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At least 811 records · Page 45Linked to original sources
PubMed1999

The artificial throat: a new method for standardization of in vitro experiments with tracheo-oesophageal voice prostheses.

After total laryngectomy, the voice can be restored successfully with a silicone tracheo-oesophageal voice prosthesis. Biofilm formation and subsequent deterioration of the silicone material of the prosthesis often limit the mean life of the device to an average of 3-5 months. Although device replacement can be considered an easy outpatient procedure, frequent replacements are inconvenient for the patient and may lead to malfunction of the tracheo-oesophageal fistula. Further understanding of the process of development and inhibition of the colonization of these polymer surfaces requires several comprehensive clinical studies. However, in vivo research of the biomaterials of the voice prostheses is difficult and time consuming. In order to simulate the natural process of biofilm development under dynamic nutrient conditions, an artificial throat was developed. Biofilm developed on Groningen button voice prostheses in vitro could not be distinguished from that formed over several months in vivo. This method can be used as a standardized approach for studying functional and structural aspects of all commercially available indwelling and non-indwelling voice prostheses, including the Groningen button, Provox, Voice Master, Blom-Singer and others under various laboratory conditions.

Ambulatory Surgical Procedures↗
PubMed1999

Knee and hip joint replacements. Longer lasting prostheses.

BACKGROUND: Conventional hip replacement prostheses consist of a metal femoral stem and head articulating with a polyethylene acetabular component fixed to the skeleton by polymethylmethacrylate 'cement'. In these prostheses the main problems are breakdown of cement and wear of the polyethylene acetabular articulation. Particles produced by this wearing process contribute to osteolysis (bone stock loss). These problems affect the long term results of joint replacements particularly in the younger, active patients. OBJECTIVE: This article discusses new advances in prosthesis design, which reduce these problems, and techniques to overcome bone loss in revision procedures. DISCUSSION: Improved fixation to the skeleton using cementless prostheses may improve long term results for younger, active patients. The problems of wear and osteolysis may be reduced by the utilisation of metal on metal or ceramic on ceramic articular surfaces.

Arthroplasty, Replacement, Hip↗
PubMed2000

Mitral valve replacement with small-sized tilting-disc mechanical prostheses may lead to moderate stenosis.

BACKGROUND: Analyzing the hemodynamics of small-sized tilting-disc mechanical prostheses implanted in the mitral position. METHODS EXPERIMENTAL DESIGN: this is a retrospective study. The mean follow-up of patients was 114+/-27 months (range 68-152 months). SETTING: departments of Cardiovascular Surgery and Cardiology in a general community hospital Patients: this study includes 9 survivors of 17 patients undergoing mitral valve replacement with this type of device between May, 1982 and July, 1991. INTERVENTIONS: all subjects underwent mitral valve replacement with size 25 mm Sorin tilting-disc mechanical prostheses. MEASURES: all patients underwent transthoracic echocardiography. Five consenting patients also underwent transoesophageal echocardiography. The following parameters were measured: peak gradient, mean gradient, peak velocity, mean velocity, pressure half-time and Doppler area. RESULTS: The ejection fraction was 50% or more in all patients. The following mean results were obtained: peak gradient: 17.4+/-2.5 mmHg; mean gradient: 8.2+/-0.6 mmHg; peak velocity: 2.1+/-0.1 m/sec; mean velocity: 1.43+/-0.06 m/sec; pressure half-time: 135.9+/-29.7 msec; Doppler area: 1.7+/-0.3 cm2. CONCLUSIONS: Valve replacement with Sorin 25 mm tilting-disc mechanical prostheses appears to originate a moderate degree of mitral stenosis and, therefore, we do not recommend their use if at all possible.

Adult↗
PubMed2000

[Valvular prostheses and their follow-up].

In use since 1961, valvular prostheses allow the correction of the severe valvular diseases when conservative procedures are not possible. Current prostheses have outstanding haemodynamic features. Mechanical prostheses have a supposedly unlimited life span but require anticoagulant treatment. Bioprostheses do not need such treatment but end up to deteriorate and need reoperation. Both can be affected by valve-related complications (thromboembolic events, endocarditis deterioration, desinsertion...): an ideal prosthesis does not exist yet. All patients with valvular prosthesis require close follow-up, where echocardiography holds proeminent place.

Bioprosthesis↗
PubMed1975

Failed femoral stems in total hip prostheses. A report of six cases.

