Bio-Inspired Nano-Composite Fabrication on Etched Human Enamel Surface
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1094-DD09-01
Bio-Inspired Nano-Composite Fabrication on Etched Human Enamel Surface Yuwei Fan, Zhi Sun, and Janet Moradian-Oldak Center for Craniofacial Molecular Biology, University of Southern California, 2250 Alcazar St., Los Angeles, CA, 90033 ABSTRACT Because of its significant potential in controlling key steps of apatite mineralization, recombinant amelogenin has been applied in different in vitro systems for the synthesis of uniquely ordered composite material similar to enamel. Here we summarize the results of a series of experiments, in which mineral deposition took place on the exposed surface of enamel from extracted human third molars soaked in calcium phosphate solution, in the presence of amelogenin and fluoride. Analysis of crystal size and morphology revealed that in the presence of both amelogenin (50-100 µg/mL) and fluoride (1 ppm), bundles of oriented rod- like fluoridated apatite crystals were formed creating a dense coating on the enamel substrate. Such organized bundles were not formed at low concentrations of rP172 (< 30 µg/mL). Preparation of such ordered nanocomposites provides a promising approach for development of new generation of dental restorative materials with improved esthetic and mechanical properties.
INTRODUCTION The highly organized hierarchical microstructure provides enamel high strength and anti-abrasive properties [1]. Mature enamel is acellular, has less than 3% protein and does not remodel. The investigation of in vitro biomimetic synthesis of enamel-like calcium phosphate structures is therefore of great interest not only in the material engineering field, but also in dentistry as an alternative dental restorative material. Recent approaches for in vitro synthesis of enamel-like structures containing hydroxyapatite (HAP) nanorods include: hydrothermal method with controlled release of calcium from Ca-EDTA [2], hydrothermal transformation of OCP rod to HAP nanorods in the presence of gelatin [3], surfactant supported HAP self-assembly [4, 5] hydrogen peroxide containing calcium phosphate paste [6] and electrochemical method taking place at 85oC [7]. Most of these synthesis methods were developed under condition of hightemperature; high pressure, extreme acidic pH or in the presence of concentrated solution of surfactants. In vitro formation of enamel-like apatite crystals under relatively mild conditions was reported for the first time by Moriwaki et al in a mineralization device using cation-selective membrane system. In such a device, the direction of calcium ion transport was controlled and the crystals formed in the membrane isolated chamber contained bundles of needle-like OCP and HAP [8]. Using similar system Iijima et al. applied a dual-membrane device as a model of enamel formation to investigate the function of amelogenin proteins on calcium phosphate mineralization [9, 10]. The coexistence of amelogenins and F was crucial for the organized rod-like apatite crystal formation on the membrane [11].
Macromolecular assembly is a critical event in enamel mineraliz
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