Nano Enhanced Surface Modification of Titanium Dental Implants for Improving Osseointegration and Biocompatibility
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Dental implants are prone to bacterial colonisation and infection which subsequently cause dental implant failure. Coating the dental implant with an antibacterial agent and a biocompatible agent can inhibit the bacterial colonisation and infection without disturbing the biocompatibility of the implant. This study aimed to coat medical grade titanium alloy implants with silver and hydroxyapatite (HA) nanoparticles. The reason for using silver was to introduce antibacterial activity to the coated dental implants; and then using HA to preserve biocompatibility and manage the silver exposure of the primary human osteoblast cells. Medical grade titanium alloy discs measuring 15 mm in diameter were polished and silver plated to produce a uniform layer of silver nanoparticles on the surface. The electroplating method was followed by nano or micro HA deposition and curing at 500 °C to produce an HA coating and thereby achieving nano silver plus nano HA (Ag+nHA ), or nano silver plus micro HA (Ag+mHA), coatings on titanium alloy. The coating quality was assessed by electron microscopy. The bonding strength of the coating was investigated by the pull-off test and chemical stability in the cell culture media was studied by conducting dialysis and dissolution experiments. A series of experiments were conducted to investigate the biocompatibility of the coatings with primary human osteoblast cells over 7 days, cell health was assessed using biochemistry and microscopy. A differentiation experiment was conducted for 21 days to investigate the osteoblast cell mineralisation on the coatings and gene expression profile of the cells. Results showed that the specimens were successfully coated with nano silver and HA particles. The pull-off test showed that the coatings had reasonable bonding strength to the substrate. Dialysis and dissolution experiments showed that the coatings were stable in the cell culture media despite some silver release from the coatings. The biocompatibility experiments showed that there was a consistent amount of silver release (1-2 mg L-1) from the silver containing specimens. The human primary osteoblast cells were healthier on Ag+nHA compared to Ag and Ag+mHA over 7 days. The differentiation experiment showed that there was a constant silver supply over 21 days from all silver containing coatings. Cell viability over 21 days was significantly higher in Ag+nHA compared to Ag and Ag+mHA (p < 0.05). Moreover, the cells were mineralised and produced Ca2+ and P in all the treatments. In conclusion, Ag+nHA was more biocompatible compared to Ag and Ag+mHA and can have a potential for clinical use.
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