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PubMed2003

Shear bond strength between titanium alloys and composite resin: sandblasting versus fluoride-gel treatment.

The aim of this study was to investigate the effect of fluoride gel treatment on the bond strength between titanium alloys and composite resin, and the effect of NaF solution on the bond strength of titanium alloys. Five titanium alloys and one Co-Cr-Mo alloy were tested. Surface of the alloys were treated with three different methods; SiC polishing paper (No. 2000), sandblasting (50-microm Al2O3), and commercially available acidulated phosphate fluoride gel (F-=1.23%, pH 3.0). After treatment, surfaces of alloy were analyzed by SEM/EDXA. A cylindrical gelatin capsule was filled with a light-curable composite resin. The composite resin capsule was placed on the alloy surface after the application of bonding agent, and the composite resin was light cured for 30 s in four different directions. Shear bond strength was measured with the use of an Instron. Fluoride gel did not affect the surface properties of Co-Cr-Mo alloy and Ni-Ti alloy, but other titanium alloys were strongly affected. Alloys treated with the fluoride gel showed similar bond strengths to the alloys treated with sandblasting. Shear bond strength did not show a significant difference (p<0.05) regardless of treatment time (5, 10, and 20 min) of fluoride gel. After the ultrasonic cleaning subsequent to the fluoride-gel treatment, residues of fluoride ion or any other titanium-fluoride complexes were not detected. NaF solution did not reduce the shear bond strength of titanium alloys. To enhance the bond strength of composite resin to titanium alloys, fluoride-gel treatment may be used as an alternative technique to the sandblasting treatment.

Composite Resins↗
PubMed2005

Quartz-crystal microbalance-dissipation technique for the study of initial adsorption of fibronectin onto tresyl chloride-activated titanium.

The immobilization of cell-adhesive proteins onto titanium implants improves biological response at the implant-tissue interface. Previous studies demonstrated the easy and direct attachment of fibronectin onto titanium with the use of a 2,2,2-trifluoroethanesulfonyl chloride (tresyl chloride) activation technique. The present study investigated the initial adsorption behavior of fibronectin on tresyl chloride-activated titanium by the quartz-crystal microbalance-dissipation (QCM-D) technique. The crystal resonant frequency and the dissipation shift of the oscillator were simultaneously measured by the injection of fibronectin/phosphate-buffered saline solution (pH = 7.4). The tresyl chloride-activated titanium surface showed a faster and greater decrease in frequency than that of untreated titanium, indicating that a greater amount of fibronectin was adsorbed in the former case during a 120-min adsorption. The dissipation-frequency plots revealed that, during the initial stage of adsorption, the bond between fibronectin and tresyl chloride-activated titanium is stronger than that between fibronectin and untreated titanium. The QCM-D technique can provide new insights into the adsorption mechanism of fibronectin.

Adsorption↗
PubMed2000

Titanium particles inhibit osteoblast adhesion to fibronectin-coated substrates.

To illuminate the effect of titanium particles on osteoblast function, we compared the adhesion force of neonatal rat calvarial osteoblasts on fibronectin-coated glass after incubation with titanium particles (80% had diameters of less than 5 microm). The cells were incubated with the particles for 1.5-72 hours. Using a micropipette single-cell manipulation system, we showed that the adhesion force of the osteoblasts to fibronectin-coated glass (1.0 microg/ml) was significantly affected by the presence of particulate debris. The adhesion force of the cells incubated with titanium particles for less than 4 hours was not significantly affected by exposure to the particles; after 4 hours, however, it was significantly reduced relative to that of controls. Aspiration of particle-challenged osteoblasts into the micropipette demonstrated that the particles were not stripped from the cell surface and therefore confirmed that the osteoblasts had ingested them. During aspiration, the particles traveled through the cytoplasm rather than on the cell surface. When the osteoblasts were exposed to the particles and cytochalasin D, they exhibited much lower adhesion forces than did the controls or the cells exposed to titanium particles only; this indicates an important role of actin filaments in the osteoblastic response to particles. Staining for F-actin also indicated an influence of internalized titanium particulate on cytoskeletal arrangement and cell spreading. Furthermore, with standard Northern blotting techniques, levels of mRNA for collagen type I and fibronectin were significantly reduced as early as 4 hours after exposure to particles compared with levels in controls, and this effect continued to 72 hours. These data indicate that direct exposure of osteoblasts to titanium particles, which we propose to be ingested by the osteoblasts, can significantly decrease osteoblast adhesion force; this may lead to decreased cellular activity and gene expression of fibronectin and collagen type I in the presence of titanium wear debris.

