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PubMedDate not supplied

A prospective clinical study in humans of an endosseous dental implant partially covered with a powder-sintered porous coating: 3- to 4-year results.

A dental implant covered partially with a porous coating (EndoPore) developed at the University of Toronto was tested. This new implant is a tapered, truncated-cone endosseous root-form implant fabricated from Ti-6Al-4V. It utilizes a powder-sintered porous surface geometry over most of its length to promote three-dimensional bone ingrowth and implant stabilization. In this trial, three implants were placed in the anterior mandibles of 52 patients and were used subsequently as free-standing units to support an overdenture. Much shorter implants, shorter initial healing periods, and simpler surgical techniques than are customary with other implant designs were used. At the time of this report, all patients with implants had passed 3 years of function, and the cumulative implant success rate was 94.8%. Analysis of carefully standardized radiographs revealed a pattern of crestal bone loss similar to earlier published dog data. On a yearly basis, the mean bone loss was 0.43 mm in year 1, 0.17 mm in year 2, and 0.13 mm in year 3.

Adult↗

PubMed1989

Comparison of titanium-tantalum and titanium-niobium alloys for application as dental implants.

For the diffusion bonding of Ti alloys to alumina, materials with a similar thermal expansion coefficient to alumina are required. Such materials were developed by alloying the biocompatible elements Ta and Nb to titanium (Ti-Ta30 and Ti-Ta40, Ti-Nb40 and Ti-Nb50). While measuring the corrosion behavior of these alloys in 0.9% saline solution, no difference could be observed. The Ti-Ta alloys are superior in their mechanical properties to Ti-Nb alloys.

Biocompatible Materials↗

PubMed1998

Intervertebral spacer as an adjunct to anterior lumbar fusion. Part II. Six-month implantation in baboons.

Failure of interbody fusions in the lumbar spine are common due to reliance on the graft for structural support during healing by creeping substitution. Support of the interspace with an implant should result in improved fusion success. The objective of this study was to evaluate the stability of the implant in vivo and its potential as an adjunct to promote interbody arthrodesis. Prototype 3, a porous coated intervertebral spacer with extension lugs made of Ti-6A1-4V, was implanted vertically between adjacent lumbar vertebrae anteriorly in four baboons undergoing anterior interbody fusion. The animals were allowed freedom of activity for 6 months before being killed. A transperitoneal approach was made exposing the L4-L5 or L5-L6 interspace. At time of killing, clinical evaluation of the implant-vertebral body construct showed stability to manual stresses applied in extension, flexion, and rotation. Serial radiographs taken during the 6 months of implantation showed no change in position or displacement of the implants. Axial and torsional cyclic loads were applied to each spine at 1 cycle/s for 20,000 cycles. Statistical analysis of the motion profiles for intact and implanted spines demonstrated no significant difference in axial or rotational displacements at the arthrodesis level or adjacent unoperated levels, L1 and L4. The in vivo 6-month study in baboons confirmed implant stability and maintenance of disc space height. Variable osseous healing was noted. Release of plasma spray beading may have resulted from improper application on the implant or micromotion within the construct. A better method to mechanically interlock the plungers is being studied. Clinical trials based on this work appear justified.

Aluminum↗

PubMed2001

Effect of nickel-titanium shape memory metal alloy on bone formation.

