Rehardening and the Protective Effect of Gamma-Polyglutamic Acid/Nano-Hydroxyapatite Paste on Surface-Etched Enamel

Many revolutionary approaches are on the way pertaining to the high occurrence of tooth decay, which is an enduring challenge in the field of preventive dentistry. However, an ideal dental care material has yet to be fully developed. With this aim, this research reports a dramatic enhancement in the rehardening potential of surface-etched enamels through a plausible synergistic effect of the novel combination of γ-polyglutamic acid (γ-PGA) and nano-hydroxyapatite (nano-HAp) paste, within the limitations of the study. The percentage of recovery of the surface microhardness (SMHR%) and the surface parameters for 9 wt% γ-PGA/nano-HAp paste on acid-etched enamel were investigated with a Vickers microhardness tester and an atomic force microscope, respectively. This in vitro study demonstrates that γ-PGA/nano-HAp treatment could increase the SMHR% of etched enamel to 39.59 ± 6.69% in 30 min. To test the hypothesis of the rehardening mechanism and the preventive effect of the γ-PGA/nano-HAp paste, the surface parameters of mean peak spacing (Rsm) and mean arithmetic surface roughness (Ra) were both measured and compared to the specimens subjected to demineralization and/or remineralization. After the treatment of γ-PGA/nano-HAp on the etched surface, the reduction in Rsm from 999 ± 120 nm to 700 ± 80 nm suggests the possible mechanism of void-filling within a short treatment time of 10 min. Furthermore, ΔRa-I, the roughness change due to etching before remineralization, was 23.15 ± 3.23 nm, while ΔRa-II, the roughness change after remineralization, was 11.99 ± 3.90 nm. This statistically significant reduction in roughness change (p < 0.05) implies a protective effect against the demineralization process. The as-developed novel γ-PGA/nano-HAp paste possesses a high efficacy towards tooth microhardness rehardening, and a protective effect against acid etching.

Natto and miso: an overview on their preparation, bioactive components and health-promoting effects

Natto and miso are two major traditional fermented soy foods in Japan. Natto is prepared by fermenting cooked soybeans with Bacillus subtilis natto. The beans of natto have a sticky outlook, slippery texture, sour aroma and nutty flavour. Bioactive components of natto are nattokinase, bacillopeptidase F, vitamin K2, dipicolinic acid and γ-polyglutamic acid. Miso is a fermented soybean paste widely used to make miso soup. The paste is produced by fermenting cooked soybeans with koji (steamed rice inoculated with Aspergillus oryzae). Bioactive compounds of miso include isoflavones and phenolic acids. In this review, the preparation, bioactive components, and health-promoting properties of natto and miso are highlighted. Sources of information referred were from Google Scholar, J-Stage, Science Direct, PubMed, PubMed Central and PubChem