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PubMed2006

Efficacy of conventional and implant-supported mandibular resection prostheses: study overview and treatment outcomes.

STATEMENT OF PROBLEM: While surgical restoration of mandibular resections has advanced dramatically with free-flap techniques, oral function and patient perceptions of function, as well as treatment outcomes, often indicate significant impairment. PURPOSE: This longitudinal prospective study was designed to determine whether conventional prostheses (CP) or implant-supported prostheses (IP) and current surgical reconstructive procedures restore patients' oral functions and quality of life to their status prior to segmental mandibulectomy with immediate fibula free-flap reconstruction. Study design and implementation, characteristics of the study sample, treatment completion rates, and selected presurgical and postsurgical functional and perceptual outcomes are presented. MATERIAL AND METHODS: Forty-six subjects were enrolled. Longitudinal evaluations of medical and dental histories, oromaxillofacial examinations, questionnaires, and sensory and functional tests were planned before and after surgery and after CP and IP treatment. Sample characteristics are described with descriptive statistics and comparisons of subject responses to questionnaire items at entry and postsurgical intervals were made with Fisher exact tests (alpha=.05). RESULTS: Conventional prostheses were completed in 33 of 46 subjects, and 16 of 33 CP subjects were treated with IP. Reasons for noncompletion of IP were recurrent/metastatic disease (16), refusal of implant therapy (7), lost to follow-up (4), treatment with a reconstruction plate (1), excessive radiation at implant sites (1), and death (1). All 16 recurrences/metastases occurred within 13 months of surgery. Only 3 of the 58 implants placed in 17 participants were considered failures. One failed due to lack of integration 31 weeks following placement, and 2 were buried due to unacceptable positioning for prosthetic restoration during denture fabrication. The remaining 55 implants were successful at final evaluation, ranging from 58 to 123 weeks following implant placement (mean duration=78.9 +/- 16.0 weeks). CONCLUSIONS: While 72% (33/46) of the subjects enrolled were able and willing to complete treatment with CP, only 35% (16/46) completed IP treatment. Careful consideration must be given to selection of the type of prosthetic rehabilitation and the timing of implant placement if an IP is planned.

Adult↗
PubMed2001

Hemodynamic performance of the 21-mm Sorin Bicarbon mechanical aortic prostheses using dobutamine Doppler echocardiography.

BACKGROUND: Small-sized mechanical aortic prostheses are commonly associated with generation of high transvalvular gradients, particularly in patients with large body surface area, and can result in patient-prosthesis mismatch. This study evaluates the hemodynamic performance of 21-mm Sorin Bicarbon bileaflet mechanical prostheses using dobutamine stress echocardiography. METHODS: Fourteen patients (7 women; mean age, 63+/-8 years) who had undergone aortic valve replacement with a 21-mm Sorin Bicarbon bileaflet mechanical prosthesis 32.4+/-5.1 months previously were studied. After a resting Doppler echocardiogram, a dobutamine infusion was started at a rate of 5 microg x kg(-1) x min(-1) and increased to 30 microg x kg(-1) x min(-1) at 15-minute intervals. Pulsed- and continuous-wave Doppler echocardiographic studies were performed at rest and at the end of each increment of dobutamine. Both peak and mean velocity and pressure gradient across the prostheses were measured, and effective orifice area, discharge coefficient, and performance index were calculated. RESULTS: Dobutamine stress increased heart rate and cardiac output by 83% and 81%, respectively (both p < 0.0001), and mean transvalvular gradient increased from 15.6+/-5.5 mm Hg at rest to 35.4+/-11.9 mm Hg at maximum stress (p < 0.0001). Although the indexed effective orifice area was significantly lower in patients with a larger body surface area, this was not associated with any significant pressure gradient. The performance index of this valve was unchanged throughout the study. Regression analyses demonstrated that the mean transvalvular gradient at maximum stress was independent of all variables except resting gradient (p = 0.05). Body surface area had no association with the changes in cardiac output, transvalvular gradient at maximum stress, and effective orifice area. CONCLUSIONS: These data show that the 21-mm Sorin Bicarbon bileaflet mechanical prosthesis offers an excellent hemodynamic performance with full utilization of its available orifice when implanted in the aortic position. The lack of significant transvalvular gradient in patients with a larger body surface area suggests that patient-prosthesis mismatch is highly unlikely when this prosthesis is used.

