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PubMed1990

[Ultimate tensile strength of plasma- and laser-welded cast titanium (Titaniumer, Ohara)].

The ultimate tensile strength (UTS) of titanium castings (Titaniumer, Ohara) as cast and after plasma-welding, laser-welding and soldering was investigated according to DIN 13912. The UTS of titanium as cast was 567 (+/- 36) MPa. After plasmawelding UTS decreased by 69% on the average, after laser-welding by 20%, after soldering with Ag65Cu20Pd15 (1060 degrees C) by 46% and after soldering with Ag72Cu20Ti8 (980 degrees C) by 63%. The highest tensile strength was observed in laser-welded titanium under the conditions described.

Dental Casting Technique↗
PubMed1991

In vivo comparison of THC:YAG laser welding to sutured closure of biliary tissue.

Percutaneous endoscopic approaches to cholelithiasis are an alternative to extracorporeal shockwave lithotripsy which offer advantages of fewer restrictions on stone size and type as well as avoidance of fragmented stone passage complications. Endoscopic techniques would be facilitated by methods of welding gallbladder tissues. The technical constraints imposed by the endoscopic approach favor nonsuture methods of fusing gallbladder tissues. To evaluate a laser method for fusing biliary tissue, we have compared the healing response of laser-welded versus polyglycolic acid suture-closed incisions in canine gallbladder tissue in vivo. The laser used was a thulium-holmium-chromium:YAG laser producing 200-microsecond, 300-millijoule pulses at 2.15 microns. Serial sacrifice of dogs that underwent laser or suture closure of incisions made in the fundus of the gallbladder revealed that all repairs healed without evidence of leakage or infection. Laser-welded cholecystotomy sites had complete fibrous healing of the wound by two weeks postoperatively and reepithelialization by three weeks after operation. Suture-closed wounds were still without complete epithelization four weeks after the procedure. Laser welding may be a useful technique in endoscopic biliary surgery.

Animals↗
PubMedDate not supplied

Laser welding of synthetic epikeratoplasty lenticules to the cornea.

We used a milliwatt continuous wave CO2 laser mounted on an operating microscope to study the feasibility of welding synthetic collagen epikeratoplasty lenticules to the cornea. In vitro studies and experimentation in rabbits and monkeys showed no welding effects using direct laser radiation with powers ranging from 17 mW to 1 W. Only tissue shrinkage was observed. Experiments using various adjunctive solders produced a temporary welding effect using 30% bovine serum albumin welded with a power of 35-45 mW, 325 microns spot size, moving the beam 5 mm/sec. The lenticules remained in place until the 4th postoperative day when epithelium grew underneath the lenticule, dislodging it. Histopathologic examination demonstrated epithelial migration over the solder displacing the epikeratoplasty lenticule and anterior stromal denaturization and disruption.

Animals↗
PubMed1987

Argon laser-welded arteriovenous anastomoses.

This study compared the healing of laser-welded and sutured canine femoral arteriovenous anastomoses. Arteriovenous fistulas 2 cm in length were created bilaterally in the femoral vessels of 10 dogs and were studied at 1 (n = 2), 2 (n = 2), 4 (n = 3), and 8 (n = 3) weeks. In each animal, one anastomosis (control) was closed with running 6-0 polypropylene sutures, and the contralateral anastomosis (experimental) was sealed with an argon laser (0.5 watt, 4 minutes of exposure, 1830 J/cm2/1 cm length of anastomosis). At removal all experimental anastomoses were patent without hematomas, aneurysms, or luminal narrowing. Histologic examination at 4 weeks revealed that laser-welded anastomoses had less inflammatory response and almost normal collagen and elastin reorientation. At 8 weeks sutured anastomoses had significant intimal hyperplasia whereas laser repairs had normal luminal architecture. Tensile strength and collagen production, measured by the synthesis of hydroxyproline and the steady-state levels of type I and type III procollagen messenger ribonucleic acids, at the anastomoses and in adjacent vein and artery specimens were similar in sutured and laser-welded repairs at 2, 4, and 8 weeks. We conclude that argon laser welding of anastomoses is an acceptable alternative to suture techniques, with the advantage of improved healing without foreign body response and possible diminished intimal hyperplasia at the anastomotic line.

Animals↗
PubMed1993

Comparison of laser-assisted anastomosis, laser welding, and microsurgical anastomosis of rabbit uterine tubes.

