0.05. Ten crowns from each group were placed in centrifuge tubes in a plastic stand and had no contact with any metallic material during the test and each crown was placed in a separate tube. Each tube was tightly closed to prevent evaporation of the solution. Two tubes containing only the artificial saliva with no crowns, was used as controls. All tubes were stored at 37°C in an incubator. At the end of day 1, crowns were removed from each tube, and the same crowns were placed in new tubes with freshly prepared artificial saliva for further 7 days. At the end of the 7th day, the crowns were removed from each tube, and placed in new set of tubes with freshly prepared artificial saliva. All tubes were stored at 37°C in an incubator for a period of 1 week and procedure repeated at the end of day 7, 14, and 21. The samples of artificial saliva collected inside each tube after the removal of crowns and the control samples at the end of day 1, 7, 14, 21, and 28 were all analyzed to determine the nickel and chromium content using flame type atomic absorption spectrophotometer (GBC 932 plus, Australia). The standardized sensitiveness of the equipment was up to 1 ppm and hence, a graph for the known concentration of 1 ppm, 2 ppm, 5 ppm, and 10 ppm nickel and chromium was plotted.

Statistical analysis

Two-way analysis of variance followed by pair-wise comparison using Bonferroni test was used for the estimation of release of nickel and chromium among the three groups over a period of 28 days.


   Results Top


Release of both metal ions nickel and chromium was seen in all the 3 groups of SSCs tested [Table 1] and [Table 2]. The ANOVA results of the experimental samples tested showed that the chromium release in each group at different days was highly significant, P < 0.01 but chromium release between the groups was not significant, P > 0.01 [Table 3].
Table 1: Mean and standard deviation of amount of chromium release from 3 groups and control

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Table 2: Mean and standard deviation of amount of nickel release from 3 groups and control

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Table 3: Two factor ANOVA results of chromium release on different days and between the groups

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It also showed that the nickel release in each group at different days and nickel release between each group is highly significant, P < 0.01 [Table 4]. Pairwise Bonferroni test showed the comparison of release of nickel and chromium in each group on different days [Table 5] and [Table 6] and Multiple comparisons - by Bonferroni test-showed the comparison of chromium and nickel release among the 3 groups on different days [Table 7] and [Table 8].
Table 4: Two factor ANOVA results of nickel release on different days and between the groups

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Table 5: Comparison of chromium release in each group on different days

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Table 6: Comparison of nickel release in each group on different days

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Table 7: Multiple comparisons - by Bonferroni test-shows the comparison of chromium release among the 3 groups on different days

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Table 8: Multiple comparisons - by Bonferroni test-shows the comparison of nickel release among the 3 groups on different days

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   Discussion Top


Saliva is a solution with low osmotic pressure comprising of chloride, bio actonate, potassium, nitrogenous compounds, sodium, and proteins.[6] In this study, SSCs were immersed in freshly prepared artificial saliva with albumin added as the protein content. To simulate the oral temperature, the study samples were placed in an incubator at 37°C. The Flame atomization method was used as it is the most prominent and convenient atomization method employed in atomic absorption spectrophotometry.

The results show there was release of nickel and chromium metal ions at the end of day 1, 7, 14, 21, and 28. However, there was no significant difference in the nickel and chromium release from SSCs among the three groups used as illustrated in [Graph 1] and [Graph 2]. It was seen that there was an increased rate of release of metal ions chromium and nickel from SSCs in each of the groups at the end of the 7th day as illustrated in [Graph 3] and [Graph 4] and the release of both the metals decreased gradually, with the increasing time period which was similar to the results of the study[5] on biodegradation of nickel and chromium from space maintainers. Though there was release of both metal ions in all the three groups there was no significant difference in the amount of release between the groups on different days as seen in [Table 4] and [Table 8].



Due to slow uptake from the gastrointestinal tract, ingested nickel compounds are considered to be relatively nontoxic, with the primary action being mainly irritation. However, when taken orally in large doses (>0.5 g), some forms of nickel may be acutely toxic to humans.[7] Toxic effects of chromium are seen only when a very high amount of 4–7 mg/kg is ingested.[8] In this study there was nickel and chromium release from all the three groups of SSCs used, which may not cause toxic effects but definitely will increase the sensitivity of patients allergic to them.

