Temporary Plastic Research Articles

Microbiological aspects of zirconia orthopedic structures

The article gives a detailed analysis of oral cavity microbiological aspects of 23 patients before and after prosthetic treatment with zirconia structures. Microbiocenoses of oral cavity in patients with defects of the dentition can be described as disbiotic. It was found that the incidence of lactobacilli and bifidobacteria was increased and frequency of occurrence of pathogens, including Staphylococcus aureus, was decreased under the influence of temporary plastic prosthesis as an intermediate step prosthetics. After applying prosthetic zirconia an increase of the normal biotopes number was seen, as well as reduce in the number of Staphylococcus aureus and the yeast fungus Candida to less than 4 lg CFU/ml. Such amounts do not cause inflammation in the oral cavity.

Lightweight Polypropylene/Stainless-Steel Fiber Composite Foams with Low Percolation for Efficient Electromagnetic Interference Shielding

Lightweight polypropylene/stainless-steel fiber (PP-SSF) composites with 15-35% density reduction were fabricated using foam injection molding. The electrical percolation threshold, through-plane electrical conductivity, and electromagnetic interference (EMI) shielding effectiveness (SE) of the PP-SSF composite foams were characterized and compared against the solid counterparts. With 3 wt % CO2 dissolved in PP as a temporary plasticizer and lubricant, the fiber breakage was significantly decreased during injection molding, and well-dispersed fibers with unprecedentedly large aspect ratios of over 100 were achieved. The percolation threshold was dramatically decreased from 0.85 to 0.21 vol %, accounting for 75% reduction, which is highly superior, compared to 28% reduction of the previous PP-carbon fiber composite foam.1 Unlike the case of carbon fiber,1 SSFs were much longer than the cell size, and the percolation threshold reduction of PP-SSF composite foams was thus primarily governed by the decreased fiber breakage instead of fiber orientation. The specific EMI SE was also significantly enhanced. A maximum specific EMI SE of 75 dB·g(-1)·cm(3) was achieved in PP-1.1 vol % SSF composite foams, which was much higher than that of the solid counterpart. Also, the relationships between the microstructure and properties were discussed. The mechanism of EMI shielding enhancement was also studied.

The effect of a novel drug-eluting plastic stent on biliary stone dissolution in an ex vivo bile perfusion model

Temporary plastic stent insertion has been considered a safe and effective bridge therapy for difficult common bile duct (CBD) stones. Infusing chemicals to directly dissolve stones through the bile duct might also be effective. However, there are no studies on the efficacy of the combination of these 2 approaches. To investigate the efficacy of a novel ethylenediaminetetraacetic acid (EDTA) and sodium cholate-eluting plastic stent on biliary stones. Ex vivo model by using different doses of active ingredient. An ex vivo bile duct model perfused with porcine bile was created. Stents coated with degradable membranes containing various concentrations of EDTA and sodium cholate were placed in the model with CBD stones. The change in the weight of stents and stones was measured every week during perfusion until the coated membranes were completely biodegraded. The time that the stents required to be fully degraded and the efficiency of stone dissolution were positively correlated with the percentage of EDTA and sodium cholate in the stent membrane. However, the 50% EDTA and sodium cholate stents achieved the greatest percentage of stone weight loss when the drugs were completely released. Ex vivo study. The EDTA and sodium cholate-eluting plastic stent effectively dissolved CBD stones and has prospect in the therapy for patients with difficult CBD stones.

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Endoscopic management of postcholecystectomy biliary leaks

ObjectiveTo evaluate the nature of bile duct injuries following cholecystectomy and the success of endoscopic retrograde cholangiopancreatography (ERCP) in their identification and management.DesignAll patients referred for ERCP with a diagnosis...

Sa1485 Sequential, Papilla-Traversing, Bilateral Self-Expandable Metal Stents (SEMS) for Malignant Hilar Obstruction

Bilateral SEMS for malignant hilar obstruction is challenging. Reported techniques involve double guidewire insertion with or without insertion of a temporary plastic stent to allow advancement of a 2nd SEMS delivery system alongside the previously deployed SEMS; or simultaneous bilateral deployment using a slim delivery profile SEMS (recently reported). We report outcomes with sequential, papillary-traversing, bilateral stenting with a new model SEMS.

