Antibacterial properties of retainers with silver nanoparticles

Abstract

We read with interest the article entitled “Streptococcus mutans counts in patients wearing removable retainers with silver nanoparticles vs those wearing conventional retainers: A randomized clinical trial” in the February issue of the Journal.1Farhadian N. Usefi Mashoof R. Khanizadeh S. Ghaderi E. Farhadian M. Miresmaeili A. Streptococcus mutans counts in patients wearing removable retainers with silver nanoparticles vs those wearing conventional retainers: a randomized clinical trial.Am J Orthod Dentofacial Orthop. 2016; 149: 155-160Abstract Full Text Full Text PDF Scopus (44) Google Scholar Since we are also working in this area, we had a few questions and would like some explanations, if possible. Regarding the synthesis of silver nanoparticles:•Silver nanoparticles can be synthesized by chemical, physical, and biological methods,2Iravani S. Korbekandi H. Mirmohammadi S.V. Zolfaghari B. Synthesis of silver nanoparticles: chemical, physical and biological methods.Res Pharm Sci. 2014; 9: 385-406Google Scholar and cytotoxicity varies accordingly.3de Lima R. Seabra A.B. Durán N. Silver nanoparticles: a brief review of cytotoxicity and genotoxicity of chemically and biogenically synthesized nanoparticles.J Appl Toxicol. 2012; 32: 867-879Crossref Scopus (399) Google Scholar How did the authors synthesize their silver nanoparticles?•Was the antimicrobial resin synthesized in bulk to standardize the amounts of silver nanoparticles in retainers delivered to patients? The cytotoxcity of stored silver nanoparticles is greater as compared with freshly prepared silver nanoparticles.4Kittler S. Greulich C. Diendorf J. Koller M. Epple M. Toxicity of silver nanoparticles increases during storage because of slow dissolution under release of silver ions.Chem Mater. 2010; 22: 4548-4554Crossref Scopus (923) Google Scholar•What was the ratio of polymer to silver nanoparticles? Was the minimum inhibitory concentration (that is, the concentration at which at least 50% of the bacteria are killed) calculated? Regarding the antibacterial properties:•Which species of S mutans was present in McFarland suspensions? The antibacterial effect can vary according to the species (eg, ATCC 25175). Regarding the intervention:•After appliance delivery, were the patients given any oral hygiene instructions or directed to use any mouthwashes? Coexposure of silver nanoparticles and sodium fluoride also affects the cytotoxicity.5Inkielewicz-Stepniak I. Santos-Martinez M.J. Medina C. Radomski M.W. Pharmacological and toxicological effects of co-exposure of human gingival fibroblasts to silver nanoparticles and sodium fluoride.Int J Nanomedicine. 2014; 9: 1677-1687Google Scholar Regarding patient-related outcomes:•The authors claimed that the color of the final appliance, which could be gray to black depending on the concentration of the silver nanoparticles (shown in the Fig), was acceptable to patients. Could colorless silver nanoparticles have been used instead?•Was there any reason to carry out the T2 test after 7 weeks, since the retention period was 1 year? Perhaps the antibacterial activity could have been analyzed at regular intervals, since there could be differences in silver ions released during the long term.•Cytotoxicity to human gingival fibroblasts should have been tested at the first stage before conducting the in-vivo study because silver has been claimed to have not only cytotoxicity but also genotoxicity.6AshaRani P.V. Low Kah Mun G. Hande M.P. Valiyaveettil S. Cytotoxicity and genotoxicity of silver nanoparticles in human cells.ACS Nano. 2008; 3: 279-290Crossref Scopus (2931) Google Scholar The urinalyses and hematologic tests should have been done as mentioned in the Discussion. We acknowledge the scientific inputs of Meryam S. Rizvi, associate professor, and Jahirul Mazumder, PhD student, Department of Bioscience, Jamia Millia Islamia University, Delhi, India, for their critical review of the study by Farhadian et al. Streptococcus mutans counts in patients wearing removable retainers with silver nanoparticles vs those wearing conventional retainers: A randomized clinical trialAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 149Issue 2PreviewThe rough surface of Hawley removable appliances provides an environment for plaque accumulation, leading to enamel demineralization. The aim of this study was to evaluate the effect of silver nanoparticles incorporated into acrylic baseplates of orthodontic retainers on Streptococcus mutans colony-forming units. Full-Text PDF Authors' responseAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 150Issue 2PreviewWe appreciate being given the opportunity to discuss the details of our study1 and hope the following explanation will be helpful. Full-Text PDF