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PubMed1990

Thermal compatibility of titanium-porcelain system.

Porcelain-fused-to metal systems are popular in restorative dentistry. Residual stress caused by a mismatch of the thermal expansion coefficient of metal and porcelain induce clinical failure of the restoration. Titanium and its alloys have been gradually used in dentistry for their adequate strength, good corrosion resistance and excellent biocompatibility. Their oxidation characteristics and low thermal expansion coefficients capacitate for matching the low fusing porcelains. This investigation examined thermal compatibility of pure titanium with two low fusing porcelains and one high fusing porcelain. Thermal expansion coefficients (alpha) of pure titanium and porcelains were measured from room temperature to 600 degrees C at a mean heating rate of 5 degrees C/min. Difference in thermal expansion values (delta alpha) was also calculated to present the residual stress in each titanium-porcelain pairs. The bonding patterns of titanium to each opaque was demonstrated similar results from the predictions of alpha and delta alpha values.

Dental Porcelain↗
PubMed1990

Cytotoxicity of oxide anodized titanium alloy evaluated by cell and organic culture study.

The cytotoxic effects of an oxide-anodized titanium alloy were investigated by cell and organic culture studies. Toxicity was estimated based on cell survival and growth rates compared with those of control materials (glass) after cultivation of cells (L 929) and chicken embryonic femurs expose to alloy plates. The oxide-anodized titanium alloy showed no cytotoxicity with respect to survival or growth rates in either cells or chicken embryonic femurs. Furthermore, the oxide-anodized titanium alloy was more acid and alkali resistant than intact titanium alloys. The results suggest that oxide-anodized titanium has greater stability and its metallic ions may be leachedless under various conditions following dental implantations. Therefore, this alloy should be suitable for use as a dental implant material.

Aluminum↗
PubMed1989

[Direction of amino acid adsorbed by surface film on titanium].

The purpose of the study was to investigate the influence of the isoelectric point and residue of an amino acid on the adsorption of the amino acid by titanium in order to elucidate the adsorption of proteins by titanium. The direction of amino acid adsorbed by a titanium surface in an electrolytic solution was determined using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared reflection absorption spectroscopy (FT-IR-RAS). Apparently, the influence of amino acid on the composition and thickness of surface films on titanium is minimal if the film is formed in an electrolytic solution. The pH of the electrolytic solution and the residue of amino acids are responsible for the direction of the amino acid adsorbed by surface film formed on titanium in solution.

Adsorption↗
PubMed1989

Thermal oxidation effect on porcelain-titanium restoration.

Titanium has good corrosion resistance, light density, high strength and excellent biocompatibility. Conventional ceramicmetal restorations were used extensively in dentistry because of their esthetic appearance and good strength properties. The purpose of this study was to investigate the influence of various thermal treatments on the bond strength and physical properties of the porcelain-titanium system. Pure titanium was treated in a porcelain furnace at temperatures ranging from 600 to 1000 degrees C, under vacuum and in air, respectively. X-ray diffraction analysis revealed that the relative peak intensity of alpha-Ti was decreased, while the TiO2 was increased when raising the firing temperature. The vickers hardness number was increased at elevated temperatures, especially over 900 degrees C, and firing in air was harder than under vacuum. The tension-shear bond strength was highest in the green stage and lowest in the 1000 degrees C treated group. The metallographic microscopic of the porcelaintitanium interface revealed a thick band-like zone in the 1000 degrees C treated sample. Therefore it seems that the excess oxidation layer of TiO2 weakened the bond strength of porcelain-titanium. Contrary to the conventional ceramic-gold alloys system, the recommended degassing procedure was not suitable for the porcelain-titanium restoration.

Dental Porcelain↗
PubMed1988

Hydroxyapatite-coated porous titanium for use as an orthopedic biologic attachment system.

The biologic attachment characteristics of hydroxyapatite (HA)-coated porous titanium and uncoated porous titanium implants were investigated. The implants were placed transcortically in the femora of adult mongrel dogs and evaluated after periods of three, six, and 12 weeks. The HA coating was applied using a modified plasma spray process to samples with pore volume and pore size of the porous coating expanded to equal the pore morphology of uncoated porous specimens. Mechanical push-out testing revealed that the bone-porous material interface shear strength increased with time in situ for both the uncoated and HA-coated implants. The use of the HA coating on porous titanium, however, did not significantly increase attachment strength. Histologic and microradiographic sections yielded similar qualitative results in the amount of bone grown into each system. After three weeks, both systems displayed primarily woven bone occupying approximately 50% of the available porous structure. Six and 12 weeks postimplantation, each system displayed more extensive bone ingrowth, organization, and mineralization, with only limited areas of immature bone. Histologically, differences were noted at the ingrown bone-porous material interface between the two implant types. The HA coating supported mineralization directly onto its surface, and a thin osseous layer was found lining all HA-coated surfaces. An extremely thin fibrous layer was observed separating the uncoated titanium particle surface from ingrown bone. There was no extensive direct apposition or lining of the ingrown bone to the uncoated porous titanium particle surfaces.

