Dear Colleagues,

In the era of nanotechnology and in the framework of sustainability, the fabrication of green nanomaterials is receiving great attention from the academic and industrial community for various applications. Moreover, green or eco-friendly nanomaterials have several advantages of sustainability, safety, a low cost, eco-friendliness, and a high performance. For this reason, they are widely used in water remediation, aerospace, automotive, construction, packaging, and biomedical applications because of their environmentally friendly behavior. Therefore, this Special Issue will focus on the recent developments, advances, and challenges related to the design, fabrication, and characterization of green nanomaterials. We invite the submission of original research, review, and perspective articles on themes including, but not limited to:

• Preparation of inorganic, organic, and hybrid nanomaterials;
• Use of novel technologies to produce green nanomaterials;
• Experiment and theoretical studies for nanomaterials;
• Interface and surface chemistry of nanomaterials;
• Green functional nanomaterials for novel applications;
• Nanomaterials for environmental remediation applications;
• Nanomaterials for photocatalysis;
• Nanofibers for biomedical applications;
• Nanocarbons and nanoclays.

We look forward to receiving your contributions.

Dr. Giuliana Gorrasi
Dr. Gianluca Viscusi
Guest Editors

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• nanostructured materials
• composites
• nanofibers
• physical properties
• green nanotechnologies
• nanoparticles
• polymer science
• surface chemistry
• nanoclay
• nanocarbons
• functional materials

Title: Caries prevention by toothpaste based on natural hydroxyapatite: a microbial study
Authors: Kan Wang; Minh Tuan Do; Sahar Mohseni; Yuko Kataoka; Nahid Iftikhar; Netheli Kuruwita; Bennett T. Amaechi
Affiliation: 1. Department of comprehensive dentistry, University of Texas Health Science Center at San Antonio, Texas, USA. 2. University of Texas at San Antonio, Texas, USA
Abstract: Use of non-fluoride toothpaste is gaining much attention, and hydroxyapatite is one of the most favored alternatives to fluoride. This in vitro study compared the efficacy, in preventing tooth surface demineralization, of natural hydroxyapatite (natHAP) in Happy™ tooth powder and toothpaste (Natural Tooth Health LLC), with toothpastes based on synthetic HAP or fluoride (1100 ppm). Methods: 140 bovine enamel blocks were assigned to 7 groups (20/group); natHAP tooth powder, natHAP-low toothpaste, natHAP-high toothpaste, natHAP-UG toothpaste, synthetic nanosized HAP (synHAP), fluoride toothpaste (NaF), and untreated control (Control). All blocks received 60-minute treatment with human saliva to develop acquired salivary pellicle, and then were subjected to 5-day demineralization for initial caries development in Microbial Caries Model using Todd Hewitt’s growth media (THB) inoculated with Streptococcus mutans and Lactobacilli acidophilus, with daily regimen of two 2-minute toothpaste treatments, three 6-minute 10% sucrose treatment, and storage in THB. Surface microhardness of each block was measured before and after treatment. Data were analyzed by paired t-test (intra-group comparison) and Tukey’s multiple comparison for inter-group comparison of percentage demineralization (%Dem). Results: All groups induced significant (p<0.05) demineralization, however, %Dem was significantly lower (p<0.001) in natHAP formulations compared to NaF and control. No significant difference between NaF (62.54±4.88%) and control (69.81±5.82%). No significant differences in %Dem among the natHAP formulations or between natHAP and synHAP. Conclusions: Toothpastes based on HAP are more efficacious than standard fluoride toothpaste in preventing caries in high caries risk situation. Natural and synthetic hydroxyapatite are equally effective in preventing caries.