Advanced Materials in Dental and Orthopedic Applications: Session II
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Biomaterials Committee
Program Organizers: Tolou Shokuhfar, University of Illinois at Chicago; Grant Crawford, South Dakota School of Mines and Technology; Terry Lowe, Colorado School of Mines; Luis Rocha, UNESP, Univ. Estadual Paulista, Faculdade de Ciências; Rajendra Kasinath, DePuy Synthes Products, LLC

Monday 2:00 PM
February 27, 2017
Room: Pacific 14
Location: Marriott Marquis Hotel

Session Chair: Holly Martin, Youngstown State University; Tolou Shokuhfar, University of Illinois at Chicago; Terry Lowe, Colorado School of Mines

2:00 PM  Invited
Rapid Mechanical Assessment of Dental Materials for the Mitigation of Cracks in Natural Teeth: Shweta Bhatnegar1; Cherilyn Sheets2; James Earthman1; 1University of California, Irvine; 2Newport Coast Oral Facial Institute
    Rapid mechanical diagnostics (RMDx) has demonstrated the ability for detecting and characterizing the severity of cracks in natural teeth. RMDx was used to determine the efficacy of resin-based and glass-ionomer sealants, and a flowable composite that were injected into cracks in extracted natural teeth. Each tooth sample was mounted in a simulated ligament/bone complex prior to RMDx testing before and after application of each material into the cracks. The results indicate that mitigation of cracks in natural teeth is possible and that the flowable composite exhibits the best results of the three materials evaluated so far. It is also evident that RMDx will be critically needed for the development of new materials for crack mitigation in dentistry.

2:30 PM  Cancelled
Orthopedic Implants with Graded Mechanical Behavior Made from Metastable Beta Ti Alloys: Rubens Caram1; Eder Lopes1; 1University of Campinas
    Femoral stems for total hip arthroplasty are generally made from Ti alloys due to high biocompatibility and low elastic modulus. While less rigid stems reduce bone stress shielding, they also lead to micromotions at the bone/implant interface. A challenge is then to develop a stem design that addresses both restrictions simultaneously. As the elastic modulus of beta Ti alloys can be manipulated by heat treatments, this work aims to introduce a new concept for a femoral stem with a graded elastic modulus using metastable beta Ti alloy. The use of aging heat treatments allows the mechanical behavior of the metastable beta Ti alloys to be tailored and, in particular, be used to construct a graded elastic modulus stem. The results revealed that it is feasible to design implants with hybrid mechanical behavior. A stem with an elastic modulus varying from 65 GPa to 110 GPa was obtained.

2:50 PM  
Preparation and Characterizations of Nano Composites Based on Biphasic Mixture of Bioactive Ceramics for Biomedical Applications: Nida Iqbal1; Muhammad Abdul Rafiq1; 1Universiti Teknologi Malaysia
    Bioactive bioceramics have been developed to promote aregeneration of bones.Among all these hydroxyapatite is the most commonly used for clinical applications due to its similarity to inorganic mineral component of bone. However, clinical application of HA is limited due to its slow rate of biodegradation which results a very slow osseointegration rate and requires the long-term stability of implants in bony tissue. Therefore, in this study, two-phaseHA/TCP ceramics was developed. Firstly, separate syntheses of HA and TCP via microwave irradiation and physical mixing of component powders in specified ratios followed by sintering was developed. The crystalline phase,chemical composition, and morphology of the prepared samples werecharacterized using (XRD) (FTIR), (EDX), and (SEM). The chemical analysis indicated the presence of a calcium phasphates phases. Scanning electron microscopy analysis showed a spheroid-like morphology. These findings suggested that two-phase HA/TCP ceramics could potentially be used for bone regeneration applications.

3:10 PM  
Repelling Biofilm Formation on Dental Materials via Piezoelectric Fillers: Santiago Orrego1; Anna Pizzano1; Kavan Hazeli2; Mary Anne Melo3; 1Johns Hopkins University; 2The University of Alabama in Huntsville; 3University of Maryland School of Dentistry
    Oral bacteria form biofilms on hard tooth surfaces and dental materials which posses threat on the structure's integrity. Current solutions to prevent biofilm formation are using bioactive resin-based dental materials incorporating anti-bacterial agents such as nanoparticles of silver (NAg), quaternary ammonium dimethacrylate (QADM), and nanoparticles of amorphous calcium phosphate (NACP). In this study, we propose a novel approach to repel the formation of biofilm by incorporating piezoelectric nanoparticles in a resin-composite dental material system. The oral biofilm viability was monitored by the live-dead assay to reveal the repelling action and mechanical evaluation was carried out. Results indicate that the piezoelectric nanoparticles prevented the formation of the biofilm without affecting the mechanical properties of the resin-composite system. The novel method of combining piezoelectric agents may have wide applicability to other adhesives for caries inhibition.

