A quantitative comparison of machined commercially pure titanium and titanium-aluminum-vanadium implants in rabbit bone

BACKGROUND: Grass group I consists of very potent allergenic components which are found in the pollen of all temperate grasses. Several post-translational modifications are predicted from the cDNA data. OBJECTIVE: The aim of this study was to identify sequential IgE-binding sites on the allergen Phl p 1 and to determine their influence on IgE reactivity. METHODS: Based on cDNA data and microsequencing results we synthesized overlapping decapeptides covering the complete Phl p 1 molecule and tested them for immunological reactivity by means of the PEPSCAN technique. In a dot test we determined the frequency of IgE reactivities to post-translationally modified structures (hydroxylated proline residues, carbohydrate structure, and disulphide formations). RESULTS: Screening by overlapping peptides demonstrated an IgE binding site on the 10 N-terminal amino acids. Comprehensive studies showed that the two hydroxyproline residues of the native Phl p 1 allergen (at positions 5 and 8) and the N-glycan (at position 9) can result in an increased IgE reactivity; 3.3% of the sera exclusively bound to the hydroxyproline bearing peptide, while only 0.4% bound to the proline containing peptide. With regard to glycosylation, we estimated that 20% of sera recognized protein and carbohydrate epitopes, while one serum exclusively bound to the glycan. The formation of disulphide bonds has no detectable effect on the IgE reactivity to Phl p 1. CONCLUSION: Our results indicate that the post-translational modifications, the carbohydrate structure and the hydroxylation of proline residues, can enhance the IgE reactivity of Phl p 1.     

Deformation and recrystallisation of powder processed commercially pure titanium

Abstract

The hot deformation behaviour of powder sintered commercially pure titanium has been compared to the behaviour of equivalent wrought metal under identical test conditions. Deformation was performed by uniaxial compression under vacuum at 900°C at nominal strains of 0·2, 0·4 and 0·65. The deformed microstructures were rapidly cooled to room temperature and subsequently annealed at 870°C. Lower grain growth, higher flow stress and greater incidence of recrystallisation were observed for the sintered metal. This behaviour is mainly attributed to the higher interstitial levels in the sintered metal which results in a lowering of the effective deformation temperature.     

ECAP of commercially pure titanium: A review

Equal Channel Angular Extrusion (ECAE) also called as Equal Channel Angular Pressing (ECAP) is an emerging mechanical or thermo mechanical method for synthesis of bulk ultra fine grained or nano materials. The uniqueness of ECAP is that the fine grains are obtained without changing any of the dimensions of the sample. The grain refinement increases the strength of CP-Ti to the strength levels of Ti-6Al-4V, a commonly used material for bio implants. Though Ti-6Al-4V alloys satisfy the biomedical requirements, the Al and V are toxic to human tissue. ECAP is an attracting technique for strengthening commercially pure titanium (CP-Ti) to a level of Ti-6Al-4V since CP-Ti has better compatibility for bio medical applications. Hence, the research is focused on ECAP of CPTi. This overview mainly focuses on the mechanical properties, corrosion resistance, wear resistance, fatigue resistance and the influence of external and internal parameters on the properties of ECAPed CP-Ti. It also highlights the methods employed for increasing the deformability of CP-Ti. Finally, the suitability of ECAP for industrial production is also discussed. The state of the art in this field is encouraging and showing positive signs of commercializing ECAP of CP-Ti in the near future.     

Effects of guided bone regeneration around commercially pure titanium and hydroxyapatite-coated dental implants. II. Histologic analysis