Animals↗
PubMed1988

Hydroxyapatite-coated titanium for orthopedic implant applications.

The interface mechanical characteristics and histology of commercially pure (CP) titanium- and hydroxyapatite- (HA) coated Ti-6Al-4V alloy were investigated. Interface shear strength was determined using a transcortical push-out model in dogs after periods of three, five, six, ten, and 32 weeks. Undecalcified histologic techniques with implants in situ were used to interpret differences in mechanical response. The HA-coated titanium alloy implants developed five to seven times the mean interface strength of the uncoated, beadblasted CP titanium implants. The mean values for interface shear strength increased up to 7.27 megaPascals (MPa) for the HA-coated implants after ten weeks of implantation, and the maximum mean value of interface shear strength for the uncoated CP titanium implants was 1.54 MPa. For both implant types there was a slight decrease in mean shear strength from the maximum value to that obtained after the longest implantation period (32 weeks). Histologic evaluations in all cases revealed mineralization of interface bone directly onto the HA-coated implant surface, with no fibrous tissue layer interposed between the bone and HA visible at the light microscopic level. The uncoated titanium implants had projections of bone to the implant surface with apparent direct bone-implant apposition observed in some locations. Measurements of the HA coating material made from histologic sections showed no evidence of significant HA resorption in vivo after periods of up to 32 weeks.

Alloys↗
PubMedDate not supplied

The mechanical properties of milled and cast titanium for ceramic veneering.

This study compared the mechanical properties of machine-milled pure titanium and cast titanium. The metals were cast or milled to the dimensions of a standard tensile bar pattern. Each group was treated under three different conditions: as-cast (or as-milled), standard heat, and extended heat. Tensile testing found no difference in the mechanical properties of as-cast and as-milled titanium. Heat treatment significantly increased the ultimate tensile strength and the yield strength of cast titanium but had no such effects on milled titanium. There was no significant difference between the two metals in the modulus of elasticity or the percentage of elongation under the three treatment conditions.

Alloys↗
PubMed1994

Use of titanium implants in pedicular screw fixation.

Several types of pedicular screw systems have been utilized to augment lumbar spine fusion. All systems are made of stainless steel, which interferes with imaging techniques, especially MRI and CT scans. In search of a solution for this problem, we decided to study the use of titanium systems in the lumbar spine. Because there were no titanium pedicle screw systems available on the market, we decided to use the titanium Alta system currently used for femur fractures. This report details our experience in using this device for lumbar spine fusion. From 1990 to 1992, 25 patients underwent thoracic and lumbar fusion with Alta titanium screws and plates. Spinal fusion was performed for a variety of conditions, including metastatic tumor, fracture, spondylolisthesis, pseudoarthrosis, and postdecompressive instability. All but two patients obtained solid fusion clinically and radiographically and considerable improvement in back pain. There was loosening of the implant in both patients. Both patients had osteoporosis. One of these two patients developed pseudoarthrosis, which required further surgery. The other patient with a metastatic tumor of the spine remained asymptomatic without change in the spine alignment despite progression of the tumor. There were no broken screws encountered during follow-up. Two patients sustained subsequent fracture of the vertebra above the fusion. One of the patients also developed a fracture below the fusion. Fusion with titanium implants allowed postoperative evaluation and subsequent periodic examination of the spinal canal with high-quality MR images as well as significant reduction of artifacts on CT scan.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Abrasive wear of ceramic, metal, and UHMWPE bearing surfaces from third-body bone, PMMA bone cement, and titanium debris.

The debris generated by the progressive wear of total joint replacement (TJR) devices is considered a primary cause of osteolysis, bone resorption, and premature failure of artificial hips and knees. The vast majority of this debris originates from the UHMWPE articulating surfaces caused by tribological interaction with the opposing metal or ceramic surface and hard particulates contained in the sinovial fluid. Entrapment of third body debris, such as cortical bone, PMMA cement, and titanium debris, between the articulating surfaces can cause abrasion of both the hard bearing surface and the UHMWPE. The propensity for abrasive wear is dependent on the relationship between the hardness of the third-body debris and the hardness of the bearing surfaces. To gain a better understanding of this relationship and its effect on wear, the abrasive wear behavior of several metal and ceramic bearing surfaces was characterized in terms of the hardness of both the third-body debris and the metal or ceramic substrate. The effects of abrasion and increased surface roughness of the metal or ceramic surfaces on wear of the UHMWPE was also determined. In addition, the amount of UHMWPE wear was quantified in terms of the amount (particles/ml) of titanium fretting-type debris contained in solution. The results of this investigation showed the resistance to abrasive wear of the metal and ceramic bearing surfaces to increase with increasing surface hardness. Bone debris, PMMA cement, and titanium debris produced visible abrasion of all metal surfaces including nitrogen ion implanted Ti-6Al-4V. The ceramic bearing surfaces showed no evidence of abrasion and produced the least amount of UHMWPE wear. The wear of UHMWPE sliding against Co-Cr-Mo was found to increase with increasing levels of 1.48 microns titanium debris added to the wear test solution. The rate of UHMWPE wear increased rapidly for concentrations of titanium debris in the test solution exceeding about 10(5) particles/ml. These test results suggest that third-body particles, both large and small, are capable of causing increased abrasive wear of UHMWPE, and that abrasion of the hard bearing surfaces will occur if the hardness of the third-body debris exceeds the hardness of the metal or ceramic bearing surface.