Six femoral stems of total joint prostheses failed and were studied. These included two short-neck Müller, one standard Müller, one new design long-neck Müller, and two Charnley prostheses. In addition, reference is made to another failed Charnley prosthesis which had not required revision at the time of the study. Reoperation and replacement of the femoral component was required in all six cases. Metal fatigue appeared to be the cause of failure in all instances. Metallographic examination of the removed prosthesis revealed no underlying defects in one prosthesis. In the other five prostheses metallurgical defects were found. Varus placement of the femoral prosthesis or loosening of the cement-prosthesis bond, or both, were identified in five of the six and were thought to have led to overload. A combination of metal defects and loosening or malpositioning was thought to be responsible for the failures. It was further indicated that current designs should be regarded as marginal in relation to long service life, until more fatigue information is available on the metallic materials currently in use.

Aged↗
PubMed2000

Can endothelial seeding enhance patency and inhibit neointimal hyperplasia? Experimental studies and clinical trial of endothelial seeded venous prostheses.

BACKGROUND: Venous prostheses have poor long-term patency; to improve this situation, experimental studies have been carried out. METHODS: Methods of endothelial cell harvesting, prosthetic seeding and implantation mainly in the inferior vena cava were studied in 127 dogs. Evaluations were conducted by angiography, gross appearance, light, scanning and transmission electron microscopic observations, histo-fluorescent staining, as well as radioimmunoassay. RESULTS: It was found that at five to ten days following implantation, the prosthetic endothelialisation could be reliably achieved in the seeded group and a 100% patency of the seeded inferior vena caval prostheses was attained at 100 days. The thickness of the neointima in the seeded group at 10 and 100 days was 299 microm and 302 microm, respectively. The metabolite of PGI2 from extrinsic arachidonic acid, 6-keto PGF1a, produced by cells from seeded graft was significantly higher than that from spontaneously formed cells and the reverse found with thromboxane B2. A temporary (one week) distal (femoral) arteriovenous fistula enhanced graft patency. These results indicated that the early endothelialisation of grafts by seeding enhanced the patency and inhibited intimal hyperplasia of venous prostheses. The clinical outcome was impressively improved from our previous experience with ten of eleven venous grafts patent over a follow-up period of six to nine years. These might result from the realization of early endothelialisation and its cells derived from seeding being able to produce significantly more PGI2 and less thromboxane B2. CONCLUSIONS: The endothelial cell seeding technique may bring us much closer to an ideal venous prosthesis.

Adolescent↗
PubMed2000

Speech rehabilitation using a voice prostheses following laryngectomy.

The most serious consequence for patients following laryngectomy is the restriction of verbal communication. Since the introduction of laryngectomy significant concerns have already been focused on the field of speech rehabilitation. The operational procedures for the speech rehabilitation include training of the oesophageal voice speech and the voice prostheses. Speech prostheses are available in our hospital since 1983. The speech quality of the speech prostheses is compared with the classical oesophageal voice or to the voice by means of a Provox speech help. Bacteriological and mycological colonisation as a function of the length of implantation are defined. Our approach to the voice rehabilitation after a laryngectomy by use of a spacer during the laryngectomy has proven successful. As a result patients do not fall into a "hole" of non verbal communication. The aim of our efforts is always to create a functioning oesophageal voice after leaving the care of the hospital.

Bacteria↗
PubMed2000

Case report: restorative maintenance of prostheses stabilised by non-endosseous implants.

For over a century, dentists have looked to dental implants to enhance the stability of dental prostheses. During this time, many approaches and different materials have been used. The purpose of this article is to report on two cases where non-endosseous implant systems were used and to outline how the replacement prostheses were customiZed to comply with the different implant types. Intramucosal inserts and sub-periosteal implants are briefly reviewed in the context of current prosthodontic practise. There are still a small number of patients with clinically acceptable intramucosal and subperiosteal implant retained prostheses, which will continue to need servicing and replacement.

Aged↗
PubMed2001

[Shock absorption by intermediate hip prostheses].

