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PubMed2000

[Scanning electron microscopy findings in titanium middle ear prostheses].

BACKGROUND: Titanium as a biomaterial in ossicular replacement has widely spread within the last couple of years. METHODS: 23 prostheses (12 PORPs, partial ossicular replacement prostheses and 11 TORPs total ossicular replacement prostheses) removed during revision surgery were studied using scanning electron microscopy. The average implantation time was 8 (range 3-15) months. The specimens were investigated regarding tissue growth, epithelialization, inflammation and cellular signs of rejection. RESULTS: Only few prostheses were totally covered by connective tissue or epithelium due to technical problems in removing the implant and the covering tissue as one specimen. But this offered the possibility to study the interface at the edges where the tissue was torn off. The connective tissue looked unremarkable. Polygonal squamous epithelium was detected on several implants. Respiratory epithelium with ciliated cells and mucus producing goblet cells was seen in two specimens. In cases of cholesteatoma or protrusion the explanted prostheses showed typical rosette-like formation of hornifying squamous epithelium. According to underlying disease a lymphocytic infiltration could be seen. There were no cellular signs of incompatibility noticed neither macrophages nor foreign body giant cells. CONCLUSIONS: From these investigations titanium seems to be a favorable biomaterial for ossicular replacement with good acceptance also in an implantation site showing chronic inflammation.

Cholesteatoma, Middle Ear↗
PubMed2004

[Tympanoplasty with hybrid prostheses].

BACKGROUND: The retrospective study reviews the hearing results of partial and total ossicular replacement plasties with prostheses composed of a hydroxylapatite head and a trimmable shaft. PATIENTS AND METHODS: 71 patients underwent tympanoplasty type III between January 1996 and January 2002. The partial (PORP) (55 patients) and total ossicular replacement prostheses (TORP) (16 patients) were a composition of a hydroxylapatite head and a trimmable hydroxylapatite-polyethylene composite shaft (HAPEX ). Hearing results were evaluated according to the guidelines of the Committee on Hearing and Equilibrium. RESULTS: In cases with a PORP the residual air-bone gap could be reduced to < or = 20 dB in 73% of the patients. The mean air-bone gap improved from 28 dB preoperatively to 17 dB postoperatively. In cases with a TORP the residual air-bone gap could be reduced to < or = 20 dB in 62% of the patients. The mean air-bone gap improved from 32 dB preoperatively to 20 dB postoperatively. CONCLUSIONS: The hearing results with prostheses composed of a hydroxylapatite head and a trimmable shaft are good and comparable to the results of authors using other synthetic ossicular prostheses. These prostheses are time-saving because the trimmable shaft can be quickly cut and shortened to an individual length.

Audiometry, Pure-Tone↗
PubMed1990

Combined mitral and aortic valve replacement with Bjørk-Shiley prostheses: long term survival and valve-related complications.

Between 1974 and 1985, combined aortic and mitral valve replacement (DVR) was performed in 209 patients using Bjørk-Shiley tilting-disc prostheses. Early and late mortality were 9.5% and 10.5% respectively for the entire series. Factors significantly influencing early mortality were: Emergency DVR, preoperative NYHA Class IV, double valve, critical stenosis, and small aortic replacement prostheses. The effect of the latter was augmented by the suboptimal orientation of the implanted prostheses. The overall survival was 74 +/- 4.4% at 12 years; but was only 40 +/- 6.1% at 8 years in patients who were in NYHA class IV preoperatively. Intermittent disc occlusion (DO) and thrombotic disc occlusion (TO), presented as early, anticoagulant related haemorrhage (AH) and prosthetic valve endocarditis (ENDO) as sporadic, and thromboembolism (TE) and paravalvular leak (PVL) as continuous risk factors. Freedom from all known valve-related complications was 77 +/- 4.5% at 12 years (DO, TO, AH, ENDO, TE, PVL: 98%, 97%, 96%, 96%, 88% and 89% respectively). Lethal DO and TO occurred in mitral prostheses. Freedom from reoperation was 95% at 5 and 12 years. Patient-related valve failure rate in this series is comparable with the other series which used mechanical prostheses and is lower than those which used bioprostheses.

