Problems with double-J stents and nephrostomy tubes

The aim of this study was to compare the backfilling capabilities of System B, Obtura II and Alphaseal. Forty-six lower premolar teeth were prepared chemomechanically and allocated to four experimental and two control groups. Ten were obturated using lateral condensation as a standard and 30 were obturated in the apical third using the System B. The latter 30 teeth were then backfilled using one of three techniques, System B, Obtura II or Alphaseal (n = 10 in each group). The remaining six teeth served as controls. Roots were radiographed from the proximal in order to evaluate voids and then placed in India ink for 65 h prior to being demineralized and rendered transparent, coronal leakage was quantified by linear measurement of ink penetration. No significant difference was found between the four groups with respect to the presence of voids radiographically (P < 0.05). The difference in leakage between the System B and Obtura II groups was not significant (P > 0.05). Both System B and Obtura II leaked significantly less than Alphaseal and lateral condensation (P < 0.001).     

An evaluation of the biocompatibility of intraocular lenses

BACKGROUND AND OBJECTIVE: The degree of cell adhesion to intraocular lenses (IOLs) was studied through the cell culture system and the morphology of adhering cells was studied using a light electron microscope and a scanning electron microscope. MATERIALS AND METHODS: Human lens epithelial cells were used as materials. The IOL materials were classified into four groups: polymethylmethacrylate (PMMA), heparin surface modified PMMA, surface passivated PMMA, and silicone. RESULTS: PMMA showed greater adhesion than did the other materials. Cells hardly adhered to silicone. Use of a light electron microscope and a scanning electron microscope revealed that cells adhered uniformly to the surface of PMMA and were elongated, but did not adhere uniformly to IOLs of other materials. Only a few cells without the tendency of elongation were noted on the silicone the second day after culture. The 14th day after culture, the surfaces of IOLs, except those of silicone, were covered with cells. CONCLUSION: Such differences in the surface adhesion and morphology of cells adhering to the IOL surface are important in evaluating IOL biocompatibility.     

In vitro evaluation of biocompatibility of experimental titanium alloys for dental restorations

Changes in energy phosphates of rabbit kidneys subjected to ischaemia-reperfusion have been measured in vivo with volume selective 31P NMR spectroscopy. The effects of pretreatment with a new lipid peroxidation inhibitor (indeno-indol derivate--code name H290/51) on the bioenergetic changes were analysed. The left kidney was moved to a subcutaneous pocket to facilitate exact positioning over the surface coil. A 1H NMR image was acquired and a 3.5-mL cube selected for 31P NMR spectra. 31P NMR spectra were recorded before occlusion of the left renal artery, during 1 h of ischaemia and 2 hours of reperfusion. Ischaemia induced drastic changes in the levels of inorganic phosphates and ATP as well as intracellular acidosis. A normalization was observed during reperfusion. Two hours after reperfusion significantly higher values for beta-ATP/Pi and intracellular pH were recorded in the animals pretreated with H290/51. The present technique allows quantitative analyses of changes in kidney bioenergetics in vivo during different experimental conditions. The importance of ischaemia-reperfusion induced lipid peroxidation for mitochondrial function is emphasized.     

Cell-seeding and in vitro biocompatibility evaluation of polymeric matrices of PEO/PBT copolymers and PLLA

Higher lipid content in gall bladder bile of sheep and goats as compared with monogastric species was due to higher proportion of glycerides. The volume of bile per gall bladder was higher in sheep than in goats. Bile from sheep and goats has a higher content of proteins and lower contents of dry matter, cholesterol and phospholipids compared with monogastric species. Biliary proteins partially purified by the ammonium sulfate precipitation method were characterized and quantified by polyacrylamide gel electrophoresis (PAGE), fast protein liquid chromatography (FPLC) and immunodiffusion. FPLC and PAGE profiles indicate that biliary proteins of sheep and goats are mainly of low mol. wt. of upto 65 KDa. Proportions of immunoglobulin (Ig) like molecules in biliary proteins precipitated by ammonium sulfate of different degrees of saturation, were 10.4 to 26.7 and 21.9 to 30.7 per cent of total proteins in bile of goats and sheep. IgG and IgA like molecules were the predominant Ig and lacked carbohydrates. On immunodiffusion such Ig like molecules did not show cross reactivity with humoral Ig. It was concluded that sheep and goats appear to secrete Ig into bile after deglycosylation and partial degradation. The proteins of smaller molecular weight may be secretory fragments or degradation products of Ig.     