OBJECTIVE: To assess laser-assisted anastomosis in fallopian tube reconstruction. METHODS: Fifty-two rabbit uterine tubes were transected and subjected to laser welding or to microsurgical or laser-assisted anastomosis in a randomized paired design, and compared with the contralateral side. The time required for the procedure, patency of the uterine tubes, amount of adhesion formation, and quality of scar tissue (grossly and histologically) were evaluated 4 weeks after surgery. RESULTS: Traditional microsurgical procedures required significantly longer operative time than laser-assisted anastomosis (64.4 +/- 2.2 versus 41.3 +/- 2.2 minutes) or laser welding (47.8 +/- 3.0 versus 24.5 +/- 3.0 minutes). Patency was established in all 52 uterine tubes. Adhesion formation was animal-dependent rather than procedure-dependent. All scars healed well and most were not visible beyond residue suture. Inflammatory cells were noted around the suture sites; however, gross observation revealed that all mucosal surfaces over the scars were smooth. One of 18 laser-welded uterine tubes developed dehiscence, whereas there was no dehiscence in laser-assisted or microsurgically anastomosed uterine tubes. CONCLUSION: Laser-assisted anastomosis is superior to laser welding or microsurgical anastomosis in rabbit uterine tubes. Laser-assisted anastomosis has potential use in fallopian tube reconstruction.

Anastomosis, Surgical↗
PubMed1994

Lung cancer risk and welding--preliminary results from an ongoing case-control study.

In a hospital-based case-control study, 391 male cases or primary lung cancer and the same number of controls--matched by sex, age, and region--were personally interviewed for their job and smoking histories. The data reported reflect the midpoint of a study aiming at a total of 1,000 cases. One objective of the study was to assess confounding by asbestos exposure in what was thought to be a welding-associated risk. While the odds ratios (OR) increased steeply with cumulative exposure to tobacco smoke and were raised also for lifelong asbestos exposure of over 4,100 working hours (OR = 1.91), the effect of welding exposure was reduced after adjustment for smoking and exposure to asbestos. Furthermore, no consistent dose-response relationship could be shown in relation to welding hours. Therefore the present study supports the hypothesis that some, if not all, of the excess risk of welders observed in the literature may be due to the exposure to asbestos. The finding that the subgroup of employees in the aircraft industry showed an increased odds ratio of 2.14 after adjustment for smoking and exposure to asbestos deserves further attention. This suggests the need for further research on the role of berryllium-containing alloys, which has been suggested by other authors.

Aged↗
PubMed1983

An investigation of fibrogenic and other toxic effects of arc-welding fume particles deposited in the rat lung.

Lung burdens of deposited particles from fumes generated by arc-welding were established in rats by single inhalation exposures, repeated intermittent exposure or by intratracheal injection. Fumes from manual metal arc-welding using flux-coated mild-steel rods (MMA-MS) were compared with those from metal inert-gas welding with stainless steel wire (MIG-SS). After initial rapid clearance of deposited material from the lungs, persistent residual deposits remained. Such residues resulting from single inhalation were small and confined mainly to peribronchial accumulations in macrophage clusters. Deposits remaining after repeated inhalation were larger and more widespread. Intratracheal administration (50 mg) established massive residual deposits, giving nodular accumulations in peribronchial, subpleural and perivascular sites, with substantial alveolar parenchymal involvement. Deposits from both types of fumes contained predominantly iron. Particles from stainless steel also contained chromium, but concentrations of this element were low in deposits from MMA-MS fumes. MMA-MS deposits contained silica, probably amorphous. Long-term studies (up to 450 days) attempted to detect evidence of fibrosis resulting from particle burdens. Low-grade collagen fibre layers developed at margins of MMA-MS nodules. Diffuse reticulin fibre networks occurred within MIG-SS aggregates. Tissue hydroxyproline levels were increased (doubled) in lungs with intratracheal burdens of MMA-MS particles, but no significant increases resulted from MIG-SS. The major lesions were nodular aggregates of particle-laden macrophages with giant-cell formation, and alveolar epithelial thickening with atelectasis.

Aerosols↗
PubMed1985

Welding fumes and chromium compounds in cell transformation assays.

Fumes generated from mild steel and stainless steel welding were collected on paper filters and tested in the BHK and SHE cell transformation assays. Fumes from the manual metal arc welding of stainless steel (MMA/SS) had a toxic and transforming effect attributable to their Cr(VI) content. The fumes from metal inert gas stainless steel (MIG/SS) welding also had a toxic effect but this was 2-3 times greater than that expected from their soluble Cr(VI) content based on the activity of soluble Cr(VI) from pure chromium compounds. When collected in an impinger, the fumes from MIG/SS were found to contain approximately 10 times the soluble Cr(VI) content of samples collected on filters. This additional Cr(VI), when collected in a water impinger, also exhibited a greater toxicity compared with that found for the additional Cr(VI) collected in an impinger filled with growth medium. This comparison implies the presence of a short-lived biologically active Cr(VI) species usually lost in conventional sampling techniques. It also implies that there is a detoxification step associated with the formation of Cr(VI) organic complexes. Relatively insoluble Cr(VI) compounds showed a higher toxic and transforming effect in the BHK assay than could be ascribed to the soluble Cr(VI) content of the medium, indicating the importance of phagocytosis as a pathway for the uptake of Cr(VI) and other toxic substances from particulates.