Corrosion caused due to microbial activity has been identified for many years. It is known that microorganisms can cause corrosion of metal alloys that are immersed in aqueous environment. Acidic waste products released by microbes and bacteria corrode metal surfaces. Thus, microbial factors too are responsible for the biodegradation of metals from stainless steel and may cause a significant release of nickel and chromium. However, this study was not based on the degradation of metal caused by microbiological factors, only artificial saliva maintained at a constant pH and constant temperature was used.


   Conclusion Top


The introduction of metal ions into the human body is an additional risk to health since these ions may be released in different places and at different levels, depending on the characteristics and solubility of the products containing them. Based on the results of this study, it can be concluded that there was measurable release of nickel and chromium from SSCs and the release was increased at the 1st week of immersion of SSCs in artificial saliva. The total release of metals from SSCs in each of the groups used was well below the critical level to cause any toxic effects so any of the group of commercially available SSC can be used in pediatric dentistry. The amount of nickel ions that is necessary to cause sensitivity varies with every individual. Sensitization may be quicker if the skin of the person is damaged earlier and can be sensitized by small amounts of the solubilized nickel. Factors such as pH, abrasion of the metal surface, the presence of other allergic conditions, race, and age and sex may also be decisive factors for the hypersensitivity reactions to occur.[9],[10] Therefore, the release of metal ions such as nickel and chromium can cause hypersensitivity reactions in patients who are allergic to them and in such patients alternative restorative material free of any contact allergen has to be used. There might be an increase in the amount of leaching out of metal ions in an acidic pH of saliva and therefore, further studies have to be done to estimate the release of nickel and chromium from SSCs under the varying oral conditions.

Acknowledgement

This dissertation has been awarded ICMR grant. I am extremely grateful to Indian Council of Medical Research.

Financial support and sponsorship

ICMR grant.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Randall RC. Preformed metal crowns for primary and permanent molar teeth: Review of the literature. Pediatr Dent 2002;24:489-500.  Back to cited text no. 1
    
2.
Tandon S. Text Book of Pedodontics. 2nd ed. Paras Medical Publishers, New Delhi. 2008 p. 362.  Back to cited text no. 2
    
3.
Menek N, Başaran S, Karaman Y, Ceylan G, Tunç ES. Investigation of nickel ion release from stainless steel crowns by square wave voltammetry. Int J Electrochem Sci 2012;7:6465-71.  Back to cited text no. 3
    
4.
Yilmaz A, Ozdemir CE, Yilmaz Y. A delayed hypersensitivity reaction to a stainless steel crown: A case report. J Clin Pediatr Dent 2012;36:235-8.  Back to cited text no. 4
    
5.
Bhaskar V, Subba Reddy VV. Biodegradation of nickel and chromium from space maintainers: An in vitro study. J Indian Soc Pedod Prev Dent 2010;28:6-12.  Back to cited text no. 5
[PUBMED]  [Full text]  
6.
Martinez JR, Barker S. Ion transport and water movement. Arch Oral Biol 1987;32:843-7.  Back to cited text no. 6
    
7.
Coogan TP, Latta DM, Snow ET, Costa M. Toxicity and carcinogenicity of nickel compounds. Crit Rev Toxicol 1989;19:341-84.  Back to cited text no. 7
    
8.
Expert Group on Vitamins and Minerals (EVM). Safe upper levels for vitamins and minerals. UK: Food Standards Agency; 2003. p. 172-9.  Back to cited text no. 8
    
9.
Wataha JC, Lockwood PE, Khajotia SS, Turner R. Effect of pH on element release from dental casting alloys. J Prosthet Dent 1998;80:691-8.  Back to cited text no. 9
    
10.
Wataha JC, Lockwood PE, Frazier KB, Khajotia SS. Effect of toothbrushing on elemental release from dental casting alloys. J Prosthodont 1999;8:245-51.  Back to cited text no. 10
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]



 

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    References
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