An in vitro evaluation of distractors used for osteogenesis

OBJECTIVE: The objective of this investigation was to evaluate and compare the mechanical behaviors of distractors used for osteogenesis under various conditions by means of common engineering standards. STUDY DESIGN: Five groups of 5 synthetic mandibles were used in this study (N = 25). The first portion of the investigation compared mandibles without intervention (group A [controls]; n = 5), mandibles that had uniform osteotomies stabilized with an external distractor (group B; n = 5), and mandibles that had simulated sagittal osteotomies rigidly fixated with 3 positional screws (group C; n = 5). The second portion of the investigation compared uniform osteotomies (group B; n = 5) and uniform corticotomies (group D; n = 5) that were stabilized with the same external distractor. The last portion of the investigation compared osteotomies stabilized with an external distractor (group B; n = 5) and osteotomies stabilized with an internal distractor (group E; n = 5). Each construct was subjected to vertical loads on a mechanical testing unit. Common engineering standards, including yield load, yield displacement, maximum load, displacement at maximum load, and stiffness, were measured, recorded, and compared by means of a 1-way analysis of variance and a Scheffé multiple comparison test or independent-samples t test. The means between groups were considered significant for P < .05. A polynomial best-fit curve was calculated for the load/displacement data for each group. RESULTS: During the first portion of the investigation, no significant differences were noted between the control, rigidly fixated sagittal osteotomy, and external distractor with osteotomy groups for displacement at maximum load (P = .19). Significant differences were noted between groups for yield displacement (P = .009), yield load (P < .001), maximum load (P < .001), and stiffness (P < .007). Failures occurred in the control and rigidly fixated groups with fractures of the synthetic mandibles. Failures occurred in the external distractor group with permanent deformation or torsion of the pins. During the second portion of the experiment, no statistically significant differences were noted between the corticotomy and osteotomy groups in stiffness (P = .363), maximum load (P = .207), or yield displacement (P = .940). Statistically significant differences were noted between groups for yield load (P = .036) and displacement at maximum load (P = .010). Failures occurred in both groups with permanent deformation or torsion of the pins. During the last portion of the investigation, statistically significant differences were noted between the external distractor and internal distractor groups in yield load (P < .001), yield displacement (P < .001), maximum load (P = .001), and displacement at maximum load (P = .01); no significant differences were noted in stiffness (P = .71). Failures occurred in the external distractor group with permanent deformation or torsion of the pins. Failures occurred in the internal distractor group with fracture of the model or displacement beyond 30.0 mm. CONCLUSIONS: Different patterns of mechanical behavior were found between the control and rigidly fixated sagittal osteotomy groups and the external distractor group, between the corticotomy and osteotomy groups, and between the internal and external distractor groups.     

DNA image cytometry and Ag-NORs-staining application in biocompatibility studies on human osteoblast cells in vitro

We report here the study of the biocompatibility of a bone graft material, the Pyrost, using a previously established in vitro model of human osteoblasts. The effect of this material on cell proliferation was evaluated by the MTS assay. Results indicated the absolute absence of cytotoxic or cytostatic effect of Pyrost on cultured osteoblasts. Viability rate was more than 90% in cells cultured with the material compared to the control. Morphological analysis, undertaken by scanning electron microscopy showed a good adhesion and a spreading of osteoblasts in contact with the material that was colonized by cultured cells. In the second part of this work, we have introduced two methods as complementary biocompatibility tests: DNA image cytometry and interphase Ag-NORs quantification. DNA content was measured in cells cultured with or without Pyrost for 3, 9, 15 and 30 days. The determination of DNA indicated that the majority of osteoblasts population was diploid without aneuploidy. The DNA index and cell distribution profile in DNA histograms were similar in all cell populations. The Ag-NORs amount was used as a parameter for cell kinetic evaluation. We have measured the Ag-NORs index like DNA quantification. The proliferation rate, evaluated by Ag-NORs counts in osteoblasts cultured with or without the material, was identical. However, a decrease in Ag-NORs index was observed from day 3 to day 15 of incubation. These results showed a satisfactory biocompatibility of the Pyrost in human osteoblasts culture. The material did not alter cell viability and had no inducing effect either on proliferation rate or on cell ploidy as demonstrated by DNA image cytometry and Ag-NORs proteins staining.     