Adult↗
PubMedDate not supplied

[Differences in polyethylene wear in hip joint prostheses with ceramic- and with metal-polyethylene combination of the articulation surfaces--a study of surgical and of autopsy materials].

Pseudocapsules of artificial hip joints with ceramic- and metal on polyethylene combination of the articulating surfaces from 126 revision arthroplasties and 41 autopsies were studied histologically with semiquantitative evaluation of the polyethylene wear. The results were compared with reports of laboratory tests in the literature. We found in the autopsy specimens as well as in the biopsies from revision arthroplasties of prostheses implanted for 4 to 8 years three times less polyethylene wear particles released from the ceramic on polyethylene prostheses. The newly established synovium surrounding prostheses with ceramic heads appeared 20% reduced in thickness with minor villous transformation. Different types of metal on polyethylene prostheses revealed no differences in wear behaviour with the exception of the bipolar prostheses which showed a markedly increased polyethylene wear.

Adult↗
PubMed2000

Biofilm formation on voice prostheses: influence of dairy products in vitro.

Laryngectomized patients use silicone rubber voice prostheses to regain their speech, however, the lifetime of these devices is limited due to biofilm formation. Following anecdotal evidence, the influence of various dairy products on biofilm formation on voice prostheses was studied, using the artificial throat-model. Biofilms were grown on Groningen and Provox2 voice prostheses by inoculating two artificial throats with the total microflora isolated from an explanted Groningen voice prosthesis. After 3 days, one throat was perfused three times daily with 650 ml dairy product; the other was perfused with phosphate buffered saline, used as a control. After 12 days the microflora on each voice prosthesis was determined. Perfusion of the artificial throat with buttermilk three times daily for 9 days reduced the amount of bacteria and yeasts in the biofilm on Groningen voice prostheses to 3% and 15% of the control, respectively. These effects were not observed with a pasteurized conservable buttermilk product. Yakult fermented milk drink, Mona mild yoghurt, Mona vifit yoghurt, semi-skimmed milk and low-fat yoghurt reduced the amount of bacteria by various degrees, ranging from 12% (Yakult) to 88% (Mona mild) of the control, but these products did not inhibit, and sometimes even stimulated, yeast growth. A combination of buttermilk and Yakult did not show a synergistic effect, as expected. Effects for the Provox2 voice prosthesis were less pronounced. These in vitro experiments in the artificial throat demonstrated that the formation of the biofilm on voice prostheses can be lessened by the daily use of certain dairy products, of which buttermilk had the strongest inhibitory effect, followed by Yakult.

Animals↗
PubMed2006

Cost of tracheoesophageal prostheses in developing countries. Facing the problem from an internal perspective.

CONCLUSIONS: All the discussants of our questionnaire agreed that the price of tracheoesophageal (TE) prostheses was too expensive for developing countries. The problem could be addressed in terms of international laws regarding companies' patent rights. TE prosthesis manufacturers from rich countries could move their manufacturing in part to developing countries. High production standards could allow TE prostheses to be exported to developed countries. Another approach to the problem may be based on a partnership between non-profit-making Western laryngological societies with specific medical and technical prosthetic know-how and local manufacturers. The aim of this cooperation could be the low-cost production of advanced TE prostheses in the developing countries. OBJECTIVES: In communities in the developing world, most laryngeal and hypopharyngeal carcinomas are diagnosed at advanced stages and require total laryngectomy. Prosthetic TE voice restoration is the method of choice for voice rehabilitation after total laryngectomy in developed countries. Unacceptably high costs are a significant limitation to Third World use of TE voice prostheses. The aims of this paper are to discuss the consequences of the high costs of TE prostheses in developing countries with head and neck surgeons working in Third World hospitals and to propose how European and American laryngological societies can promote TE speech in the developing countries. MATERIAL AND METHODS: A questionnaire was given to a group of expert head and neck surgeons working in developing countries and their answers and suggestions discussed.

