Abstract: Objective To construct a sustained release system of exogenous protein on the root surface using layer-by layer self-assembly coating technique. Methods Eighteen healthy mandibular second premolars were collected and randomly divided into 6 groups, group a-e were experimental groups with acid etching, group f was a control group without etching. Each group went through layer-by-layer adsorption experiments under different conditions. Samples were collected and detected absorbance on day 1-9 in each group to calculate the concentration of protein release. Results All sets of samples showed sustained-release trend （P〈0.05）. Etching group showed a significant increase of protein release compared with control group （P〈O.05）; Release rate and amount increased with the protein concentration in the materials （P〈0.05）; More adsorption times leaded to larger release amount and prolonged time （P〈0.05）. Conclusion Sustained release system of exogenous protein can be constructed on the root surface using layer-by layer self-assembly coating technique.

Key words: Layer-by-Layer, Root surface conditioning, Sustained release system, Protein absorption