Effects of hemodynamics on thromboembolism in coronary stents and prototype flow cells in vitro

Thromboembolism was studied as heparinized (3 U/ml) bovine blood was gravity fed through a conduit with a deployed coronary stent or a prototype flow cell. The initial flow rate was established with a pinch valve, and monitored with a clamp-on ultrasonic probe. Emboli production was continuously monitored using a light scattering microemboli detector. Accumulated thrombus at the end of the experiment was assessed gravimetrically in stents or by magnetic resonance imaging in flow cells. Hemodynamic parameters were varied to assess their effects on thromboembolism. With the flow cells, the hemodynamics were controlled by varying the geometry of the stagnation zones. With the stents, the flow characteristics were altered by placing 75% stenoses upstream and/or downstream of the stent. The average values of the shear stress and residence time around the stent were modeled using the commercial fluid dynamics software FLUENT. Combining the computed hemodynamic parameters with the experimental results showed that 1) thrombus accumulation decreased with increasing shear stress and increased with increasing residence time; 2) embolization was promoted by high shear, and did not correlate with the amount of thrombus accumulated at the end of the experiment; and 3) a reconfiguration of the magnetic resonance imaging system is necessary to monitor thrombus accumulation continuously.     

Research progress on corrosion behaviors and biocompatibility of rare-earth magnesium alloys in vivo and in vitro

As yet,Mg alloys acting as the medical implants have drawn extensive attention,due to their spontaneous degrada bility,effective load-transmissibility and the excellent biocompatibility,particularly in bone tissue reconstruction and vascular radial-support.Regrettably,they were inevitably affected by the tension/compression-torsion,dynamic erosion and corrosion fatigue under complex service conditions,which lead to premature failure of implantation-materials.Micro-alloying addition is an effecti...     

An in vitro evaluation of the tensile and shear strengths of four adhesives used in orthodontics

Patients with dysphagia as a result of neurologic disease can be effectively evaluated and managed, particularly if the dysphagia is recognized before any medical complications such as aspiration pneumonia appear. Management can be cost-effective and efficient when assessment not only defines symptoms but their underlying anatomic or physiologic cause and treatment is designed to eradicate the abnormalities in structure or function. The specific nature of the oropharyngeal dysphagia may also point to the nature of the underlying neurologic damage or disease process. Involvement of a speech-language pathologist early in the neurogenic patient's dysphagia care can speed recovery and reduce cost.     

Direct gene delivery to synovium. An evaluation of potential vectors in vitro and in vivo

OBJECTIVE: To assess the abilities of various vectors to transfer genes to the synovial lining of joints. METHODS: Vectors derived from retrovirus, adenovirus, and herpes simplex virus as well as cationic liposomes and naked plasmid DNA were evaluated. Each construct contained the lac Z marker gene; and one retroviral construct, and one plasmid also contained a gene encoding human interleukin-1 receptor antagonist. Gene expression was under the control of the human cytomegalovirus promoter in all vectors except the retrovirus, where the endogenous 5' long terminal repeat was retained as the promoter. Cultures of rabbit synovial fibroblasts were exposed to these vectors and stained with X-gal to identify lac Z+ cells. Vectors were then injected directly into rabbits' knee joints, and gene transfer and expression were assessed by X-gal staining and polymerase chain reaction (PCR). RESULTS: Adenovirus was a highly effective vector both in vitro and in vivo, with lac Z gene expression persisting for at least 28 days. However, an inflammatory response was noted in vivo. Cells infected in vitro and in vivo with herpes simplex virus also expressed the lac Z gene at high levels, but expression was limited by cytotoxicity. Retroviruses, in contrast, were effective only under in vitro conditions, permitting cell division. Liposomes gave variable in vitro results; when injected into joints in vivo, gene expression was low and was detectable for only a few days, even though a PCR signal persisted for at least 28 days. Unexpectedly, plasmid DNA was captured by the synoviocytes and expressed transiently following intraarticular injection. CONCLUSION: None of the vectors was ideal for in vivo gene delivery to synovium, although adenovirus was clearly the most effective of those tested. Retroviruses, although poor vectors for in vivo gene delivery, are well suited for ex vivo gene transfer to the synovial lining of joints.     