Adult↗
PubMed1983

Thrombotic catastrophe in the patient with multiple Björk-Shiley prostheses.

Thrombosis of the Björk-Shiley prosthesis has been a recognized problem for many years. Review of 172 patients at the University of Kentucky Medical Center who had one or more Björk-Shiley valves inserted between January, 1975, and July, 1980, revealed special problems in those patients with multiple prostheses. Diagnosis and therapy prove more difficult, and the cumulative incidence of thrombosis in the patients with multiple prostheses is 26.8% at six years. Projected long-term use of multiple Björk-Shiley prostheses is discouraged.

Aortic Valve↗
PubMed1976

An electric cutter for all surgical prostheses.

A new electric cutter for surgical prostheses has been developed and was compared with surgical scissors for efficacy. This comparison of the two methods was done by cutting the edges of nine popular prostheses. It was concluded from gross and microscopical results after pulling both edges of the grafts cut by the two methods that the electric cutter is much more effective for surgical prostheses.

Blood Vessel Prosthesis↗
PubMed1975

Late stenosis of Starr-Edwards cloth-covered prostheses.

During a two-year period (August, 1971, to July, 1973) 1 Starr-Edwards Model 2400 and 135 Starr-Edwards Model 2320 aortic prostheses were inserted without postoperative antiocagulant therapy. Seven of these valves (including the Model 2400 prosthesis) have been replaced because of substantial transvalvular gradients resulting from fibrous overgrowth of the valve orifice. Symptoms associated with aortic stenosis occurred an average of nine months after the initial operation. Six patients had severe anemia (packed cell volume less than 30%) and hemolysis (serum lactic dehydrogenase greater than 900 units). Gradients across the prostheses ranged from 66 to 105 mm Hg with a mean of 87 mm Hg. One valve was size 8A, 3 were 10A, and 1 was 12A. Fibrous ingrowth was not observed in an earlier group of 23 patients receiving the Model 2310 or Model 2320 prosthesis who were placed on long-term anticoagulant therapy. These findings, coupled with a 9% incidence of thromboembolism at one year, indicate that patients having these prostheses inserted should receive long-term anticoagulant therapy.

Adult↗
PubMed1997

Long-term follow-up of small (size 20 and 21) Medtronic-Hall aortic valve prostheses.

BACKGROUND: Our goal was to study the long-term follow-up of patients having aortic valve replacement and to focus particularly on the patients receiving small prostheses. METHODS: Four hundred twenty-eight Medtronic-Hall valves were implanted (156 size 20 or 21 mm, 149 size 22 or 23 mm, and 123 size 25 or 27 mm). Group 20-21 had a higher number of female patients, more associated coronary lesions, and more patients with aortic stenosis. RESULTS: The actuarial survival rate at 8 years was 80% for group 20-21, 80% for group 22-23, and 76% for group 25-27 (p = not significant). In group 20-21, the actuarial event-free rates at 8 years were as follows: thromboembolic complications, 94%; prosthetic valve endocarditis, 99%; reoperation, 98%; and hemorrhagic complications, 78%. The only factors of prognostic value in this group were age and associated coronary lesions. CONCLUSIONS: The durable nature of the results obtained with the Medtronic-Hall 20- and 21-mm prostheses compared with large-diameter prostheses allows the use of a simple and reliable surgical technique and should mean that indications for ring enlargement become rare.

