Abhijit Chanda

Wear and friction behaviour of UHMWPE-alumina combination for total hip replacement

Abstract The wear and friction behaviour of ultra high molecular weight polyethylene (UHMWPE) against high purity fine grained alumina, the ideal material combination for total hip joint prosthesis, were studied under different contact pressures and sliding velocities using a pin-on-disc type wear and friction monitor. The wear heights in wet conditions were found to be much lower than those in dry conditions, which followed a power law relationship with load after 3–5 km of sliding. Efforts were also made to find out the sequence of dominating wear mechanisms.

Strategies for delivering bone morphogenetic protein for bone healing

Bone morphogenetic proteins (BMPs) are the most significant growth factors that belong to the Transforming Growth Factor Beta (TGF-β) super-family. Though more than twenty members of this family have been identified so far in humans, Food and Drug Administration (FDA) approved two growth factors: BMP-2 and BMP-7 for treatments of spinal fusion and long-bone fractures with collagen carriers. Currently BMPs are clinically used in spinal fusion, oral and maxillofacial surgery and also in the repair of long bone defects. The efficiency of BMPs depends a lot on the selection of suitable carriers. At present, different types of carrier materials are used: natural and synthetic polymers, calcium phosphate and ceramic-polymer composite materials. Number of research articles has been published on the minute intricacies of the loading process and release kinetics of BMPs. Despite the significant evidence of its potential for bone healing demonstrated in animal models, future clinical investigations are needed to define dose, scaffold and route of administration. The efficacy and application of BMPs in various levels with a proper carrier and dose is yet to be established. The present article collates various aspects of success and limitation and identifies the prospects and challenges associated with the use of BMPs in orthopaedic surgery.

Enhanced bone regeneration with carbon nanotube reinforced hydroxyapatite in animal model

In order to improve the inherently poor mechanical properties of hydroxyapatite (HAp) and to increase its feasibility as load bearing implant material, in the present investigation, functionalised (HFC1 and HFC2) and non-functionalized (HC1 and HC2) multi-walled carbon nanotubes were used as reinforcing material with HAp. Significant improvement with respect to fracture toughness, flexural strength and impact strength of the composites was noticed. In vitro biological properties of HAp-carbon nanotube (CNT) biocomposites have also favored uniform and systematic apatite growth on their surface. Subsequently, in vivo osseous ingrowth at bone defect of rabbit femur was evaluated and compared using radiology, push out test, fluorochrome labeling, histology and scanning electron microscopy after 2 and 4 months respectively. The results demonstrated growth of web like soft callus from the host bone towards the implant, ensuring strong host bone interaction. Toxicological studies of the liver and kidney cells exhibited no abnormality, thereby confirming non-toxicity of the CNT in the animal body. Host-implant biomechanical strength showed high interfacial strength of the composites, indicating their high potentials to be used for bone remodeling applications.

Animal trial on zinc doped hydroxyapatite: A case study

Abstract Calcium hydroxyapatite (HAp) has widely been used as bone substitute due to its good biocompatibility and bioactivity. In the present work, hydroxyapatite was doped with zinc (Zn) to improve its bioactivity. The study reports the technique to synthesize Zn-doped HAp powder using a simple, economic route and the influence of this dopant on the physical, mechanical and biological properties of the HAp. Porous blocks were prepared by sintering at 1150 °C and the sintered samples were characterized using XRD and FTIR. In vitro bioresorption behavior of the sintered blocks was assessed in simulated body fluid (SBF) maintained in a dynamic state. The in vivo study was exclusively conducted to evaluate healing of surgically created defects on the tibia of adult New Zealand rabbit after implantation of HAp. Local inflammatory reaction and healing of wound, radiological investigations, histological and SEM studies, oxytetracycline labeling and mechanical push-out test were performed up to 60 days post-operatively. It was observed that Zn substituted HAp showed better osteointegration than undoped HAp. Radiology revealed progressively less contrast between implant and surrounding bone. New bone formation in Zn-doped HAp was more prompt. Mechanical push-out test showed high interfacial strength (nearly 2.5 times) between host bone and doped implant.

Safety and efficacy of additive and subtractive surface modification of Ti6Al4V endosseous implant in goat bone

Growing interest of endosseous implant research is focused on surface modification to achieve early and strong osseointegration. The present study compared the behaviour of hydroxyapatite coated, zinc doped hydroxyapatite coated and hydrothermally treated titanium (Ti6Al4V) with machined Ti6Al4V implants (control) on osseointegration. The surface characterization and bacterial affinity test for implants were performed. Forty eight (48) cylinders (4 types in each animal) were placed in the humerus bone of 12 black Bengal goats. Bone-implant interface was examined with histological, radiological parameters and scanning electron microscopy on 42nd, 90th, and 180th day post-implantation. Surface roughness alterations of bone-detached implants with time were analyzed by non-contact profilometer. Push-out test (90th day) was performed to assess the strength of bony integration of implants. The coated implants revealed direct and early bone-implant contact but high bacterial affinity and coating resorption/cracks. Low bacterial affinity and strongest osseointegration was observed with hydrothermally treated implants. Poor bacterial affinity and delayed but strong fixation were evident with control implant. Based on the results of laboratory and animal experiments, we conclude that the hydrothermal modification of titanium implant is the more suitable way to achieve safe and effective osseointegration than the other three implant types for endosseous application.

