Adhesive bonding of titanium nitride-plated stainless steel for magnetic attachments

The purpose of this study was to evaluate adhesive bonding of resin to titanium nitride ion-plated stainless steel in order for magnetic attachments to survive in the oral environment. Two primers, Cesead II Opaque Primer (CPII) and Metal Primer II (MPII), and one bonding agent, Super-Bond C&B (SB), were used. The surfaces of stainless steel disks were ground and then plated with titanium nitride. After the primer and SB resin were applied, a self-curing resin was bonded to the metal surfaces. Shear bond strengths were determined after 24 h of water storage and after 2,000 thermocycles. Titanium nitride ion-plated stainless steel showed bond strength comparable to the non-plated material. After thermocycling, all specimens of the group no primer/no SB were debonded. The bond strengths of groups CPII/no SB, MPII/no SB and no primer/SB were significantly lower bond strengths than groups CPII/SB and MPII/SB. An appropriate combination of primer and bonding agent should be selected when bonding a magnetic attachment to the denture base.

In vitro corrosion behavior of cast iron-platinum magnetic alloys

OBJECTIVE

The objective of this study was to investigate the corrosion resistance of cast Fe-Pt alloys of varying compositions for use as attachment keepers and to make a comparison with the corrosion resistance of magnetic stainless steel.

METHODS

The corrosion behavior of cast Fe-Pt alloy keepers (Fe-40 at%Pt, Fe-38 at%Pt, Fe-37 at%Pt and Fe-36 at%Pt) was evaluated by means of an immersion test and an anodic polarization test. The solutions used were a 1.0% lactic acid aqueous solution (pH=2.3) (10 ml) and 0.9% NaCl solution (pH=7.3) (10 ml). As a control, the corrosion resistance of a magnetic stainless steel keeper (SUS 447J1: HICOREX) was also measured.

RESULTS

Chromium and platinum ions were not detected in either the 1.0% lactic acid or 0.9% NaCl solutions. The only released ions detected were the Fe ions in the 1.0% lactic acid solution. The amounts of Fe ions released from the Fe-40 at%Pt and Fe-38 at%Pt alloys were significantly (p<0.05) lower than from the Fe-37at%Pt, Fe-36 at%Pt and SUS 447J1 alloys. In the anodic polarization test, the potentials at the beginning of passivation for the four Fe-Pt alloys were higher than for the SUS 447J1 alloy in both solutions.

SIGNIFICANCE

The Fe-Pt alloys, especially the alloys with higher Pt percentages (Fe-40 and 38 at%Pt), indicated a high corrosion resistance compared to the magnetic stainless steel keeper. A reduction in the Pt percentage may decrease the corrosion resistance in the oral environment.

Corrosion resistance of a magnetic stainless steel ion-plated with titanium nitride

This in vitro study evaluated the corrosion resistance of a titanium nitride (TiN) ion-plated magnetic stainless steel (447J1) for the purpose of applying a magnetic attachment system to implant-supported prostheses made of titanium. The surface hardness of the TiN ion-plated 447J1 alloy with varying TiN thickness was determined prior to the corrosion testing, and 2 micrometers thickness was confirmed to be appropriate. Ions released from the 447J1 alloy, TiN ion-plated 447J1 alloy, and titanium into a 2% lactic acid aqueous solution and 0.1 mol/L phosphate buffered saline (PBS) were determined by means of an inductively coupled plasma atomic emission spectroscopy (ICP-AES). Long-term corrosion behaviour was evaluated using a multisweep cyclic voltammetry. The ICP-AES results revealed that the 447J1 alloy released ferric ions into both media, and that the amount of released ions increased when the alloy was coupled with titanium. Although both titanium and the TiN-plated 447J1 alloy released titanium ions into lactic acid solution, ferric and chromium ions were not released from the alloy specimen for all conditions. Cyclic voltamograms indicated that the long-term corrosion resistance of the 447J1 alloy was considerably improved by ion-plating with TiN.

Spectroscopic studies of three osseointegrated implants

OBJECTIVES

The purpose of this study was to investigate the surface characteristics of titanium implants.

METHODS

The chemical state of the surfaces of three types of osseointegrated titanium implant, Brånemark (Nobelpharma, Göteborg, Sweden), IMZ (Friatec, Mannheim, Germany) and ITI-Bonefit (Straumann, Waldenburg, Switzerland), were analysed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).

RESULTS

The outermost layers of the implants investigated were speculated to be TiO2. In the Brånemark implants pure titanium was found under the TiO2 layer. By contrast, in the IMZ and ITI-Bonefit implants which are titanium plasma spray coated, oxygen atoms were observed at considerable depths by AES, and the material under the TiO2 layer showed a chemical shift by XPS. Furthermore, shifted peaks were not of pure titanium or of titanium oxide.