Costs and Cost Analysis↗
PubMed2001

Interaction of Staphylococcus epidermidis from infected hip prostheses with neutrophil granulocytes.

This study focuses on the interaction of Staphylococcus epidermidis isolated from granulation tissue covering infected hip prostheses and neutrophil granulocytes. Bacterial strains isolated from normal flora were used as controls. The bacteria were well characterized with routine methods and further characterized with random amplified polymorphic DNA analyses and slime tests. Phagocytosis and chemiluminescence (CL) assays were used in the neutrophil interaction studies. The prostheses strains were ingested to a lesser extent than strains from normal flora (p < or = 0.001). There was no significant difference between the prostheses strains and the normal flora strains in terms of total CL response. However, the extracellular CL response from the neutrophils was lower in comparison with the normal flora when interacting with the prostheses strains. The results of this study support the notion that S. epidermidis strains isolated from infected hip prostheses have an enhanced capacity to resist phagocytosis and that most of these strains elicit a reduced inflammatory response, measured as the production of extracellular oxidative metabolites from the neutrophils, compared to normal flora.

DNA, Bacterial↗
PubMedDate not supplied

Development of a thermal cross-linking heparinization method and its application to small caliber vascular prostheses.

The authors developed a heparinization method for biomaterials without using chemical reagents and applied it to small caliber vascular prostheses. The vascular prostheses (4 mm diameter expanded polytetrafluoroethylene [e-PTFE], fibril length 90 microns) heparinized by thermal cross-linking, and control grafts (4 mm diameter e-PTFE, fibril length 30 microns), were implanted in the carotid arteries of eight adult dogs. Four pairs of grafts were explanted 1 hr after implantation, and the remaining four pairs were explanted 7 days after implantation. Patency was assessed macroscopically, and the grafts were examined microscopically. The anti thrombogenicity of the vascular prostheses heparinized by thermal cross-linking was good in comparison with that of the control group. However, on the outer surface of the grafts, the author found more infiltration of fibroblasts into the wall of the control grafts than in the heparinized grafts. The author surmised that heparinized gelatin injected into the interfibril space of the graft inhibited cellular infiltration. The infiltration of inflammatory cells was slight in both grafts. Thus, the author was successful in heparinizing the vascular prostheses by thermal cross-linking and obtaining slow release of heparin to maintain early antithrombogenicity. The high concentration of heparin in the graft wall, however, was thought to be an obstacle to integration of the vascular prostheses.

Animals↗
PubMedDate not supplied

Polyester arterial prostheses. Recent developments from the Czech Republic and Poland.

To evaluate recent developments in the design and production of polyester vascular prostheses in eastern Europe, a series of in vitro physical and chemical tests and an in vivo study was performed on three new prototype devices from the Czech Republic and one from Poland. The in vitro results for these four prostheses, referred to as the Ra-1n (warp knitted, uncrimped), Ra-1v (warp knitted, crimped), Mikrofroté (weft knitted, uncrimped), and Dallon (warp knitted, crimped) prostheses, were compared against values for three commercial devices of western origin, namely the Triaxial, the Vasculour II, and the Cooley II grafts. The animal trial involved implanting the four prototype devices as a thoracoabdominal bypass in dogs for eight different periods ranging from 4 hrs to 6 months and undertaking histologic and structural investigations on the retrieved grafts. Because of its poor long-term dimensional stability in vivo, the continued use of a weft knitted structure, like the Mikrofroté prosthesis, is to be deprecated. Conversely, the introduction of a more dimensionally stable warp knitted structure in three prototypes is to be acknowledged. However, the presence of surface contaminants was most likely responsible for the excessive inflammatory reaction generated by all four prostheses during the first month in vivo, which resulted in delayed healing performance. In addition, an unusually high surface carbon-oxygen ratio suggests that the crimping process needs further refinement. Improved cleaning and packaging procedures are essential before these products can complete against existing commercial prostheses of western origin. In conclusion, these new developments illustrate that the technology of warp knitting, which is now spreading worldwide, should be evaluated.

Animals↗
PubMed1997

Life span of silicone gel-filled mammary prostheses.