PURPOSE OF THE STUDY: The bipolar prosthesis was developed in an attempt to alleviate acetabular wear of conventional metallic endoprostheses. The prosthesis was designed to achieve low-friction metal-on-polyethylene inner bearing motion while decreasing shear stress across the acetabular cartilage. Although good clinical results were obtained, the principle of a persistent inner mobility was contested and some authors have assigned the delay of cartilage erosion to the shock absorption capacity of the polyethylene. The present study was focused on assessing the vibration and shock damping effect of metal monoblock and bipolar head prostheses. MATERIAL AND METHODS: The transmission of the shock wave through these two types of prostheses was studied in vitro. The two heads were first tested in a rigid environment to eliminate all external parasite frequencies. The impact excitation was applied with a hammer connected to an oscillometer. A second accelerometer was connected to the prosthesis stem. Shock wave transmission was analyzed. Secondly, the head was tested with a system vibrating in the same order of frequencies as the skeleton, with and without pre-constraint. The frequency response functions were analyzed. RESULTS: For the metallic prosthesis, the frequency of vibration recorded on the femoral stems was in a large frequency range from 0 Hz to 10 KHz. For the bipolar prosthesis, all the high frequencies of the shock wave were eliminated and only shock wave frequencies from 0 to 500 Hz were recorded. In an environmental system vibrating below 100 Hz, the metallic head did not express high frequencies of vibration. The coefficient of shock absorption was not significantly different for the two heads. DISCUSSION: In the first rigid environment, the metallic head did not filter the high frequency components of the shock wave and the bipolar head tended to eliminate high frequency components due to the flattening effect of the impulse load by the polymer. But, the lower leg is not a rigid structure and the musculo-skeletal system vibrates in frequencies below 100 Hz. In similar conditions, the increased shock-absorbing effect of the polyethylene is far more difficult to observe. For the metallic prosthesis, the recorded frequency of vibration also belongs to a small domain of frequency, from 0 Hz to 100 Hz. The range of frequency is similar for the two types of prostheses. CONCLUSION: Even though polyethylene is characterized by a more pronounced damping capacity than metallic materials, in experimental conditions simulating the vibratory characteristics of the human body, the introduction of a high-density polyethylene liner does not afford any additional shock-absorbing effect compared with a metallic head. It cannot explain cartilaginous sparing.

Equipment Failure Analysis↗
PubMed1975

[Remote results of multivalvular prostheses in patients with acquired heart defects].

The authors examined remote results in 57 patients who had had multivalvular prostheses placed: 35-with mitral and tricuspid valve prostheses, 10-with mitral and aortic valves and 3-with replacement of all 3 valves. Observation period lasted from 3 months to 5 years. Positive results were seen in 42 patients (73.6%). Mortality rate was 21.5%. The main cause of lethal outcomes was myocardial insufficiency in the majority of patients with mitral and aortic prostheses.

Adult↗
PubMedDate not supplied

[Future development of heart valve surgery. New prostheses and access routes].

Valvular surgery has evolved in the last year with the development of new valvular prostheses and new minimally invasive implanting techniques. We discuss the advantages of the new mechanical aortic prostheses of superior hemodynamic characteristics, which avoid the need to widen the valvular ring in many cases. At the same-time, we emphasize on the use of new biological aortic prostheses, with minimal transvalvular gradient and less incidence of calcification. The advantages and disadvantages of the different minimally invasive techniques are analyzed without reaching yet a definite conclusion on their application.

Forecasting↗
PubMedDate not supplied

Tooth- and implant-supported prostheses: a retrospective clinical follow-up up to 8 years.

PURPOSE: The purpose of this study was to evaluate clinical treatment outcome of fixed prostheses in different sizes and with combinations of different numbers of teeth and implants as abutments. MATERIALS AND METHODS: A total of 115 implants were placed in 36 patients, 75 (65%) in the maxilla and 40 (35%) in the mandible. The implants were connected to 85 abutment teeth, 50 in the maxilla and 35 in the mandible. Of the prosthetic restorations, 19 were gold ceramic, 17 were gold acrylic, three were titanium acrylic, one was titanium ceramic, and one was titanium composite. The observation period ranged from 14 months to 8.9 years. The treatments comprised both fixed partial dentures supported by one tooth and one implant as well as complete-arch fixed prostheses supported by a number of teeth and implants. RESULTS: A total of nine implants were lost, three during healing and six after loading. The postloading cumulative implant survival rate was 89.8% after 5 years. Five abutment teeth were lost, and of the 41 prostheses included in the study, only two (5%) were lost during the observation period. Marginal bone loss was registered around 46 implants at the 1-year follow-up examination. During the following observation period, only slight changes in the marginal bone level adjacent to the implants and teeth were registered. The magnitude of technical complications was low. CONCLUSION: This investigation confirms the findings in similar studies that treatments with periodontally healthy teeth and implants splinted together in rigid one-piece superstructures show excellent long-term follow-up results.

Acrylic Resins↗
PubMed1999

Evaluation of obturator prostheses using vibration analysis.

