In this study, the mechanical properties of an implanted calcium phosphate (CaP) cement incorporated with 20wt% poly (DL-lactic-coglycolic
acid) (PLGA) microparticles were investigated in a rat cranial defect. After 2, 4 and 8 weeks of implantation, implants were
evaluated mechanically (push-out test) and morphologically (Scanning Electron Microscopy (SEM) and histology). The results of the
push-out test showed that after 2 weeks the shear strength of the implants was 0.4470.44MPa (average7sd), which increased to
1.3471.05MPa at 4 weeks and finally resulted in 2.6072.78MPa at 8 weeks. SEM examination showed a fracture plane at the
bone–cement interface at 2 weeks, while the 4- and 8-week specimens created a fracture plane into the CaP/PLGA composites, indicating
an increased strength of the bone–cement interface. Histological evaluation revealed that the two weeks implantation period resulted in
minimal bone ingrowth, while at 4 weeks of implantation the peripheral PLGA microparticles were degraded and replaced by deposition
of newly formed bone. Finally, after 8 weeks of implantation the degradation of the PLGA microparticles was almost completed, which
was observed by the bone ingrowth throughout the CaP/PLGA composites.
On basis of our results, we conclude that the shear strength of the bone–cement interface increased over time due to bone ingrowth into
the CaP/PLGA composites. Although the bone–cement contact could be optimized with an injectable CaP cement to enhance bone
ingrowth, still the mechanical properties of the composites after 8 weeks of implantation are insufficient for load-bearing purpose
