Thermal incompatibility analysis of metal-ceramic systems based on flexural displacement data

The feasibility of simple tests or analytical methods for prediction of residual stress states in metal-ceramic (MC) prostheses has not been demonstrated. Biomaterial metal-ceramic strips have been proposed to provide sensitive measures of transient and residual stress states through the measurement of midpoint deflection after cooling from the ceramic sintering temperature. The objective of this study was to apply the elastic-viscoelastic analogy to calculate transient and residual midpoint deflections in MC biomaterial strips and to compare these values with deflections measured with a beam-bending viscometer (BBV). Calculations and measurements were made for five MC systems that were found from a clinical study to be "thermally compatible" systems. Metal strips, 64 mm in length, 3 mm wide, and either 0.5 mm, 1.0 mm, or 2.0 mm in thickness, were veneered with four 0.25-mm thick layers of opaque porcelain. Midpoint deflection of the MC strips (ceramic oriented in the posterior position) was measured during cooling from an initial temperature of 700 degrees C. In general, the directions of the measured residual deflections did not agree with the "textbook" convention that negative deflections are associated with positive thermal contraction mismatch (alpha(M) - alpha(c) > 0) regardless of metal thickness. For a metal thickness of 0.5 mm, the residual midpoint deflection for all thermal contraction mismatch cases, except one, was positive (upward deflection) whereas the residual midpoint deflections were all negative when the metal thickness was increased to 1 or 2 mm, independent of the thermal contraction mismatch. The best agreement between calculated and measured values of residual midpoint deflection (+16 microns vs. +14 +/- 2.3 microns, respectively was obtained for MC biomaterial strips with a Ni-Cr alloy (0.5 mm thick) while the largest difference (+346 microns vs. +61 +/- 43.8 microns) was obtained for MC bimaterial strips with a Au-Pd allow (0.5 mm thick). In all but one case, changes in deflection direction as a function of metal thickness were correctly predicted by the viscoelastic analysis. The results of this study indicate that a viscoelastic model is useful for estimating thermal compatibility conditions of MC systems.     

Properties of lens epithelial cells in albino rabbits--morphological alteration and its influence

We studied changes of epithelial cells in injured lens, after extracapsular cataract extraction (ECCE) in culture solution and in vivo changes in epithelial cells after phacoemulsification and aspiration (PEA) using light and electron microscopy. The epithelial cells at the injured site of the lens were transformed into spindle cells indicating healing and contraction of the lesion. In the culture solution, epithelial cells which had been seen only on the side of the anterior capsule extended and proliferated over the equatorial zone to the posterior capsule covering the whole posterior capsule 6 weeks after an ECCE. Spindle cells were seen in the region with folds in the posterior capsule. In vivo, formation of Soemmering's ring was observed in the equatorial zone after PEA suggesting regeneration of the lens in the electron microscopic aspect. At the edge of the anterior capsule, appearance of spindle cells formation of folds in the anterior and posterior capsules at this site as well as formation of membrane similar to the lens capsule could be seen, and this phenomenon resembled the healing process of the injured lens. Observation of the spindle cells at the cut edge of the anterior capsule showed cells which were extending psudopodia into collagen and they appeared to be engaged in ameboid movement. We considered that this ameboid movement would trigger off contraction of the wound and formation of folds at the cut edge of the anterior capsule.     

Rupture of silicone gel filled testicular prosthesis: causes, diagnostic modalities and treatment of a rare event

PURPOSE: Rupture of the envelope of silicone gel filled testicular prostheses is rare and alleged to be unlikely without intraoperative needle puncture. We observed that it may be caused by chronic intermittent trauma or a single acute increase of pressure, and report diagnostic and therapeutic modalities. MATERIALS AND METHODS: Four cases treated by us during the last 10 years are presented. One patient had testicular implants for Klinefelter's syndrome, whereas the other 3 had been treated for female-to-male transsexualism. Diagnosis was confirmed by ultrasonography and magnetic resonance imaging. The fibrous capsule surrounding the ruptured prosthesis was left intact to allow en bloc surgical extirpation. Histological evaluation of the resected specimen was performed. RESULTS: Rupture of silicone gel filled testicular implants may be caused by acute or chronic pressure without intraoperative needle puncture. CONCLUSIONS: Magnetic resonance imaging offers superior diagnostic accuracy and should be regarded the gold standard in the evaluation of implant rupture. Ultrasonography is an acceptable alternative. In cases when gross symptoms of scrotal inflammation are lacking replacement of implants is facilitated by the fibrous capsule that forms around any prosthesis. Transcapsular migration of silicone particles was observed even when the fibrous capsule was intact.     

