Near net-shape fabrication of hydroxyapatite glass composites

Abstract

Near net-shape fabrication of hydroxyapatite (HA) glass composites has been attempted by infiltrating a glass into porous HA performs. Main efforts were put to develop glasses that are chemically compatible with HA at elevated temperatures. After extensive investigations in the phosphate and borosilicate systems, glasses of (50-55)SiO2-(20-25)B203-(10-20)Li2O-(0-6)CaO (wt%) composition were successfully developed. The glass shows good chemical compatibility with HA at elevated temperatures. Dense HA/glass composites can be fabricated at 850-950 degress C by the melt infiltration process. Investigations demonstrated a good near net-shape capability of the process, where the linear shrinkage induced by the infiltration process is less than 0.1%. Preliminary mechanical tests showed that the fracture strength and toughness of the infiltrated HA/glass composite are comparable with dense HA.

Morphological transitions in aggregates of thermosensitive poly(ethylene oxide)‐b‐poly(N‐isopropylacrylamide) block copolymers prepared via RAFT polymerization

“…The aggregation behavior of both block and graft copolymers bearing PEO and PNIPAM in aqueous solutions have been investigated in terms of copolymer composition, concentration, molecular architectures, and low molecular weight additives. [17][18][19][20][21][22][23][24][25][26][27][28][29] Tenhu and coworkers investigated the effect of copolymer composition and concentration using two series of PEO-b-PNI-PAM samples. 17 Nyström et al studied the effect of the length of PEO on the micellization behavior of a series of PEO-b-PNIAPM copolymers.…”

“…[9][10][11][12][13][14][15][16] Among all these stimuliresponsive double hydrophilic block copolymers, poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PEO-b-PNIAPM) has attracted much attention in terms of both synthesis and aggregation behavior. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Above the lower critical solution temperature (LCST) of PNIAPM ($32 C), 34,35 the block copolymers form aggregates with PNIPAM chains comprising the core, stabilized by PEO corona chains. The aggregation behavior of both block and graft copolymers bearing PEO and PNIPAM in aqueous solutions have been investigated in terms of copolymer composition, concentration, molecular architectures, and low molecular weight additives.…”

Contact fracture of full-ceramic crowns subjected to occlusal loads

“…Research on ceramic crowns over the past two decades has focused primarily on net-shape processing (Tabellion, 2006;Zhu et al, 2004), machining (Bindl and Mö rmann, 2005;Sulaiman et al, 1997), improving the structural properties of full-ceramic systems (Kelly, 1997;Lawn et al, 2004;Quinn et al, 2005) and analyzing clinical failures (Kelly, 1999;Scherrer et al, 2006;Taskonak and Sertgoz, 2006). In practice, full-ceramic crowns are usually fabricated into layer structures with esthetic, but comparatively weak, veneer porcelains on stiff and strong ceramic support cores.…”

Temperature‐Controlled Assembly and Release from Polymer Vesicles of Poly(ethylene oxide)‐block‐ poly(N‐isopropylacrylamide)

“…[2] In addition, polymers are far more polydisperse than lipids, and poly-dispersity generally broadens and obscures phase transitions. Although a wide range of thermally responsive block copolymers of poly(ethylene oxide)-block-poly(N-isopropylacrylamide) (PEO-b-PNIPAm) have been recently synthesized, [14][15][16][17][18][19][20][21][22][23][24][25][26] only spherical micelles or gels have been reported. In this Communication, we describe the synthesis and preparation of the first thermoresponsive polymersomes from diblock copolymers of PEO-b-PNIPAm with a narrow polydispersity index (PDI; ≤ 1.2).…”

“…[37][38][39][40][41][42][43] A second architecture, stable above the LCST, uses hydrophilic PEO as the corona and PNI-PAm as the core block for directly integrating hydrophobic molecules, which are released when the temperature is decreased below the LCST. [14][15][16][17][18][19][20][21][22][23][24][25][26] For the latter PEO-b-PNIPAm system, spherical micelles and gels, but not vesicles, have been observed above the LCST over a surprisingly wide range of f PEO values (0.25-53.8 wt %). [14,16,17,24,25] Variables such as polymer composition and processing steps (e.g., sonication, stirring) are expected to have a strong influence on the morphologies of PEO-b-PNIPAm assemblies in water.…”