It is not clear whether surface bioactive chemistry plays an important role in the early osseointegration of micro-structured titanium implants that have the same surface topography at the micrometer and submicrometer scales. In this study, magnetron sputtering methodology was employed for the preparation of Sr coating on sandblasted and acid-etched (SLA) titanium implant without changing the surface characteristics. The study of the surface morphology of the coating was carried out with the use of scanning electron microscopy, and the chemical composition of the surface was examined by X-ray energy-dispersive spectrometry. Twenty SLA implants together with 20 Sr-SLA implants were randomly inserted into the proximal tibia of 20 rats. The early osseointegration of the Sr-SLA implant was compared with SLA implant by removal torque test and histological analysis following two and eight weeks of implantation, correspondingly. As revealed by the surface characteristics, both Sr-SLA and SLA surfaces exhibited similar typical isotropic irregular indentations. The strontium ions were effectively incorporated into the SLA surface (the atomic ratio is 2%). Following two and eight weeks of healing, significant increases in removal torque values ( p < 0.05) were taken into observation in respect of Sr-SLA implant. Histologically, the Sr-SLA implants displayed significantly higher bone-to-implant contact percentages and bone area ratio in comparison with the SLA implant at eight weeks ( p < 0.05). At two weeks, the bone-implant contact percentages, together with bone area ratio of Sr-SLA surface appeared to be a little bit slightly greater than that of SLA surface. But the statistical difference was not significant. These results indicated that the chemical modification with Sr incorporated by magnetron sputtering treatment in moderately rough surfaced implants remarkably increases early bone apposition.
Keywords: Osseointegration; rat model; strontium; surface modification; titanium implant.