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PubMed1996

Cast titanium dental implants for the posterior mandible.

The purpose of this paper is to present the results of the evaluation of five patients who received titanium dental implant replicas of extracted molars and pre-molars, placed in the posterior mandible. The replicas were placed in the sockets where the molars and bicuspids had been extracted. The implant replicas were fabricated in two parts, an abutment portion and a root portion connected by a titanium screw. The root portion was made of cast titanium. The abutment portion was made of a high noble metal to which porcelain could be fused, so that the crown restoration could be made directly on the abutment. The patient's ages ranged from 27 to 63 years. Four were male and one was female. The implants were placed three to six weeks after extraction. All implants integrated. The longest follow-up with the implant in function was five years.

Adult↗
PubMed1997

All-cast-titanium removable partial denture for a patient with a severely reduced interarch distance: a case report.

A patient had a maxillary posterior edentulous area and severely reduced interarch distance that precluded the use of a conventional removable partial denture. An all-cast-titanium denture base and occlusal surface was designed to fabricate a removable denture to restore the edentulous area. Titanium was cast in a centrifugal casting machine with electric are melting design. The desirable characteristics of titanium, such as favorable mechanical properties, low density, and comparatively low cost, make this metal particularly effective and suitable for construction of an all-cast-metal denture base with a metal occlusal surface.

Adult↗
PubMed1997

[Investigation of castability and layered structure on margin of titanium cast crown].

Previous studies on dental applications of pure titanium were mainly focused on its mechanical properties rather than its clinical aspects. The purpose of this study was to evaluate the margin castability and mechanical properties of C. P. titanium for better understanding of its suitability for clinical application. To simulate the crown margins, flat wax patterns, which had two different margin thicknesses, i.e., 20 and 40 degrees sharp edges respectively, were used. These patterns were cast using two casting systems, centrifugal and pressure systems. There were statistically significant differences between the samples made from the two types of patterns in terms of cast deficiency at the margins observed with a light microscope and the increased length of the margins measured with a video micrometer, but not between the samples made with the two different systems. Both the thickness of layered structures measured by a metallurgical light microscope and the micro-hardness by a Dynamic Hardness Tester were lowest at the apex of the margins in all samples. These observations were more evident among 20 degree samples than 40 degree samples. The layered structures were different among the casting systems. In conclusion, pure titanium is suitable for clinical application as restorative material when used appropriately.

Crowns↗
PubMed1997

Bone reactions to early occlusal loading of two-stage titanium plasma-sprayed implants: a pilot study in monkeys.

This pilot study analyzed the bone reactions to early loaded titanium plasma-sprayed implants. A total of 24 titanium plasma-sprayed implants (12 in the maxilla and 12 in the mandible) (Primary Healing Implant, Legnano) were inserted into four Macaca fascicularis monkeys with instruments specially designed to obtain a precise fit of the implant in the bone socket. A metal superstructure was cemented into 10 mandibular and 10 maxillary implants 15 days after implant insertion. The four remaining implants were used as controls. Eight months after implant placement, a block section was carried out, the defect was filled with nonresorbable hydroxyapatite, and all 24 implants were retrieved. The implants were treated to obtain thin ground sections that were examined under normal and polarized light. Histologic analysis showed that bone was observed around the implant surface in all implants. Morphometric analysis demonstrated that bone lined 67.2% (SD = 3.1%) of the maxillary implant surface, and 80.71% (SD = 4.6%) of the mandibular implant surface. No differences were found in the percentage of bone-implant contact in the control implants. In the loaded implants, however, the bone around the implants had a more compact appearance. The study demonstrated that it is possible to obtain a high percentage of bone-implant contact in early loaded titanium plasma-sprayed implants.

Animals↗
PubMedDate not supplied

The use of implant-supported ceramometal titanium prostheses following sinus lift and augmentation procedures: a clinical report.

