5204
Tamer Mohamed Hamdy Mahmoud Ibrahim
Effect of Impregnation of Calcium Phosphate Based Nanofillers on Acrylic Bone Cement (In-Vitro Study)
Calcium phosphate; CaP; Hydroxyapatite; HA; Polymethyl Methacrylate; PMMA; Bioactivity; Sol-gel; Ion release; EDX; Compressive strength; Bone filler; Bone cement.
Objectives: preparation and characterization of amorphous nano-hydroxyapatite fillers by sol-gel method and incorporating the prepared fillers in two different concentrations 02 and 40 weight % into traditional polymethyl methacrylate (PMMA) bone cement to test the chemical properties (calcium and phosphorus ion release and hydroxyapatite crystals formation) and the compressive strength of the prepared amorphous nHA/PMMA composite. Methods: Calcium phosphate (CaP) fillers were prepared by the sol-gel method. Characterization was done by means of X-ray diffraction (XRD) analysis and Fourier transform infrared spectroscopy (FTIR). Surface morphology, microstructure and particle size of the prepared particles was assessed by scanning and Transmission electron microscopy (SEM and TEM). In addition, decomposition and stability of the prepared CaP was analyzed by Differential scanning calorimetry (DSC)/Thermal gravimetric analysis (TGA). The change in pH after CaP dissolution in physiologic fluid was measured by pH-meter for 1, 3, 7 and 14 days and was extended for 7 more successive days after fixation of the pH value. Manual blending of the prepared nano filler; 0 weight %, 20 weight % and 40 weight % concentrations, into commercially available PMMA bone cement was done to prepare the polymer/nHA composite in an attempt to be used as bioactive bone cement. A total of 45 specimens (5 specimens per group) were then tested for the calcium and phosphorus ion release using inductively coupled plasma (ICP), hydroxyapatite crystals formation analyzed by energy dispersive x-ray spectroscopy (EDX) and compressive strength using universaltesting machine. Results: Results of characterization of the prepared CaP confirmed preparation of a high purity amorphous nHA powder with uniform, rod-like, smooth surface particle, homogenously distributed particles with a size range of 3-10 nm and a very little degree of agglomeration. The prepared nHA powder showed thermal stability up to temperature of 200 °C. Moreover, the pH changes of 5% CaP Tris-buffer solution over time was (7.59) which lied within physiological limits (6.5 to 7.8). ICP results revealed that 40 weight % filler specimens had the highest statistically significant calcium and phosphorus ion release values compared to 20 weight % filler and control specimens (0 weight % filler). Surface examination of specimens using SEM and EDX revealed that formation of amorphous calcium phosphate (ACP) patches with mean Ca/P atomic % (1.22) on the surface of 20 weight % filler specimens, while 40 weight % filler specimens showed formation of calcium-deficient hydroxyapatite (CDHA) deposits on the surface with Ca/P atomic % (1.5). No patches were precipitated on control specimens. Results of compressive strength revealed that the control grouphad the highest statistically significant compressive strength value (92.5 MPa) compared to 20 weight % filler specimens (80.4 MPa) and 40 weight % filler specimens (71.3 MPa). Moreover, all prepared composite groups exceeded the minimum requirements of (70 MPa) set by ASTM F-451-99 standard. Significance: Addition of 20 and 40 weight % amorphous nHA fillers to PMMA bone cement improved their bioactivity. CDHA was precipitated on the surface of 40 weight % amorphous nHA/PMMA composite with the highest resemblance to bone HA. Addition of 20 weight % and 40 weight % amorphous nHA fillers to PMMA bone cement decreased its compressive strength without compromising its effectiveness for use as bone cement.
2016
Ph.d
Cairo
Dental Medicine