Actins↗
PubMed1995

Mechanical and histological evaluation of hydroxyapatite-coated, titanium-coated and grit-blasted surfaces under weight-bearing conditions.

Cylindric titanium rods with different surfaces were axially implanted into the femora of sheep. The three surfaces were grit-blasted titanium, plasma-sprayed titanium and plasma-sprayed hydroxyapatite (HA). After 2 months, a 2-cm segment of the femoral shaft was completely resected to load the implant, and the animals were allowed full weight-bearing for 9 months. Biomechanical and histological evaluation of the implants was undertaken 2 months after implantation and 9 months after the segmental resection. The mechanical testings of well-fixed implants were performed 9 months after segmental resection. Loosening of 45% of the titanium-coated implants was observed in the first 3 weeks, but thereafter, no further loosening occurred. The HA-coated implants remained entirely fixed for 3 weeks, but thereafter, a progressively increasing incidence of loosening up to 55% after 9 months of loading was detected as subsidence on X-radiographs. The maximum push-out strength of the titanium-coated implants was 4.9 MPa compared with 2.3 MPa for HA-coated ones. No significant mechanical interlock between the grit-blasted surface and bone was observed. The HA coating was found to be delaminated in all unstable implants, whereas the titanium coating remained completely intact. Morphometric analyses of well-fixed rods showed complete bony ingrowth onto the HA surface, whereas the contact area between the bone and the two titanium surfaces was less than 40%. Concerning clinical significance bony ingrowth with long-term mechanical interlock between the implant surface and the bone cannot be achieved by grit-blasting or HA-coating.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Subcellular distribution of titanium in the liver after treatment with the antitumor agent titanocene dichloride. A study using electron spectroscopic imaging.

In the present study, the subcellular distribution of titanium in the liver of mice was determined 24 and 48 h after application of a therapeutic (ED100; ED = effective dose) and a toxic (LD25; LD = lethal dose) dose (60 and 80 mg/kg, respectively) of the antitumor agent titanocene dichloride by electron spectroscopic imaging at the ultrastructural level. At 24 h, titanium was mainly accumulated in the cytoplasm of endothelial and Kupffer cells, lining the hepatic sinusoids. Titanium was detected in the nucleoli and the euchromatin of liver cells, packaged as granules together with phosphorus and oxygen. One day later titanium was still present in cytoplasmic inclusions within endothelial and Kupffer cells, whereas in hepatocyte nucleoli only a few deposits of titanium were observed at 48 h. At this time titanium was mainly accumulated in the form of highly condensed granules in the euchromatin and the perinucleolar heterochromatin. It was found in the cytoplasm of liver cells, incorporated into cytoplasmic inclusion bodies which probably represent lysosomes. Sometimes these inclusions were situated near bile canaliculi and occasionally extruded their content into the lumen of bile capillaries. This observation suggests a mainly biliary elimination of titanium-containing metabolites. These results confirm electron spectroscopic imaging to be an appropriate method for determining the subcellular distribution of light and medium-weight elements within biological tissues. Insights into the cellular mode of action of titanocene complexes or titanocene metabolites can be deduced from the findings of the present study.

Animals↗
PubMed1999

Exposure of macrophage-like cells to titanium particles does not affect bone resorption, but inhibits bone formation.