This clinical report presents rationale and clinical procedures involved in the use of ceramometal implant-supported titanium-cast prostheses for the rehabilitation of patients with atrophic maxillae requiring iliac crest grafting procedures. Favorable clinical results have been obtained, although clinical observation periods have been limited. The present observations suggest that osseointegrated ceramometal titanium prostheses could form a valuable part of restorative therapy following augmentation procedures. Furthermore, these titanium prostheses may be a meaningful contribution to implant prosthodontics, facilitating restorations of optimum biocompatibility.

Adult↗
PubMed1998

Laparoscopic anterior spinal arthrodesis with rhBMP-2 in a titanium interbody threaded cage.

Anterior lumbar interbody arthrodesis is commonly performed for conditions involving infection, deformity, and instability. The purpose of this investigation was to determine the effective dose of recombinant human bone morphogenetic protein-2 (rhBMP-2) as a bone graft substitute inside a titanium threaded interbody fusion cage using a nonhuman primate model of laparoscopic anterior lumbar interbody arthrodesis. Eight adult rhesus monkeys underwent laparoscopic exposure of the lumbosacral spine followed by insertion of a hollow titanium threaded cylindrical cage (Sofamor-Danek, Memphis, TN, U.S.A.). Before insertion, the chamber of the cage was filled with a collagen sponge delivery vehicle soaked with either 0 mg/ml (sham, buffer only), 0.75 mg/ml (low dose), or 1.5 mg/ml (high dose) of rhBMP-2 (Genetics Institute, Cambridge, MA, U.S.A.). Fusions were evaluated in a blinded fashion with plain radiographs and computed tomography (CT) scans 12 and 24 weeks after surgery, and by manual palpation and histology after euthanasia 24 weeks after surgery. All five monkeys treated with a cage filled with rhBMP-2 obtained a solid fusion as assessed by manual palpation. The two monkeys that received no growth factor did not achieve solid fusions. Plain radiographs were of limited value, with fusions best assessed on sagittally reconstructed CT scans. Scans from the two animals treated without growth factor showed ingrowth of bone only into the outer edges of the cage, but not through the center. Scans from the rhBMP-2-treated animals demonstrated arthrodesis with continuous bone growth through the cage. Histologic analysis demonstrated normal mature trabecular bone surrounding and growing through the cages, which correlated with the CT scan findings. We conclude that rhBMP-2 delivered in a threaded titanium interbody cage can serve as a bone graft substitute in a nonhuman primate model. Sagittal reconstructed CT may be a better method to assess for fusion with this device.

Animals↗
PubMed1998

On the variability of cross-sectional dimensions and torsional properties of rectangular nickel-titanium arch wires.

Twenty-five rectangular superelastic or conventional work-hardened nickel-titanium alloy wires, commonly used in the 0.018-inch edgewise technique, supplied by seven different manufacturers, along with one braided nickel-titanium and two beta-titanium wires, were studied with respect to wire dimensions, edge bevel, and mechanical properties in longitudinal torsion at 37 degrees C. The wires were twisted 25 degrees and studied in deactivation, simulating application of torque to an individual tooth. Standard Siamese brackets. with stated slot heights of 0.018 inches and measured slot heights of 0.0187 inches, were used. Most wires were within +/-0.0005 inches of the stated dimensions, but had more edge bevel than previously reported for stainless steel and chrome-cobalt alloy wires. Variations in wire dimensions and edge bevel led to variable torsional (third-order) clearance. The torsional stiffness varied among manufacturers within the various wire sizes, this being the result of differences in actual cross-sectional geometry and material properties. None of the tested wires exhibited superelastic properties under the current conditions, and only one wire had a superelastic tendency.

Dental Alloys↗
PubMed1998

Mechanisms of bone resorption: analysis of proinflammatory cytokines in peritoneal macrophages from titanium implant--an experimental design.