Biocompatible Materials↗
PubMed1994

Laminin localization and gelatinolytic activity of epithelial rest of Malassez grown on titanium.

The purpose of this study was to examine laminin localization in epithelial rests of Malassez grown on titanium and their gelatinase activity. Laminin localization was confirmed by immunocytochemistry in all epithelial cells grown on titanium. The conditioned medium from the epithelial cells grown on titanium exhibited 72kD- and 92 kD-gelatinase activities by gelatin zymography. Those results suggest that laminin contributes to the epithelial cell attachment to titanium and that gelatinases may be mobilized for epithelial cell movement on titanium.

Animals↗
PubMed1993

[A study of hygienic standard for titanium in the source of drinking water].

The smell and taste thresholds of titanium in water were tested. The results indicated that the concentration of smell and taste thresholds for Titanium were 4.329mg/L and 3.332mg/L respectively. The threshold below value of autopurification was 0.1mg/L. The toxicity assessment showed that the acute toxicity of titanium by oral route was of low order according to the toxicity classification. There was no obvious cumulative effect, nor was there mutagenesis demonstrable. Chronic toxicity test of titanium in rats showed that the maximum non-effective concentration was 1.08mg/L. It is suggested that the maximum allowable concentration of titanium in drinking water may be 0.1 mg/L.

Animals↗
PubMed1993

Bone-graft reconstruction of the monkey orbital floor with iliac grafts and titanium mesh plates: a histometric study.

Bone-graft reconstruction of large orbital defects has been difficult because of a lack of marginal support of the grafts and unpredictable resorption. A titanium mesh orbital plate has been developed to provide this marginal support for bone grafts. However, the problem of unpredictable bone-graft resorption remains. To determine if this plate has any effect on graft resorption, this study was designed to quantitate the dimensions and composition of bone autografts (1) with and without titanium plate support and (2) in the anterior and posterior orbit. Bilateral full-thickness large orbital floor defects were surgically created in five monkeys, and a titanium orbital floor plate was fixed with screws into the right orbit. Two iliac crest grafts were measured and placed transversely and without fixation in each orbit, one anterior and the other posterior to the axis of the globe. The orbits were retrieved 28 weeks after surgery and were analyzed histologically and histometrically. Comparison of the supported and nonsupported grafts revealed no differences in their histologic appearance. There were three significant histometric findings: (1) resorption of bone was similar for those grafts which spanned an orbital floor defect and those which were supported by a titanium plate; (2) resorption of grafts in the posterior orbit did not differ from that of grafts in the anterior orbit; and (3) resorption of approximately one-third of bone-graft thickness and width had taken place during the 28-week study interval. We conclude that the benefits of bone-graft support by a titanium mesh orbital floor plate are not offset by any alteration in bone-graft resorption.

Animals↗
PubMed1996

Postoperative magnetic resonance imaging with titanium implants of the thoracic and lumbar spine.

Within recent years, the technologies of radiological imaging and spinal instrumentation have exponentially increased. New methods of preoperative imaging, that is, magnetic resonance imaging (MRI) and computed tomography, have allowed for a better understanding of surgical pathology. Such an understanding is likely to lead to a more successful surgical experience, which certainly is the case with spine surgery with instrumentation. However, after implantation of most instrumentation, imaging is greatly impaired. Metallurgic advancements in titanium were sought to reduce postoperative imaging problems. The purpose of this study is to assess the presence and extent of artifacts seen on postoperative MRI scans in patients with titanium spinal implants. Six patients, four with degenerative spine disease and two with neoplasms, had thoracic and/or lumbar spinal fixation performed with titanium instrumentation. All patients underwent postoperative conventional MRI with the use of T1-weighted, T2-weighted, and gradient-echo sequences. The scans and individual sequences were then analyzed for image quality. A progressive and significant increase in imaging artifact related to the titanium spinal instrumentation was observed on the T1-weighted, T2-weighted, and gradient-echo sequences. Titanium spinal instruments do not allow optimal postoperative imaging on conventional MRI scanners.