CONCLUSION

The three titanium implants investigated were found to have different surface characteristics when examined by spectroscopy. As these implants show similar osseointegration it is suggested that they may be found to interact differently with vital bone.

[Choroidal lesions and surgical treatment of bullous retinal detachment]

To define choroidal lesions of bullous retinal detachment, we performed indocyanine green angiography (IA) on 20 eyes of 10 patients with bullous retinal detachment. Four of these eyes were treated with sclerectomy and sclerostomy (Gass), and the benefit was evaluated. IA showed the following choroidal abnormalities: choroidal filling delay in the macular region (6 of 18 eyes, 33%) and underneath the leaking sites (9 of 18 eyes, 50%), localized (1 eye, 5%) and extended (18 eyes, 90%) choroidal venous dilatation, and intrachoroidal hyperfluorescence (all eyes, 100%). After the surgical treatment, retinal detachments resolved within 9 weeks (mean 5.3 weeks). Since choroidal filling delay, choroidal venous dilatation and intrachoroidal hyperfluorescence were observed, it is suggested that choroidal congestion plays a causative role in bullous retinal detachment. Sclerectomy and sclerostomy seemed to be beneficial in treatment of this condition.

Effect of anti-allergic agents on chemotaxis of neutrophils by stimulation of chemotactic factor released from hepatocytes exposed to ethanol

In an attempt to clarify a mechanism of neutrophil infiltration in the liver of alcoholics and possible therapeutic effect of antiallergic agents on accumulation of these cells in the liver, we investigated chemotaxis of neutrophils by stimulation of a chemotactic factor released from rat hepatocytes exposed to ethanol. When hepatocytes were incubated with more than 30 mM ethanol for 24 hr, chemotactic activity for both rat and human neutrophils was demonstrated in the conditioned medium. An enhanced chemotactic activity of the conditioned medium was reduced in the presence of antibody against KC/gro protein, one of the interleukin-8-related cytokines in rodents. Antiallergic agents such as azelastine or ketotifen at a concentration of > 0.01 microM markedly reduced chemotaxis of neutrophils. Prednisolone at a concentration of > 10 microM also reduced chemotaxis of neutrophils. These results suggest that neutrophil accumulation in the liver of human alcoholics could be induced by a chemotactic factor produced by the ethanol-treated hepatocytes and that antiallergic agents could be effective against the extent of alcoholic hepatitis by reducing chemotaxis of neutrophils.

Modulation of ischemia-reperfusion-induced hepatic injury by Kupffer cells

To elucidate the role of Kupffer cells in ischemia-reperfusion-induced hepatic injury, hepatic injury induced by ischemia-reperfusion was analyzed after modulation of Kupffer cell function. Ischemia of the liver was performed by occlusion of both the portal vein and hepatic artery, which enter into the left lateral and median lobes of the liver. Blood flow in the ischemic lobe was reduced, in contrast to an increased blood flow in the nonischemic lobe during occlusion of the veins. Although hepatocyte damage was not demonstrated by ischemia for < 60 min, hepatic injury was found after reperfusion of the liver, and activation of Kupffer cells was morphologically demonstrated by electron microscopies. Suppression of Kupffer cells, induced by previous administration of gadolinium chloride or latex particles, reduced the grade of hepatic injury induced by ischemia-reperfusion. On the other hand, stimulation of Kupffer cell phagocytosis, induced by administration of latex particles at the time of reperfusion, aggravated the ischemia-reperfusion-induced hepatotoxicity, which was then reduced by simultaneous administration of superoxide dismutase. Kupffer cells, isolated from the rats treated with the ischemia-reperfusion procedure, have been found to release increased amounts of oxygen radical intermediates. These results suggest that hepatic injury induced by ischemia-reperfusion is modulated by the function of Kupffer cells and that superoxide anion released from Kupffer cells could play an important role in ischemia-reperfusion hepatic injury.

Generation of chemotactic factor by hepatocytes isolated from chronically ethanol-fed rats

In an attempt to clarify a mechanism of polymorphonuclear cell and/or macrophage infiltration in alcoholic liver disease, we investigated a novel chemotactic and activating factor generated by rat hepatocytes isolated from the chronically ethanol-fed rats. Hepatocytes and hepatic macrophages were isolated from rat liver by perfusion and digestion with collagenase and subsequently by differential centrifugation on a metrizamide gradient. Rat polymorphonuclear cells were prepared from blood by the dextran sedimentation and Hypaque-Ficoll technique. Chemotactic activity was measured as migration of polymorphonuclear cells or hepatic macrophages using a chemotactic chamber. When hepatocytes isolated from the ethanol-fed rats were cultured in vitro, chemotactic activity for rat polymorphonuclear cells and hepatic macrophages was demonstrated in the culture supernatant. Inhibitors of transcription and protein synthesis reduced generation of chemotactic factor from these hepatocytes. Chemotactic activity of the conditioned medium was reduced after trypsin (0.25%, 37 degrees C, 30 min) or heat (56 degrees C, 30 min) treatment. The chemotactic activity was eluted at molecular weights of 20-25 kDa and 40-45 kDa following Sephadex G-150 chromatography. Superoxide anion production by polymorphonuclear cells and hepatic macrophages under the stimulation of phorbolmyristate acetate was enhanced in the presence of this chemotactic factor. This chemotactic factor may contribute to the pathogenesis of alcoholic liver disease.

