A Double-Blind Randomized Controlled Trial (RCT) of Titanium-13Zirconium versus Titanium Grade IV Small-Diameter Bone Level Implants in Edentulous Mandibles - Results from a 1-Year Observation Period

Background: The use of endosseous dental implants has become common practice for the rehabilitation of edentulous patients, and a two-implant overdenture has been recommended as the standard of care. The use of small-diameter implants may extend treatment options and reduce the necessity for bone augmentation. However, the mechanical strength of titanium is limited, so titanium alloys with greater tensile and fatigue strength may be preferable. Purpose: This randomized, controlled, double-blind, multicenter study investigated in a split-mouth model whether small-diameter implants made from Titanium-13Zirconium alloy (TiZr, Roxolid™) perform at least as well as Titanium Grade IV implants. Methods and Materials: Patients with an edentulous mandible received one TiZr and one Ti Grade IV small-diameter bone level implant (3.3 mm, SLActive®) in the interforaminal region. The site distribution was randomized and double-blinded. Outcome measures included change in radiological peri-implant bone level from surgery to 12 months post-insertion (primary), implant survival, success, soft tissue conditions, and safety (secondary). Results: Of 91 treated patients, 87 were available for the 12-month follow-up. Peri-implant bone level change (-0.3 ± 0.5 mm vs -0.3 ± 0.6 mm), plaque, and sulcus bleeding indices were not significantly different between TiZr and Ti Grade IV implants. Implant survival rates were 98.9 percent and 97.8 percent, success rates were 96.6 percent and 94.4 percent, respectively. Nineteen minor and no serious adverse events were related to the study devices. Conclusion: This study confirms that TiZr small-diameter bone level implants provide at least the same outcomes after 12 months as Ti Grade IV bone level implants. The improved mechanical properties of TiZr implants may extend implant therapy to more challenging clinical situations.

[Titanium-alloy vs. CoCr-alloy in removable prosthodontics--a clinical study]

Different types of titanium-alloys instead of CoCr-alloys have been tested as material for the framework of removable partial dentures (RPD). Adequate casting and processing techniques have been developed which enable to fabricate frameworks of complex designs and the problem limits porosity. This opened new possibilities for the use of titanium-alloys with improved properties (E-module). The aim of this study was to summarise the use of titanium in removable prosthodontics and to evaluate prospectively the use of the Ti6A17Nb-alloy for RPDs in a small group of patients. Two identically designed RPDs from CoCr-alloy (remanium GM 800+) and Ti6A17Nb-alloy (girotan L) were produced for ten patients. They had to wear each RPD during six months, first the CoCr-RPD and then the Ti6A17Nb-RPD. A questionnaire (visual analogue scale = VAS) was completed by the patients after one, three and six months of function for each RPD. Prosthetic complications and service needed were recorded. After the end of the entire observation period of twelve months, the patients remained with the Ti6A17Nb-RPD and answered the questionnaire after another six months. All parameters regarding the design of the RPDs were positively estimated by the dentist. Minimal, not significant differences were noted by the patients concerning comfort, stability and retention (VAS). Clinically, no differences in technical aspects or regarding biological complications were observed after six-months periods. The Ti6A17Nb-alloy (girotan L) for the framework of RPDs was judged by patients and professionals to be equivalent to RPDs made from CoCr-alloy. No differences in material aspects could objectively be observed. The Ti6A17Nb-alloy can be beneficial for patients with allergies or incompatibility with one or several components of the CoCr-alloy.

Investigation of the Ti-Al-Cb system as a source of alloys for use at 1200⁰-1800⁰F

"Materials Central, Contract No. AF 33(616)-6125, Project No. 7351."

Titanium and titanium alloy fasteners

"NAI-58-22. Manufacturing Methods Branch, Contract no. AF 33 (600)-30375, Project no. 7-417, Industrial Resources Division, Air Material [!] Command, United States Air Force, Wright-Patterson Air Force Base, Ohio."

Nondestructive testing techniques for titanium billets.

Mode of access: Internet.