Aortic Valve↗
PubMed2005

[Composite prostheses for the repair of abdominal wall defects: comparative study of physical and/or chemical barriers].

INTRODUCTION: Composite biomaterials designed for the repair of abdominal wall defects are usually composed of a reticular component and a second component, or barrier, which is laminar (absorbable or non-reabsorbable) and which is placed in contact with the visceral peritoneum. This study was designed to evaluate how the composition of this second component affects the biological behavior of the biomaterial and the formation of adhesions. MATERIAL AND METHODS: Defects (7 x 5 cm) comprising all the tissue planes except the skin were created in the anterior abdominal wall of white, New Zealand rabbits. In group A (n = 12) the defects were then repaired with composite prostheses with a non-reabsorbable physical barrier, polypropylene + ePTFE (PL + ePTFE) and PL + polyurethane (PL + PU). In group B (n = 12) the defects were repaired with a reabsorbable chemical barrier, polyester + a polyethyleneglycol/glycerol film (PO + gl) and PL + hyaluronate (PL + hy). Fourteen days after surgery, the animals were sacrificed and specimens were taken for light and scanning electron microscopy and immunohistochemical labeling for macrophages (RAM-11). Adhesions forming at the prostheses/visceral peritoneum interface were quantified. RESULTS: All the materials showed optimal tissue infiltration and mesothelialization. Adhesion formation was similar in prostheses with a physical barrier (PL + ePTFE, 0.49 +/- 0.14%; PL-PU, 0.29 +/- 0.2%). In contrast, those with a chemical barrier showed a significant difference in adhesion formation (PO + gl, 0.55 +/- 0.06%; PL + hy, 18.55 +/- 4.96%; p < 0.05). CONCLUSIONS: Physical barriers seem to induce similar adhesions, while adhesions formed to prostheses with chemical barriers can vary considerably, possibly depending on the chemical composition of the barrier.

Animals↗
PubMed1996

Expandable versus conventional esophageal prostheses: easier insertion may not preclude subsequent stent-related problems.

BACKGROUND: Although expandable esophageal endoprostheses may be easier to insert and are associated with fewer procedure-related perforations, data comparing clinical results with these stents to those obtained with conventional prostheses are sparse. METHODS: We reviewed the records of all patients undergoing esophageal stent placement at our institution between October 1983 and July 1995 to define relative risks, clinical results, and need for reintervention prior to death, contrasting conventional to a variety of expandable esophageal endoprostheses. RESULTS: Over the period of review, 47 patients had conventional prostheses (CP) and 38 had expandable prostheses (EP) placed. Fifteen of 44 patients with CP and 14 of 38 with EP for malignancy also had esophago-airway fistulas. Insertion complications, prestent and poststent dysphagia scores, and complete fistula occlusion rates were comparable. Subacute complications were higher in the patients receiving EP (80%) than in those receiving CP (60%), possibly related to the prospective accumulation of data in patients receiving EP. Survival data were virtually identical and approximated 3 months for either group. CONCLUSIONS: Although both CP and EP improve dysphagia and occlude tracheoesophageal fistulae, patients ill enough to require a prosthesis do poorly regardless of prosthesis design. Moreover, although EP may be easier to insert than CP, stent- and patient-related problems persist and may require additional intervention.

Aged↗
PubMed2000

Treatment outcomes of fixed or removable implant-supported prostheses in the edentulous maxilla. Part I: patients' assessments.