Animals↗
PubMed1986

Toxic and genotoxic action of electric-arc welding fumes on cultured mammalian cells.

Welding fumes generated by manual metal arc welding (MMAW) with an automatic welding machine were extracted with water and both the soluble and insoluble fractions were investigated for mitotic delay and for sister chromatid exchange (SCE) induction in cultured Chinese hamster lung (Don) cells. Five flux-coated electrodes of varying composition were chosen as representative of those available. In general, water-soluble and water-insoluble fractions induced SCE in proportion to their chromium(VI) content, and any contribution from chromium(III), fluorides, nickel, manganese or other fume constituents was minor. However, mitotic delay could not be explained in terms of the chromium(VI) concentration alone. This indicated that other components of both the soluble and insoluble fractions of the fumes were capable of inducing mitotic delay. The activity of insoluble fume fractions, either in mitotic delay- or in SCE-induction, was markedly less than that of soluble fractions. This was presumably because of the lower, though still significant, bioavailability of 'insoluble' components of the fume particles.

Air Pollutants, Occupational↗
PubMed2001

Concentrated autologous plasma protein: a biochemically neutral solder for tissue welding.

BACKGROUND AND OBJECTIVE: Xenographic or allographic serum protein solders used for laser welding may have immunologic and/or pathogenic complications. The objective of these studies was to develop a safe, autologous solder. STUDY DESIGN/MATERIALS AND METHODS: Five methods of preparing concentrated autologous plasma protein solder (CAPPS) were evaluated. Next, the CAPPS was evaluated via (1) thermal denaturation studies using differential scanning calorimetry, (2) tissue welding studies to characterize both acute and healing properties. RESULTS: The optimal concentration method to produce CAPPS rapidly was a dialysis method using chemical (osmotic) forces. The CAPPS showed similar denaturation profiles to serum albumin (SA) solders. Acutely, CAPPS provided comparable breaking strengths to SA solders. At 7 days, there was no significant difference in breaking strength or histology between 50% human SA solder and CAPPS (using a porcine skin model). CONCLUSIONS: These studies demonstrate that the CAPPS system provides acceptable acute and chronic properties for laser welding.

Animals↗
PubMed1984

Laser-welded vs soldered nonprecious alloy dental bridges: a comparative study.

The high cost of gold alloy has caused the dental profession to begin substituting nonprecious alloy for the framework in porcelain fused to metal bridges. Especially in long-span bridges it may be advantageous to make multiple castings and then join them for a better fit. As opposed to the highly successful soldering of gold, soldered nonprecious alloy bridges have a great failure rate in the mouth. Removal of and remaking of the bridges is thus the result. This study compares nonprecious units that have been laser-welded with those conventionally soldered. Seven identical bridges of three units were cast in a popular alloy composed of 74-78% nickel, 12-15% chromium, 4-6% molybdenum, and 1.8% maximum beryllium. One served as a control, while the remaining six were all cut in the same place. Of these, three were soldered with a gas oxygen torch. The other three were welded with a Nd-YAG laser. Better and stronger joints unlikely to fracture in the mouth were found with the laser-welded specimen.

Chromium Alloys↗
PubMed1989

Crosslinking of extracellular matrix proteins: a preliminary report on a possible mechanism of argon laser welding.

In order to elucidate the biochemical mechanism of laser welding of tissues, we have compared protein profiles from argon laser-treated specimens with controls. Extracellular matrix components from untreated and laser-welded skin and blood vessels were extracted with guanidine hydrochloride and separated by SDS polyacrylamide gel electrophoresis. When compared with matched, untreated tissues, protein electrophoretic profiles from laser-treated samples showed several changes. In both tissue types, argon laser treatment decreased the concentration of a 235 kd protein that migrates between the alpha and beta chains of type I collagen. Laser-treated blood vessels showed significantly more low molecular weight protein at the dye front than in control tissue, whereas significantly more high molecular weight protein appeared in laser-treated skin samples when compared with untreated tissue. These results suggest that the argon laser may either degrade or crosslink proteins in vivo. Laser-induced protein crosslinks may be the biochemical basis of argon laser welding.

Animals↗
PubMed1983

Urine chromium as an estimator of air exposure to stainless steel welding fumes.

Welding stainless steel with covered electrodes, also called manual metal arc welding, generates hexavalent airborne chromium. Chromium concentrations in air and post-shift urine samples, collected the same arbitrarily chosen working day, showed a linear relationship. Since post-shift urine samples reflect chromium concentrations of both current and previous stainless steel welding fume exposure, individual urine measurements are suggested as approximate although not exact estimators of current exposure. This study evaluates the practical importance of such measurements by means of confidence limits and tests of validity.