The aim of this study was to determine the biocompatibility of NiTi alloy on bone formation in vivo. For this purpose we used ectopic bone formation assay which goes through all the events of bone formation and calcification. Comparisons were made between Nitinol (NiTi), stainless steel (Stst) and titanium-aluminium (6%)-vanadium (4%) alloy (Ti-6Al-4V), which were implanted for 8 weeks under the fascia of the latissimus dorsi muscle in 3-month-old rats. A light-microscopic examination showed no chronic inflammatory or other pathological findings in the induced ossicle or its capsule. New bone replaced part of the decalcified matrix with mineralized new cartilage and bone. The mineral density was measured with peripheral quantitative computed tomography (pQCT). The total bone mineral density (BMD) values were nearly equal between the control and the NiTi samples, the Stst samples and the Ti-6Al-4V samples had lower BMDs. Digital image analysis was used to measure the combined area of new fibrotic tissue and original implanted bone matrix powder around the implants. There were no significant differences between the implanted materials, although Ti-6Al-4V showed the largest matrix powder areas. The same method was used for measurements of proportional cartilage and new bone areas in the ossicles. NiTi showed the largest cartilage area (p < or = 0.05). Between implant groups the new bone area was largest in NiTi. We conclude that NiTi has good biocompatibility, as its effects on ectopic bone formation are similar to those of Stst, and that the ectopic bone formation assay developed here can be used for biocompatibility studies.

Alloys↗

PubMed2002

Evaluation of the titanium Ti-6Al-7Nb alloy with and without plasma-sprayed hydroxyapatite coating on growth and viability of cultured osteoblast-like cells.

BACKGROUND: Osseointegrated dental implants are currently recognized as a standard treatment method in dentistry. Titanium (Ti) and its alloys are the metals of choice for endosseous parts of currently available dental implants. Ti-6Al-4V is the most used Ti alloy, however; an improved version, Ti-6Al-7Nb, has been recently developed. METHODS: Rat osteoblast-like cells (osteo- 1 culture) were used to analyze the biocompatibility of Ti-6Al-7Nb alloy with and without hydroxyapatite (HA) coating. The cells were grown on culture Petri dishes on the top of either plain Ti-6Al-7Nb or HA-coated Ti-6Al-7Nb disks. Osteo-1 cells grown on plain culture dishes were used as controls. Growth and cell viability curves were obtained by scanning electron microscopy. For the growth and viability curves, 10(4) cells were seeded on 35 mm dishes. Cells from each group were counted, in triplicate at 3, 7, 11, and 15 days after seeding using the Trypan blue dye exclusion assay. RESULTS: The cells grew as multiple layers on both Ti-6Al-7Nb substrates, showing extracellular matrix only when grown on HA-coated Ti-6Al-7Nb disks. The cells grown on HA-coated Ti-6Al-7Nb grew more slowly than the other 2 groups, with significantly smaller cell numbers than control cultures at the end of the experimental time. Additionally, the HA coated Ti-6Al-7Nb group presented smaller percentage of cell viability when compared to the control group. However, no significant differences were observed between the Ti groups. CONCLUSIONS: The presence of HA on the Ti-6Al-7Nb surface impaired the cell growth and viability of osteo-1 cells. However, this coating improved the extracellular matrix formation. Thus, our cell viability and structural studies showed that Ti-6Al-7Nb with or without HA coating has relevant physical and biological properties as an implant material.

Analysis of Variance↗

PubMed1981

Interface mechanics of porous titanium implants.

The interfacial shear properties of bone tissue growth into porous coated Ti-6-A1-4V femoral implants have been examined as a function of the pore size of the porous surface. Three particle size range powders (297 microns, 420-500 microns, 595-707 microns) were used to fabricate cylindrical implants which were inserted into the femoral medullary canal of dogs for 6 months. Push-out tests on the removed femurs are reported and reveal: (i) that those implants residing in cortical bone exhibited significantly higher shear properties than the equivalent implants in cancellous bone and (ii) that the interfacial shear strength and stiffness decreased with increasing pore diameter within the range 175-325 microns. The extent of bone ingrowth into the surface of the implants was measured using quantitative optical microscopic techniques. This indicated that the percentage of bone which had grown into the surface was inversely proportional to the square root of the pore size and that further the shear properties of the interface were proportional to the extent of bone ingrowth.

Animals↗

PubMed1993

The shear strength and the failure mode of plasma-sprayed hydroxyapatite coating to bone: the effect of coating thickness.