Adult↗
PubMed1993

Titanium. A review of investments for high temperature casting.

Conventional silica (SiO2) based dental casting investments are used for the casting of pure titanium using casting machines specifically developed for this metal. Highly reactive molten titanium reduces SiO2 and titanium is in turn oxidised. For this reason possible alternatives to SiO2 have been studied in the past decade and MgO and Al2O3 are the most common in current commercial investments released for titanium casting. The surface of titanium castings presents a layered structure and its evaluation in relation to clinical performance requires further study. It is also urgently required to know setting and thermal behaviour of the newly developed investments for successful compensation of metal shrinkage.

Aluminum Oxide↗
PubMedDate not supplied

[Use of titanium alloys for medical instruments].

On the ground of an analysis into properties of titanium and its alloys the fields of their possible utilization for making various medical instruments are proposed. Because of their insufficient hardness and wear-resistance the titanium alloys cannot be recommended for making medical instruments with thin cutting edges. For the reasons of their insufficient strength, low wear-resistance and substandard modulus of elasticity, it is inexpedient to use titanium alloys in making many types of clamping medical instruments. Nor is it advisable to employ titanium alloys in handles of the instruments, for this may lead to a contact corrosion of their working parts. The use of titanium alloys is recommended for making bone-joining members, retracting medical instruments, of the spatula and speculum types, some kinds of non-magnetic pincers and ultrasonic medical instruments.

Alloys↗
PubMed1996

Titanium for prosthodontic applications: a review of the literature.

Titanium has become a material of great interest in prosthodontics in recent years. A growing trend involves the use of titanium as an economical and biocompatible replacement for existing alloys for fixed and removable prostheses. However, long-term results of titanium casting, joining, and porcelain bonding have to be evaluated before this wonder metal can be used routinely in clinical dentistry. This article describes the development and properties of titanium and reviews the literature related to the use of titanium in prosthodontics, for the purpose of evaluating the present status and future trends in its use.

Chromium Alloys↗
PubMed1996

Crevice corrosion of cemented titanium alloy stems in total hip replacements.

Twenty-eight cemented Müller straight femoral stems of titanium forged alloys were mainly revised for causing pain in the patient. The pain pattern differed from aseptic loosening and pain recurred only 14.5 months on average after implantation. The character of pain was dull, permanent, and increased at rest. Some patients reported pain relief while walking. Revisions were performed on average 25.5 months after primary implantation. Data from medical records, radiographs, histology of tissues taken at revision surgery, intraoperative pH measurements, examination of retrieved stems and bone cement fragments were gathered. In the radiographs debonding was visible only in 3 cases; a spindle shaped thickening of the femora occurred 9 months on average after recurrence of pain. After a further 11 months (average), scalloping osteolyses appeared. Abraded particles like metallic titanium alloy, titanium corrosion products, polymethylmethacrylate, xray contrast medium, and polyethylene were detected. Metallic particles dominated in the joint capsule whereas more corrosion products impregnated the cement to bone interface. The distal surfaces of the stems were corroded at a higher rate, whereas the proximal regions more often were subject to abrasion. Measurements of the pH of the corroded stems revealed values of high acidity. Recurrence of pain and subperiosteal apposition of bone are due to diffusion of acid; subsequent scalloping osteolyses develop due to particle induced foreign body granulomas. The mechanism of crevice corrosion of cemented titanium based alloys does not seem applicable to cobalt and iron based implant alloys. Titanium alloys can no longer be recommended for cementation, but are as safe as ever for anchorage without cement.

Adult↗
PubMed1996

Influence of soft tissue contamination on the integration of titanium implants. An experimental study in rabbits.

In the present study, the influence of peroperative soft tissue contamination on the healing of titanium implants was studied in 9 lop-eared rabbits. Titanium implants (Brånemark System) were inserted in the tibiae, a location with cortical bone only, in such a way that one group was inserted the standard way (control), and another group was contaminated for 30 s in the adjacent soft tissues, prior to insertion. The implants were allowed to heal for 12 weeks and were then retrieved together with surrounding bone, fixed, dehydrated and embedded in plastic resin. About 10 micron thick ground sections were prepared for light microscopic morphometry. The mineralized bone-to-titanium contact, and the amount of bone occupying the threads, were calculated for each implant, and the results of the two groups were compared. All retrieved implants were clinically stable at the end of the experiment. Regarding bone-to-titanium contact and bone area within the threads, a statistically nonsignificant difference was observed between the 2 groups. This study indicated that peroperative soft tissue contamination of c.p. titanium implants does not prevent osseointegration from occurring, when studied in the rabbit tibia.

Animals↗