Patient satisfaction with current impotence therapy

One hundred ninety-eight impotent men were evaluated between July 1993 and June 1994. A "patient goal-directed" approach was used in all cases. Treatment options presented to patients included: oral yohimbine, vacuum constriction devices, penile self-injection therapy, penile prostheses, and testosterone supplementation when clinically indicated. Thirty-two percent of patients declined treatment, and 67% chose nonsurgical therapy. Only two patients (1%) chose penile prostheses. In August 1994, a survey addressing satisfaction with therapy was mailed to all patients, and 99 men (50%) responded. Of the treated respondents, 80% stated that their therapy was "easy to use," and 70% reported that they were "able to have intercourse." Patients prefer nonsurgical impotence therapy, which restores satisfactory sexual function in most men.     

Induced tissue transformation and heart surgery

This article reports the research which led to the use of animal connective tissues in the construction of valvular prostheses and those which led to the use of electrically stimulated skeletal muscle for cardiac assistance. Although, very different at first glance these research have in common the transformation of biological tissues by physical or chemical means to adapt them to a new function. 1) Once implanted in a different species, animal connective tissues are destroyed by immunological reactions and collagen degeneration. These lesions can be prevented by both maskage of the antigenic groups and intermolecular crosslinking using Glutaraldehyde. The durability of such chemically treated tissues is based upon the stability of the biological material (concept of bioprosthesis) and not upon cell survival or tissue regeneration by host cell ingrowth (concept of graft). The valvular bioprostheses made from Glutaraldehyde treated pericardial tissue, keep after this treatment their advantage of biological tissues: they are not thrombogenic and do not require anticoagulation contrary to mechanical valves. Although they have a limited durability up to 10 to 15 years due to tissue calcification, they represent 40% of the valvular prostheses used in clinical practice today. 2) The clinical use of electrostimulated skeletal muscle has been delayed for a long time because of fatigue lesions. An original protocol of progressive sequential stimulation prior to the use of muscle prevents fatigue by the transformation of type I fatigable myosin into type II non fatigable myosin. The conditionned muscle i.e.: the latissimus dorsi, is then wrapped around the ventricles to either reinforce cardiac contraction or to replace a portion of the heart. In the past 10 years, this new operation of "dynamic cardiomyoplasty", has been performed in 84 patients suffering from the end stage heart failure in our institution and in over 500 patients throughout the world with significant functional improvement.     

Rheumatoid arthritis and hydroxyapatite-coated hip prostheses: five-year results. International ABG Study Group

Medium- and long-term results from cemented total hip arthroplasty (THA) in patients with rheumatoid arthritis (RA) show a higher incidence of infection and aseptic loosening when compared to other diagnoses. Early results using uncemented prostheses are variable. Hydroxyapatite (HA) coatings are thought to improve early osseointegration in uncemented THA. In a prospective, international, multicenter clinical study, 32 RA patients who received 33 uncemented HA-coated prostheses were followed up for a minimum of 5 years. Medium-term clinical results are excellent. No infection or aseptic loosening has been recorded. Excellent osseointegration was observed radiographically. Bone remodeling was consistent with mainly proximal to midstem stress transfer. We conclude that uncemented, proximally HA-coated prostheses are a promising alternative to cemented prostheses for RA patients.     