An evaluation of fit factors and dissolution efficiency for the comparison of in vitro dissolution profiles

Dissolution efficiency (D.E.), the area under a dissolution curve between defined time points, and the fit factors (f1 and f2) have been compared for the characterisation of dissolution profiles, using data from three batches of a product in nine different packs stored under two conditions. The factors f1 and f2 offer ease of calculation and a simple measure of similarity between pairs of dissolution profiles. This is well suited to the qualitative determination of 'similarity' as required by the FDA's SUPAC Guide. However, they do not provide information on individual batches, including their consistency. In contrast, D.E. does provide such information is well-suited to making quantitative comparisons amongst batches. Because D.E. has a simple physical meaning, it is easier to interpret D.E. data then corresponding f1 and f2 results. The confidence limits in D.E. values provide a useful measure of the variability in batch dissolution and allow the statistical significance of difference in D.E. between pairs of batches to be determined. Both of the above measures lead to the same conclusions regarding the similarity in protective power amongst the nine packs under test and to the value of added desiccant in maintaining the dissolution profile of the product when stored under high humidity conditions. It is concluded that D.E. offers a suitable alternative to the single point dissolution measurement for QC of immediate release products.     

Effect of different dialysis membranes on platelet function. A tool for biocompatibility evaluation

Intradialytic coagulative and platelet activation, one of the main consequences of blood-membrane contact, was studied in a group of 5 RDT patients with a comparative evaluation of 3 different dialytic membranes: Cuprophan (CU), Polysulfone (PS) and Cellulose Triacetate (CT). Each patient underwent 5 consecutive dialysis sessions with the above mentioned membranes. Intradialytic platelet activation was studied through a morpho-functional evaluation between the mean platelet volume (MPV) and Serotonin (S), beta-Thromboglobulin (beta-TG) and Platelet Factor 4 (PF4) serum levels. These determinations were made before HD (time 0) and after 30', 120', and 240'. We also checked the intradialytic status of thrombogenesis and fibrinolysis determining aPTT, thrombin time, fibrinogen, antithrombin III (AT III), alpha-2 antiplasmin and plasminogen, at the same time intervals. All membranes tested (CU, PS, CT) caused appreciable intradialytic platelet activation, above all after 15' and at the end of dialysis sessions, more marked for CU than PS or CT. In particular MPV showed a decrease throughout the session (-5% at 30' and -9% at 240') while S, beta TG and PF4 peripheral blood levels showed a significant increase at the same intervals with CU membrane. Lastly coagulative and fibrinolytic parameters showed no significant differences among any of the membranes tested.     

Coronary stents: In vitro aspects of an angiographic and ultrasound quantification with in vivo correlation

BACKGROUND: The validity of quantitative coronary angiography (QCA) after stent placement has been questioned because the optical density of a metallic stent, added to the density of a contrast-filled lumen, could affect border definition. METHODS and RESULTS: We deployed 3.0- and 4.0-mm Palmaz-Schatz, Wiktor, Multilink, NIR, and InStent stents in precision-cast phantoms. Central lumens of 2.0 mm were created. There was no difference between the "true" diameters of any stented lumen by both QCA and quantitative ultrasonic (QCU) measurement poststenting. QCA systematic error (SE) varied from 0.01 for the Wiktor stents to 0.14 mm for the Palmaz-Schatz stents; the random error (RE) was 0.03 to 0.14 mm. QCU SE varied from 0.05 to 0.11 mm, and RE ranged from 0.01 to 0.07 mm. At the next stage, 4.0-mm Wiktor and Palmaz-Schatz stents were deployed into the phantom lumens; 1.5-, 2.0-, 2.5- and 3.0-mm lumens were created inside the stents. QCA and QCU measurements of 1.5- to 2.5-mm residual lumens were overestimated by 0.1 to 0.3 mm. In the 3. 0-mm residual lumen within the Wiktor stent, QCA underestimated the luminal size by -0.1 mm. There was no QCA inaccuracy for a 3.0-mm lumen within the Palmaz-Schatz stent. In patients, in 25 stented segments in both the Palmaz-Schatz and Wiktor groups, there was no difference between QCA and QCU diameters. CONCLUSIONS: QCU is sufficiently precise for the assessment of the coronary lumen after stenting. QCA can be used as an accurate method of poststent assessment, except when a very mild recurrence within a highly opaque stent is measured. In that instance, QCA may underestimate the luminal diameter.     

