Effects of Restoring the Primary Dentition with Stainless-Steel Crowns on Children’s Salivary Nickel and Chromium Levels, and the Associations with Saliva pH: a Preliminary Before-After Clinical Trial
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Nickel and chromium existing in stainless-steel crowns (SSCs, used in pediatric dentistry) might be cytotoxic and allergenic. However, no in vivo studies have examined their salivary levels in children using SSCs, or in young children without SSCs. Also, the effect of acidity on metal ion release has not yet been evaluated in any previous in vivo studies in the whole literature. Therefore, this preliminary before-after clinical trial was conducted. Salivary nickel/chromium levels of 30 children before and after 2 months of placement of SSCs were measured using atomic absorption spectrophotometry. Salivary pH was measured with a digital pH meter. The effects of treatment, pH, number of SSCs, gender, and age on salivary ions were analyzed statistically (α = 0.05, β = 0.15). Salivary nickel concentrations increased from 4.9010 ± 4.7390 to 5.6320 ± 4.7210 μg/L (P = 0.000, paired t test). Chromium increased from 0.3273 ± 0.5214 to 0.4199 ± 0.6404 μg/L (P = 0.016). Saliva pH increased from 6.81 ± 0.52 to 7.04 ± 0.47 (P = 0.000). Ion levels were not correlated with pH (P > 0.14), except chromium in the follow-up (rho = − 0.435, P = 0.016). Nickel increase (but not chromium increase) was correlated with pH increase (rho = 0.367, P = 0.046). Age was only correlated with baseline chromium (rho = 0.373, P = 0.042). Being male was associated with baseline/follow-up nickel levels (P ≤ 0.030). SSC number was not correlated with ions or pH (P > 0.36). It was shown for the first time that SSCs might increase salivary nickel and chromium concentrations and reduce saliva acidity. Nickel increase might be in line with pH elevation. The raised pH might be associated with reduced chromium release. Boys might have higher nickel levels than might girls, with or without SSCs.
KeywordsSalivary nickel and chromium discharge Pediatric dental treatment Stainless-steel crowns (SSC) Atomic absorption spectrophotometry
Source of Funding
The study was funded by the authors and their institution.
Leila Basir and Razieh Meshki searched the literature, conceived the assessment of effects of SSC treatment on nickel release, designed the study, supervised the experiments, and mentored the thesis. Azam Behbudi searched the literature, conceived the assessment of effects of SSC treatment on nickel release, designed and performed the experiments, and wrote the thesis. Vahid Rakhshan searched the literature, conceived the assessment of the role of salivary pH, SSC number, age, and gender as well as the extents of salivary chromium release, designed the study, specified and implemented the statistical analyses, interpreted and discussed the findings, and drafted/revised the article.
Compliance with Ethical Standards
Protocol ethics were approved by the institutional review board of the university according to the Helsinki declaration (ethical code: IR.AJUMS.REC.1395.11).
Conflict of Interest
The authors declare that they have no conflict of interest.
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