Micro + Nano: Conserving the Gold Standard Microroughness to Nanoengineer Zirconium Dental Implants

Zirconium has achieved popularity as a biomaterial for dental and orthopedic implants; however, its bioinertness can compromise implant-tissue integration, especially in compromised patient conditions. More recently, various nanoengineering strategies have been explored to enhance the bioactivity of Ti-based implants; however, nanoengineering of Zr-based implants has not been adequately explored. In this pioneering attempt, we report on the optimized fabrication of various nanostructures on microrough Zr surfaces and explore the influence of the underlying surface topography. In-depth optimization of electrochemical anodization (EA) is performed by tuning various parameters, including substrate topography, voltage/current and time, onto microrough (micromachined) and extremely rough Zr substrates, which represent clinically relevant implant surfaces. Variations of EA factors yielded various nanotopographies, including nanotubes, nanograss and nanotemplates, offering different topographical and chemical combinations. EA optimization and precise current-voltage recording was performed to arrive at clinically translatable and reproducible nanostructures on Zr surfaces. This study will pave the way toward the fabrication of the next generation of nanoengineered Zr-based orthopedic and dental implants.

Titanium-Tissue Interface Reaction and Its Control With Surface Treatment

Titanium (Ti) and its alloys are widely used for medical and dental implant devices-artificial joints, bone fixators, spinal fixators, dental implant, etc. -because they show excellent corrosion resistance and good hard-tissue compatibility (bone formation and bone bonding ability). Osseointegration is the first requirement of the interface structure between titanium and bone tissue. This concept of osseointegration was immediately spread to dental-materials researchers worldwide to show the advantages of titanium as an implant material compared with other metals. Since the concept of osseointegration was developed, the cause of osseointegration has been actively investigated. The surface chemical state, adsorption characteristics of protein, and bone tissue formation process have also been evaluated. To accelerate osseointegration, roughened and porous surfaces are effective. HA and TiO2 coatings prepared by plasma spray and an electrochemical technique, as well as alkalinization of the surface, are also effective to improve hard-tissue compatibility. Various immobilization techniques for biofunctional molecules have been developed for bone formation and prevention of platelet and bacteria adhesion. These techniques make it possible to apply Ti to a scaffold of tissue engineering. The elucidation of the mechanism of the excellent biocompatibility of Ti can provide a shorter way to develop optimal surfaces. This review should enhance the understanding of the properties and biocompatibility of Ti and highlight the significance of surface treatment.

Corrosion of Al2O3-Ti composites under inflammatory condition in simulated physiological solution

Alumina-titanium composites have shown good mechanical properties which makes them promising for orthopedic applications. The placement of an orthopedic implant involves an invasive procedure which stimulates a localized inflammatory response causing an acidic environment around the implant. This makes the study on corrosion more critical. Therefore, the aim of the present paper was to study the corrosion behavior of the composites with 75 vol% and 50 vol% Ti content (with alumina balance) fabricated by Spark Plasma Sintering under acidic condition representing inflammation and in two elapsed times (1 h and 1-day) using polarization and electrochemical impedance spectroscopy tests. For comparison, the experiments were also conducted in normal physiological solution after 1 h, and pure Ti (100vol%Ti) was fabricated by the same process and analyzed, similarly. Furthermore, behavior of the samples was studied after 48 days of immersion in the acidic and normal solutions using SEM, ATR-FTIR, AFM, and ICP-OES. The results of corrosion tests showed very good passivation behavior of 100vol%Ti and the composite containing 75vol.%Ti. The superiority of the 75vol.%Ti composite in corrosion characteristics in both solutions was also found. Its corrosion resistance was 20.3 MΩcm² under the inflammatory condition after 1-day, which was 39% higher than that of 100vol.%Ti under the same condition. The results of SEM indicated both corroded and mineral deposition zones on all materials' surfaces and the ATR-FTIR results revealed additional adsorbed bands related to water adsorption, OH and carbonate groups after immersion. The AFM analysis showed rougher morphology, particularly for 75 vol% Ti where the Rq was increased about 50 nm, and the ICP-OES results indicated 65.87% and 61.94% deposition of solution calcium on 75vol.%Ti and 50vol.%Ti, respectively. The acidic/inflammatory condition influenced the corrosion processes of all materials. Lower pH caused the passivation to occur sooner and the corrosion resistance to be higher.

Development of Ti-Nb-Zr alloys with high elastic admissible strain for temporary orthopedic devices

A new series of beta Ti-Nb-Zr (TNZ) alloys with considerable plastic deformation ability during compression test, high elastic admissible strain, and excellent cytocompatibility have been developed for removable bone tissue implant applications. TNZ alloys with nominal compositions of Ti-34Nb-25Zr, Ti-30Nb-32Zr, Ti-28Nb-35.4Zr and Ti-24.8Nb-40.7Zr (wt.% hereafter) were fabricated using the cold-crucible levitation technique, and the effects of alloying element content on their microstructures, mechanical properties (tensile strength, yield strength, compressive yield strength, Young's modulus, elastic energy, toughness, and micro-hardness), and cytocompatibilities were investigated and compared. Microstructural examinations revealed that the TNZ alloys consisted of β phase. The alloy samples displayed excellent ductility with no cracking, or fracturing during compression tests. Their tensile strength, Young's modulus, elongation at rupture, and elastic admissible strain were measured in the ranges of 704-839 MPa, 62-65 GPa, 9.9-14.8% and 1.08-1.31%, respectively. The tensile strength, Young's modulus and elongation at rupture of the Ti-34Nb-25Zr alloy were measured as 839 ± 31.8 MPa, 62 ± 3.6 GPa, and 14.8 ± 1.6%, respectively; this alloy exhibited the elastic admissible strain of approximately 1.31%. Cytocompatibility tests indicated that the cell viability ratios (CVR) of the alloys are greater than those of the control group; thus the TNZ alloys possess excellent cytocompatibility.