Plasma-sprayed hydroxyapatite coated (HAC) 50 and 200 microns thick on Ti-6Al-4V cylinders was transcortically implanted in the femora of canines to evaluate in detail the effect of coating thickness on the pushout shear strength and failure mode examined under scanning electron microscope after the periods of 4, 6, 8, and 12 weeks. The HAC coating exhibited higher shear strength at 50 microns than at 200 microns. Its failure mode was conclusively at or near the HAC-bone interface, and the slight attack of body fluid had not degraded the implant to the extent that failure occurred at the HAC-Ti alloy interface after 12 weeks of observation. For 200 microns-HAC, failure was found at the HAC-bond interface, inside the HAC lamellar splat layer and at the HAC-Ti alloy substrate interface, depending on the period of implantation. It was also deduced that the variation of failure mode of 200 microns-HAC with time could not be accounted for by the attack of body fluid alone; the degradation must be a synergetic adverse result of residual stress in the HAC and the attack of body fluid.

Analysis of Variance↗

PubMed2001

Effect of early exposure on the integration of dental implants: Part 2--Clinical findings at 6 months postloading.

Implant exposure during initial healing after placement has been considered important in both implant integration and postloading effects. This study evaluated the effect of early implant exposure on the clinical findings prerestoration and 6 months postrestoration. Forty-eight implants (24 CPTi and 24 Ti-13-13) were placed in maxillary and mandibular posterior sites in six baboons. Implant exposure was evaluated for 24 of the submerged implants at placement and at each weekly visit for 3 weeks after implant placement. The crestal bone level at maxillary posterior sites was measured at 6-month uncovering, and mandibular sites were measured at 3-month uncovering. All sites were again measured 6 months after restoration placement. Periotest readings were recorded at implant uncovering and again 6 months postloading. Arbitrary groupings of the Periotest values were assigned as good = -7 to -1; guarded = 0 to +2; and poor = +3 to +27. At 6 months postloading, there were no statistical differences between CPTi and Ti-13-13 for change in crestal bone height in either arch. The mean change in maxillary crestal bone height varied from a 0.59- to 1.35-mm loss. The differences between the mean exposed and nonexposed changes were not statistically significant The mean change in mandibular crestal bone height varied from a 0.25- to 0.88-mm loss. Changes in crestal bone height for nonexposed sites from 3-month implant uncovering to 6 months postloading were statistically significant at the mesial, buccal, and lingual aspects. The mean change for the nonexposed distal aspect approached significance. The differences between the mean exposed and nonexposed changes were not statistically significant. The overall percentage of maxillary implants in the good category for nonexposed sites decreased by 41% from uncovering to 6 months after loading, while no change occurred for exposed sites; the percentage of implants in the good category was comparable for early exposed and nonexposed sites (57% and 59%, respectively). At 6 months after loading, the percentage of implants in the good category was more favorable for early exposed (88%) than nonexposed sites (50%). A one-stage implant approach should provide similar postloading clinical results as the two-stage surgical approach.

Alveolar Bone Loss↗

PubMed2005

Analysis of the effects of different materials in a tooth implant-supported fixed prosthesis using finite element method.

In this study, design optimization of a tooth implant-supported fixed prosthesis was investigated theoretically. A three-dimensional finite element analysis was utilized to simulate the stress distribution and deformation, with an emphasis on the material selection for various parts of the prosthesis. This mandibular prosthesis was supported by six implants. The properties of 3 different materials for implants and 4 different materials for framework were incorporated into 12 different models. For the loading conditions used, it was found that the largest displacements occurred at the far ends of the framework and that the resulting deflection was highly dependent on the material properties of the framework. The simulations showed that the stress in the framework was mainly concentrated near the holes in the lower surface and that the highest values of von Mises stresses occurred in the lingual part of the prosthesis. Furthermore, the modeling results revealed that more rigid frameworks led to a corresponding decreased stress in the retaining screws and that high-stress concentration areas moved from the neck of the implant towards the base of it, as the value of Young's modulus increased. It was concluded that the first best model was the Cr-Co alloy for the framework and the Ti alloy for the implant and the second best choice was the Cr-Co alloy for both the framework and the implant.