The discussion on possible side effects of implanted silicone has resulted in a growing number of patients inquiring whether or not their mammary prostheses are intact and when failure of the prostheses is to be expected. Between November 1988 and May 1995, 182 patients had their silicone mammary prostheses replaced, repositioned, or removed one to three times. Capsular contraction, dislocation, pain paresthesia, and/or suspected rupture were common indications for surgery. To try and be able to provide an indication as to the correlation of implant age and integrity, we recorded the status of all 426 prostheses observed during secondary surgery. In this selected group of patients, approximately 50 percent of the mammary prostheses with an implant age of 7 to 10 years showed gel bleed or rupture. Applying the survival Kaplan-Meier curve, 50 percent of implants may be expected to bleed or be ruptured at the age of 15 years. Rupture was observed more frequently than gel bleed. It seems that there is no chronologic relation between gel bleed and rupture.

Adult↗
PubMed2003

The effect of prosthesis design on vibration of the reconstructed ossicular chain: a comparative finite element analysis of four prostheses.

HYPOTHESIS: It was hypothesized that the differences in the bioacoustic performance of ossicular replacement prosthesis designs, and insertion positions, could be quantified using finite element analysis. BACKGROUND: Many designs of prosthesis are available for middle ear surgery. The materials used, and the shape of the implants, differ widely. Advances in computer simulation technologies offer the possibility of replicating the in vivo behavior of the different prostheses. If this can be achieved, insight into the design attributes required for improved biofunctionality may be gained. METHODS: Micro-computed tomography and nuclear magnetic resonance imaging were used to obtain geometric information that was translated into a finite element model of the outer and middle ear. The forced frequency response across the hearing range of the normal middle ear was compared with the middle ear reconstructed with partial and total ossicular replacement prostheses. RESULTS: The amplitude of vibration of the footplate was more similar to that of the normal ear when a Kurz total ossicular replacement prosthesis was implanted than when a Xomed total ossicular replacement prosthesis was implanted. This may be attributed to the latter's titanium link. Partial ossicular replacement prostheses were stiffest and had lower umbo vibrations and higher stapedial footplate vibrations. In all cases but one, the vibration of the prostheses had resonances that caused the vibration of the stapes footplate to be noticeably different from normal. CONCLUSION: The authors confirmed the hypothesis that finite element modeling can be used to predict the differences in the response of ossicular replacement prostheses. This study shows that computer simulation can potentially be used to test or optimize the vibroacoustic characteristics of middle ear implants.

Acoustic Impedance Tests↗
PubMed1993

Complications in the tissue integrated prostheses components: clinical and mechanical evaluation.

Cases demonstrating complications in osseointegrated implant supported prostheses are described. These complications occurred in the prostheses framework or veneer, in the fixation screw, in the abutment post or screw as well as in the implant body. The two main reasons for the complications were lack of passive fitting between the restoration and the abutment; and destructive occlusal contacts. The destructive occlusal contacts may develop during the time of wear of the prostheses material or by changes in the opposite restoration. Overloading or bending moments exerted on the prostheses via these occlusal contacts resulted in loosening or fracture in one of the implant-prostheses components. The benefit of acrylic resin or composite material in reducing stresses in the light of the possible long-term, harmful occlusal changes that might develop as a result of their wear should be considered.

Bite Force↗
PubMed2005

Is the guideline the cause of structural failure in current polyester vascular prostheses? An experimental study.

To evaluate the impact of the guideline on the structural failure of current polyester vascular prostheses, we studied seven unsealed polyester vascular prostheses. An accelerated time test was used for assessing degradation of polymeric medical materials at pH 7.4 in phosphate buffer at a temperature of 95 degrees C. Probe burst strength was determined on the guideline and on standard parts of the prostheses during the accelerated time test. Weight-average molecular weights of the guideline and of the standard parts in all knitted grafts during the accelerated time test were measured. The guideline was significantly weaker than the standard parts in most prostheses. The guideline had significantly lower values of weight-average molecular weights than the standard parts in most knitted grafts. This study showed that guideline degeneration was one factor responsible for the structural failure of some current polyester vascular prostheses.