Diagnosis and therapy of the rupture of both cruciate ligaments, the medial collateral ligament and abscission of both menisci in a ram. A case report

This report describes the case history of a 1.5-year-old ram admitted to the Clinic for Food Animals and Horses, University of Berne, Switzerland, because of an acute severe lameness of the left rear limb. Clinical and radiographic examination revealed disruption of the stifle joint with rupture of both cruciate ligaments, the medial collateral ligament, and disruption of both menisci from their attachments. The ruptured ligaments were replaced by synthetic ligament prostheses. Long-term examination at 12 months after implantation revealed slight instability of the stifle joint, caused by degeneration of the medial meniscus, and signs of arthrosis deformans. The new formed periarticular connective tissue contributed to the stability of the stifle joint, so that a good functional result was achieved. Necropsy findings at 14 months after implantation confirmed that the synthetic ligament prostheses were intact and the medial meniscus was detached from its insertion and incorporated into the joint capsule. At microscopic examination of the synthetic band prosthesis, ingrowth of collagen and fibrous tissue was evident.     

Focal corneal decompensation caused by an anterior capsulotomy remnant

Capsule contraction syndrome, an infrequent but sight-compromising condition, can usually be managed by a neodymium:YAG (Nd:YAG) anterior capsulotomy. The anterior capsule can be split from the visual axis to the periphery with multiple spokes. In this patient, however, these spokes closed, leaving the small anterior capsulotomy indistinguishable from its pre-capsulotomy appearance. A subsequent Nd:YAG laser circumcision of the thickened capsulotomy margin restored the patient's sight. The excised capsular doughnut fell into the anterior chamber angle and resulted 34 months later in localized corneal decompensation. Removal of the capsular remnant markedly improved the corneal changes. The experience from this case suggests that multiple Nd:YAG relaxing incisions may be a safer way to manage capsule contraction syndrome than complete circumcision of the anterior capsule. If the latter approach is taken, the capsular remnant should not be cut completely free of the anterior capsule.     

测定钢铁中氮含量的国际标准方法对比试验

验证和比较钢铁中氮量测定的两种国际标准方法ISO10 70 2和ISO10 72 0。试验结果表明 ,在ISO10 72 0方法中 ,可以用锡囊盛放标准溶液 ,而且锡囊的使用效果要比镍囊的好。对比两种方法的测定结果 ,当氮含量大于 0.0 10 0 %时 ,测定结果没有明显偏差。小于 0.0 10 0 %时 ,还需要进一步实验才能得出结果。     

A within-subject comparison of mandibular long-bar and hybrid implant-supported prostheses: psychometric evaluation and patient preference

Although it has been shown that patients are more satisfied with prostheses supported by implants than with conventional dentures, there have been few direct comparisons of the various designs of implant-supported prostheses. This within-subject crossover clinical trial was designed to compare two forms of removable prostheses which are frequently prescribed for the edentulous mandible: a long-bar overdenture supported by 4 implants and a two-implant hybrid overdenture. Sixteen completely edentulous subjects were given a new maxillary conventional denture: Ten of them received the mandibular long-bar prosthesis first and six the hybrid. After a two-month adaptation period, psychometric measures of various aspects of the prostheses and physiological tests of masticatory efficiency were carried out over three weeks. The mandibular prostheses were then changed and the procedures repeated. At the end of the study, subjects were asked to choose the mandibular prosthesis that they wished to keep, and final psychometric measures were taken. In this paper, the results of the psychometric assessment and patient preference are presented. Subjects assessed factors such as general satisfaction, quality of life, stability, retention, comfort, esthetics, ease of cleaning, speaking, and chewing, and how well-chewed foods were before being swallowed. Most of the factors except ease of cleaning and speaking were rated significantly better with long-bar overdentures than with hybrid ones. These results are consistent with the fact that all subjects chose long-bar overdentures, reporting stability, ease of chewing, and comfort as the most important factors influencing their choice. These results suggest that, although subjects assign high ratings for most factors to hybrid overdentures, they find long-bar overdentures to be significantly more stable, comfortable, and easier for chewing.     