STATEMENT OF PROBLEM: Distinct clinical parameters determine whether fixed or removable implant-supported prostheses are indicated to restore the edentulous maxilla. However, there is a strong belief that fixed implant prostheses meet with greater patient acceptance and satisfaction, but this may differ from the patients' perceptions, their psychological responses to treatment, and their assessments of the treatment outcome. PURPOSE: This prospective clinical study compared the treatment outcomes of fixed and removable implant-supported restorations in the edentulous maxilla with the main emphasis on the patient's point of view. MATERIAL AND METHODS: Twenty patients who requested an implant-supported superstructure to restore the edentulous maxilla were asked to complete a questionnaire measuring their satisfaction with the present situation and the psychologic impact of their oral health status with their responses marked on a Visual Analog Scale (VAS). Ten patients were treated with a fixed, screw-retained implant prosthesis (group 1), and 10 were treated with a removable, implant-supported and bar-retained overdenture (group 2). Six months after prosthetic rehabilitation, patients were again given the questionnaire to assess their psychologic well-being and satisfaction with the implant-supported restoration. RESULTS: Both prosthesis designs were associated with significant improvements in comfort and retention, function, esthetics and appearance, taste, speech, and self-esteem. No difference was found between the 2 groups with respect to how the patients assessed the implant therapy. However, the results indicated that patients in group 2 experienced greater differences between pretreatment and posttreatment scores for the parameters esthetics, taste, and speech. Treatment costs per unit were significantly higher in group 1 than in group 2. CONCLUSION: Patients in groups 1 and 2 were similarly satisfied with their implant-supported prostheses in the edentulous maxilla with regard to their well-being and the cost-utility, irrespective of whether the restoration was fixed or removable.

Adult↗
PubMed1996

A longitudinal study of resin-bonded prostheses.

Resin-bonded fixed partial dentures, without definitive tooth preparation and current resinous cements and perceptive treatment, have had an inordinate number of dislodgments in initial restorative efforts. A longitudinal examination of resin-bonded prostheses was performed after a mean observation time exceeding 6 years. To prevent stress fatigue fractures of the cement bondings, one proximal groove was prepared in dentin for each anterior abutment and the inner surfaces of the frameworks were silicoated. Five of 34 prostheses debonded, and the bond strength between resin and high gold alloys was too low to resist fatigue fractures during this study. The results of this study and other reports suggested a need for increased retention and resistance form of the frameworks to improve longevity of resin-bonded prostheses.

Adult↗
PubMed1997

Theoretical study of the effects of tooth and implant mobility differences on occlusal force transmission in tooth/implant-supported partial prostheses.

STATEMENT OF PROBLEM: Despite their mobility differences under occlusal loads, a natural tooth and an implant are often used together to support fixed prostheses. In some situations, tooth/implant-supported partial prostheses include cantilever extensions, especially in the posterior region where the bone is inadequate for placement of an additional implant. PURPOSE: In this study, engineering beam theory was used to study the effects of the mobility differences between the implant and the tooth on the force and moment distribution, due to occlusal loads in tooth/implant-supported prostheses. METHODS: The prosthesis was treated as a linear elastic beam and the supports were modeled as springs with (vertical) translational and rotational stiffness. The bending moments and forces on the supports were calculated as functions of the parameters that describe the geometry, position of the occlusal load, and stiffness ratios (namely, implant or tooth) of the springs. RESULTS: Bending moments on the supports were more sensitive to the relative rotational mobility between the supports and their individual values than to the relative translational mobility. The moment at the implant was minimized when the supports had similar mobilities. A preliminary design concept was introduced and eliminated the moment at the implant without significantly increasing the magnitude of the moment at the tooth. Cantilevering the prosthesis resulted in moderately increased bending moments and considerable tensile forces on the supports for a broad range of the parameters that describe the geometry and loading. CONCLUSIONS: From this simulation, it is suggested that cantilever extensions should be avoided or supported by a short implant, which will only restrain the vertical movement of the cantilever end.

Algorithms↗
PubMed1997

A longitudinal clinical assessment of spark erosion technology in implant-retained overdenture prostheses: a preliminary report.