The purpose of this study was to determine which treatment of a large osseous defect adjacent to an endosseous dental implant would produce the greatest regeneration of bone and degree of osseointegration: barrier membrane therapy plus demineralized freeze-dried bone allograft (DFDBA), membrane therapy alone, or no treatment. The current study histologically assessed changes in bone within the healed peri-implant osseous defect. In a split-mouth design, 6 implants were placed in edentulous mandibular ridges of 10 mongrel dogs after preparation of 6 cylindrical mid-crestal defects, 5 mm in depth, and 9.525 mm in diameter. An implant site was then prepared in the center of each defect to a depth of 5 mm beyond the apical extent of the defect. One mandibular quadrant received three commercially pure titanium (Ti) screw implants (3.75 x 10 mm), while the contralateral side received three hydroxyapatite (HA) coated root-form implants (3.3 x 10 mm). Consequently, the coronal 5 mm of each implant was surrounded by a circumferential defect approximately 3 mm wide and 5 mm deep. The three dental implants in each quadrant received either DFDBA (canine source) and an expanded polytetrafluoroethylene membrane (ePTFE), ePTFE membrane alone, or no treatment which served as the control. Clinically, the greatest increase in ridge height and width was seen with DFDBA/ePTFE. Histologically, statistically significant differences in defect osseointegration were seen between treatment groups (P < 0.0001: DFDBA/ePTFE > ePTFE alone > control). HA-coated implants had significantly greater osseointegration within the defect than Ti implants (P < 0.0001). Average trabeculation of newly formed bone in the defect after healing was significantly greater for HA-coated implants than for titanium (P < 0.0001), while the effect on trabeculation between treatments was not significantly different (P = 0.14). Finally, there were significantly less residual allograft particles in defect areas adjacent to HA-coated implants than Ti implants (P = 0.0355). The use of HA-coated implants in large size defects with DFDBA and ePTFE membranes produced significantly more osseointegration histologically than other treatment options and more than Ti implants with the same treatment combinations. The results of this study indicate that, although the implants appeared osseointegrated clinically after 4 months of healing, histologic data suggest that selection of both the implant type and the treatment modality is important in obtaining optimum osseointegration in large size defects.     

Microstructural and mechanical assessment of transient liquid phase bonded commercially pure titanium

Diffusion joining of commercially pure titanium was successfully prepared via transient liquid phase bonding in vacuum environment. The process was carried out using AMS 4772 silver-based filler alloy at 900–1000°C for various holding time under the vacuum of 6?×?10^?7?Torr. Optical and scanning electron microscopy equipped with an EDS analyzer was conducted for microstructural evaluations. Mechanical properties were also investigated by shear test, fractographic assessment and X-ray diffraction analyses. The tendency to achieve isothermally solidified joint increased by increasing bonding time. No sign of athermal solidification was detected of sample bonded at 1000°C for 90?min. Consequently, the bonding condition of a high quality joint was obtained. Elemental analyses revealed that filler alloy’s elements (Ag, Cu) distributed more uniformly in fully isothermal solidified bond, whereas the aggregation of these elements is considerable in athermally solidified bond. Shear test results represented that the highest shear strength attributed to the sample bonded in isothermal solidified condition (bonded at 1000°C for 90?min).     

Functional adaptation and ingrowth of bone vary as a function of hip implant stiffness

The purpose of the present study was to test the hypothesis that cortical bone loss, trabecular bone density and the amount of bone ingrowth vary as a function of stem stiffness in a canine cementless hip replacement model. The study was motivated by the problem of cortical bone atrophy in the proximal femur following cementless total hip replacement. Two stem stiffnesses were used and both designs were identical in external geometry and porous coating placement. The high stiffness stem caused approximately 26% cortical bone stress-shielding and the low stiffness stem caused approximately 7.5% stress-shielding, as assessed by beam theory. Each group included nine adult, male canines who received unilateral arthroplasties for a period of six months. The animals with the low stiffness stems tended to lose less proximal cortical bone than the animals with high stiffness stems (4% +/- 9 as opposed to 11% +/- 14), but the difference was not statistically significant (p = 0.251). However, the patterns of bone ingrowth into the implant and change in medullary bone density adjacent to the implant were fundamentally different as a function of stem stiffness (p < 0.01). Most importantly, while the high stiffness group had peaks in these variables at the distal end of the stem, the low stiffness group had peak values proximally. These different patterns of functional adaptation are consistent with the idea that reduced stem stiffness enhances proximal load transfer.     

Fatigue fracture of the welded joints of commercially pure titanium after thermal cycling

The results of investigation are given on the structural state and variation of mechanical properties characteristic of welded joints of commercially pure titanium subjected to static and cyclic loading after thermal-cycling treatment (TCT). On the basis of the pattern of variation in relative specimen deflection, fatigue-damage growth is estimated quantitatively for specimens cyclically deformed to the point where initiation and propagation of a main crack begins.     

