Papers by Author: Cheng Luo

Abstract: In an effort to investigate the growth mechanism of nacre, a conventional vapor diffusion method for CaCO3 crystal precipitation was applied to in vitro growth of calcium carbonate on freshwater H. cumingii Lea shell. In a 10mM/L CaCl2 solution without any additives, aragonite deposit was obtained on the nacre surface, specifically at the edges of nacreous tablets. At the early stage of the deposition (up to 4 hr), the deposit did not take any specific form. After 12hr of deposition, the deposit exhibited faceted morphology characteristic of crystalline. Further increasing the deposition time resulted in the formation of well-faceted crystals of tower-like shape. Both Raman spectra and X-ray diffraction patterns showed that the deposit consists of aragonite polymorph of calcium carbonate.

Abstract: Titanium dental implant screws were implanted into the pearl sacs of a fresh water bivalve (hyriopsis cumingii Lea) by replacing the pearls. After 45 days of cultivation, the implant surfaces were deposited with a nacre coating with iridescent luster. The coating was about 200-600 µm in thickness and composed of a laminated nacreous layer and a transitional non-laminated layer that consisted mainly of vaterite and calcite polymorphs of calcium carbonate. The transitional layer was around 2-10 µm thick in the convex and flat region of the implant surface and could form close contact with titanium surface; while the transitional layer was much thicker in the steep concave regions and could not form close contact with the titanium surface. The improvement to the design of the dental implant with respect to this coating method was suggested in the paper. The results suggest that it is possible to fabricate a biologically active and degradable, and mechanically tough and strong nacre coating on titanium dental implant by this novel coating technology.