Effects of an apatite-surface on macrophage polarization, VEGF expression, and biomechanical anchorage

Early osseointegration is a critical determinant of implant success. In this study, we systematically compared the surface characteristics and the osteoimmunological cascade of early healing—macrophage polarization, vascular endothelial growth factor (VEGF) expression, osteoconduction, histomorphometric osseointegration, and biomechanical stability—of commercially available modified sandblasted, large-grit, acid-etched-surface (modified SLA-surface; SLActive ® , Straumann AG, Switzerland) and apatite-surface (Osstem TSIII BA, Osstem, Republic of Korea) implants. Surface morphology/roughness of apatite and modified-SLA implants were assessed by Field emission scanning electron microscopy (FE-SEM) and profilometry. Immunoangiogenic responses were evaluated in a rat calvarial defect model using immunofluorescence for CD11c, CD163, and vascular endothelial growth factor (VEGF). Early osseointegration was tested in rat femoral condyles (bone area, bone-to-implant contact (BIC)) and canine mandibles (BIC, removal torque) at set intervals. FE-SEM showed a distinct micro- or nanoscale topography. Profilometry confirmed the presence of comparable microroughness (2.143 vs . 2.223 μm). In rat calvarial defects, the apatite-surface showed a higher CD163 (M2) signal and M2/M1 ratio than the modified SLA-surface on days 4 and 7 ( P <0.05), and a higher VEGF signal on days 4 and 6 ( P <0.05). In rat femur condyles, bone area was comparable; however, on day 7, BIC was significantly higher on the apatite-surface than on the modified SLA-surface ( P <0.05). In canine mandibles, removal torque was significantly higher on the apatite-surface at both 3 and 6 weeks ( P <0.05), and BIC was also significantly higher at 3 and 6 weeks (P<0.05). Within the limits of the present preclinical models, the apatite-surface was associated with a shift toward M2-polarized macrophages, increased VEGF expression, and improved early osseointegration compared with the modified SLA-surface.