We examined the capacity of culture supernatants of macrophage-like cells exposed to titanium particles to influence bone formation and bone resorption, our aim being to elucidate the mechanism of implant loosening. A mouse macrophage-like cell line, J774, was exposed to titanium particles and the concentrations of prostaglandin E2, tumor necrosis factor-alpha, interleukin-1alpha, and interleukin-6 in the supernatants were measured. Titanium particles stimulated the J774 cells to release tumor necrosis factor-alpha, whereas prostaglandin E2, interleukin-1alpha and interleukin-6 concentrations remained low. The bone resorptive activity of the supernatants was measured by determining 45Ca release from cultured pre-labeled newborn mouse calvariae. The culture supernatants of J774 cells exposed to titanium particles showed no significant difference in bone resorptive activity in mouse calvariae from that of culture supernatants of J774 cells not exposed to titanium particles. The bone-forming activity of the supernatant was evaluated by determining bone nodule formation and alkaline phosphatase activity in cultured mouse calvaria cells. The bone-forming activity of the supernatants exposed to titanium particles was significantly decreased compared with the supernatants of unexposed J774 cells. This inhibition was reversed by the addition of anti-tumor necrosis factor-alpha neutralizing antibody. We conclude that tumor necrosis factor-alpha released from J774 cells exposed to titanium particles played an important role in the inhibition of bone formation rather than in the stimulation of bone resorption.

Alkaline Phosphatase↗
PubMed1994

Histochemical and confocal laser scanning microscopy study of the bone-titanium interface: an experimental study in rabbits.

The aim of our study was an analysis of the presence of an unmineralized bone matrix between mineralized bone and titanium screws in rabbit tibiae. A microscopical analysis, using a histochemical technique, was performed on the titanium-bone interface of commercially pure titanium implants placed in rabbit tibiae and harvested after 2 months. Thin ground sections of the specimens were prepared by the cutting-grinding system and stained using the von Kossa method for calcium salts and basic fuchsin for osteoid. The microscopical and morphometrical evaluation showed that bone covered about 40% (+/- 7.5%) of all implants. Mineralized bone was, however, in direct contact with the titanium surface on only about 10% of the implant, while in the remaining 30% the mineralized bone was separated from the implant by an unmineralized tissue. This basophilic, probably osteoid matrix, could represent the medium that allows the biochemical exchanges between bone and cells under the influence of the implant. A small, optically translucent gap (1-5 microns), probably an artifact, was present in some areas between titanium and bone. Confocal laser scanning microscopy (CLSM) in a fluorescent mode showed the presence at the interface of a fluorescent material. Results from our study showed that light microscopy of thin ground sections allowed a good analysis of the real nature of the titanium-bone interface. Moreover, this double staining technique showed the presence of an unmineralized bone matrix at most of the bone-titanium interface.

Animals↗
PubMed1994

Accuracy of titanium cast crowns obtained from calcia base mold.

A calcia base investment has high stability even with melted titanium and, therefore, can produce an excellent titanium casting. In this study, titanium powder was distributed to a calcia base investment as an expanding agent, and the firing temperature of the mold was controlled at 800 degrees C. The calcia base investment with 6.1% wt titanium powder expanded 1.7% during 2 h heating at 800 degrees C. The marginal discrepancies between the die and the titanium crown were improved by the addition of the titanium powder to the investment. The mean thickness of the cement layer between the epoxy teeth and the crown using 6.1% wt titanium powder content was from 40-80 microns.

Calcium Compounds↗
PubMed2005

In vitro biological effects of titanium rough surface obtained by calcium phosphate grid blasting.

Surface roughness modulates the osseointegration of orthopaedic and dental titanium implants. High surface roughness are currently obtained by blasting of titanium implants with silica or aluminium oxide abrasive particles. This process may cause the release of cytotoxic silicium or aluminium ions in the peri-implant tissue. To generate a biocompatible roughened titanium surface, we currently develop an innovative grid-blasting process using biphasic calcium phosphate (BCP) particles. Titanium alloy (Ti6Al4V) discs were either polished, BCP grid-blasted or left as-machined. BCP grid-blasting created an average surface roughness of 1.57 +/- 0.07 microm compared to the original machined surface of 0.58 +/- 0.05 microm. X-ray photoelectron spectroscopy indicated traces of calcium and phosphorus and relatively less aluminium on the BCP grid-blasted surface than on the initial titanium specimen. Scanning electronic microscopy observations and measurement of mitochondrial activity (MTS assay) showed that osteoblastic MC3T3-E1 cells were viable in contact with the BCP grid-blasted titanium surface. In addition, our results indicate that MC3T3-E1 cells expressed ALP activity and conserved their responsiveness to bone morphogenetic protein BMP-2. The overall results clearly indicate that this calcium phosphate grid-blasting technique increases the roughness of titanium implants and provides a non-cytotoxic surface with regard to mouse osteoblasts.