STATEMENT OF PROBLEM: As adapted for the dental profession, spark erosion technology permits precise machining of retentive metal overdenture frameworks for use in implant prosthetics. PURPOSE: The resultant prostheses are retentive and provide a number of benefits offered by both conventional overdenture and fixed prosthetic designs. MATERIAL AND METHODS: Preliminary data collected from an ongoing 5-year clinical trial were reviewed to qualitatively assess the clinical results obtained from 25 spark eroded implant-retained overdenture prostheses placed in 24 subjects. RESULTS: Throughout an evaluation period of 13.33 months (range 4 to 19 months), subject responses measured by questionnaire were uniformly good. Few complications were encountered and were limited to resin denture base/tooth fractures or retentive component failures that were easily repaired. CONCLUSION: Overdenture prostheses retained by spark eroded milled frameworks offer an acceptable treatment alternative for patients undergoing dental implant therapy.

Dental Alloys↗
PubMed2003

Serial Doppler echocardiographic evaluation of small-sized sorin bicarbon prostheses.

OBJECTIVE: The Sorin Bicarbon prosthesis (Sorin Biomedica, Saluggia, Italy) is a bileaflet valve with curved-profile leaflets, a rolling hinge mechanism, and a pyrolytic carbon-coated titanium alloy housing and sewing ring. Although the Sorin Bicarbon prosthesis has been implanted in greater than 80,000 patients, and reference values on the hemodynamic performance of valve prostheses are needed to avoid patient-prosthesis mismatch, few Doppler echocardiographic data are available on the prosthesis in the aortic position. The aim of this study is to provide a detailed echocardiographic evaluation of the hemodynamic performance and regression of left ventricular hypertrophy after aortic valve replacement with the Sorin Bicarbon prosthesis. METHODS: The study included 182 patients who received a 21-mm (n = 61) or 23-mm (n = 121) Sorin Bicarbon prosthesis for pure or prevalent aortic stenosis who underwent serial echocardiograms at 3, 6, and 12 months after aortic valve replacement. RESULTS: Mean and peak gradients significantly decreased (P <.001) during follow-up to values of 12 +/- 3 and 22 +/- 6 mm Hg for the 21-mm prosthesis and values of 11 +/- 4 and 19 +/- 6 mm Hg for the 23-mm prosthesis at 1 year. Left ventricular mass index showed a 17% decrease to 120 +/- 27 g/m(2) in recipients of the 21-mm prosthesis (P <.001) and a 21% decrease to 123 +/- 29 g/m(2) in recipients of the 23-mm prosthesis (P <.001). A larger prosthesis size was the only predictor of a higher left ventricular mass index regression. Among recipients of the 21-mm prosthesis, body surface area of greater than 1.85 m(2) was associated with a lower regression of left ventricular mass index. The effective orifice area index was 1.00 +/- 0.11 and 1.08 +/- 0.14 cm(2)/m(2) in recipients of the 21-mm and 23-mm prostheses, respectively. CONCLUSIONS: Size 21 mm and 23 mm Sorin Bicarbon prostheses show low transprosthetic gradients, with significant reduction of left ventricular mass index during the first postoperative year. The reported effective orifice areas might be useful for aortic valve replacement in patients with a small aortic annulus to avoid patient-prosthesis mismatch.

Aged↗
PubMed1998

Cardiac valve endothelial cells: relevance in the long-term function of biologic valve prostheses.

OBJECTIVE: For reasons that are still unclear, biologic heart valve prostheses undergo degeneration after implantation. We studied the possible role of the immune system in this process. METHODS: We examined the expression of immunologically relevant molecules by human cardiac valve endothelium in situ and in vitro and studied re-endothelialization of implanted allogeneic and xenogeneic valvular surfaces using explanted bioprostheses and valves obtained from donor hearts at cardiac retransplantation. RESULTS: We demonstrate that human cardiac valve endothelial cells express molecules capable of initiating immune responses and might therefore play a role in the degeneration of viable cardiac valve prostheses. Also, we show evidence of re-endothelialization on the surfaces of xenografts and allografts but not on valves obtained from previously transplanted hearts. CONCLUSION: Inasmuch as valves from previously transplanted hearts seem to be free from degeneration, we conclude that reduction of the immunogenicity of allograft valve prostheses by HLA matching or immunosuppressive treatment might further improve long-term results after allograft valve replacement.

