Changes in the Properties of Functional Water for Dental Use after Preservation by Freezing

DOI
  • Koichi YOSHIDA
    Toho Dental College Department of Endodontics, Division of Oral Functional Science and Rehabilitation, Asahi University School of Dentistry
  • Takaichi YOSHIDA
    Toho Dental College
  • Tomomi ITO
    Department of Endodontics, Division of Oral Functional Science and Rehabilitation, Asahi University School of Dentistry
  • Toshio TONOUCHI
    Department of Endodontics, Division of Oral Functional Science and Rehabilitation, Asahi University School of Dentistry
  • Tatsuya SAITO
    Department of Endodontics, Division of Oral Functional Science and Rehabilitation, Asahi University School of Dentistry
  • Yoshiaki TAKITANI
    Department of Endodontics, Division of Oral Functional Science and Rehabilitation, Asahi University School of Dentistry
  • Satoshi KAWANO
    Department of Endodontics, Division of Oral Functional Science and Rehabilitation, Asahi University School of Dentistry

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Other Title
  • 歯科医療用機能水の氷結保存前後における諸性質の変化

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Abstract

 Purpose: Freezing electrolyzed functional water with no convection limits contact with oxygen. Precipitation of substances dissolved in the water limits the amount of those substances in the water. This helps to protect components in the water and allows prolonged storage with little loss of antimicrobial potency. Functional water with various properties was generated and preserved by freezing under various conditions to ascertain changes in those properties after thawing.<br> Materials and Methods: A 2-chamber functional water generator and storage tank was fabricated. Electrolysis of a saline solution yielded acidic water and alkaline water. Ten ml of each aqueous solution was collected when water was generated, and each solution’s pH, ORP (mV), and residual chlorine concentration (ppm) were measured. Sixty ml of each aqueous solution was injected into a container (80 ml) and then frozen at −17°C for 24 and 168 hrs. The container was then thawed at room temperature (23°C) for about 2 hrs. The solution’s properties were then measured again. Conditions for this experiment were: addition of 3 amounts of sodium chloride (factor A): 0.3, 0.6, and 0.9 wt%; 2 electrolytic currents (factor B): 2 and 4 A; 2 methods of storage (factor C): closed or open container; and 2 freezing times (factor D). Conditions were randomly varied and 3 repetitions were performed. Conditions were analyzed using 4-way analysis of variance, and the same data were subjected to Welch’s t-test to examine the method and duration of freezing and storage. The properties of functional water immediately after generation were subjected to regression analysis using the equation for a line describing the same solution’s properties after thawing.<br> Results: Analysis revealed that a thawed solution of acidic electrolyzed water retained its acidity (a pH of less than 2.2). Its ORP was 1,100 mV or greater. After preservation by freezing, the chlorine concentration (ppm) in the solution decreased over time from 263 ppm. Addition of a large amount of sodium chloride and use of a high electrolytic current preserved the chlorine concentration when the container was closed. When a solution was frozen for 168 hrs in a closed container and thawed, y=0.5251x−36.212 (r=0.919**). Solutions that were preserved in an open container and then thawed had properties similar to those of a hypochlorite solution as defined in pharmaceutical legislation. If alkaline water was generated with a high electrolytic current, the thawed solution tended to be slightly alkaline. The ORP of a thawed solution changed from −849.2 to +224.94-301 mV.<br> Conclusion: Acidic electrolyzed water that was frozen in an open container for 168 hrs retained sufficient antimicrobial potency. A frozen solution of alkaline electrolyzed water that was thawed had properties similar to those of alkaline water for cleaning.

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