Computer Simulation↗

PubMed1997

New titanium alloys for biomaterials: a study of mechanical and corrosion properties and cytotoxicity.

Three new titanium alloys with Zr, Nb, Ta, Pd and In as alloying elements were developed and compared with currently used implant metals, namely, pure Ti and Ti-6Al-4V alloy, in terms of mechanical and corrosion properties, and cytotoxicity. New alloys showed comparable mechanical properties with that of the Ti-6Al-4V alloy, but increased corrosion potential, somewhat decreased breakdown potential and increased corrosion rate. There were no significant differences in cell growth on the surface of the various metal specimens, indicating that the cells cannot differentiate between the passivated surfaces of the various Ti metals.

Alloys↗

PubMed2006

Enhanced osteogenic promotion around dental implants with synthetic binding motif mimicking bone morphogenetic protein (BMP)-2.

Synthetic receptor binding motif mimicking bone morphogenetic protein-2 (BMP-2) was covalently linked to titanium (Ti) surfaces through a chemical conjugation process. The composition and properties of surface-modified Ti were investigated by XPS as well as by measuring surface radioactivity. In vitro tests were conducted with osteoblast-like MC3T3-E1 cells to assess cell attachment, morphology, and expression of osteogenic marker in the cells grown on modified Ti surfaces. In addition, in vivo experiments involved implants in mandibular bone defects of beagles to evaluate the effect of surface modification on bone regeneration. Results of XPS measurements showed a complete and homogeneous peptide overlayer on the Ti surfaces; the content was further measured by gamma counting. Biological evaluations showed that the biochemically modified Ti samples were active in terms of cell attachment behavior. The MC3T3-E1 cell growth rate, marker protein expression, and alkaline phosphatase production of the peptide-modified surfaces were all higher than those of control Ti. Importantly, the implants in the canine mandibles showed significant increase of bone growth when modified with bioactive peptide, thereby confirming that biochemical modifications of Ti surfaces can enhance the rate of bone healing as compared with untreated Ti surfaces.

Amino Acid Motifs↗

PubMed2007

Histological assessment of titanium and polypropylene fiber mesh implantation with and without fibrin tissue glue.

Polypropylene (PP) and titanium (Ti) meshes are well-known surgical implants that provoke a relative low foreign body reaction. Firm stabilization of the implant is important to prevent migration and subsequent failure of the operation. Fibrin tissue glues are commercially available adhesives and are widely accepted and applied in the medical field for hemorrhage, surgical bleeding, support of wound healing, wound and tissue gluing, sealing, and closure but also as antiadhesive agent in certain applications. The objective of this study was to evaluate the additional histological effect of fibrin glue application combined with two different types of meshes. Six pieces of mesh of each were subcutaneously implanted for 3, 6, and 12 weeks, with and without fibrin glue. After excision, processing, and staining, light microscopic analysis was performed on the sections, using subjective histological description and histomorphometry. Capsule quality, capsule thickness, interstitial quality, and total score were evaluated. To compare the samples with glue and without glue, analysis of variance (ANOVA) tests were carried out. No complications were observed. In general, the glue remnants remained visible at 3 and 6 weeks of implantation, accompanied by an inflammatory reaction and macrophage activity. At 12 weeks, all samples showed good tissue integration without evidence of glue. Evidently, the samples with glue demonstrated a prolonged inflammatory response and were surrounded by fibrous tissue capsules that were significantly thicker compared with the samples without glue (p < 0.05).

Analysis of Variance↗

PubMed2005

High surface energy enhances cell response to titanium substrate microstructure.