Adult↗
PubMed1993

Mechanical properties of laser welds of titanium in dentistry by pulsed Nd:YAG laser apparatus.

The use of titanium in dentistry is increasing, and an adequate method of joining titanium units of restorations is needed. This study examined the welding of titanium with a normal pulse Nd:YAG laser. Laser welding of titanium was effective when performed in an argon atmosphere. ANOVA for the three-point bending test showed a correlation between the bending strength of a weld, the atmosphere under which the irradiation is performed, and the intensity of the irradiation.

Analysis of Variance↗
PubMed1994

Exposure to cobalt in the welding process with stellite.

In some small factories producing moulds for ceramic tiles using a cobalt alloy (stellite), environmental and biological (CoU) monitoring was conducted for eight workers employed in gas-shielded arc (MAG) and oxy-acetylene welding processes. During oxy-acetylene braze-welding, the exposure to cobalt is very low as are urinary cobalt concentrations. On the other hand, during the MAG welding process, the exposure levels can exceed the TLV-TWA levels and correlated well with CoU at the end of a working shift. Two MAG welders followed for two consecutive weeks, showed different patterns of urinary cobalt excretion: under the same environmental conditions, the higher CoU was found in the worker with greater past exposure. This aspect needs further evaluation before adopting CoU as a current indicator of occupational exposure to the metal.

Air Pollutants, Occupational↗
PubMed1984

Inhalation toxicity study of welding fumes: effect of single or repeated exposure on the lungs of rats.

An inhalation toxicity study of L fumes generated from the manual metal arc (MMA) welding of mild steel with a Lime electrode and S fumes generated from the MMA welding of stainless steel with a Lime-titania electrode has been carried out in rats. A method allowing continuous exposure of rats to a reasonably uniform fume concentration was established. Rats wer exposed to 1000 mg/m3 fumes for 1 h in the single exposure study and to 400 mg/m3 fumes for 30 min/day, 6 days/week, for 2 week in the repeated exposure study. Physical and chemical characteristics of the fumes, such as chemical composition, water solubility and particle size, were evaluated. Exposure to S fumes produced greater changes in lung weight and morphology than exposure to L fumes. Histopathological signs of respiratory irritation, such as mucus granules in the alveoli and hyperplasia of mucus cells in the bronchial epithelium, and bronchiectasia were observed only in the rats exposed to S fumes. Fume elements deposited in alveolar macrophages were qualitatively analyzed by means of an electron probe X-ray micro-analyzer and were essentially identical to those in the welding fumes.

Air Pollutants, Occupational↗
PubMed1982

Biochemical studies of rat lung following exposure to potassium dichromate or chromium-rich welding fume particles.

Rats were examined for biochemical changes at the lung surface and in lung tissue 1, 4, and 13 weeks after a single instillation of the soluble of insoluble fraction of stainless steel welding particles, or potassium dichromate containing concentrations of hexavalent chromium (CrVI) equivalent to those found in the welding particles. Most of the toxicity of the welding particles 1 week after instillation could be related to the content of soluble CrVI, though the insoluble particles also produced changes at the alveolar surface. The regression of inflammatory changes 4 and 13 weeks after instillation was probably due to the removal of soluble components such as CrVI from the lung.

Air Pollutants↗
PubMed2006

Sequelae of fume exposure in confined space welding: a neurological and neuropsychological case series.

Welding fume contains manganese (Mn) which is known to be bio-available to and neurotoxic for the central nervous system. Although an essential metal, Mn overexposure may cause manganism, a parkinsonian syndrome. The present welder study sought to improve the clinical portrait of manganism and to determine dose-effect relationships. The welders were employed in the construction of the new Bay Bridge (San Francisco) and welded in confined spaces for up to 2 years with minimal protection and poor ventilation. Neurological, neuropsychological, neurophysiological, and pulmonary examinations were given to 49 welders. Clinical cases were selected on the basis of apriori defined criteria pertaining to welding history and neurological/neuropsychological features. Among the 43 eligible welders, 11 cases of manganism were identified presenting with the following symptoms: sleep disturbance, mood changes, bradykinesia, headaches, sexual dysfunction, olfaction loss, muscular rigidity, tremors, hallucinations, slurred speech, postural instability, monotonous voice, and facial masking. Significant associations between outcome variables and cumulative exposure index (CEI) or blood Mn (MnB) were obtained with CEI for variables implicating attention and concentration, working and immediate memory, cognitive flexibility, and verbal learning; and with MnB for executive function, cognitive flexibility, visuo-spatial construction ability, and visual contrast sensitivity. This study strongly suggests that neuropsychological features contribute in a dose-effect related way to the portrait of manganism usually characterized by tremor, loss in balance, diminished cognitive performance, and signs and symptoms of parkinsonism.

Adult↗