Cytokines, and interleukin-6 in particular, are inflammatory peptide mediators that are extensively studied as regulators of bone tissue homeostasis. They seem to be involved in osteoclast activation and bone resorption and probably play a role in osseointegrated implant rejection. In this study we investigate the ability of titanium implants to cause an imbalance in the homeostatic equilibrium of cytokines using the peritoneal cavity of DB-A2 mice as a model. The inflammatory response was evaluated as a messenger ribonucleic acid expression determined by the semiquantitative reverse transcriptase--polymerase chain reaction technique in peritoneal macrophages from titanium-implanted mice. Interleukin-6 release was detected by a specific quantitative enzyme-linked immunosorbent assay. Our results have shown that titanium implants do not significantly stimulate the proinflammatory cytokine system compared to the control group. The enzyme-linked immunosorbent assay test confirms, after a peak in secretion at day 1 compared with basal levels, a clear decrease in interleukin-6 at basal levels on following control at 6 and 9 days after implantation. The study of the interaction between implanted biomaterials and inflammatory mediators seems to be very promising. Perhaps a better understanding of the mechanisms of bone resorption could lead to finding a new clinical solution for patients with osseointegrated implant rejection.

Animals↗
PubMed1998

Corrosion resistance and ion dissolution of titanium with different surface microroughness.

In vitro corrosion resistance and ion dissolution of commercial pure titanium with different surface microroughness are studied adopting constant potential meter and atomic absorption spectroscopy. In terms of the surface roughness, titanium samples are divided into 5 groups: smooth surface, machining surface, 2 different microroughness surfaces and macrorough surface. Each group contains three category samples under different treatments: natural oxidation (24 h exposure to air), oxidation under 400 degrees C (400 degrees C, 45 min thermal oxidation), oxidation under 700 degrees C (700 degrees C, 45 min thermal oxidation). In Hanks corrosion media, comparative studies through constant potential anode polarization curves and titanium release rates of the 5 groups of Ti samples demonstrates that oxidation under 400 degrees C best increase corrosion resistance and decrease ion release sharply, oxidation under 700 degrees C is better than natural oxidation. Ti samples with a different surface roughness all have good corrosion resistance and their corrosion resistance drop with the raising of surface roughness. Comparing with macrorough surface and machining surface, microrough surfaces have better corrosion resistance and a lower ion release rate which are similar to those of smooth surfaces. Moreover, the corrosion resistance of machining surface Ti is the lowest. It is hypothesized that surface treatment methods such as surface thermal oxidation, surface aging and so on will improve the corrosion resistance and decrease the ion release rate of rough surface effectively by increasing the thickness of surface protection film, improving its structural uniformity and facilitating the formation of ordered, compact surface protection film.

Biocompatible Materials↗
PubMed1997

[Analysis of pure titanium implants-bone interface by TOF-SIMS].

In order to study the Titanium-bone interaction and integration mechanism, the titanium implant was implanted in the tibia of 9 Newzealand rabbits, and the Ti-bone interface performed for 1, 3, and 6 months were examined and analyzed by fluorescence microscope and advanced TOF-SIMS techniques. The results showed that Ti-bone tissue was integrated closely in a very reactive manner. Both physical and chemical integration occurred in the Ti-bone interface. The Ti-bone could diffuse into the bone tissue though the diffusion was very limited. It was up to 100 microns in depth during the early period. The diffusion density was high, and later in a smooth distribution. Furthermore, while Ti+ diffused into the bone tissue, other elements such as Ca+, OH-, O-, etc, could also diffuse into titanium in exchange. The growth pattern around the bone tissue was in two fashions, one was implantefugal and the other was implantopetal. In this study, based on the ionic distribution, osmosis and impurity elements distribution, the Ti-bone integration mechanism was discussed at molecular and atomic level.

Animals↗
PubMed2000

Metallorganic routes to nanoscale iron and titanium oxide particles encapsulated in mesoporous alumina: formation, physical properties, and chemical reactivity.