3T3 Cells↗
PubMed2005

The effect of the surface modification of titanium using a recombinant fragment of fibronectin and vitronectin on cell behavior.

The surface of titanium implants is in direct contact with host tissue and plays a critical role in determining biocompatibility. Fibronectin (FN) and vitronectin (VN) are major cell adhesive proteins found in the extracellular matrix (ECM) of various tissues, and in circulating blood. The aim of this study was to evaluate the engineered biomimetic surface of titanium by using recombinant fragment of FN(8-10) and VN(NTD) that contains the binding site for integrins. MC3T3-E1 cells seeded upon the FN(8-10)-coated titanium showed a marked increase in cell adhesion, proliferation, and differentiation over VN(NTD)-coated titanium. In addition, we confirmed that the surface properties of titanium prefer for FN(8-10) over VN(NTD) (p<0.05) in protein adhesion. These results suggest that the FN(8-10)-modified titanium surface can be used to improve the osseointegration of titanium implants by enhancing bone formation.

3T3 Cells↗
PubMed2005

Bioactivity of titanium following sodium plasma immersion ion implantation and deposition.

Bio-activation of titanium surface by Na plasma immersion ion implantation and deposition (PIII and D) is illustrated by precipitation of calcium phosphate and cell culture. The bioactivity of the plasma-implanted titanium is compared to that of the untreated, Na beam-line implanted and NaOH-treated titanium samples. Our data show that the samples can be classified into two groups: non-bioactive (untreated titanium and beam-line Na implanted titanium) and bioactive (Na-PIII and D and NaOH-treated titanium). None of the four types of surfaces exhibited major cell toxicity as determined by lactate dehydrogenase (LDH) release. However, the LDH release was higher on the more bioactive PIII and NaOH-treated surfaces. From a morphological point of view, cell adherence on the NaOH-treated titanium is the best. On the other hand, the cell activity and protein production were higher on the non-bioactive surfaces. The high alkaline phosphatase activity per cell suggests that the active surfaces support an osteogenic differentiation of the bone marrow cells at the expense of lower proliferation. The use of Na-PIII and D provides an environmentally cleaner technology to improve the bioactivity of Ti compared to conventional wet chemical processes. The technique is also particularly useful for the uniform and conforming treatment of medical implants that typically possess an irregular shape and are difficult to treat by conventional ion beam techniques.

Animals↗
PubMed2007

Effect of titanium carbide coating on the osseointegration response in vitro and in vivo.

Titanium has limitations in its clinical performance in dental and orthopaedic applications. This study describes a coating process using pulsed laser deposition (PLD) technology to produce surfaces of titanium carbide (TiC) on titanium substrates and evaluates the biological response both in vitro and in vivo. X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of 18.6-21.5% TiC in the surface layer, accompanied by oxides of titanium 78.5-81.4% in the following concentrations: 11.1-13.0% Ti(2)O(3), 50.8-55.8% TiO(2), 14.5-14.7% TiO. Expression of genes central to osteoblast differentiation (alkaline phosphatase, A2 pro-collagen type 1, osteocalcin, BMP-4, TGFbeta and Cbfa-1) were up-regulated in all cell lines (primary human osteoblasts, hFOB1.19 and ROS.MER#14) grown on TiC compared with uncoated titanium when measured by semiquantitative PCR and real time-PCR, whilst genes involved in modulation of osteoclastogenesis and osteoclast activity (IL-6 and M-CSF) were unchanged. Bone density was shown to be greater around TiC-coated implants after 2 and 4 weeks in sheep and both 4 and 8 weeks in rabbits compared to uncoated titanium. Rapid bone deposition was demonstrated after only 2 weeks in the rabbit model when visualized with intravital staining. It is concluded that coating with TiC will, in comparison to uncoated titanium, improve implant hardness, biocompatibility through surface stability and osseointegration through improved bone growth.

