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At least 1,081 records · Page 60Linked to original sources
PubMed1997

Early presence of endothelial-like cells on the flow surface of porous arterial prostheses implanted in the descending thoracic aorta of the dog.

The purpose of this study was to investigate early arterial graft healing and its sources in porous Dacron prostheses after very short implantation periods in the dog, using extensive histologic examination of serial sections. Preclotted Dacron prostheses 6 cm long and 8 mm in diameter were implanted in the descending thoracic aorta (DTA) of 14 dogs, and retrieved at 7 days (n = 6), 10 days (n = 4), and 14 days (n = 4). The flow surface was assessed for thrombus coverage, endothelial-like cell (ELC) coverage, and the number of microvessel ostia. Where an ELC island was identified under the stereomicroscope, full-wall longitudinal tissue samples were taken, and embedded in resin for light microscopy study of 6-microns, H&E-stained serial sections to determine general healing and interstitial tissue presence. If there was more than one ELC island, another full-wall sample was taken and embedded in paraffin for staining with laminin, collagen IV, and smooth muscle alpha-actin antibodies, and PTAH. All grafts were patent with very little thrombus. Islands of endothelial-like cells were found for each time period, and on all 14-day grafts. Endothelial-like cell coverage was highest at 14 days. On 7- and 10-day grafts, cells proved to be endothelium were found in the middle of the flow surface, unconnected to either pannus or perigraft tissue ingrowth. Healing occurs as early as 7 days in porous knitted Dacron grafts. The source at periods earlier than 10 days appears to be cells from the blood stream.

Animals↗
PubMed1978

Complications due to cloth wear in cloth-covered Starr-Edwards aortic and mitral valve prostheses--and their management.

Five cases of complications due to cloth wear in cloth-covered composite-seat Starr-Edwards aortic and mitral valvular prostheses are described. The complications of cloth wear were recurrent systemic emboli in three patients, two with aortic and one with mitral prosthesis, and severe hemolytic anemia in two patients with aortic prosthesis. The over-all incidence of clinically significant complications due to cloth wear in aortic and mitral valve prosthesis was 2.5 per cent. The diagnosis of cloth wear is impossible before reoperation and it was made by exclusion of other causes of recurrent transient cerebral ischemic attacks or systemic emboli and by exclusion of other causes of hemolytic anemia. Clinical and laboratory findings suggestive of cloth wear are described. Aggressive management of complications of cloth wear by reoperation is likely to prevent disabling or lethal consequences. Porcine xenograft aortic and mitral bioprostheses were used in these patients to replace the cloth-covered valvular prostheses. The symptoms due to cloth wear were abolished in all patients by reoperation, and all patients are off anticoagulants postoperatively. The operative mortality rate for reoperation in this small group of patients was zero.

Adult↗
PubMed1980

Hemodynamic evaluation of patients with combined mitral and aortic prostheses.

Complete hemodynamic evaluation of patients with combined aortic and mitral mechanical valve prostheses presents a difficult technical problem. Yet such patients with cardiac symptoms postoperatively often require this evaluation to determine the diagnosis and the advisability of reoperation. A 4 year experience with 22 patients requiring such evaluation is reviewed. Eight patients (36 percent) required reoperation for malfunction of the prosthesis. Four (18 percent) had major complications of the cardiac catheterization study, but no fatalities or residual permanent defects resulted. In 17 cases transthoracic left ventricular needle entry was used. A standardized procedure of this type for both pressure measurement and angiographic studies has evolved, providing reasonable efficiency and a relative degree of safety. The patient is positioned in the right anterior oblique position for optimal needle entry into the left ventricular apex and angiographic visualization of mitral prosthetic incompetence and the myocardial contractile pattern. A 16 gauge needle with side holes but no end hole allows ventriculography to be performed after chamber entry using the prostheses as reference points under fluoroscopic guidance. Retrograde catheterization of the aortic prosthesis, transseptal left atrial catheterization with anterograde crossing of the mitral prosthesis and transapical pressure measurement with a similar needle, combined with quantitative left atrial angiography, are alternative choices for study.