Iron and titanium oxide nanoparticles have been synthesized in parallel mesopores of alumina by a novel organometallic "chimie douce" approach that uses bis(toluene)iron(0) (1) and bis(toluene)titanium(0) (2) as precursors. These complexes are molecular sources of iron and titanium in a zerovalent atomic state. In the case of 1, core shell iron/iron oxide particles with a strong magnetic coupling between both components, as revealed by magnetic measurements, are formed. Mössbauer data reveal superparamagnetic particle behavior with a distinct particle size distribution that confirms the magnetic measurements. The dependence of the Mössbauer spectra on temperature and particle size is explained by the influence of superparamagnetic relaxation effects. The coexistence of a paramagnetic doublet and a magnetically split component in the spectra is further explained by a distribution in particle size. From Mössbauer parameters the oxide phase can be identified as low-crystallinity ferrihydrite oxide. In agreement with quantum size effects observed in UV-visible studies, TEM measurements determine the size of the particles in the range 5-8 nm. The particles are mainly arranged alongside the pore walls of the alumina template. TiO2 nanoparticles are formed by depositing 2 in mesoporous alumina template. This produces metallic Ti, which is subsequently oxidized to TiO2 (anatase) within the alumina pores. UV-visible studies show a strong quantum confinement effect for these particles. From UV-visible investigations the particle size is determined to be around 2 nm. XPS analysis of the iron- and titania- embedded nanoparticles reveal the presence of Fe2O3 and TiO2 according to experimental binding energies and the experimental line shapes. Ti4+ and Fe3+ are the only oxidation states of the particles which can be determined by this technique. Hydrogen reduction of the iron/iron-oxide nanoparticles at 500 degrees C under flowing H2/N2 produces a catalyst, which is active towards formation of carbon nanotubes by a CVD process. Depending on the reaction conditions, the formation of smaller carbon nanotubes inside the interior of larger carbon nanotubes within the alumina pores can be achieved. This behavior can be understood by means of selectively turning on and off the iron catalyst by adjusting the flow rate of the gaseous carbon precursor in the CVD process.

Journal Article↗
PubMed2001

Dinuclear titanium(IV) complexes from amino acid bridged dicatechol ligands: formation, structure, and conformational analysis.

Amino acid bridged dicatechol ligands 3a-e-H4 form dinuclear double-stranded coordination compounds [(3a-e)2Ti2(OCH3)2]2- with titanium(IV) ions. Due to the directionality of the ligands, the chirality of the strand, and the chiral complex units, up to seven isomers, I-VII, can be obtained for the double-stranded complexes of ligands 3a-e-H4. The composition of the mixture of isomeric compounds in solution is strongly dependent on the conditions of complex formation. Under thermodynamic control, only a few isomers are obtained, one of which is the major component of the mixture. X-ray structure analyses were performed for K2[(3b)2Ti2(OH)2] and K2[(3d)2Ti2(OH)2] (type I), and for the meso complex Na2[(3e)(3e')Ti2(OCH3)2]. A conformational analysis that uses Ramachandrans method revealed that the conformation of the amino acids in the ligand strands can be compared with those found for amino acids in helical peptide structures. The most favored isomer of [(3)2Ti2(OCH3)2]2- appears to be of type I, with the catecholamide unit located at the N terminus of the ligand strand that binds to a lambda-configurated titanium(IV) complex unit and the dihydroxybenzyl group at the C terminus that coordinates to a delta-configurated titanium(IV) complex unit. The lambda configuration at the N terminus induces the conformation of a right-handed helix in the amino acid residue, while the delta configuration induces the less favored left-handed helix.

Amino Acids↗
PubMed2002

Dramatically synergetic effect of carboxylic acid additive on tridentate titanium catalyzed enantioselective hetero-diels-alder reaction: additive acceleration and nonlinear effect.