3:30 PM Break

3:50 PM  
Surface Modified Drug Releasing Total Hip Implant: R. Manoj Kumar1; Pallavi Gupta1; Partha Roy1; Debrupa Lahiri1; 1Indian Institute of Technology Roorkee
    Despite sterilization and aseptic procedure, bacterial infection remains a key challenge in total hip arthroplasties. This fact emphasizes urgent need for developing new implant systems, which should release drug in a controlled manner without sparing its mechanical and tribological properties. Currently available means for loading and releasing drug are not as effective, as the release is either for too short period or there is a problem with mechanical integrity and osteointegration on drug releasing surfaces. In the present study, we are aiming to modifying different parts of total hip implant to load drug and get it released for longer time. We have taken the inner lining of acetabular cup and femoral stem surface as the regions to load drug. We have also developed techniques to modify these surfaces and load drug in a way to release for longer time, but without affecting mechanical, tribological and biological behavior of the surface.

4:10 PM  
Tailoring of the Mechanical Properties of Alloys of the Ti-Zr-Mo System through Alloying and Heat Treatments: Caio Xavier1; Carlos Grandini1; Luis Rocha1; 1UNESP
    Titanium and its alloys are widely used as biomaterials. This study provides a detailed study of the effect of the chemical composition and heat treatment conditions in alloys belonging to the Ti15ZrxMo system. The aim is to optimize the mechanical properties of the alloys for use in orthopedic implants systems. The alloys were melted in an arc voltaic furnace, with four different alloys compositions: Ti-15Zr, Ti-15Zr-5Mo, Ti-15Zr-10Mo and Ti-15Zr-15Mo, allowing samples to be obtained with α, α+β and β phase microstructures. The heat treatments conditions were 600ºC/6h, 12h and 24h, 900ºC/8h and 1000ºC/8h. For the as cast alloys, in the Ti-15Zr it was only possible to observe the presence of a lamellar structure composed of α phase, the Ti-15Zr-5Mo shown a microstructure of β phase matrix with fine needle of α phases at the grain boundaries. The Ti-15Zr-10Mo and Ti-15Zr-15Mo alloys showed only beta type grain boundary. Consequently, the hardness of the materials increased with the raise of the amount of Mo in the alloys, while the elastic modulus decreases. Also, it was observed that the mechanical properties of the β alloys can be tailored by heat treatment, essentially when it is carried out at 600°C (Financial support: CAPES, CNPQ FAPESP).

4:30 PM  
The Effects of Inclusions on the Fatigue Performance of Superelastic Nitinol Fine Wires: Janet Gbur1; John Lewandowski1; 1Case Western Reserve University
    Advances in minimally invasive surgeries and miniaturization of medical devices place a greater demand on materials for biomedical applications. In particular, the use of fine wires/strands in various devices and tools produce enhanced performance requirements from small cross-sections of material. Successful implementation requires a better understanding of the relationships between material composition and processing to the fatigue and fracture behavior. Small wire diameters also provide challenges to material characterization, testing and evaluation. In this study, the effects of inclusions on the fatigue and fracture behavior of fine, superelastic Nitinol wires are investigated. Wire samples were examined via optical metallography and SEM techniques. Cyclic lifetime was evaluated in flex bending fatigue and rotating bending fatigue, followed by SEM analysis of fracture surfaces. The effects of material microcleanliness on the tension and fatigue performance will be summarized.

4:50 PM  
Thermomechanical Processing of Beta-Ti Alloys for Load-bearing Implant Applications: Stefan Pilz1; André Reck2; Mariana Calin1; Jens Freudenberger1; Martina Zimmermann2; Jürgen Eckert3; Annett Gebert1; 1Leibniz Institute for Solid State and Materials Research Dresden, Dresden, Germany; 2Institute of Materials Science, Dresden University of Technology, Dresden, Germany; 3Department Materials Physics, Montanuniversität Leoben, Leoben, Austria
     Beta-Ti alloys based on the Ti-Nb system are promising candidates to replace alpha and alpha+beta alloys in the field of load-bearing bone implants, because of their superior properties, such as a low Young’s modulus and good biocompatibility. One goal is to further improve their mechanical properties towards higher static and dynamic strength. The focus of this work is to investigate the influence of different thermomechanical processing routes on the microstructure and mechanical properties for the beta Ti-40Nb alloy. SEM, EBSD and XRD are used to analyze the effect of different cold-rolling and annealing steps on the evolution of phase composition, texture and grain structure. The mechanical properties are characterized using microhardness, tensile and fatigue tests. Grain refinement, e.g., leads to an increase of the yield strength of 35 %, compared to the solution treated state. This work is funded by the DFG as part of SFB/Transregio 79.

5:10 PM  
Microstructures and Properties of Mg AZ Alloys Subject to High Shear Deformation: Casey Davis1; Jacob Edick2; Terry Lowe1; 1Colorado School of Mines; 2Boston Scientific Corporation
    High Shear Deformation (HSD) via a proprietary severe plastic deformation (SPD) process was applied to achieve ultrafine grained microstructures in MgAlZn alloys for medical applications. Because of the fine scale of structures present Transmission Kikuchi Diffraction (TKD) was used to reveal micro-scale textures and grain structures. We show that ECAP-C results in grain sizes less than 200 nm. By imposing specific strain paths and temperature histories grain size, texture, twinning, dislocation density, and precipitate size distributions were controlled to establish relationships between strength, ductility, and corrosion resistance.