Titanium (Ti) is used for implantable devices because of its biocompatible oxide surface layer. TiO2 surfaces that have a complex microtopography increase bone-to-implant contact and removal torque forces in vivo and induce osteoblast differentiation in vitro. Studies examining osteoblast response to controlled surface chemistries indicate that hydrophilic surfaces are osteogenic, but TiO2 surfaces produced until now exhibit low surface energy because of adsorbed hydrocarbons and carbonates from the ambient atmosphere or roughness induced hydrophobicity. Novel hydroxylated/hydrated Ti surfaces were used to retain high surface energy of TiO2. Osteoblasts grown on this modified surface exhibited a more differentiated phenotype characterized by increased alkaline phosphatase activity and osteocalcin and generated an osteogenic microenvironment through higher production of PGE2 and TGF-beta1. Moreover, 1alpha,25OH2D3 increased these effects in a manner that was synergistic with high surface energy. This suggests that increased bone formation observed on modified Ti surfaces in vivo is due in part to stimulatory effects of high surface energy on osteoblasts.

Alkaline Phosphatase↗

PubMed1999

In vitro and in vivo behaviour of Ca- and P-enriched anodized titanium.

The influence of different surface preparations on titanium biocompatibility and bone integration was evaluated. Commercially grade 2 titanium rods (diameter 2 mm, length: 3 mm), vacuum annealed and hydrofluoric acid etched was selected for its promising surface characteristics to achieve good direct osseointegration. Some rods were surface modified by Anodic Spark Discharge anodization and a thin layer (approximately 5 microm) of amorphous TiO2 containing Ca and P (Ti/AM) was obtained. Some of the Ti/AM specimens underwent a further hydrothermal treatment to produce a thin outermost layer (approximately 1 microm) of hydroxyapatite (Ti/AM/HA). Cytotoxicity tests (direct contact: ISO 10993-5) showed good cytocompatibility for all tested samples. Ti and tissue culture substrate + DMEM control, respectively, were associated with a significant higher proportion of attached cells than Ti/AM and Ti/AM/HA (P < 0.0005), but this was in the normal range of 10-20% of unattached cells for cytocompatible materials. Histomorphometric analysis conducted on samples inserted in the cancellous bone of distal femoral epiphysis of Sprague-Dawley rats gave the following results at 4 and 8 weeks: Affinity index (AI%) data proving the surface osteconductive properties of non-anodized acid etched Ti (AI-4 weeks: 67.1 +/- 17.0%; AI-8 weeks: 74.8 +/- 11.5%). Ti/AM samples showed the lowest values (AI-4 weeks: 45.8 +/- 15.9%; AI-8 weeks: 68.5 +/- 13.6%) while the best performances of the Ti/AM/HA samples (AI-4 weeks: 60.4 +/- 21.8%; AI-8 weeks: 79.5 + 9.37%) indicated that hydroxyapatite allowed a higher bone to implant contact respect to Ti only. Further investigations should be performed in order to better understand the mechanism of observed in vitro behaviour and to achieve information on long-term osseointegration process.

Analysis of Variance↗

PubMed1994

Wear induced by motion between bone and titanium or cobalt-chrome alloys.

We studied the wear generated by motion between polished and shot-blasted titanium-alloy (Ti-6Al-4V) or cobalt-chrome alloy (Co-Cr) surfaces and cortical bone in vitro. Semicircular sections of human proximal femoral cortex were reamed to fit metal cylinders of each alloy. The cylinders were then fitted in the bone, loaded and rotated in physiological saline. Ti-alloy resulted in more wear both of the bone and of the metal than did Co-Cr alloy. Metal wear was reduced and bone wear was increased by shot-blasting, a procedure which introduces surface residual stresses and roughens the metal surface. We conclude that when there is gross motion between a metal implant and bone, Ti-alloy is likely to generate more wear debris than Co-Cr alloy. The least wear both of bone and of metal was produced by polished Co-Cr.

Bone Density↗

PubMed2002

Growth of bioactive surfaces on dental implants.