Efficacy and safety of biodegradable stents for refractory benign esophageal strictures: the BEST (Biodegradable Esophageal Stent) study

Benign esophageal strictures refractory to standard dilation therapy present a challenging problem. Temporary plastic and metal stents have been proposed with inconclusive results. To evaluate the efficacy and safety of a new biodegradable stent for the treatment of refractory benign esophageal strictures (RBESs). Prospective study from 2 European endoscopy centers. Twenty-one patients (11 men/10 women, mean age 60.2 ± 17.6 years) with RBESs defined according to the Kochman criteria treated by placement of a biodegradable stent (Ella stent). Clinical and endoscopic follow-up was scheduled at 1, 2, 3, and 6 months and later only in case of dysphagia recurrence. Pre- and poststenting dysphagia status was graded according to a 5-point scale. Minor and major complication rates were prospectively assessed. Stent insertion was technically successful in all of the patients. At 4 and 7 weeks, stent migration occurred in 2 patients (9.5%). At 3-month endoscopy, the stent appeared to be almost completely fragmented in all remaining patients. The median pre- and poststenting dysphagia scores were 3 (range 3-4) and 1 (range 0-2), respectively (P < .01), with a median follow-up of 53 weeks (range 25-88 weeks). In detail, 9 of 20 patients (45%) were dysphagia free at the end of the follow-up. No major complications occurred. Severe poststenting pain requiring analgesics developed in 3 patients, and minor bleeding was observed in 1 patient. Limited follow-up; nonrandomized study. In this preliminary study, the biodegradable stent showed a favorable risk/benefit ratio, achieving complete relief of dysphagia in nearly 50% of RBES patients without the occurrence of major complications. The use of this stent may be a valuable alternative to repeat endoscopic dilation. Larger studies with longer follow-up are needed.

A Magnetic Retrieval System for Stents in the Pancreaticobiliary Tree

Clinical endoscopic intervention of the pancreaticobiliary tree [endoscopic retrograde cholangiopancreatography (ERCP)] often concludes with the insertion of a temporary plastic stent to reduce the risk of post-ERCP complications by promoting continued flow of bile and pancreatic fluids. This stent is later removed once the patient has fully recovered, but today this necessitates a second endoscopic intervention. The final goal of this work is to obviate the second intervention. This is to be achieved by adding a magnetic ring to the stent such that the stent is removed using a hand-held magnet, held in a suitable position ex vivo . This paper details the design, optimization, and both ex vivo and in vivo testing of the magnetized stent and hand-held magnet, which has been accomplished to date. The optimized design for the hand-held magnet and the modified stent with a magnetic attachment performs in line with simulated expectations, and successful retrieval is achieved in the porcine ex vivo setting at 9-10 cm separation. This is comparable to the mean target capture distance of 10 cm between the entry point to the biliary system and the closest cutaneous surface, determined from random review of clinical fluoroscopies in ten human patients. Subsequently, the system was successfully tested in vivo in the acute porcine model, where retrieval at an estimated separation of 5-6 cm was captured on endoscopic video. These initial results indicate that the system may represent a promising approach for the elimination of a second endoscopic procedures following placement of pancreatic and biliary stents.

Synthesis of organic-inorganic polymer structures via the interaction of orthoboric acid with m-phenylene-bismaleimide

The structure and properties of products arising from the reaction of orthoboric acid with m-phenylene-bismaleimide in melt at 200°C have been studied by spectral and physicochemical methods. The data of IR spectroscopy and thermomechanical analysis suggest that, under the chosen conditions, chemical interaction between the reagents occurs. The conversion increases with the time of reaction and the content of m-phenylene-bismaleimide. High-temperature plasticizers, such as diphenyl and triphenylphosphate, unexpectedly favor formation of more rigid polymer structures, whereas a “temporary plasticizer” (decamethylene glycol) hinders interaction between orthoboric acid and m-phenylene-bismaleimide. The temperature corresponding to a 20% weight loss of the polymer synthesized during heating in air at orthoboric acid: m-phenylene-bismaleimide = 80: 20 is 440–445°C, and the carbon-containing fragments are present in the pyrolysate up to 800°C. The polymer samples retain their shape in air for long time and in water vapor for several days. The hydrolytic stability of the products increases with the content of m-phenylene-bismaleimide.