Adult↗
PubMed1992

Hemodynamic evaluation by Doppler echocardiography of small (less than or equal to 21 mm) prostheses and bioprostheses in the aortic valve position.

To assess resting hemodynamics of an unselected group of patients with prostheses or bioprostheses sized less than or equal to 21 mm implanted into the aortic valve position during a 7-year period, 46 of 50 eligible patients were examined by Doppler echocardiography. The valves were Carpentier-Edwards (CE) supraannular 21 mm (n = 8), Medtronic-Hall (MH) 20 mm (n = 8) and 21 mm (n = 21), and the rest (n = 9) were other valves with only 1 to 3 patients in each group. Gradients, valve areas and dimensionless obstruction indexes (ratio of subvalvular/valvular velocities and velocity time integrals) were compared. By analysis of variance, gradients did not differ significantly between the CE supraannular 21 mm, the MH 20 and 21 mm prostheses (peak/mean 25 +/- 8/14 +/- 5, 31 +/- 13/16 +/- 6 and 25 +/- 10/13 +/- 5 mm Hg; p = not significant). Only 2 patients had a mean gradient greater than 25 mm Hg. The valve area was slightly larger for the MH 21 mm group compared with the CE supraannular 21 mm group (1.34 +/- 0.15 vs 1.16 +/- 0.14 cm2, p less than 0.05). The dimensionless obstruction indexes did not differ (CE supraannular 21 mm 0.36 +/- 0.07/0.40 +/- 0.07 (velocities/velocity time integrals), MH 20 mm 0.40 +/- 0.12/0.47 +/- 0.12, MH 21 mm 0.38 +/- 0.05/0.44 +/- 0.06; p = not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Mechanical cardiac valvular prostheses.

Mechanical cardiac valvular prostheses currently enjoy a 60% to 40% market-share advantage over tissue prostheses in the United States and worldwide. Only the Starr-Edwards caged Silastic (Dow Corning) ball, Medtronic-Hall, St. Jude Medical, and Omniscience valves remain available in the United States. Although each valve has certain advantages and disadvantages, no design has achieved functional mechanical perfection. Late follow-up of valve-related complications from the literature favors the St. Jude Medical and Medtronic-Hall valves.

Adolescent↗
PubMed1986

Atherosclerosis in vascular grafts for peripheral vascular disease. Part 2. Synthetic arterial prostheses.

Thirty-nine synthetic (32 Dacron and 7 Teflon) arterial prostheses (from 38 patients with peripheral arterial disease) removed after periods between 2 months and 18 years, were examined by histology and immuno-histology. The grafts were initially permeated by thrombus containing platelet antigens and this became organised and converted to granulation, and then to fibrous, tissue. The newly-formed tissue contained 'foreign-body' giant-cells in contact with the plastic prosthesis and showed evidence of permeation by plasma proteins. In grafts of over 2 years duration, this reactive tissue no longer contained platelet antigens but invariably revealed bound lipid, identifiable as apolipoprotein-B-containing lipoproteins (LpB), and fibrinogen-related antigens (FRA), in a distribution resembling that seen in atherosclerotic arteries. LpB and FRA were also seen in organised, or partially organised, mural thrombi in older grafts. The oldest grafts additionally showed stenosis, calcification or aneurysm formation. Lipid deposition increases with the age of grafts; is independent of the nature of the plastic fibre used or its mode of fabrication; and sometimes contributes to graft failure. Immuno-histology indicates that this is an insudative process indistinguishable from 'true' atherosclerosis which occurs in graft-linings of prostheses of long duration and in old mural thrombi in grafts and that the lipid in these lesions derives from plasma LpB rather than from platelets. This source for the lipid suggests that the insudative and thrombogenic theories of atherogenesis can be reconciled.

Adult↗
PubMed1991

Velocity and turbulence measurements past mitral valve prostheses in a model left ventricle.