Obturator prostheses have been extensively used in the functional rehabilitation of maxillectomy patients. The purpose of this study was to evaluate in vitro the vibration movements of three types of obturator prostheses. Three types of bulbs were used: the solid type, the buccal flange type, and the hollow type. Modal analysis was performed to identify the better form. The three types of obturator prostheses were excited by a shaker, and the frequency response functions were recorded on an FFT analyzer to identify their modal shapes. In addition, transient response simulations were carried out, and decay rates of the resultant transient response waves were compared to evaluate the energy absorption after the obturator prosthesis had experienced an impact. The results showed that the modal shapes were closely similar, while the amplitudes at the rests and clasps of the hollow type bulb were the smallest. In the transient response simulation, the decay rates of the hollow type were significantly the highest (p < 0.01). In this study, modal analysis demonstrated that the hollow type obturator prosthesis showed the steepest vibration decay slope, indicating that it might be the best among the three types of bulbs for use in clinical treatments.

Analysis of Variance↗
PubMed1976

Preliminary report: Evaluation of tissue ingrowth into experimental Replamineform vascular prostheses.

A new experimental arterial prosthesis has been developed by replacing the minimal surface microporous calcite structure of sea urchine spines. Prostheses having a 4 mm. inside diameter and a homogenous 15 to 20 mu porous network have been prepared in bioelectric polyurethane and segmented polyurethane. Ten prostheses were placed in the femoral and carotid arteries of dogs weighing 27 to 35 kilograms and were harvested at a time interval of 3 to 14 days to characterize the tissue ingrowth. Eight of the ten prostheses were widely patent at time of harvest, with tissue ingrowth evident as early as the third day and with complete fibroblastic and capillary penetration of the 1 mm. thick walls developed by the end of one week. By 2 weeks there was uniform formation of 50 to 100 mu well organized neointimal surfaces.

Animals↗
PubMed2003

Gingival prostheses--a review.

Gingival replacement is often a component of comprehensive prosthodontics. Gingival prostheses may be fixed or removable and may be made from acrylics, composite resins, silicones or porcelain-based materials. Undercuts or dental attachments are used to secure removable prostheses, which are esthetically pleasing and easy to maintain. This paper describes several clinical situations in which gingival prostheses were used effectively.

Acrylic Resins↗
PubMed2003

The influence of oral implant-supported prostheses on articulation and myofunction.

The aim of the present research was to assess articulation and myofunction in patients wearing fixed or removable prostheses supported by oral implants. 164 edentulous patients with implant supported prostheses were divided in four subgroups, dependent on their dental status, and compared to control groups of forty five subjects having a natural dentition. More than fifteen articulatory and myofunctional parameters were evaluated. The results showed that subjects with prostheses on implants tend to have more articulation problems than controls. Especially patients with a complete fixed prosthesis on implants in the upper jaw seemed to experience problems pronouncing /s/ and /z/. There also seemed to be influences of age and hearing factors.

Adult↗
PubMed1992

[A 12-year clinical experience of cardiac valve replacement with domestic tilting disc valve prostheses in 1013 cases].

1013 patients with cardiac valve replacement during a 12-year period from 1978 to 1990 were reported. 566 cases were implanted with Shanghai-made tilting disc valve prostheses and 447 with Lanzhou-made (C-L valves). Mitral valve replacement (MVR) in 753 patients, aortic valve replacement (AVR) in 102 and double valves replacement (DVR) in 158. The overall early mortality rate was 6.2% with 4.9%, 7.8% and 11.3% after MVR, AVR and DVR respectively. Follow-up study was made in 3097.43 patient-year (mean 3.26 years). The late death rate was 1.6% patient-years and with 1.4, 1.8 and 3.2 after MVR, AVR and DVR respectively. The incidence of late valve-related complication (% patient-years) were: thromboembolism 0.39, anticoagulant-related hemorrhages 0.77, prostheses failure 0.22, prosthetic valve endocarditis 0.38, periprosthetic leak 0.12, and reoperations 0.38. The domestic tilting disc valve prostheses are considered to be qualified valves with low mortality and satisfactory results.

Adolescent↗
PubMed1992

Failures and complications in 127 consecutively placed fixed partial prostheses supported by Brånemark implants: from prosthetic treatment to first annual checkup.

Ninety-six partially edentulous maxillae and mandibles were consecutively treated with 127 freestanding fixed prostheses supported by 354 implants. The patients were followed for 1 year and the overall success rate was 98.6% for the examined implants. None of the inserted prostheses was lost during the observation period. The most commonly reported problems during the first year of function were related to loose gold screws and esthetic complaints, complications that were easily resolved. Furthermore, the total number of complications was low and was less than has been reported for routine full-arch fixed prostheses.

Adolescent↗