Acute Management of Stoma-Related Colocutaneous Fistula by Temporary Placement of a Self-Expanding Plastic Stent

Colocutaneous fistulas are frequently the result of complications related to previous operative procedures and are a major cause of morbidity. Most are initially treated conservatively, with a large percentage eventually requiring further surgery for definitive treatment. The use of a temporary colonic stent for the management of colostomy-related colocutaneous fistula has not been previously described. Two patients with colocutaneous fistula related to end colostomies and opening into midline laparotomy wounds were treated by temporary plastic stenting. A removable Polyflex silicone stent was inserted into the stoma. Stent redeployment was needed on several occasions following partial stent expulsion. Midline wound healing was achieved in both cases by 6 weeks post-stent insertion, and complete fistula closure occurred in 1 case. Temporary stent placement in certain cases may aid in the management of a colocutaneous fistula associated with a colostomy to allow fecal diversion from wounds and aid fistula closure.

Benign Refractory Esophageal Strictures: Preliminary Results from the BEST (Biodegradable Esophageal STent) Study

Background and aim: Benign esophageal strictures refractory to standard dilation therapy are a challenging problem. Temporary plastic and metal stenting has been proposed with inconclusive results. We therefore evaluated the safety and efficacy of a new biodegradable stent (BD Ella Stent) for the treatment of refractory benign esophageal strictures. Patients and Methods: 12 patients (6M/6F, mean age 52.4 range 41-78) with benign esophageal strictures (anastomotic (n=2), post-surgery (n=1), post-radiotherapy (n=4), post-caustic ingestion (n=1), peptic (n=3) and idiopathic (n=1) classified as refractory following the Kochman criteria, were treated by placement of a biodegradable BE Ella stent. Strictures were located in the distal esophagus in 6 patients, in the middle in 3 and in the proximal esophagus in 3. The mean number of dilating sessions before stenting was 6.8+1.6. Patients were followed at regular interval and endoscopy was scheduled at months 1, 2, 3, 6 and afterwards in case of dysphagia recurrence. Pre and post-stenting dysphagia status as well as complications were prospectively collected. Results: Stents were successfully placed in all patients. No early complications occurred. Pre-stenting mean dysphagia score was 2.8+0.68. At 3 months, stents were endoscopically in place, but partially fragmented in 3/6 patients. Stent migration was observed in 2 patients (17%). One of these patients was treated again by a second biodegradable stent and is still under follow-up and free of dysphagia. The other patient did not require further treatment because of resolution of the stricture and absence of symptoms at the time of migration. Minor bleeding without a significant drop in Hb lwas observed in 1 patient. After a median follow-up of 22 weeks (4-32), mean dysphagia score was 0.25+0.12 with 10/12 patients free of dysphagia and 2 patients with persistent but mild dysphagia (grade 1in one patients and grade 2 in a second patient). Conclusions: In this preliminary evaluation, the biodegradable stent afforded a significant relief of dysphagia in a small group of patients with refractory benign esophageal strictures. A larger study with longer follow-up is required to validate these results.

Type III Choledochal Cyst Variant: First Description of a “Closed Choledochocele” with Biliary and Pancreatic Drainage Via the Accessory Duct

Type III choledochal cysts, also called choledochoceles, are rare congenital or acquired malformations of the terminal biliary tree of unknown etiology. These cysts can predispose a patient to biliary colic, obstructive jaundice, or idiopathic recurrent pancreatitis through an obstructive mechanism as the normal flow of bile is disrupted. They have been described in two anatomic variants 1) both the pancreatic and bile ducts drain into the choledochocele 2) the choledochocele is a cystic outpouching into the duodenum proximal to a normal ampulla. Endoscopic ultrasound and ERCP are primary tools to help diagnosis these anomalous formations and needle-knife sphincterotomy has recently been used to treat these cysts in symptomatic patients. We report the case of a 23 year-old white female with no previous past medical history who developed acute pancreatitis two weeks after completing an unremarkable first pregnancy. On EUS, she was found to have a Type III choledochocele with no apparent drainage into the duodenum. Bile was seen draining from the accessory duct. Subsequent ERCP via the minor papilla revealed communication of the ventral pancreatic and common bile ducts within a choledochocele which did not communicate with the duodenum. The bile duct appeared to empty retrograde into the ventral pancreatic duct and subsequently out to the duodenum via the accessory duct. To facilitate biliary and pancreatic duct drainage, the choledochocele was accessed and opened with a needle-knife followed by biliary sphincterotomy and temporary plastic biliary stent placement. Six weeks following the procedure, she continues to feel well. This case represents the first description of a “closed choledochocele” with biliary and pancreatic drainage via the accessory duct.[figure1]Figure