This paper describes the successful development of a group of highly efficient chiral tridentate titanium catalysts for hetero-Diels-Alder reaction of Danishefsky's diene and a variety of aldehydes through ligand and additive diversity. Dramatically synergetic effect of carboxylic acid additives and influence of substituent in chiral Schiff base ligands on the enantioselectivities of the reaction are reported. It was found that a chiral drug Naproxen (A21) was a highly efficient additive for Ti-catalyzed HDA reaction, affording 2-substituted 2,3-dihydro-4H-pyran-4-one in up to 97 % ee and >99 % yields. Quantitative study of the effect of chiral carboxylic acid A21 revealed that the reaction could be accelerated by one order of magnitude. Another interesting feature of present catalytic system is the existence of significant positive nonlinear effect, which indicates that the heterochiral Schiff base-titanium complexes may have higher stability than their homochiral counterparts. As a result, the homochiral Schiff base-titanium complexes with higher ee than that of starting ligand will react with carboxylic acid additive to form the more active species and predominate the catalytic process. The isolation and characterization of stable heterochiral ((+/-)-L1)2Ti complex has also been successful, which strongly supported the explanation for positive nonlinear effect observed in the catalytic system.

Journal Article↗
PubMed2003

Mesostructured dye-doped titanium dioxide for micro-optoelectronic applications.

Optically transparent, mesostructured titanium dioxide thin films were fabricated using an amphiphilic poly(alkylene oxide) block copolymer template in combination with retarded hydrolysis of a titanium isopropoxide precursor. Prior to calcination, the films displayed a stable hexagonal mesophase and high refractive indices (1.5 to 1.6) relative to mesostructured silica (1.43). After calcination, the hexagonal mesophase was retained with surface areas > 300 m2 g-1. The dye Rhodamine 6G (commonly used as a laser dye) was incorporated into the copolymer micelle during the templating process. In this way, novel dye-doped mesostructured titanium dioxide films were synthesised. The copolymer not only directs the film structure, but also provides a solubilizing environment suitable for sustaining a high monomer-to-aggregate ratio at elevated dye concentrations. The dye-doped films displayed optical thresholdlike behaviour characteristic of amplified spontaneous emission. Soft lithography was successfully applied to micropattern the dye-doped films. These results pave the way for the fabrication and demonstration of novel microlaser structures and other active optical structures. This new, high-refractive index, mesostructured, dye-doped material could also find applications in areas such as optical coatings, displays and integrated photonic devices.

Journal Article↗
PubMed2006

A comparison of slurry sampling electrothermal vaporization and slurry nebulization inductively coupled plasma mass spectrometry for the direct determination of trace impurities in titanium dioxide powder.

A comparison of slurry sampling (SS)-ETV-ICP-MS and slurry nebulization (SN)-ICP-MS for direct determination of trace impurities in titanium dioxide powder is made. The particle size effect, matrix effect and analytical characteristics of SSETV-ICP-MS and SN-ICP-MS are compared. The results have shown that SSETV-ICP-MS has a lower particle size effect and matrix effect compared to SN-ICP-MS. The analytical performance of the two methods reveals that SSETV-ICP-MS and SN-ICP-MS have similar relative detection limits (in the nanogram per liter level); however, the former has a lower absolute detection limit than the latter. Although the precision for SSETV-ICP-MS is a little worse than that for SN-ICP-MS, it is still acceptable for real sample analysis. The two methods were successfully applied for the determination of trace impurities in titanium dioxide powder samples with particle sizes of less than 50 nm, but only SSETV-ICP-MS could be applied for the determination of trace impurities in titanium dioxide powder samples with a particle size of 1 microm.

Journal Article↗
PubMed2003

Gold-coated fused-silica sheathless electrospray emitters based on vapor-deposited titanium adhesion layers.

