Mechanical evaluation of implanted calcium phosphate cement incorporated with PLGA microparticles

In this study, the mechanical properties of an implanted calcium phosphate (CaP) cement incorporated with 20 wt% poly ( dl-lactic- co-glycolic acid) (PLGA) microparticles were investigated in a rat cranial defect. After 2, 4 and 8 weeks of implantation, implants were evaluated mechanically (push-out...

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Bibliographic Details
Published in:Biomaterials 2006-10, Vol.27 (28), p.4941-4947
Main Authors: Link, Dennis P., van den Dolder, Juliette, Jurgens, Wouter J.F.M., Wolke, Joop G.C., Jansen, John A.
Format: Article
Language:English
Subjects:
Absorbable Implants - standards
Animals
Biocompatible Materials - chemistry
Biocompatible Materials - standards
Bone Cements - chemistry
Bone Cements - pharmacology
Bone ingrowth
Calcium Phosphates - chemistry
Calcium Phosphates - pharmacology
Injectable CaP/PLGA cement
Lactic Acid - chemistry
Materials Testing
Mechanical properties
Microscopy, Electron, Scanning
Osteogenesis - drug effects
Particle Size
Polyglycolic Acid - chemistry
Polymers - chemistry
Rats
Rats, Wistar
Skull - drug effects
Skull - pathology
Skull - ultrastructure
Stress, Mechanical
Time Factors
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Summary:In this study, the mechanical properties of an implanted calcium phosphate (CaP) cement incorporated with 20 wt% poly ( dl-lactic- co-glycolic 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 0.44±0.44 MPa (average±sd), which increased to 1.34±1.05 MPa at 4 weeks and finally resulted in 2.60±2.78 MPa 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 purposes.
ISSN:0142-9612
1878-5905
DOI:10.1016/j.biomaterials.2006.05.022