A Procera® Custom Abutment Fabricated by Scanning the Provisional Abutment

Patient: The patient was a 56-year-old male presenting with a missing maxillary right central incisor. Subsequently, an endosseous implant was fiited. After a 6 month healing period, a provisional abutment was fabricated to an optimal shape on the provisional titanium component. After confirming custom-guided tissue healing and appropriate emergence profile, the provisional abutment was scanned using the Procera® scanner. The CAD/CAM custom titanium definitive abutment and the definitive porcelain fused to the metal crown were delivered as an esthetic implant restoration.Discussion: Compared to conventional procedures, the following advantages can be seen: 1. There is no access hole in the provisional restorations. 2. Appropriate soft-tissue contours can be induced by modification of provisional restoration. 3. A definitive abutment with the identical contours can be reliably obtained using CAM. 4. An extra temporary plastic component is not necessary. The disadvantages are: 1. The provisional abutment using the temporary cylinder has to be made. 2. The Procera® scanner has to be set up chair-side. 3. The patient has to wait during scanning.Conclusion: A custom Procera® abutment with an ideal emergence profile can be fabricated by scanning the provisional abutment with appropriate soft-tissue contours.

A new approach to preserve fertility by using a coated nitinol stent in a patient with recurrent cervical stenosis

The incidence of hematometra caused by cervical stenosis after conization is <1%. Nevertheless, if dilatation was unsuccessful, further therapy often remains unclear, and the clinical consequences can be severe, including hysterectomy. Case report. University hospital. A 33-year old patient who developed recurrent cervical stenosis with consecutive hematometra after two conizations during lactation amenorrhea that could not be treated by dilatation and insertion of a temporary plastic catheter according to the manufacturer's instructions. Insertion of a coated nitinol stent in the cervical canal after dilatation and hysteroscopic removal of the hematometra. Normal menstruation, future pregnancy. The patient was free of symptoms, had a normal menstruation, and has become pregnant. The insertion of a coated vessel stent in the uterine cervix appears to be a valid alternative in patients with recurrent cervical stenosis and hematometra after conization to preserve childbearing function.

Hot stage extrusion of p-amino salicylic acid with EC using CO 2 as a temporary plasticizer

The aim of the current research project was to explore the possibilities of combining pressurized carbon dioxide with hot stage extrusion during manufacturing of solid dispersions of the thermally labile p-aminosalicylic acid ( p-ASA) and ethylcellulose 20 cps (EC 20 cps) and to evaluate the ability of the pressurized gas to act as a temporary plasticizer. The thermal stability of the p-ASA was investigated using DSC, TGA and HPLC. The compound decomposes completely upon melting. Below 110 °C and under atmospheric conditions, the compound is thermally stabile for 10 min. Pressurized carbon dioxide was injected into a Leistritz Micro 18 intermeshing co-rotating twin-screw melt extruder using an ISCO 260D syringe pump. Carbon dioxide acted as plasticizer for p-ASA/EC 20 cps, reducing the processing temperature during the hot stage extrusion process. HPLC showed that without carbon dioxide injection, approximately 17% of p-ASA degraded, while less than 5% degraded with CO 2 injection. The experiments clearly showed that injecting pressurized carbon dioxide broadens the application of hot stage extrusion to thermally labile compounds in a one step process.

Gibt es eine nichtchirurgische Therapie der Gallenwegskarzinome?

Nonsurgical treatment aims at controlling disease and improving survival and quality of life in patients with nonresectable, recurrent metastatic cholangiocarcinomas. After R0 resection, percutaneous or intraluminal radiotherapy with adjuvant radiochemotherapy may improve survival. Available data, however, are still unsatisfactory, and the efficacy of adjuvant radiochemotherapy after R0 resection remains to be confirmed. Exclusive chemotherapy fails to improve survival postoperatively while, in adequate patients, neoadjuvant chemotherapy can improve R0 resection results. Palliative chemotherapy yielded improved survival and quality of life in only one small prospective randomized trial and cannot be generally recommended at present. Previous biliary stenting for relieving jaundice is mandatory. Beyond established regimens employing 5-fluorouracil/leukovorin and gemcitabine plus platin-based agents, ongoing trials are focussing on topoisomerase-and thyrosine kinase inhibitors. Palliative stenting of malignant bile duct stenoses may eliminate or at least relieve jaundice and pruritus. Single stenting is sufficient for distal bile duct stenoses. In patients with liver metastasis and life expectancy of <6 months, temporary plastic prostheses with 4-6-month patency are sufficient. When the prognosis is for >6 months, self-expanding permanent metal stents, with their significantly longer patency, are superior. In hilar tumors, obstruction of plastic prostheses occurs earlier than in distal bile duct stenoses. Thus, patients with Bismuth II-IV tumors benefit from self-expanding metal stents. These may be inserted by an endoscopic, retrograde approach, percutaneously, or by a combined rendez-vous maneuver. The superiority of bilateral vs unilateral stenting has yet to be proven in Bismuth II-IV tumors. Photodynamic therapy followed by stenting appears to improve survival rates by delaying stent occlusion rather than by regression of the tumoric disease itself.