工业纯钛TA2热变形过程的流变行为本构方程

利用Gleeble-3800热模拟实验机研究了工业纯钛TA2的热变形行为.变形温度为750~1000℃,步长50℃,应变速率分别为0.01、0.1、1和10 s^-1.实验结果表明,TA2在热压缩变形过程中发生了加工硬化以及动态回复、动态再结晶.随着变形温度的降低和应变速率的增加,流变应力逐渐增加.为了准确预测TA2的高温流变行为,基于实验数据和双曲正弦Arrhenius模型构建了考虑应变影响的本构方程,本构方程中材料常数α、n、Q、lnA与应变之间存在6阶多项式关系.本文所提出考虑应变影响的本构方程可以用于研究工业纯钛TA2的高温流变行为.     

Carpal bone titanium implant arthroplasty. 10 years' experience

In 1984, in an effort to address the silicone wear particle problem, titanium implants were developed for the scaphoid, lunate, and trapeziometacarpal joint. The design of these implants closely resembled their silicone counterparts, though some modifications were made to accommodate the properties of unalloyed titanium and enhance their stability. Carpal bone implants act as articulating spacers to help maintain the relationship of adjacent carpal bones after local resection procedures. Their use allows carpal stabilization procedures and provides functional mobility with good strength and pain relief. Their surgical application began in 1985. The 10-year clinical experience seems very promising to date.     

Corrosion resistance of laser nitrided commercially pure titanium and Ti-13Nb-13Zr biomedical alloys

C.P. Titanium and Ti-13Nb-13Zr alloys are widely used in biomedical applications as dental and orthopedic implants. However these materials are vulnerable to Surface corrosion. The aim of this investigation is to enhance the corrosion resistance of the above alloys through laser nitriding technique. Laser nitriding was performed using Nd: YAG laser. The Electrochemical properties of nitrided layer will be investigated in simulated body solution using potentiodynamic polarization technique. The results will be compared with those obtained on untreated alloys tested in same conditions. The laser nitrided and the corroded samples will also be characterized using XRD and SEM. The enhancement of wear resistance of the above samples will also be presented in this paper.     

Deformation and recrystallization textures in commercially pure aluminum

The deformation and recrystallization textures of commercially pure aluminum (99.6 pct) containing large intermetallic particles (FeAl₃) are measured by neutron diffraction, and the orientation distribution functions (ODF’s) are calculated. Sample parameters are the initial grain size (50 and 350 μm) and the degree of deformation (15 to 95 pct reduction in thickness by cold-rolling). The textural results are compared with microstructural observations and good correlations are found. The intermetallic particles may act as nucleation sites giving nuclei with a wide spread of orientations. Thereby the particles can have a randomizing effect on the textural development during recrystallization. In specimens deformed at medium degrees of deformation the randomizing effect of particles is maximum. At lower and higher degrees of deformation the effect of particles is less as other nucleation sites become more effective. In general, the randomizing effect of particles is limited due to a low growth rate of nuclei of random orientation compared with nuclei of other orientations.     

Microstructural characterization of warm-worked commercially pure aluminum

The deformation microstructures of commercially pure aluminum deformed by plane strain compression to 50 pct thickenss reduction at temperatures between 100 °C and 300 °C, under two strain rates, 5×10⁻² s⁻¹ and 5×10⁻⁴ s⁻¹, have been characterized by transmission electron microscopy. As the deformation temperature increases, the deformation microstructure gradually changes from a checkerboard pattern into an equiaxed subgrain structure with increasing subgrain size. The fraction of geometrically necessary boundaries (GNBs) found in warm-worked aluminum is much less than that found at room temperature. The average misorientation of dislocation boundaries appears to be independent of deformation temperature and strain rate. The constancy of the average misorientations is a combined effect of the variation of the fractions of GNBs and incidental dislocation boundaries (IDBs) and the variation of the average misorientations of GNBs and IDBs. Scaling theory can apply to both boundary misorientations and subgrain sizes that formed at different temperatures and strain rates. Subgrain size distributions for different temperatures and strain rates all resemble a lognormal distribution.     