A novel, multi-barrier, drug eluting calcium sulfate/biphasic calcium phosphate biodegradable composite bone cement for treatment of experimental MRSA osteomyelitis in rabbit model

This article discloses the development of an effective and versatile technology to prepare a novel antibiotics-loaded biodegradable composite bone cement to treat methicillin-resistant Staphylococcal (MRSA) osteomyelitis and reports its detail in vitro characterization, drug loading efficiency, physico-mechanical properties, drug elution in simulated body fluid (SBF) and human plasma, merits and demerits over poly-methyl methacrylate (PMMA) cement. Chronic osteomyelitis in rabbit tibia (42) was induced by MRSA and composite cement was implanted to evaluate its safety and efficacy over PMMA cement and parenteral treated animals with histopathology, radiographs, bone/plasma drugs concentration, and SEM for 90days. The composite cement showed higher setting time, degradability, pH rise, injectability, in vitro drug elution but lesser mechanical strength than PMMA cement. Antibiotics release from cement beads was faster in SBF than plasma. Further, in vivo antibiotics elution from composite (42days) showed effective concentration against MRSA without eliciting drug-toxicity. Platelets activation by composite was an extraordinary feature. The in vivo studies also proved the superiority of composite cement than other treatment methods in terms of faster infection control and osteosynthesis. Based particularly on drug elution and in vivo results, this newly developed cement can successfully be used in clinical cases of chronic osteomyelitis.

Effect of bone morphogenetic protein on Zn-HAp and Zn-HAp/collagen composite: A systematic in vivo study

Due to good biocompatibility and osteoconductivity, hydroxyapatite (HAp) and its composite with different polymers have been widely investigated for the application in the field of bone tissue engineering. The present study reports the, in vivo performance of zinc doped HAp and HAp/collagen composite (HAC) using bone morphogenetic protein-2. It was done for a span of two months on New Zealand rabbit model. After two months postoperatively, there was no marked inflammatory reaction in experimental groups and control groups. The histological images showed well-formed bony matrix with well differentiated haversian system. From the fluorochrome labeling study, it was observed that higher amount of new bone formed in case of bone morphogenetic protein-2 (BMP-2) loaded Zn-HAp (50%) and HAC (27%) specimens than control. The percentage of new bone formation was significantly higher in case of BMP loaded Zn-HAp group than BMP loaded HAC group. From the SEM images similar trend was observed. As the HAC specimen consists of amorphous phase, it had a negative impact on new bone formation.

Clinical Outcome of Hydroxyapatite Coated, Bioactive Glass Coated, and Machined Ti6Al4V Threaded Dental Implant in Human Jaws: A Short-Term Comparative Study.

Introduction:Growing aspect of endosseous implant research is focused on surface modification of dental implants for the purpose of improving osseointegration. The aim of this study was to evaluate and compare the clinical outcome (ie, osseointegration) of hydroxyapatite coated, bioactive glass coated and machined titanium alloy threaded dental implants in human jaw bone after implantation. Materials and Methods:One hundred twenty-six implants (45 hydroxyapatite coated, 41 bioactive glass coated, and 40 machined titanium implants) have been placed in incisor areas of 62 adult patients. Outcome was assessed up to 12 months after prosthetic rehabilitation using different clinical and radiological parameters. Surface roughness of failed implants was analyzed by laser profilometer. Discussion:Hydroxyapatite and bioactive glass coating materials were nontoxic and biocompatible. Least marginal bone loss in radiograph, significantly higher (P < 0.05) interface radiodensity, and less interfacial gaps were observed in computed tomography with bioactive glass coated implants at anterior maxilla compared to other 2 types. Conclusion:Bioactive glass coated implants are equally safe and effective as hydroxyapatite coated and machined titanium implants in achieving osseointegration; therefore, can be effectively used as an alternative coating material for dental implants.

Effect of Zinc Doping on Biological Properties of Biphasic Calcium Phosphate Ceramics in Orthopaedic Animal Model

Addition of dopants in biomaterial has emerged as a vital regulator of bone formation and bone regeneration due to their significant role in the biological processes. We report the effect of zinc ion doping on various properties of biphasic calcium phosphate (BCP) dense body in vitro and in vivo. Zinc (<3 wt%) was successfully incorporated into both calcium hydroxyapatite (HAp) and β-tricalcium phosphate (TCP) via simple wet chemical route. BCP pellets were prepared by mixing HAp and TCP in a definite proportion, compacted and then sintered. The sintered pellets were checked with XRD, FTIR in addition to hardness and fracture toughness. A systematic in vivo study was conducted to evaluate healing of surgically created defects on the femur of rabbit after implantation of doped and undoped dense BCP for 4 months. Characterization of these sintered dense bodies revealed that zinc dopant had marked influence on the physical properties of the dense bodies as well as their mechanical properties. Fluorochrome labelling, histological analysis and radiology were performed post operation after two and four months to study angiogenesis, bone formation and osseous ingrowth. The findings suggested that addition of Zn dopants to the BCP ceramics demonstrated excellent bone formation and that may pave the new insight in bone tissue engineering.

Effect of Annealing on Fracture Toughness Evaluation of Ba0.5Sr0.5Co0.8 Fe0.2O3−δ (BSCF) at Different Temperatures

An experimental study on the fracture toughness of BSCF samples were conducted at room temperature as well as elevated temperatures (upto 800°C). The results showed a typical variation of fracture toughness and fracture stress with temperature. It decreased upto 600°C and then increased to reach a comparatively higher value at 800°C. Without annealing the samples showed comparatively higher fracture toughness because of the presence of compressive residual stress.