A new finger joint prosthesis

A new finger joint prosthesis is being developed for the proximal and distal interphalangeal positions. Currently available "joint spacer" prostheses provide relief from pain and cosmetic improvement, but relatively poor long-term function. The new prosthesis employs a mechanical hinge at the joint. It is fabricated from titanium alloy (6A14V). The hinge mechanism avoids direct metal to metal contact by using high density polyethylene bearings. In vitro tests of the hinge mechanism have passed 75 million cycles of continuous flexure without failure (n = 12). The hinge also incorporates a mechanical limit stop to prevent hyperextension. The hinge mechanism is enclosed in a sealed elastomeric jacket that isolates the hinge from connective tissue ingrowth. The jacket, equivalent to an artificial synovial membrane, has an integrally textured exterior surface designed to promote tissue attachment to the implant to stabilize tissue capsule formation around the joint. To test the in vivo efficacy of the new design, a series of 12 devices were implanted in the knee joint position of adult rabbits. A jacketed prosthesis was implanted on one side, whereas 2 weeks later an unjacketed control was implanted contralaterally. The animals then were maintained for an 8 week period. At sacrifice, the implants were removed, and the response of the surrounding tissues was studied histologically. At the time of implantation, the range of motion of the joints was approximately 100-105 degrees. There was a progressive loss in range of motion observed in both groups. The fibrous tissue capsule around the jacketed implants, however, was significantly reduced in thickness compared with the controls (mean thickness, 1.5 mm vs. 4.5 mm).(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of time-dependent and quantitative properties of contraction from left ventricular pressure

Several mechanical indices predicted from a model of cardiac muscle contraction are tested. In the in-vivo canine heart, dp/dtmax and t-dp/dt, the time interval from onset of contraction to dp/dtmax, were measured. The product of these parameters Ap = t-dp/dtmax was calculated. t-dp/dt was shortened when heart rate was elevated and remained constant when ventricular end diastolic volume was changed. Ap increased with augmentation of ventricular end diastolic volume. To achieve constant muscle length when heart rate is changed, analogous tension measurements (assigned as dT/dtmax, t-dT/dt and AT) of prestretched Walton Brodie strain-gauge arch had been taken instead of pressure measurements. In the experiments in which Tmax, maximal isometric tension, was not changed for various heart rates, AT was also unchanged. These results are consistent with the predictions that t-dp/dt and Ap can be used as two independent mechanical indices: 1) t-dp/dt for the evaluation of the "time-dependent properties" of contraction and 2) Ap, for the evaluation of the "quantitative properties" of contraction. The advantages of applying these two mechanical indices for use in the intact ejecting heart, instead of the well-established parameters Vmax and Po are emphasized.     

Health risks for women with breast implants

Women who have undergone implantation of a breast prosthesis have been exposed to a variety of health risks, many of which were unknown to them at the time of surgery. Recognition of health hazards has prompted the Food and Drug Administration to restrict implantation of these devices while study of safety and efficacy are undertaken. Capsule contracture, or the contraction of the fibrous tissue surrounding the prosthesis, is the most frequently occurring complication. Exposure to an implant does not appear to heighten the risk for breast cancer, but the opacity of a prosthesis substantially reduces the diagnostic capability of mammography. Silicone, used in the manufacture of implants, is linked to immunologic changes that result in connective tissue disorders. Most often this condition is scleroderma. Damaging effects from toluenediamine, a disintegration product of the polyurethane coating, have been reported. Whether the concentration of this chemical reaches toxic levels in women with prostheses remains to be clarified by current investigations.     

Total versus partial musculofascial coverage for steroid-containing double-lumen breast implants in augmentation mammaplasty

The use of intraluminal steroids in double-lumen breast implants is effective in preventing fibrous capsular contraction around the implant. This technique has not been accepted widely, however, and remains controversial primarily because steroid-related complications, including extrusion, late inferior migration, and atrophy of the skin, have been associated with their use. This nonrandomized retrospective study of 76 patients (146 breasts) who underwent submuscular augmentation of the breast through inframammary and periareolar incisions compares results after total musculofascial coverage of the implant with partial muscle coverage of the implant. In patients with partial muscle coverage of the implant, 7.8% steroid-related complications were observed. In the group with total musculofascial coverage of the implant, no steroid-related complications and no symptomatic contractions of the capsule were observed. Our study suggests that total musculofascial coverage provides a statistically significant margin of protection from steroid-related complications compared with techniques using only partial muscle coverage of the implant in patients who underwent cosmetic augmentation mammaplasty.     