Experience in the morbidity associated with double-J catheter indwelling and its management

Placement of internal ureteral stents for internal urinary diversion and prevention of urological complications has been well established. However, indwelling stents have occasionally been associated with patient morbidity and intolerance. A total of 255 patients while the internal ureteral stent had been used were analyzed. The symptoms including urinary frequency (42.0%), hematuria (41.6%) and suprapubic pain (20.4%), loin pain (17.3%) and micturition pain (16.9%) accounted for the major complaints of the stent indwelling patients. The major complications, i.e. stent migration, heavy encrustation, pyelonephritis, fragmentation, intolerance and penetration of collecting structure, were occasionally observed. These complications increase secondary morbidity in patients. The double-J stents should be used carefully with regard to the prevention and treatment of untoward conditions as early as possible.     

An evaluation of orthokeratology

Twenty-three orthokeratology (OK) patients and 16 cosmetic hard contact lens (CL) patients were evaluated. Initially, each patient underwent a complete examination including central and peripheral keratometry, specular microscopy, axial length determination, uncorrected visual acuity, and cycloplegic refraction. The patients were then re-evaluated every three months. When the retainer lens stage was reached, the contacts were removed, and the patients were again re-examined for six additional months. Nine of ten CL patients remained in the study, during which time there was no improvement in unaided visual acuity or spherical equivalent. Both the central horizontal and vertical meridians flattened during this time. Twenty of 21 OK patients were also studied. A different technique of fitting contact lenses was used for this group, which produced significant changes in uncorrected visual acuity (P > 0.01) and spherical equivalent (0.1 > P > 0.05), but not in the central or peripheral corneal curvature. Five of the OK patients failed to respond. Six had variable, unpredictable responses, and nine had good responses. Analysis of the information in this study demonstrates that an OK procedure utilizes techniques of fitting that differ from standard contact lens techniques. The responses to OK are unpredictable and uncontrollable. The quality of uncorrected vision is worse than with contacts or glasses, and the chances of attaining 6/12 (20/40) uncorrected vision are small. Once lenses are removed, the corneal parameters return toward prefit levels.     

A hydrogel based on a polyaspartamide: characterization and evaluation of in-vivo biocompatibility and drug release in the rat

This paper deals with the characterization of a new microparticulate hydrogel obtained by gamma irradiation of alpha, beta-poly[N-(2-hydroxyethyl)-DL-aspartamide] (PHEA). When enzymatic digestion of PHEA hydrogel was evaluated using various concentrations of pepsin and alpha-chymotrypsin no degradation occurred within 24 h. In-vivo studies showed that this new material is biocompatible after oral administration to rats. PHEA hydrogel was also studied as a system for delivery of diflunisal, an anti-inflammatory drug. In-vitro release studies in simulated gastrointestinal juice (pH 1 or 6.8) showed that most of the drug was released at pH 6.8. In-vivo studies indicated that diflunisal-loaded PHEA microparticles significantly improved the gastric tolerance and oral bioavailability of the drug in comparison with free diflunisal. These results suggest the potential application of PHEA hydrogel as a new delivery system for the oral administration of anti-inflammatory drugs.     

Concepts in biocompatibility testing of dental restorative materials

Due to the diversity of adverse biological effects which might be caused by dental restorative materials, biocompatibility assessment cannot rely on a single test but has to be based on a planned and structured approach (concept). First, the possible harm evoked by the material, the known data, and suitable biological and other test methods available must be taken into consideration. Modern regulatory concepts require for this purpose the services of experts to propose the appropriate set of required tests for a given material. The use of standards is generally emphasized because of better comparability of the data. Other tests may be chosen if more appropriate. Modern scientific concepts of biocompatibility testing are based on the need for rapid and cost-effective test methods, avoiding animal tests whenever possible. While formerly in vitro experiments did not take into account the special clinical situation in which the material would be used, modern concepts try to simulate important parameters of the in vivo situation as closely as possible. This may be achieved, for example, by including suitable barriers between the material and the target cells, by constructing appropriate target cells, and by choosing clinically relevant markers for measuring the biological effects caused by the material. There are indications so far that through this approach the number of animal tests can be reduced. The use of these methods may also lead to a better understanding of the mechanisms behind the biological reactions (mechanistic approach) in describing the biocompatibility of dental restorative materials.