in vitro Study of a Novel Method to Repair Human Enamel
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1274-QQ08-10
in vitro Study of a Novel Method to Repair Human Enamel Song Yun1, Yanjun Ge2, Yujing Yin1, Hailan Feng2, Haifeng Chen1,* 1 Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, China 2 Department of Prosthodontic, Peking University School and Hospital of Stomatology, Beijing, 100081 China * Corresponding author. ABSTRACT The chemical regeneration method of human enamel was improved for the probable clinical application: an oral medical device was designed to significantly reduce the necessary amount of remineralization liquid; the reactive liquid phase system was redesigned, thus the solution could be stored for long time. INTRODUCTION Dental enamel is the outmost layer of the human tooth [1]. Since there are no living cells in mature enamel, once been damaged, it cannot be self-repaired. In our previous work, we succeeded to synthesize human-enamel-like FA structures through liquid deposition [2]. This method provided a new approach to repair teeth with shallow surface caries, or other types of enamel defect. However, this method demands mass reactive liquid to soak the teeth in vitro, while the liquid can hardly be storage for long term (>1d). Therefore, it cannot be directly applied in clinical practice. In order to gain the clinical maneuverability of this method, we improved it on two main aspects. At first, the pretreatment step was modified and the reactive liquid phase system was redesigned. An oral medical device to assist the reconstruction process was designed with its detailed operating steps. EXPERIMENT Instruments and materials At first a polymer hollow hemisphere shell of about 4-5mm in diameter and 2mm in height, with two circular hole of 2mm interval was prepared (Fig.1). The liquid phase was divided to two separated reactive solutions – Solution A [contents 0.20M HEDTA, 0.20M Ca(NO3)2, 0.62M KOH] and Solution B [contents KH2PO4 0.12M, KF 0.04M]. These two types of solution were chemical stable and could be kept individually for more than one month. While in use, mixing A and B would generate a chemical solution at pH 6.0 which contents 0.10M HEDTA-Ca, 0.06M H2PO4- and 0.02M F-, the same as the reaction conditions of the previous liquid deposition method.
Figure 1. The polymer hollow hemisphere shell repair device on an in vitro tooth (a) and on an oral cavity model (b) The demand quantity of reactive solution The demand quantity of reactive solution, or the minimum volume of the hollow hemisphere device, was calculated by the following processes. The mass of the closely arranged deposited fluorapatite (FA) crystals, mc, the density of the crystal, dc, and the volume of the deposited crystal film, Vc, (which was equal to the product of the area of enamel base for them to deposit, S, and the average height of the crystals, hc) obeyed the following relational expression, m=dc·Vc=dc·S·hc
(1)
Meanwhile, the crystal mass was also related with the quantity of reactive solution in the aqueous system as the following relational expression, m=M·n=
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