Surgery for aortic dissection associated with congenital bicuspid aortic valve

The Distribution Moment (DM) model has simulated experimental data on skeletal muscle, but it has not been used previously to study the mechanics of active contraction in cardiac muscle. In contrast to previous models of striated muscle contraction, all parameters have physical meaning and assumptions concerning biophysical events within the cell are consistent with available data. In order to simulate cardiac muscle deactivation using the DM model it was necessary to make the cross-bridge detachment rates large for large displacements from the neutral equilibrium position of a cross-bridge. To examine the effect of cooperativity on cardiac muscle contraction, we used the DM model's tight coupling scheme with binding of one or two calcium sites regulating contraction. As observed experimentally, our model predicted a reduction of isometric tension development following rapid shortening lengthening transients when contraction is regulated by either one or two calcium binding sites. The predicted deactivating effect increased if the transient was applied late in the twitch when contraction is regulated by two calcium binding sites, but not when it is regulated by one site. This is the first study in which deactivation has been simulated without making any provisions for length-dependent calcium trononin dissociation.     

L-2-Hydroxyglutaric aciduria: neuropathological correlations and first report of severe neurodegenerative disease and neonatal death

Chromolaena odorata (formerly Eupatorium odoratum) is used as a traditional medicine in Vietnam (Nghiem, 1992), where its Vietnamese common name is "co hoi." While it has been widely considered a weed by agriculturalists (Holm et al., 1991), the aqueous extract and the decoction from the leaves of this plant have been used throughout Vietnam for the treatment of soft tissue wounds, burn wounds, and skin infections. A number of clinical studies done by Vietnamese as well as foreign medical workers has demonstrated the efficacy of this extract on the wound-healing process. In this article, the effect of the Eupolin extract on hydrated collagen lattice contraction by human dermal fibroblasts, an in vitro model of wound contraction, is described. The significant inhibition of collagen gel contraction by Eupolin extract at 50 to 200 micrograms/ml is demonstrated in various concentrations of collagen. When the extract at 50 to 150 micrograms/ml was washed out of the lattices and replaced by fresh medium without Eupolin, the contraction of collagen by cells was resumed. The visualization of cells in the lattices by incubation in a tetrazolium salt for 2 h showed live cells at 50 to 150 micrograms/ml of extract. In contrast, all cells were killed in the higher extract doses of 300 or 400 micrograms/ml. These preliminary results showing the inhibitory effect of Eupolin extract on collagen contraction suggest that a clinical evaluation of its effect on wound contraction and scar quality should be made. This work illustrates that traditional remedies that are used by folk practitioners to improve healing can be examined in a scientific manner using in vitro wound-healing models. It could be that the synergistic properties of components of the natural extract contribute to the positive effects demonstrated on various wound-healing mechanisms.     

Intersubject and interswallow variability in topography of esophageal motility

Topographic plots linking averaged manometric data in time and space suggest that sequential contraction segments form esophageal peristalsis. A system capable of plotting individual swallows was developed to verify this observation and to determine intersubject and interswallow variability in their topographic appearance. Fourteen volunteers were studied with a novel computerized assimilation method capable of generating topographic contour plots as well as conventional wave forms for analysis. Contraction segments in the proximal body and lower sphincter were identified in all subjects as being separate from the remainder of the esophagus with little interswallow variation. The appearance of peristalsis through the distal body was more variable because of its intermittent separation into two dominant contraction segments (59.8% of swallows) that had poorly correlated contraction strength (median r = 0.15). Intersubject variability exceeded interswallow variability in topographic landmarks, resulting in distinctive topographic "fingerprints" of peristalsis for each subject. We conclude that topographic plotting of single swallows is feasible and confirms the presence of sequential contraction segments in the esophagus. Interswallow variability helps demonstrate two segments within the smooth-muscle body, an anatomical region of seeming homogeneity, that have sufficient contraction independence to indicate separate neuromuscular units responding to different contractile influences.     