Antigens, CD↗
PubMed1993

Tissue-integrated dental prostheses: the first 78 months of experience at the Mayo Clinic.

During a 78-month period at the Mayo Clinic, 1,778 Brånemark endosseous dental implants were placed in the edentulous or partially edentulous jaws of 353 consecutive patients who ranged in age from 8 to 82 years. The largest treatment category involved edentulous mandibles, which accounted for 53% of the total restorations. Approximately 76% of the threaded cylindrical implants supported 312 oral prostheses at the end of the study period. The implant survival rate was 97.8% in the mandible and 88.8% in the maxilla. Complications associated with this treatment included loss of implant anchorage in bone, soft tissue problems, and mechanical difficulties related to design and function of the prostheses. All complications were managed without loss of continuous function of the prostheses, except in four patients who resumed wearing a conventional removable maxillary complete denture. This experience demonstrates that Brånemark endosseous dental implants are predictable and can provide lasting integration under function when placed and loaded in accordance with the recommended protocol.

Adolescent↗
PubMed1995

Manipulation of rubber dam septa: an aid to the meticulous isolation of splinted prostheses.

Splinted prostheses are a problem in endodontic isolation. The traditional solution of resorting to a slit-dam technique results in an unrestrained curtain of rubber dam which not only allows for saliva seepage but can serve to compromise the endodontic access opening. This article introduces a simple, yet effective, method of improving the seal of isolated splinted prostheses. It relies on the manipulation and ligation of rubber dam septa with dental floss. Two pictorial clinical reports depict the technique and demonstrate the ease of attaining isolation with splinted prostheses.

Child↗
PubMed2001

In vitro interaction of bacteria with polypropylene/ePTFE prostheses.

The infection of an implanted prosthetic material can have serious consequences on the tissue integration of the implant and the scarring process in the host, and may even necessitate replacement of the prosthesis. This study was designed to explore the in vitro effects of Staphylococcus aureus (Sa) and Staphylococcus epidermidis (Se) on polypropylene (PL) and expanded polytetrafluoroethylene (ePTFE) prostheses. Fragments of PL and ePTFE were placed in a medium previously inoculated with Sa, Se or Sa + Se (1 x 10(8) cfu Sa or/and Se). Bacterial effects on the biomaterials were evaluated for 30 days through scanning electron microscopy (SEM). In order to confirm the presence of bacteria on the prostheses, specimens were Gram stained and challenged with an antibody against protein-A (a specific Sa bacterial wall component). In both methods, specimens were examined by light microscopy. The presence of bacteria as microcolonies or biofilms was detected at PL filament cross-over regions after 30 days. Bacterial colonization of the ePTFE fragments was observed in internodal areas, which led to the deformation of prosthetic filaments. The present findings indicate that Sa and Se colonize the cross-over regions of the PL filaments, whereas in ePTFE prostheses, it is the internodal areas which are mostly affected. The latter areas are of difficult access to defence agents.

Biocompatible Materials↗
PubMed1997

Friction in hip prostheses.

Although the reduction of frictional torques was the driving force behind the design of the Charnley prosthesis, later concerns about wear and subsequent loosening of this and other hip replacements have dominated debate within the bioengineering community. To stimulate discussion on the role of friction in loosening, a review of the frictional characteristics of different prostheses was undertaken. The use of simple laboratory screening-type machines in the frictional assessment of different material combinations is discussed together with experiments performed on single axis simulators using both conventional and experimental prostheses. In particular, recent developments in the use of soft layer components are highlighted. Further, the possible link between excessively high frictional torques and loosening is discussed in the light of current results obtained from explanted prostheses.

Alloys↗