Mechanical properties and microstructure of powder metallurgy Ti-xNb-yMo alloys for implant materials

In this study, a series of Ti-xNb-yMo (x = 5-40 wt.% in 5 wt.% increments; and y = 3, 5, 10 wt%) alloys were fabricated by powder metallurgy and studied with respect to their microstructures, compressive mechanical properties and hardness. Increases in Nb and Mo content led to decreases in compressive and yield strengths, elastic modulus and hardness of the sintered alloys. Among the studied alloys, Ti-10Nb-3Mo alloy exhibited the optimum combination of strength and ductility. Alloys with a lower amount of Nb (≤ 25 wt.%) and Mo (≤ 5 wt.%) developed Widmanstätten structure, while further increase in Nb and Mo additions led to the microstructure predominantly consisting of β phase with varying regions of α + β phase. The effects of sintering temperature on elastic modulus and hardness were also investigated for Ti-xNb-3Mo alloys.

Machining of coarse grained and ultra fine grained titanium

Machining of titanium is quite difficult and expensive. Heat generated in the process of cutting does not dissipate quickly, which affects tool life. In the last decade ultra fine grained (UFG) titanium has emerged as an option for substitution for more expensive titanium alloys. Extreme grain refinement can be readily performed by severe plastic deformation techniques. Grain refinement of a material achieved in this way was shown to change its mechanical and physical properties. In the present study, the microstructure evolution and the shear band formation in chips of coarse grained and UFG titanium machined to three different depths and three different feeding rates was investigated. A change in thermal characteristics of commercial purity Ti with grain refinement was studied by comparing heating/cooling measurements with an analytical solution of the heat transfer boundary problem. It was demonstrated that an improvement in the machinability can be expected for UFG titanium. © 2012 Springer Science+Business Media, LLC.

Materials machining study of titanium alloy using a high speed camera

The research aim is to study and analyze the shear zone by application of merchant circle during machining of titanium alloy (Ti6Al4V). The thermo-mechanical reaction during machining plays an important role in defining machinability of titanium alloys. The scientific community is concerned about machining of titanium alloy due to problems occurring in the shear zone that affect tool life. Studying the cutting action contributes to understanding and addressing these problems effectively. For this purpose, an experimental setup, utilizing a high speed camera will be used to study the shear zone. The shear zone characteristics are studied by analyzing the images captured by a high speed camera placed near to the shear zone during machining. The experimental design consists of conducting a series of turning trials using combination of cutting parameters namely constant spindle speed (n) 770 rpm; feed rate (f) of 2 and 4 mm/rev; and depth of cut (d) of 1 and 2 mm. The length of cut (L) of 10 mm remains constant and no coolant is used for all trials. The images obtained from the camera are analyzed against the theory of orthogonal cutting using merchants circle.

In situ preparation and protein delivery of silicate/alginate composite microspheres with core-shell structure

It is predicted that with increased life expectancy in the developed world, there will be a greater demand for synthetic materials to repair or regenerate lost, injured or diseased bone (Hench & Thompson 2010). There are still few synthetic materials having true bone inductivity, which limits their application for bone regeneration, especially in large-size bone defects. To solve this problem, growth factors, such as bone morphogenetic proteins (BMPs), have been incorporated into synthetic materials in order to stimulate de novo bone formation in the center of large-size bone defects. The greatest obstacle with this approach is that the rapid diffusion of the protein from the carrier material, leading to a precipitous loss of bioactivity; the result is often insufficient local induction or failure of bone regeneration (Wei et al. 2007). It is critical that the protein is loaded in the carrier material in conditions which maintains its bioactivity (van de Manakker et al. 2009). For this reason, the efficient loading and controlled release of a protein from a synthetic material has remained a significant challenge. The use of microspheres as protein/drug carriers has received considerable attention in recent years (Lee et al. 2010; Pareta & Edirisinghe 2006; Wu & Zreiqat 2010). Compared to macroporous block scaffolds, the chief advantage of microspheres is their superior protein-delivery properties and ability to fill bone defects with irregular and complex shapes and sizes. Upon implantation, the microspheres are easily conformed to the irregular implant site, and the interstices between the particles provide space for both tissue and vascular ingrowth, which are important for effective and functional bone regeneration (Hsu et al. 1999). Alginates are natural polysaccharides and their production does not have the implicit risk of contamination with allo or xeno-proteins or viruses (Xie et al. 2010). Because alginate is generally cytocompatible, it has been used extensively in medicine, including cell therapy and tissue engineering applications (Tampieri et al. 2005; Xie et al. 2010; Xu et al. 2007). Calcium cross-linked alginate hydrogel is considered a promising material as a delivery matrix for drugs and proteins, since its gel microspheres form readily in aqueous solutions at room temperature, eliminating the need for harsh organic solvents, thereby maintaining the bioactivity of proteins in the process of loading into the microspheres (Jay & Saltzman 2009; Kikuchi et al. 1999). In addition, calcium cross-linked alginate hydrogel is degradable under physiological conditions (Kibat PG et al. 1990; Park K et al. 1993), which makes alginate stand out as an attractive candidate material for the protein carrier and bone regeneration (Hosoya et al. 2004; Matsuno et al. 2008; Turco et al. 2009). However, the major disadvantages of alginate microspheres is their low loading efficiency and also rapid release of proteins due to the mesh-like networks of the gel (Halder et al. 2005). Previous studies have shown that a core-shell structure in drug/protein carriers can overcome the issues of limited loading efficiencies and rapid release of drug or protein (Chang et al. 2010; Molvinger et al. 2004; Soppimath et al. 2007). We therefore hypothesized that introducing a core-shell structure into the alginate microspheres could solve the shortcomings of the pure alginate. Calcium silicate (CS) has been tested as a biodegradable biomaterial for bone tissue regeneration. CS is capable of inducing bone-like apatite formation in simulated body fluid (SBF) and its apatite-formation rate in SBF is faster than that of Bioglass® and A-W glass-ceramics (De Aza et al. 2000; Siriphannon et al. 2002). Titanium alloys plasma-spray coated with CS have excellent in vivo bioactivity (Xue et al. 2005) and porous CS scaffolds have enhanced in vivo bone formation ability compared to porous β-tricalcium phosphate ceramics (Xu et al. 2008). In light of the many advantages of this material, we decided to prepare CS/alginate composite microspheres by combining a CS shell with an alginate core to improve their protein delivery and mineralization for potential protein delivery and bone repair applications

