title: Mechanical evaluation of implanted calcium phosphate cement incorporated with PLGA microparticles.
abstract: In this study, the mechanical properties of an implanted calcium phosphate (CaP) cement incorporated with 20wt% 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+/-0.44MPa (average+/-sd), which increased to 1.34+/-1.05MPa at 4 weeks and finally resulted in 2.60+/-2.78MPa 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 purposes.
authors.affiliation: Radboud University Nijmegen Medical Centre, Department of Periodontology & Biomaterials, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Dennis P
authors.initials: DP
authors.lastname: Link
authors.forename: Juliette
authors.initials: J
authors.lastname: van den Dolder
authors.forename: Wouter J F M
authors.initials: WJ
authors.lastname: Jurgens
authors.forename: Joop G C
authors.initials: JG
authors.lastname: Wolke
authors.forename: John A
authors.initials: JA
authors.lastname: Jansen
mesh_terms: D020341:Absorbable Implants / Q000592:standards*; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000592:standards; D001843:Bone Cements / Q000737:chemistry* / Q000494:pharmacology; D002130:Calcium Phosphates / Q000737:chemistry* / Q000494:pharmacology; D019344:Lactic Acid / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010012:Osteogenesis / Q000187:drug effects; D010316:Particle Size; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D012886:Skull / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D001672:Biocompatible Materials; D001843:Bone Cements; D002130:Calcium Phosphates; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C020243:calcium phosphate