Animals↗
PubMed2004

The effect of a 3-methacryloxypropyltrimethoxysilane and vinyltriisopropoxysilane blend and tris(3-trimethoxysilylpropyl)isocyanurate on the shear bond strength of composite resin to titanium metal.

OBJECTIVES: The aim of this study was to evaluate the reactions of silanes prior to attaching the composite to titanium and evaluate these silanes as coupling agents. Veneered titanium may be used as a prosthetic material. METHODS: Two silane solutions, a mixture of both gamma-methacryloxypropyltrimethoxysilane and vinyltriisopropoxysilane, and tris(3-trimethoxysilylpropyl)isocyanurate were prepared as 2 wt% in two different (95% 2-propanol and 90% acetone) solutions. A control, 2 wt% gamma-methacryloxypropyltrimethoxysilane was prepared in both solutions. These six silane solutions were applied onto flat titanium surfaces. The samples (N = 250) were divided into two main groups: air-dried (room temperature) and heat cured for 1 h at 110 degrees C. Sinfony veneering composite was applied and light-cured on the titanium. The control group was non-silanized. The specimens were assigned to two subgroups: not thermocycled, and thermocycled (5000 cycles, 5-55 degrees C). Shear bond strength of the composite was tested at a crosshead speed of 1.0 mm min(-1). Fresh silane solution hydrolysis, and condensation reaction on titanium surface were monitored by FTIR spectrometry. RESULTS: Dry samples could be successfully tested, while thermocycling after 3700 cycles had gradually de-bonded the composite from the silanized titanium substrate. For dry samples, statistical analysis (ANOVA) showed that solvent and silane significantly affected the shear bond strength. The silane mixture in 2-propanol reacted at room temperature yielded 11.3 MPa (Standard deviation, SD, 3.6 MPa) and on the other hand, tris(3-trimethoxysilylpropyl)isocyanurate in 2-propanol yielded 10.7 MPa (SD 8.0 MPa) and gamma-methacryloxypropyltrimethoxysilane 20.4 MPa (SD 12.2 MPa). Non-silanized samples yielded 4.8 MPa (SD 2.1 MPa). SIGNIFICANCE: In all solvents used, silanes reacted chemically with the titanium surface and covalent Si-O-Ti- and -Si-O-Si- bonds were evident.

Analysis of Variance↗
PubMed2004

Pure titanium casting into zirconia-modified magnesia-based investment molds.

OBJECTIVE: Molten titanium is highly reactive with common mold materials at elevated temperatures. The aim of this investigation was to improve the accuracy of pure titanium casting by adding unreactive zirconia into magnesia-based investment material. METHODS: An automatic thermal expansion laser-recording machine (TEM-1000/Pantos, Nippon Co.) was used to measure thermal expansion of investment materials. An automatic argon-casting machine (Castmatic-S, Iwatani Co.) was used to cast pure titanium samples. A stereomicroscope was used (Nikon SM-2T, Japan) to measure marginal discrepancy on a metal die. A Vickers microhardness indenter (MXT-50, Matsuzawa Seiki Co.) determined the Vickers hardness (VH) of the titanium samples. Interfacial reactivity of the titanium was evaluated with an X-ray diffractometer (Rigaku D/max VIII, Tokyo, Japan). A dental X-ray machine was used to examine internal porosity of the castings. Data was analysed with paired t-test (p < 0.05), ANOVA/Tukey's HSD test (p < 0.001) and Spearman's correlation test (p < 0.05). RESULTS: Addition of 5.0-6.0 mass% of zirconia to a magnesia-based investment material significantly increased its thermal expansion value (p < 0.05). ANOVA indicated significant marginal discrepancy differences within the zirconia-added group (p < 0.001). There was a significant correlation between thermal expansion at 750 degrees C and marginal discrepancy (p < 0.05). The addition of zirconia decreased interfacial reactivity and the VH of titanium. SIGNIFICANCE: Under appropriately adjusted conditions, the addition of zirconia to magnesia-based mold materials may be used to produce high quality pure titanium castings.

Analysis of Variance↗
PubMed2005

Novel method for titanium crown casting using a combination of wax patterns fabricated by a CAD/CAM system and a non-expanded investment.

