Biomimetic Synthesis Of Enamel-like Hydroxyapatite

Hydroxyapatite (HAP) is the main component of human tooth enamel, however at present the synthesized HAP can not meet the demand of tooth enamel restorative in composition, architecture, or characteristics. In this paper, HAP crystals with composition, configuration and morphology similar to natural tooth enamel were synthesized by biomimetic way mimicking biomineralization process of tooth enamel. The results will lay the foundation for the new dental restorative materials.Based on investigation of the characteristics of natural tooth enamel both in composition and morphology, the effect of four functional groups, which commonly consist in proteins, and bovine collagen of I type on the biomimetic synthesized HAP crystals were studied respectively. Then, a gel system with different pH was adopted to further mimic the biomineralization process of natural tooth enamel. And the effect of bovine collagen of I type and proteins from developing SD rats teeth on the composition, configuration and morphology of HAP crystals were investigated in the gel system. The results were showed as follows:1. The inorganic composition of mature tooth enamel was HAP containing other ions. These HAP crystals might adsorb some Ca²⁺ ions on their surfaces, which caused them to be positively charged and easily adsorbed to negatively charged SAMs. The morphology of HAP in mature tooth enamel was needle-like, and they paralleled each other to be bundles.2. The SAMs were soaking in different biomimetic solutions (1.0SBF at 37℃ and 1.5SBF at 50℃) to study their ability to induce HAP deposition. The results showed that in 1.0SBF, HAP particles were deposited on SAMs with -SO₃H, -COOH and -OH groups. However, in 1.5SBF HAP particles were deposited on all the four SAMs. From the results, it can be concluded that when the process of biomineralization progresses in body fluid, the -SO₃H, -COOH and -OH groups can adsorb Ca²⁺ and induce HAP deposition by heterogeneous nucleation. While in tissue fluid with higher degree of supersaturation, -NH2 groups may induce HAP mineralization by attracting apatite nuclei from homogeneous nucleation in the solution.