ABSTRACT
Post-implantation failure associated with insufficient host tissue integration at the bone-implant interface and aseptic loosening is a major concern in orthopaedics as well as in dentistry. To overcome the failure in early stages of implantation, prosthetic design combining the mechanisms of porosity guided bone ingrowth along with topographic manipulation of osteogenic cells over bacterial colonization would be an ideal choice, although achieving such a goal is highly challenging. In this study, facile rapid hydrothermal synthesis of nanostructures with simultaneous deposition of hydroxyapatite on the titanium alloy surface was demonstrated by using an aqueous sodium tripolyphosphate and calcium hydroxide mixture. Nanostructures with wire-like morphology exhibited significantly higher osteogenic related gene expression (COL I, OPN, and OCN) through differentiation of adipose derived mesenchymal stem cells as well as the bactericidal response against S. aureus and E. coli as compared to other nanotopographic features. The same also exhibited elongated cell morphology with the highest expression of paxillin towards cell boundaries as compared to the polished surface with flattened cell morphology and localized expression of paxillin around the nucleus. Implantation of treated porous Ti6Al4V samples representing a multiscalar hierarchy with wire-like nanostructures accelerated osteochondral healing in rabbits without any major signs of infection. Also, significantly higher bone formation was observed within the defects implanted with treated porous Ti6Al4V (44.0%) as compared to that of untreated porous samples (36.9%) as well as empty defects (19.6%).
ABSTRACT
Cementless fixation for orthopedic implants aims to obviate challenges associated with bone cement, providing long-term stability of bone prostheses after implantation. The application of porous titanium and its alloy-based implants is emerging for load-bearing applications due to their high specific strength, low stiffness, corrosion resistance, and superior osteoconductivity. In this study, coagulant-assisted foaming was utilized for the fabrication of porous Ti6Al4 V using egg-white foam. Samples with three different porosities of 68.3%, 75.4%, and 83.1% and average pore sizes of 92, 178, and 297 µm, respectively, were prepared and subsequently characterized for mechanical properties, osteogenesis, and tissue ingrowth. A microstructure-mechanical properties relationship study revealed that an increase of porosity from 68.3 to 83.1% increased the average pore size from 92 to 297 µm with the subsequent reduction of compresive strength by 85% and modulus by 90%. Samples with 75.4% porosity and a 178 µm average pore size produced signifcant osteogenic effects on human mesenchymal stem cells, which was further supported by immunocytochemistry and real-time polymerase chain reaction data. Quantitative assessment of bone ingrowth by micro-computed tomography revealed that there was an approximately 52% higher bone formation and more than 90% higher bone penetration at the center of femoral defects in rabbit when implanted with Ti6Al4 V foam (75.4% porosity) compared to the empty defects after 12 weeks. Hematoxylin and eosin (H&E) and Masson trichrome (MT) staining along with energy-dispersive X-ray mapping on the sections obtained from the retrieved bone samples support bone ingrowth into the implanted region.
Subject(s)
Titanium/chemistry , Alloys , Animals , Bone and Bones , Chemical Phenomena , Egg Hypersensitivity , Humans , Osteogenesis , Porosity , Rabbits , X-Ray MicrotomographyABSTRACT
The microstructure of Ti-35Nb-7.2Zr-5.7Ta (TNZT) and Ti-35Nb-7.2Zr-5.7Ta-0.5B (TNZTB) alloys under different heat treatment conditions has been analyzed. The solution-treated and water-quenched TNZT sample consists mainly of ß phase with a very small amount of fine athermal ω precipitate. Precipitation of α can be observed when solution-treated samples are directly aged at 580°C for 8 h. The microstructure of the samples subjected to single-stage aging at 300°C or 400°C consists of ω precipitates in equiaxed ß grains. Second stage aging at 580°C for 8 h after first stage of aging at 300°C or 400°C results in the replacement of ω precipitates by secondary α. In all of these samples, the amount of ω or α phase was very small, and therefore they could not be detected by X-ray diffraction studies. However, analysis of selected area diffraction patterns obtained from transmission electron microscopy studies confirms their presence. The addition of boron leads to the formation of dispersed precipitates of TiB in the ß matrix of the TNZT alloy and also refines the ß grains in the microstructure. However, other microstructural features of the TNZTB alloy are similar to those of the TNZT alloy.
ABSTRACT
In the present study, the effects of heat treatment on the microstructure of Ti-13Zr-13Nb (TZN) and Ti-13Zr-13Nb-0.5B (TZNB) alloys have been investigated. Depending on the heat treatment conditions, the microstructure of the heat treated TZN alloy consisted mainly of elongated and/or equiaxed α, ß or martensite. Slow cooling (furnace or air cooling) from the solution treatment temperature produced α and ß phases in the microstructure. Rapid cooling (water quenching) resulted in martensite and retained ß when the solution treatment temperature was above or close to ß transus. However, martensite was not formed after water quenching from a solution treatment temperature which was below ß transus due to partitioning effect of the alloying elements. Increasing the cooling rate from the furnace cooling to the air cooling led to finer microstructure. Aging of water quenched samples transformed the martensite, if present, into α and ß, and the morphology of α phase changed from elongated to equiaxed and enhanced the growth of α. The microstructure of all the TZNB samples consisted of dispersed precipitated particles of TiB in the matrix. The majority of the boride particles showed an acicular (needle like) morphology. The other phases present in the TZNB alloy were similar to those in the similarly heat treated TZN alloy. Moreover, a growth of α phase was observed in the microstructure of TZNB alloy when compared with that of TZN alloy.
Subject(s)
Alloys/radiation effects , Biocompatible Materials/radiation effects , Titanium/radiation effects , Boron/radiation effects , Hot Temperature , MicroscopyABSTRACT
Even though laryngeal malignancies are the most frequent primary malignancies of the upper aero digestive tract except for oral cavity cancers, laryngeal chondrosarcomas are rare tumors, constituting less than 1% of all laryngeal tumors. We present a rare case of chondrosarcoma arising from the right arytenoid cartilage with sub glottic extension. The mode of presentation and management of the case is presented along with a review of the literature.
ABSTRACT
Ectopic teeth presenting in bath the tonsils with hatnartomatous lesion has not been reported earlier. We present here a case of benign hamartoma of both the tonsils bearing 7 teeth in a 13 year old girl and also discuss about unusual Ectopic sites of tooth eruption as well as benign lesions of tonsil.
ABSTRACT
A dizzy patient always remains a challenge to an E.N.T. surgeon. History is the key role and may be the only positive clue. An overall neurological assesment with special emphasis on nystagmus should be given. A comprehensive workout has been attempted in this study of vestibular disorders.