Thrombogenesis and hemolysis have both been linked to the flow dynamics past heart valve prostheses. To learn more about the particular flow dynamics past mitral valve prostheses in the left ventricle under controlled experimental conditions, an in vitro study was performed. The experimental methods included velocity and turbulent shear stress measurements past caged-ball, tilting disc, bileaflet, and polyurethane trileaflet mitral valves in an acrylic rigid model of the left ventricle using laser Doppler anemometry. The results indicate that all four prosthetic heart valves studied create at least mildly disturbed flow fields. The effect of the left ventricular geometry on the flow development is to produce a stabilizing vortex which engulfs the entire left ventricular cavity, depending on the orientation of the valve. The measured turbulent shear stress magnitudes for all four valves did not exceed the reported value for hemolytic damage. However, the measured turbulent shear stresses were near or exceeded the critical shear stress reported in the literature for platelet lysis, a known precursor to thrombus formation.

Blood Flow Velocity↗
PubMed1975

Fabrication of intraoral radiotherapy prostheses.

An accurate, short method of fabricating intraoral radiotherapy prostheses has been described. With it, there is no need of mounting casts on an articulator, wax-up, or flasking. Almost all procedures can be accomplished by the dental technician. Most important, the prostheses can be ready for use a few hours after the impressions are made. The technician can prepare the walls and cylinders beforehand and keep them in stock until needed. Also, it would be advisable for the radiotherapist to be present at the initial fastening of the bases to the cylinders. In this manner, the accuracy of the function of the prosthesis will be assured.

Denture Design↗
PubMed1982

Oral motor patterns and their relation to oral prostheses.

The mechanism of support for oral prostheses varies qualitatively and quantitatively, depending on the type of prosthesis worn. Some prostheses are partially supported by natural teeth, and others rely for their support on the residual tissues, mucosa, alveolar bone. Nondental prosthetic support demonstrates progressive longitudinal changes and poses special problems for the denture wearer. In this review, the masticatory system is considered as a biomechanical interaction of three components: function/dysfunction adaptive responses, and TMJs. It appears that oral behavior is related to all three components, but its role is not completely understood.

Adaptation, Physiological↗
PubMed1983

A mold technique for construction of orbital prostheses.

The technique described provides a simplified method for construction of molds for orbital prostheses. This technique results in molds that permit the fabrication of initial and duplicate flexible prostheses that accommodate a single ocular component.

Eye, Artificial↗
PubMed1984

Custom prostheses used to support oral and maxillofacial surgery.

The number and complexity of oral and maxillofacial surgical procedures have increased markedly in the last 5 years. Various custom prostheses, both cast metal and acrylic resin, used to provide surgical fixation, stabilize skin grafts, and contour bone used to augment atrophic mandibles, were described. While these prostheses may appear complex, their fabrication in the dental laboratory involves standard techniques that are accomplished routinely. The complexity of the modality lies in the uniqueness of each patient's treatment plan, which requires a special level of understanding and cooperation by all members of the professional treatment team.

Adolescent↗
PubMed1987

Alternative prosthodontic technique for tissue-integrated prostheses.

This modified technique for fabrication of tissue-integrated prostheses saves valuable clinical time for the dentist and treatment time for the patient. The technique differs in that a modified denture is placed in the mouth the day of the second operation, impression copings are eliminated at the final impression, the framework is fabricated before jaw relation records, a high-content palladium alloy is used for the framework, the master cast is flasked similar to a complete denture technique, and the access openings are closed with a light-cured resin. Prerequisites for a tissue-integrated prosthesis are not violated and comparable results are achieved. The technique can also be used in maxillary arches and, with slight modifications, for partially edentulous patients. This technique has been used 3 years for 35 jaws in 37 patients, with 184 fixtures. Four fixtures have failed, producing a 98% success rate. All prostheses have remained continuously stable. Economy of clinical time and laboratory procedures in the prosthodontic phase increase the acceptance of osseointegration in clinical dentistry. The cooperative efforts of all disciplines will provide a greater acceptance of this treatment modality, which will enhance the patients' quality of life.