OBJECTIVES: For titanium casting, most commercial investments for titanium recommend casting at a low mold temperature to reduce oxidation. However, the thermal expansion values of the molds at low casting temperatures may be insufficient. The purpose of the current study was to investigate the possibility of obtaining accurate titanium crown casts using wax pattern fabricated by a CAD/CAM system with a non-expanded mold. METHODS: Three types of experimental magnesia-based investments (A, B and C) were made and their properties were evaluated for dental use. Two kinds of wax patterns for full-coverage coping crowns (S-0: cement space of 0 microm; S-20: cement space of 20 microm) were fabricated using a commercial CAD/CAM system. A traditional method (TM) using inlay wax was performed for comparison. The investment for titanium casting was decided from the fundamental data of experimental investments. Titanium crowns were replaced on the stone die and the thickness of the cement layer was evaluated. RESULTS: There were no significant differences for the setting time and setting expansion among the experimental investments, but the aluminous cement content played a role in hardening and contracting the mold. The fit of the titanium crowns differed significantly between the TM and the CAD/CAM system. The ranges of thickness obtained from the TM, S-0 and S-20 were 20.78-357.88 microm, 25.12-107.46 microm and 17.84-58.92 microm, respectively. SIGNIFICANCE: High quality titanium crown casting was obtained using a combination of wax patterns fabricated by a CAD/CAM system and a non-expanded MgO-based investment.

Analysis of Variance↗
PubMedDate not supplied

Titanium basal joint arthroplasty: a finite element analysis and clinical study.

PURPOSE: To define the mechanics and determine the clinical outcome of titanium implant arthroplasty in trapeziometacarpal arthritis. METHODS: For the finite element analysis (FEA) a 2-dimensional FEA mesh of the titanium arthroplasty was constructed with 8-node quadrilateral elements and analyzed. Flexion-extension displacement of the metacarpal was analyzed. For the clinical study, between 1996 and 2003, 47 patients (50 thumbs) with Eaton stage 3 trapeziometacarpal arthritis were treated with titanium basal joint arthroplasty. The average follow-up period was 2 years. Disabilities of the Arm, Shoulder, and Hand questionnaire answers and grip and pinch measurements were obtained before surgery and at the final follow-up evaluation. Failure was defined strictly as the point when revision to the standard soft-tissue interposition arthroplasty became inevitable. RESULTS: In the FEA the titanium implant showed pistoning behavior with maximum stress concentration in the midmetacarpal shaft of 1.92 MPa. The convex sphere of the implant rotates and lifts out of the trapezial crater with a high stress concentration of 0.51 MPa at the radial and ulnar corner of the trapezium. In the clinical study treatment failed in 10 of the patients before 9 months. All were converted successfully to a standard ligament reconstruction tendon interposition. The remaining 80% of the patients showed significant improvement in Disabilities of the Arm, Shoulder, and Hand questionnaire scores albeit with continued weakness at the 2-year follow-up evaluations. The reconstructed thumbs never attained the strength of the contralateral thumbs; even in the success group residual swelling was not uncommon with any increase in activity level. CONCLUSIONS: Anecdotal quotations show success rates for titanium implant arthroplasty for basal joint arthritis to be as high as 97%. Our results are quite to the contrary in that high failure rates were common early in the follow-up period. Our FEA results are confirmed by the clinical study. Titanium implant arthroplasty may have a role in low-demand patients with good bone stock; however, we have stopped offering titanium hemiarthroplasty to patients at our institution.

Arthritis↗
PubMedDate not supplied

Is galvanic corrosion between titanium alloy and stainless steel spinal implants a clinical concern?