The effect of crack closure on the grain size dependence of fatigue crack growth threshold

Recent studies (I-7) clearly indicate a strong dependence of fatigue threshold parameter, A K on grain size in several alloy systems. Attempts to explain these observations on the basis of crat~tortuosity (1,8), fracture surface roughness (5,9) and crack closure (6) appear to present a fairly clear picture of the mechanisms that cause a reduction in crack growth rates at threshold. In general, it has been shown that coarse grained microstructures exhibit higher fatigue threshold in low carbon steels (1,5) aluminium alloys (7) and titanium alloys (6). In spite of these observations, there exists (10-1#) considerable uncertainity about the manner in which the AK~L depends on prior austenitic grain size in quenched and tempered steels. Studies in quenched and tempered steels demonstrating both an increase (3,12,14) as well as a decrease (11,12) in AKth with an increase in prior austenitic grain size can be sought to illustrate this point. Occasionally , the absence of any sensitivity of AKth to the variations in prior austenitJc grain size has also been reported (11,13). While a few investigators (5-7) comfortably rationalised the grain size effects on AK~L on the basis of crack closure by a comparison in terms of the closure-free component of the thresho~Ifc~, AK -f such an approach has yet to be extended to high strength steels, An attempt has been made in t~et ,pthrg sent study to explai. n the effect of pri, or austeniti.c grain size on &Kth on the basis of crack closure measurements in a high strength steel.

A fluctuation-based probe to athermal phase transitions

We focus on athermal phase transitions where in discrete and dissipative avalanches are observed in physical observables as the system jumps from one metastable state to another, when driven by an external field. Using higher order statistics of time dependent avalanches, or noise, in electrical resistivity during temperature-driven martensite transformation in thin nickel-titanium films, we demonstrate evidence suggesting the existence of a singular `global instability' or divergence of the correlation length as a function of temperature at the transition. These results not only establish a mapping of non-equilibrium first order phase transition and equilibrium critical phenomena, but perhaps also call for a re-evaluation of many existing experimental claims of self-organized criticality.

Processing Response of Boron Modified Ti-6Al-4V Alloy In (alpha plus beta) Working Regime

Titanium alloys like Ti-6A-4V are the backbone materials for aerospace, energy and chemical industries. Hypoeutectic boron addition to Ti-6Al-4V alloy produces a reduction in as-cast grain size by roughly an order of magnitude resulting in the possibility of avoiding ingot breakdown step and thereby reducing the processing cost. In the present study, ISM processed as-cast boron added Ti-6Al-4V alloy is deformed in (alpha+beta)-phase field, where alpha-lath bending seemed to be the dominating deformation mechanism.