Blood Vessel Prosthesis↗
PubMed1993

Occupational allergic contact dermatitis caused by exposure to acrylates during work with dental prostheses.

Between 1974 and 1992, we were consulted by 4 patients (an orthodontist, 2 dental technicians and a dental worker trained in-house) who had developed occupational allergic contact dermatitis from working with dental prostheses. All patients had positive allergic patch test reactions to methyl methacrylate (MMA), the acrylate which is the most widely used in work with prostheses. All but the orthodontist also reacted to dimethacrylates, which are used in cross-linked dental prostheses. The last patient, investigated in 1992, had been exposed mainly to light-cured acrylics, which are similar in composition to dental composite resins. These acrylics, only recently introduced into prosthetic work, contain more potent acrylic sensitizers than MMA. Accordingly, dental personnel working with prostheses may face a higher risk of sensitization than previously. To detect cases of occupational allergic contact dermatitis, we suggest that patients working with dental prostheses should be patch tested with MMA, 2-hydroxyethyl methacrylate, dimethacrylates, epoxy acrylates and urethane acrylates.

Acrylic Resins↗
PubMed1999

Complications in partially edentulous implant patients: a 5-year retrospective follow-up study of 133 patients supplied with unilateral maxillary prostheses.

BACKGROUND: Numerous studies have reported successful outcomes for restoration of fully edentulous patients with Brånemark implants. However, some studies indicate more mechanical problems in restored partially edentulous situations. PURPOSE: The objective was to study patients with potential risk for mechanical complications after implant treatment. MATERIALS AND METHODS: Patients were retrospectively evaluated 5 years after implant treatment in upper jaw Appelgate-Kennedy Class II situations. Altogether 422 implants ad modum Brånemark were installed in 137 consecutively treated patients. One hundred thirty-three prostheses were placed and followed-up for 5 years, according to routine clinical protocols. RESULTS: The overall 5-year implant cumulative survival rate (CSR) was 94.0%. The corresponding CSR for loaded implants and prostheses was 97.7% and 98.4%, respectively, and the overall marginal bone loss was 0.8 mm (+/- 0.6 mm) after 5 years. Sixteen abutment screws fractured in seven patients (5%) and 17 prostheses (13%) presented loose abutment or gold screws during the follow-up period. Significantly more problems were reported in association with prostheses that included the canine (p < .05), and significantly more gold screws were working loose when only two implants were supporting the frameworks (p < .01). CONCLUSIONS: Upper jaw implant treatment in unilateral free-end situations seems to involve more mechanical problems than other implant treatment groups when only two implants can be installed and when the canine tooth is missing. However, most of these complications are easily adjusted, and the clinical survival of implants and prostheses is the same for these groups compared to other groups of partially edentulous implant patients.

Adult↗
PubMed2004

Fixed implant-supported prostheses in elderly patients: a 5-year retrospective study of 133 edentulous patients older than 79 years.

BACKGROUND: An increasing number of elderly patients are treated with implants, but results for the elderly patient in terms of implant success and adaptation to implant prostheses are contradictory. OBJECTIVE: To retrospectively study the 5-year clinical and radiologic performances of fixed implant-supported prostheses placed in edentulous elderly patients and to compare those results with the results of using similar prostheses in a control group of younger patients. MATERIALS AND METHODS: The study group comprised 133 edentulous patients who were 80 or more years of age and who were consecutively treated with fixed implant-supported prostheses between January 1986 and August 1998. Altogether 761 Brånemark System implants (Nobel Biocare AB, Göteborg, Sweden) were placed in 139 edentulous jaws. The control group comprised 115 edentulous patients who were younger than 80 years and who were treated consecutively from March 1996 to November 1997 with similar prostheses. In this group 670 implants were placed in 118 edentulous jaws. Information was collected from all postinsertion visits, including the fifth annual checkup, and changes of marginal bone levels were analyzed from intraoral radiographs. RESULTS: The 5-year cumulative survival rate (CSR) for implants in the maxilla was 93.0% in the study group and 92.6% in the control group; the corresponding CSRs for implants in the mandible were 99.5% and 99.7%. The most common complications for patients in the study group were soft tissue inflammation (mucositis) and cheek and lip biting (p < .05) whereas resin veneer fractures were the most common complications for the control group. Overall 5-year marginal bone loss for the study group was 0.7 mm (standard deviation [SD], 0.45) in the upper jaw and 0.6 mm (SD, 0.50) in the lower jaw. Differences in bone levels and bone loss between the two groups did not reach significant levels (p > .05). CONCLUSIONS: Implant treatment in the elderly patients showed treatment results comparable to those observed in younger age groups. However, indications of more problems with adaptation could be observed and were reflected in more postinsertion problems. Cleaning problems and associated soft tissue inflammation (mucositis) as well as tongue, lip, and cheek biting were significantly more often observed among the elderly patients (p < .05).