BACKGROUND CONTEXT: Surgeons are hesitant to mix components made of differing metal classes for fear of galvanic corrosion complications. However, in vitro studies have failed to show a significant potential for galvanic corrosion between titanium and stainless steel, the two primary metallic alloys used for spinal implants. Galvanic corrosion resulting from metal mixing has not been described in the literature for spinal implant systems. PURPOSE: To determine whether galvanic potential significantly affects in vitro corrosion of titanium and stainless steel spinal implant components during cyclical compression bending. STUDY DESIGN/SETTING: Bilateral spinal implant constructs consisting of pedicle screws, slotted connectors, 6.35-mm diameter rods and a transverse rod connector assembled in polyethylene test blocks were tested in vitro. Two constructs had stainless steel rods with mixed stainless steel (SS-SS) and titanium (SS-Ti) components, and two constructs had titanium rods with mixed stainless steel (Ti-SS) and titanium (Ti-Ti) components. METHODS: Each construct was immersed in phosphate-buffered saline (pH 7.4) at 37 C and tested in cyclic compression bending using a sinusoidal load-controlling function with a peak load of 300 N and a frequency of 5 Hz until a level of 5 million cycles was reached. The samples were then removed and analyzed visually for evidence of corrosion. In addition, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to evaluate the extent of corrosion at the interconnections. RESULTS: None of the constructs failed during testing. Gross observation of the implant components after disassembly revealed that no corrosion had occurred on the surface of the implants that had not been in contact with another component. The Ti-Ti interfaces showed some minor signs of corrosion only detectable using SEM and EDS. The greatest amount of corrosion occurred at the SS-SS interfaces and was qualitatively less at the SS-Ti and Ti-SS interfaces. CONCLUSIONS: The results from this study indicate that when loaded dynamically in saline, stainless steel implant components have a greater susceptibility to corrosion than titanium. Furthermore, the galvanic potential between the dissimilar metals does not cause a discernible effect on the corrosion of either. Although the mixture of titanium alloy with stainless steel is not advocated, the results of this study suggest that galvanic corrosion is less pronounced in SS-Ti mixed interfaces than in all stainless steel constructs.

Alloys↗
PubMed2003

Thermal expansion and microstructural analysis of experimental metal-ceramic titanium alloys.

UNLABELLED: Statement of problem Low-fusing porcelains for titanium veneering have demonstrated inferior color stability and metal-ceramic longevity compared to conventional porcelains. PURPOSE: This study evaluated the microstructure and thermal expansion coefficients of some experimental titanium alloys as alternative metallic substrates for low-fusing conventional porcelain. MATERIALS AND METHODS: Commercially pure titanium (CP Ti) and various metallic elements (Al, Co, Sn, Ga, In, Mn) were used to prepare 8 titanium alloys using a commercial 2-chamber electric-arc vacuum/inert gas dental casting machine (Cyclarc). The nominal compositions of these alloys were the following (wt%): I: 80Ti-18Sn-1.5In-0.5Mn; II: 76Ti-12Ga-7Sn-4Al-1Co; III: 87Ti-13Ga; IV: 79Ti-13Ga-7Al-1Co; V: 82Ti-18In; VI: 75.5Ti-18In-5Al-1Co-0.5Mn; VII: 85Ti-10Sn-5Al; VIII: 78Ti-12Co-7Ga-3Sn. Six rectangular wax patterns for each test material (l = 25 mm, w = 3 mm, h = 1 mm) were invested with magnesia-based material and cast with grade II CP Ti (control) and the 8 experimental alloys. The porosity of each casting was evaluated radiographically, and defective specimens were discarded. Two cast specimens from CP Ti and alloys I-VIII were embedded in epoxy resin and, after metallographic grinding and polishing, were studied by means of scanning electron microscopy and wavelength dispersive electron probe microanalysis. One specimen of each material was utilized for the determination of coefficient of thermal expansion (CTE) with a dilatometer operating from room temperature up to 650 degrees C at a heating rate of 5 degrees C/minute. RESULTS: Secondary electron images (SEI) and compositional backscattered electron images (BEI-COMPO) revealed that all cast specimens consisted of a homogeneous matrix except Alloy VIII, which contained a second phase (possibly Ti(2)Co) along with the titanium matrix. The results showed that the coefficient of thermal expansion (CTE) varied from 10.1 to 13.1 x 10(-6)/ degrees C (25 degrees -500 degrees C), depending on the elemental composition. CONCLUSION: The CTE of titanium can be considerably changed by alloying. Two-phase alloys were developed when alloying elements were added in concentrations greater than the maximum solubility limit in alpha-titanium phase.

Aluminum↗