Dental Alloys↗
PubMed1989

Cast metal, resin-bonded prostheses: a 10-year retrospective study.

A sample of 99 resin-bonded prostheses placed over a 10-year period were examined by four clinicians using a standardized criteria sheet. Areas examined included hard tissues, periodontium, retainer and pontic design, retention, the effect of occlusion on framework design and retention rate, and bonding media. The data from 7- and 10-year retrospective studies were compared for meaningful trends. Results showed (1) caries on retainer teeth was 3%, (2) gingival index of the retainer teeth was less than the gingival index of the rest of the mouth (0.7 +/- 0.5 versus 0.9 +/- 0.6), (3) the respective mean probing depths of retainer teeth of 34 patients in the 7- and 10-year studies were 2.2 +/- 0.4 mm and 1.9 +/- 0.7 mm, (4) the debond rate of all the prostheses from all causes was 31%, (5) the debond rate comparing etched metal and perforated retainers from all causes was 32% and 31% [corrected], respectively, and (6) 83% liked the prosthesis; 17% were noncommittal. The authors concluded that the resin-bonded prosthesis may be considered a permanent restoration and a valuable asset in the clinician's armamentarium.

Adult↗
PubMed1994

Survival of fixed implant-supported prostheses related to cantilever lengths.

Various lengths of cantilevers for fixed implant-supported prostheses have been recommended in the literature. No scientific data are available for selecting specific lengths, and different views are reported. Authors contend that longer cantilevers lead to increased risk of failure. This study examined survival of fixed implant-supported prostheses using different cantilever lengths and offers clinical support for the contention.

Dental Implantation, Endosseous↗
PubMed1987

An X-ray photoelectron spectroscopy study of the external surface of explanted microporous polyurethane vascular prostheses.

XPS has been used to examine the external surfaces of microporous polyurethane vascular prostheses implanted for up to 6 months in dogs. The phenomena of bilirubin absorption and physical degradation were investigated, using three different chemical washes to clean the prostheses. Very little evidence for chemical change was found, indicating a predominant role for the mechanical or biochemical ablation of degraded material.

Animals↗
PubMed1993

Expanded polytetrafluoroethylene arterial prostheses in humans: histopathological study of 298 surgically excised grafts.

The expanded polytetrafluoroethylene vascular prosthesis is considered to be the best synthetic alternative for peripheral arterial reconstruction. Most studies on the healing characteristics of expanded polytetrafluoroethylene prostheses have been carried out on animals, and very few data are available on prosthesis implanted in humans long term. We implanted 298 expanded polytetrafluoroethylene grafts as arterial substitutes in humans. The mean duration of implantation was 523 d and the grafts were implanted mainly for infrainguinal or axillofemoral bypass. The cellular and collagen infiltration of the microporous expanded polytetrafluoroethylene structure was generally poor. Infiltration occurred mainly in the external region of the prosthetic wall and increased with the duration of implantation. The external reinforcement was not a major factor in limiting tissue infiltration. The luminal surfaces were covered with a thin, irregular layer of organized fibrin, interspersed with exposed expanded polytetrafluoroethylene areas. Mineral deposits were observed in five cases. Despite poor healing, the clinical performance of expanded polytetrafluoroethylene vascular prostheses is relatively good. Since the chief advantage of this material is good mechanical stability in vivo, any modifications of the graft to improve healing characteristics or thrombogenic properties should not be made at the expense of stability in vivo.

Adult↗
PubMed1995

Negative Poisson ratios and strain-dependent mechanical properties in arterial prostheses.

The elastic properties of two artificial arterial prostheses have been measured. One is a fibrillar polyurethane (PU) material, the other is an expanded polytetrafluoroethylene (ex-PTFE). It is shown that the conventional assumption of incompressibility is invalid for both materials and that changes in the thickness of the prosthetic artery wall must be measured directly. The ex-PTFE shows highly strain-dependent properties, the most significant being that of large negative through-thickness Poisson ratios, up to -11. These results have important consequences for matching the properties of prostheses to natural materials.

Anisotropy↗