Adaptation, Physiological↗
PubMed1992

Closing sounds and related complaints after heart valve replacement with St Jude Medical, Duromedics Edwards, Björk-Shiley Monostrut, and Carbomedics prostheses.

OBJECTIVE: To measure the noise produced and related subjective complaints after implantation of four different mechanical heart valve prostheses and to identify further factors related to the patient and prosthesis that influence noise generation and complaints. DESIGN: Sound pressure was measured 5 and 10 cm and 1 m from the point of maximal impulse on the body surface by a calibrated meter in quiet rooms with either a decibel(A) filter or octave filters. The patients were asked about their complaints and examined physically. SETTING: The measurements were conducted in silent rooms of ear, nose, and throat departments. The patients had been operated on either in a university hospital or a community hospital. MAIN OUTCOME MEASURES: Sound pressures of frequency bands and sound pressures measured in dB(A) at various distances. Complaints registerd were: sleep disturbance, disturbance during daytime, "wants a less noisy prosthesis," and "can hear the closing click". PATIENTS: 143 patients after heart valve replacement with St Jude Medical (n = 35), Duromedics Edwards (n = 38), Carbomedics (n = 34) and Björk-Shiley Monostrut (n = 36) prostheses operated on between 1984 and 1988 were matched for valve position, ring size, and body surface area. RESULTS: Duromedics Edwards (33.5 (6) dB(A)) and Björk-Shiley Monostrut valves (31 (4) dB(A)) were significantly louder than St Jude Medical (24 (4) dB(A)) and Carbomedics (25 (6) dB(A)) prostheses (p = 0.0001) (mean (SD)). The louder valves were significantly more often heard by the patients (p = 0.0012) and caused more complaints both during sleep (p = 0.024) and during the daytime (p = 0.07). Patients with these valves were more likely to want a less noisy valve (p = 0.0047). Patients with symptoms were younger, had better hearing, and were more likely to be in sinus rhythm. As well as the type of prostheses, the valve diameter and body height also had an effect on sound emission. CONCLUSIONS: The intensity of the closing click of mechanical valve prostheses was significantly different for various designs. Patient complaints were related to the objectively measured sound pressure. Noise production should be considered when a mechanical valve is selected.

Adult↗
PubMed1999

An economic model to estimate the relative costs over 20 years of different hip prostheses.

STUDY OBJECTIVE: To determine the relative costs of prostheses and factors associated with changes in these cost rankings. DESIGN AND SETTING: Economic model using published data. MAIN RESULTS: The main cost drivers are current costs and revision rates. Expected revision costs are a small proportion of the expected total costs. There are few competitors to the "gold standard" Charnley in terms of total expected costs over 20 years. There is no monetary advantage in using higher cost prostheses in older patients even if they were to have lower revision rates. There may be a monetary case for using prostheses with higher costs and lower revision rates in younger patients. CONCLUSIONS: The most cost effective prosthesis in older patients is the Stanmore. The Charnley, Exeter Polished and Muller Straight Stem are marginally more costly than the Stanmore. The study inevitably lacks good data on survival for newer prostheses. This does not affect the ability to make choices for older patients. Data are needed, however, on survival of cemented prostheses for younger patients.

Age Factors↗