Gold-coated fused-silica electrospray (ES) emitters based on vapor-deposited adhesion layers of titanium have been manufactured to investigate the possibilities of producing durable ES emitters applicable in chip-based analytical devices. The stabilities of the emitters were studied by both electrospray and electrochemical experiments and a marked increase in the emitter lifetime, compared to that for Cr/Au coated emitters, was found for the Ti/Au emitters in the ES durability tests. This indicates that Ti (rather than Cr) adhesion layers should be used in association with large-scale fabrication of ES emitters by vapor-deposition techniques. The lifetime of about 500-700 hours also allowed the Ti/Au-coated emitter to be used as an integrated part of a capillary liquid chromatography column coupled to a mass spectrometer in a series of LC/MS experiments. The Ti/Au coating was further studied by electrochemical techniques and scanning electron microscopy in conjunction with X-ray spectroscopy. It is shown that the eventual failure of the Ti/Au emitters in ES experiments was due to an almost complete detachment of the gold layer. Experimental evidence suggests that the detachment of the gold coating was due to a reduced adhesion to the titanium layer during oxidation in positive electrospray. Most likely, this was caused by the formation of an oxide layer on the titanium film. It is thus shown that unlimited emitter stabilities are not automatically obtained even if the metallic adhesion layer is stabilized by an oxide formation under positive electrospray conditions.

Journal Article↗
PubMed2001

A Study on the Adsorption Characteristics of Orthophosphates on Rutile-Type Titanium Dioxide in Aqueous Solutions.

Rutile-type titanium dioxide is widely used as a pigment for paint, coating ink, paper, plastic products, and cards because of its very whiteness and outstanding hiding property. It has two weak properties to be improved, however, one being its coagulation in compounding and the other its decreasing whiteness owing to poor heat resistance. To solve these problems, a study on the treatment of titanium dioxide surfaces by adsorption technology has been performed. Experiments have been carried out to establish the adsorption isotherms of orthophosphates on titanium dioxide and to investigate the effect of organic solvents on adsorption. It is shown that the adsorption isotherms vary with pH. A Freundlich adsorption isotherm is suitable for the acidic and basic regions, while a Langmuir adsorption isotherm is suitable for the region of pH 5-8 where a maximum adsorption has been achieved. In aqueous solutions containing organic solvents, the adsorption was strongest with aqueous solutions containing 1 wt% toluene and weakest with those containing 1 wt% ethanol. Among the alcohols used, the adsorption was strongest with the aqueous solution containing 1 wt% butanol and weakest with that containing 1 wt% ethanol, thus showing a correlation with the molecular weight of the alcohol. Copyright 2001 Academic Press.

Journal Article↗
PubMed2003

Determination of titanium by slurry sampling graphite furnace atomic absorption spectrometry with the use of fluoride modifiers.

A method for the determination of titanium in graphite furnace atomic absorption spectrometry with slurry sampling was developed. Titanium forms thermally stable carbides in the graphite tube that leads to decreased sensitivity and severe memory effects. Various fluorinating agents, BaF(2), NH(4)F, and CHF(3) (Freon-23) were therefore examined in order to reduce or eliminate these problems. Ti was determined, at various concentration levels, in certified reference materials (CRMs) using ultrasonic slurry sampling graphite furnace atomic absorption spectrometry (USS-GFAAS). The three CRMs, GBW 07601 (Human Hair Powder), GBW 07602 (Bush Branches and Leaves), and GBW 07411 (Chinese Soil), contained 2.7 microg g(-1), 95 microg g(-1), and 0.41% Ti, respectively. For comparison, determinations of Ti were made with modifiers (BaF(2) and NH(4)F) and without modifier, using 5% CHF(3) (in argon) for cleaning the graphite furnace. Good accuracy was obtained using aqueous Ti standards for calibration. A homogeneity study showed that Ti was evenly distributed in all the samples at the mg-microg level. The relative standard deviations (RSDs) obtained for the three CRMs were 16%, 11%, and 8% ( n=30). In spite of the wide range of Ti concentrations in the present samples, the same wavelength (365.4 nm) could be used for analysis by varying the slurry sample concentration. The precision was best for the material with the highest titanium content in spite of the fact that only 3 microg of sample was introduced into the furnace.

Journal Article↗