Effects Of Magnesium-dropped Titanium Nanostructures On The Biological Properties Of Fibroblasts

Background:The Soft tissue sealing depends not only on the epithelial attachment,but also more importantly on the reconstruction of fibrous connective tissue attachment in order to firmly support the epithelial barrier to prevent peri-implantitis and maintain the long-term success rate of the implant denture.The abutment is an important component of implant denture,its collar surface is mainly in contact with soft tissue,so an ideal abutment collar surface should facilitate the binding between the soft tissue and abutment,as well as the formation of a stable and firm abutment soft tissue combination.Currently,the abutment collar surface is mainly employed the smooth surface in the clinic.However,studies have shown that the smooth surface is adverse to the adhesion and proliferation of fibroblasts,and the formed collagenous fiber is parallel with the surface with low adhesive strength and is easily to be separated from the abutment surface.A slightly rough surface is more beneficial to connective tissue adhesion than the smooth surface,and various metal cations are important for cell adhesion and proliferation via regulating cell biological properties.But there is a lack of in-depth study on the effects of magnesium dropped titanium nanostructures on the biological properties of fibroblasts.Objective:This study aims to obtain one titanium surface with nanostructure by alkali-heat-treatment,then load Mg²⁺on the nanostructure by ion exchange technology,in order to explore the effects of magnesium dropped titanium nanostructures on the biological properties of fibroblasts.Methods:After step-by-step polishing,alkali heat treatment,and alkali heat treatment together with ion exchange treatment,three different titanium surfaces were obtained,respectively: smooth group?S?,alkali heat group?AH?,and alkali heat magnesium ion group?AH-Mg?.The surface morphology of the each group was observed by scanning electron microscope?SEM?,the surface roughness was measured by atomic force microscope?AFM?,and the hydrophilic/ hydrophobic property was tested by contact angle meter?CAM?,the composition of chemical elements on specimen surface was analyzed by energy disperse spectroscopy?EDS?and the release concentration of magnesium ions was measured by inductively coupled plasma emission spectrometry?ICP-MS?.L929 fibroblasts were inoculated on the surface of the specimens.The effects of the three surfaces on the biological properties of fibroblasts were evaluated by the experiments of cell adhesion,cell proliferation,adhesion spot,collagen arrangement and sedimentation.Results:1.Group AH and group AH-Mg had the same sponge-like nanostructure surface,with about 80²00nm diameter,pores and the surface roughness Ra value was 0.45?m for both groups,Mg²⁺was successfully introduced into the surface of AH-Mg group.2.The promoting effect on the early adhesion of L929 cells: group AH-Mg > group AH > group S?P < 0.05?.3.The effect on the proliferation of L929 cells: group AH-Mg > group AH > group S?P < 0.05?.4.Focal adhesion formation at 24h: group AH-Mg > group AH > group S?P < 0.05?,the cell spreading range of group AH-Mg and group AH was larger than that of group S,and there was obvious pseudopodia protruding in group AH and group AH-Mg.5.Collagen arrangement and sedimentation: at 14 d,the collagen fibers in group S were parallel to the surface,whereas the collagen fibers of group AH and group AH-Mg were more denser and had pleiotropy?including vertical to the surface?;The collagen sedimentation on the surface of group AH and group AH-Mg increased,with significant difference with group S?P < 0.05?.Group AH-Mg did not increase the final collagen sedimentation compared with group AH?P > 0.05?,but accelerated the formation of collagen at the early stage.Conclusions:1.Alkali heat treatment combined with ion exchange technology could successfully construct a sponge-like magnesium dropped titanium nanostructure with pores size ranging 80-200 nm.2.The Mg²⁺dropped nanostructure can promote the adhesion and proliferation of fibroblasts,and change the orientation of collagen fibers as well as accelerate the formation of collagen at the early stage.