Mechanism of accumulation of macrophages in galactosamine-induced liver injury: effect of lipoxygenase inhibitors on chemotaxis of spleen cells

In an attempt to clarify a mechanism of macrophage infiltration in galactosamine-induced hepatic injury, we investigated chemotactic factor(s) generated by murine hepatocytes exposed to galactosamine. Hepatocytes, isolated from murine liver by perfusion and digestion with collagenase, were incubated with galactosamine. Conditioned medium was collected 24 h later and chemotaxis of murine spleen cells was measured by stimulation of the conditioned medium using a modified Boyden chamber. Chemotactic activity was demonstrated in the conditioned medium of hepatocytes exposed to more than 3 mM galactosamine. Chemotactic activity of the conditioned medium was not reduced after freeze-thawing, and found to be dialyzable (molecular weight < 12,000). Trypsin (0.25%, 37 degrees C, 30 min) or heat (56 degrees C, 30 min) treatment reduced chemotactic activity of the conditioned medium. Furthermore, chemotaxis of spleen cells was decreased in the presence of lipoxygenase inhibitors (azelastine, ketotifen). These results suggest that accumulation of macrophages in the liver could be mediated by chemotactic factor produced by the galactosamine-treated hepatocytes, and that this mechanism may contribute to the pathogenesis of hepatic injury induced by galactosamine.

Role of endotoxin-responsive macrophages in hepatic injury

Although administration of 100 mg galactosamine caused severe hepatic injury in C3H/HeN mice, splenectomy reduced the grade of this hepatotoxicity. However, this hepatic injury was scarcely detected in the endotoxin-resistant C3H/HeJ mice. In addition, in contrast to high lethality in C3H/HeN mice with a combined administration of galactosamine and endotoxin, splenectomy rendered C3H/HeN mice slightly resistant to this treatment. Further resistance was demonstrated in C3H/HeJ mice. In an attempt to clarify the role of endotoxin-responsive spleen cells in the pathogenesis of hepatic injury, we investigated galactosamine-induced hepatic injury by transfer of lipopolysaccharide-treated C3H/HeN or C3H/HeJ spleen cells. Both oxygen-derived free radical production and the proportion of macrophages in spleen cells were markedly enhanced in C3H/HeN mice after an intraperitoneal injection of lipopolysaccharide. Further increase in oxidative free radical production was found in the dish-adherent cells (macrophages). These enhancements were not demonstrated in lipopolysaccharide-treated C3H/HeJ spleen cells. Although hepatic injury was not demonstrated in both C3H/HeN and C3H/HeJ mice treated with 35 mg galactosamine alone, severe hepatotoxicity was found in these galactosamine-treated mice when they received lipopolysaccharide-activated C3H/HeN spleen cells, especially macrophages. Simultaneous administration of superoxide dismutase with the activated spleen cells reduced the grade of hepatic injury. On the other hand, hepatic injury was not demonstrated in the galactosamine-treated C3H/HeN or C3H/HeJ mice when they received lipopolysaccharide-treated C3H/HeJ spleen cells, although 3H-galactosamine incorporation into hepatocytes was nearly identical in both C3H/HeN and C3H/HeJ mice. These results suggest that oxidative free radicals of lipopolysaccharide-responsive macrophages could contribute to the pathogenesis of galactosamine-induced hepatic injury.

Oxygen-derived free radical generating capacity of polymorphonuclear cells in patients with ulcerative colitis

Oxygen-derived free radical generating capacity of polymorphonuclear cells in 27 patients with ulcerative colitis, 10 with acute bacterial diarrhea and 20 healthy volunteers, was measured by the luminol-dependent chemiluminescence method by stimulation of formyl-methionyl-leucyl-phenylalanine. Oxidative free radical generating capacity of polymorphonuclear cells in patients with active ulcerative colitis was markedly enhanced as compared with control (p less than 0.01), while this enhanced free radical production by the cells was not detected at remission stage. Serial analyses revealed that oxidative free radical production by the cells in patients with ulcerative colitis was markedly enhanced with clinical deterioration of the disease, but it returned to normal level with an improvement of clinical features. These results suggest that the increased oxidative free radical production by polymorphonuclear cells could be related to the pathogenesis or aggravation of ulcerative colitis.