Some metallic materials, such as pure titanium, Ti-6Al-4V, are used for dental and orthopedic implants under load-bearing conditions. However, they do not form a chemical bond with bone, which would achieve a good implant-bone fixation in service. In recent works, it has been demonstrated that an in vitro, chemically deposited, bone-like apatite layer with bone-bonding ability could be induced on a titanium surface. By reproducing that chemical procedure, in this work, a dense bone-like apatite layer was formed on the surface of the titanium in simulated body fluid. In addition, the different steps and kinetics of the layer-formation have been studied, because the observation of the samples in the wet state by means of the environmental scanning electron microscope has allowed the observation in situ of the apatite deposition process over a number of days. One of the most important features of the present study is that it can be carried out on a single titanium sample and the process is not interrupted at any stage. One of the main drawbacks of this chemical method is that the samples covered with apatite are susceptible to contamination by bacteria. The behavior of different types of antibiotics used to avoid this contamination has also been studied using the environmental scanning electron microscope. Finally, osteoblast cells have been cultured on the apatite-coated titanium samples to assess their biocompatibility.

Alloys↗

PubMed1993

Evaluation of the effect of the femoral articular surface material on the wear of a metal-backed patellar component.

Wear characteristics of metal-backed, polyethylene patellar components were tested using cobalt-chromium, titanium alloy (Ti), and ion-implanted titanium alloy (IITi) articular surfaces. Patellar components were cycled in a bovine serum bath at 3 Hz for 1 million cycles, under a compressive load that varied from 343 N at 0 degree flexion to 2255 N at 120 degrees flexion. After testing, the polyethylene articular surfaces of the patellar components were evaluated for wear and graded using a subjective numbering system. Overall wear damage to the polyethylene surface was much worse with both Ti and IITi than with cobalt-chromium. Differences in mean wear scores were statistically significant when cobalt-chromium was compared with either Ti or IITi, but there were no statistically significant differences between Ti and IITi. Polyethylene surfaces that articulated against Ti femoral surfaces had more severe scratching. The IITi test group had areas of delamination not observed in the other test groups. Subjective evaluation of the metal surfaces showed evidence of wear damage as well. The metal articular surface of IITi resisted scratching as long as the treated surface was intact. In the high-stress areas, however, such as the edges of the intercondylar notch, the ion-implanted surface quickly wore away, exposing the untreated titanium alloy. The cobalt-chromium femoral articular surface had the least amount of scratching and no evidence of loss of metal.

Alloys↗

PubMed2005

In vitro interaction between surface-treated Ti-6Al-4V titanium alloy and human peripheral blood mononuclear cells.

The Ti-6Al-4V titanium alloy is widely employed as an implant material. The effects of Ti-6Al-4V samples, tested in both an untreated state and one in which the samples were subjected to a glow-discharge treatment performed with the use of air, on human peripheral blood mononuclear cells (PBMC) were studied. Apoptosis, undetectable after 24-h contact of PBMC with the two sample types, is induced after 48 h by treated samples, and, after 48 h, but in the presence of 1.5 microg/mL PHA, by both sample types. The expression of intercellular adhesion molecule-1 (ICAM-1) always increases, in comparison with control, in PBMC put in contact with the two sample types. In the same way, a remarkable increase in tumor necrosis-alpha (TNF-alpha) release in the culture medium is registered, when PBMC are put in contact with the two sample types for 24 and 48 h. Human umbilical-vein endothelial cells (HUVEC) cocultured for 48 h with PBMC, previously incubated with the two sample types for 24 h, show an increase in ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1) protein expression in comparison with control (HUVEC cocultured with control PBMC), indicating that inflammatory phenomena might occur. Taken together, these results suggest that, although plasma-treated titanium alloy shows a better biocompatibility in comparison with the untreated one, attention must be paid to the careful control of the first signs of inflammation.

Alloys↗