Microstructural characterization of warm-worked commercially pure aluminum

The deformation microstructures of commercially pure aluminum deformed by plane strain compression to 50 pct thickenss reduction at temperatures between 100 °C and 300 °C, under two strain rates, 5×10⁻² s⁻¹ and 5×10⁻⁴ s⁻¹, have been characterized by transmission electron microscopy. As the deformation temperature increases, the deformation microstructure gradually changes from a checkerboard pattern into an equiaxed subgrain structure with increasing subgrain size. The fraction of geometrically necessary boundaries (GNBs) found in warm-worked aluminum is much less than that found at room temperature. The average misorientation of dislocation boundaries appears to be independent of deformation temperature and strain rate. The constancy of the average misorientations is a combined effect of the variation of the fractions of GNBs and incidental dislocation boundaries (IDBs) and the variation of the average misorientations of GNBs and IDBs. Scaling theory can apply to both boundary misorientations and subgrain sizes that formed at different temperatures and strain rates. Subgrain size distributions for different temperatures and strain rates all resemble a lognormal distribution.     

Microstructural characterization of warm-worked commercially pure aluminum

The deformation microstructures of commercially pure aluminum deformed by plane strain compression to 50 pct thickness reduction at temperatures between 100 °C and 300 °C, under two strain rates, 5 × 10⁻² s⁻¹ and 5 × 10⁻⁴ s⁻¹, have been characterized by transmission electron microscopy. As the deformation temperature increases, the deformation microstructure gradually changes from a checkerboard pattern into an equiaxed subgrain structure with increasing subgrain size. The fraction of geometrically necessary boundaries (GNBs) found in warm-worked aluminum is much less than that found at room temperature. The average misorientation of dislocation boundaries appears to be independent of deformation temperature and strain rate. The constancy of the average misorientations is a combined effect of the variation of the fractions of GNBs and incidental dislocation boundaries (IDBs) and the variation of the average misorientations of GNBs and IDBs. Scaling theory can apply to both boundary misorientations and subgrain sizes that formed at different temperatures and strain rates. Subgrain size distributions for different temperatures and strain rates all resemble a lognormal distribution.     

Bone ingrowth to implant surfaces in an inflammatory arthritis model

Many studies have shown enhanced bone apposition to implants coated with hydroxyapatite, but the optimum implant texture, especially in abnormal trabecular bone, is unclear. The purpose of this project was to evaluate the histological and mechanical properties of cylindrical implants with three different surface textures that were placed in the cancellous bone of the distal femur of the rabbit after the production of an inflammatory knee arthritis. The three implant surfaces included a beaded surface (Group A), a beaded surface coated with hydroxyapatite (Group B), and a smooth surface coated with hydroxyapatite (Group C). The right knees of 36 rabbits were injected with carrageenan twice a week for 2 weeks. Then bilateral implantations were performed, with 12 rabbits in each group receiving identical implants in the right and left knees. The rabbits were killed 6 weeks after surgery. Mechanical (push-out test) and histomorphometric analyses were performed to determine the quality and quantity of bone ingrowth. In Group A, there was virtually no direct contact (a 20-60-microm clearance) between the bone and the beaded surfaces. Direct contact between the bone and the implant surfaces was seen in Groups B and C. The thickness and number of trabeculae were smaller on the arthritic side than on the control side for all groups but were not different between groups for either the control or the arthritic side. Mechanical testing showed that the shear strength of the interface was weaker on the arthritic side in all groups. The results suggest that inflammatory arthritis induced by carrageenan may influence the quality of local bone (osteopenic changes) and hence compromise the bone apposition and mechanical stability of the interface between the implant and bone.     

Surface layer of commercially pure VT1-0 titanium after electric-explosion alloying and subsequent treatment by a high-intensity pulsed electron beam

The structure, phase composition, and mechanical, tribological, and corrosional properties of commercially pure VT1-0 titanium are investigated after electric-explosion alloying and subsequent treatment by a high-intensity pulsed electron beam. Treatment conditions that greatly increase the properties of the titanium are identified. The physical factors at work here are considered.