Identification, genomic organization, and analysis of the group III capsular polysaccharide genes kpsD, kpsM, kpsT, and kpsE from an extraintestinal isolate of Escherichia coli (CP9, O4/K54/H5)

Group III capsular polysaccharides (e.g., K54) of extraintestinal isolates of Escherichia coli, similar to group II capsules (e.g., K1), are important virulence traits that confer resistance to selected host defense components in vitro and potentiate systemic infection in vivo. The genomic organization of group II capsule gene clusters has been established as a serotype-specific region 2 flanked by regions 1 and 3, which contain transport genes that are highly homologous between serotypes. In contrast, the organization of group III capsule gene clusters is not well understood. However, they are defined in part by an absence of genes with significant nucleotide homology to group II capsule transport genes in regions 1 and 3. Evaluation of isogenic, TnphoA-generated, group III capsule-minus derivatives of a clinical blood isolate (CP9, O4/K54/H5) has led to the identification of homologs of the group II capsule transport genes kpsDMTE. These genes and their surrounding regions were sequenced and analyzed. The genomic organization of these genes is distinctly different from that of their group II counterparts. Although kps(K54)DMTE are significantly divergent from their group II homologs at both the DNA and protein levels phoA fusions and computer-assisted analyses suggest that their structures and functions are similar. The putative proteins Kps(K54)M and Kps(K54)T appear to be the integral membrane component and the peripheral ATP-binding component of the ABC-2 transporter family, respectively. The putative Kps(K54)E possesses features similar to those of the membrane fusion protein family that facilitates the passage of large molecules across the periplasm. At one boundary of the capsule gene cluster, a truncated kpsM (kpsM(truncated) and its 5' noncoding regulatory sequence were identified. In contrast to the complete kps(K54)M, this region was highly homologous to the group II kpsM. Fifty-three base pairs 3' from the end of kpsM(truncated) was a sequence 75% homologous to the 39-bp inverted repeat in the IS110 insertion element from Streptomyces coelicolor. Southern analysis established that two copies of this element are present in CP9. These findings are consistent with the hypothesis that CP9 previously possessed group II capsule genes and acquired group III capsule genes via IS110-mediated horizontal transfer.     

Patient satisfaction with dentures made by dentists and denturologists

BACKGROUND: Within Quebec and elsewhere in Canada, patients requiring removable prostheses consult either dentists or denturologists. In this article, we describe the socioeconomic characteristics of 410 edentulous individuals seeking replacement of their dentures, and compare the levels of satisfaction experienced by the patient groups provided with conventional dentures by dentists and by denturologists. METHODS: All subjects responded to announcements seeking participants in a clinical trial. The announcements indicated that all participants would receive new prostheses. Data were collected via telephone interviews. Sociodemographic variables included sex, age, education level and family income. Subjects were asked to evaluate their present maxillary and mandibular prostheses for general satisfaction, stability, comfort, ability to chew, ability to clean and appearance. Age, cost and the provider (dentist or denturologist) of the original prostheses were also recorded, and responses were then compared between the groups of subjects treated by dentists (N = 91) and denturologists (N = 319). RESULTS: There were no significant differences in the sociodemographic characteristics of the two groups, except for a small difference in mean age (two years). Both groups had paid approximately the same amount for their complete prostheses. As expected, most individuals were satisfied with their maxillary prostheses, but dissatisfied with their mandibular prostheses. Significantly more subjects in the denturologist treatment group than the dentist treatment group gave their mandibular prostheses a poor rating for general satisfaction (p = 0.003), comfort (p = 0.04) and stability (p = 0.016). CONCLUSIONS: These results suggest that the edentulous patients treated by dentists and denturologists share similar sociodemographic characteristics, and pay a similar cost for treatment. However, those treated by denturologists seem to be more dissatisfied with their mandibular prostheses than those treated by dentists.