The effect of pressurized carbon dioxide as a plasticizer and foaming agent on the hot melt extrusion process and extrudate properties of pharmaceutical polymers

The aim of the current research project was to explore the possibilities of combining pressurized carbon dioxide with hot melt extrusion of polyvinylpyrrolidone-co-vinyl acetate 64, Eudragit ® E100 and ethylcellulose 20 cps, to evaluate the ability of the pressurized gas to act as a temporary plasticizer as well as to produce a foamed polymeric material. Pressurized carbon dioxide was injected into a Leistritz Micro 18 intermeshing co-rotating twin-screw melt extruder using an ISCO 260D syringe pump. The physicochemical characteristics of the polymers before and after injection of carbon dioxide were evaluated using MDSC, dissolution measurements, specific surface area measurements, porosity, dynamic vapour sorption and microscopy. An extruder set up and screw configuration were configured and optimized for injection of pressurized CO 2. Carbon dioxide acted as plasticizer for all three polymers, reducing the processing temperature during the hot melt extrusion process. The specific surface area and the porosity of the polymers was increased after treatment with carbon dioxide, resulting in enhanced dissolution. The macroscopic morphology was changed to a foam-like structure due to expansion of the carbon dioxide at the extrusion die. This resulted in improved milling efficiency.

Use of a temporary plastic stent to facilitate the placement of multiple self-expanding metal stents in malignant biliary hilar strictures

Although endoscopic palliation of malignant biliary hilar obstruction is preferable to surgery or percutaneous drainage, it remains technically challenging. This is especially true when multiple self-expanding metal stents (SEMS) are placed, because difficulty is commonly encountered in passing the second SEMS at the level of the previously deployed initial stent. We have devised a method of deploying multiple metal stents by using a temporary plastic stent, which makes deployment of the second stent much easier. After guidewire placement, a plastic stent is deployed in a subhilar position. The initial SEMS is deployed, with the plastic stent maintaining a passage for the second SEMS. After the second SEMS is deployed, the plastic stent is retrieved. This technique has been used successfully in 7/8 patients, all of whom presented with symptomatic jaundice secondary to malignant hilar obstruction of various etiologies (cholangiocarcinoma, n=4; metastatic disease, n=3; and hepatocellular carcinoma, n=1). Drainage was successful in all cases, with significant improvement in symptoms and cholestasis. This simple technique lessens the technical difficulty of placing bilateral hilar SEMS.

The effect of pressurized carbon dioxide as a temporary plasticizer and foaming agent on the hot stage extrusion process and extrudate properties of solid dispersions of itraconazole with PVP-VA 64

The aim of the current research project was to explore the possibilities of combining pressurized carbon dioxide with hot stage extrusion during manufacturing of solid dispersions of itraconazole and polyvinylpyrrolidone-co-vinyl acetate 64 (PVP-VA 64) and to evaluate the ability of the pressurized gas to act as a temporary plasticizer as well as to produce a foamed extrudate. Pressurized carbon dioxide was injected into a Leistritz Micro 18 intermeshing co-rotating twin-screw melt extruder using an ISCO 260D syringe pump. The physicochemical characteristics of the extrudates with and without injection of carbon dioxide were evaluated with reference to the morphology of the solid dispersion and dissolution behaviour and particle properties. Carbon dioxide acted as plasticizer for itraconazole/PVP-VA 64, reducing the processing temperature during the hot stage extrusion process. Amorphous dispersions were obtained and the solid dispersion was not influenced by the carbon dioxide. Release of itraconazole from the solid dispersion could be controlled as a function of processing temperature and pressure. The macroscopic morphology changed to a foam-like structure due to expansion of the carbon dioxide at the extrusion die. This resulted in increased specific surface area, porosity, hygroscopicity and improved milling efficiency.

Endoscopic Techniques to Diagnose and Manage Biliary Tumors

Malignancies of the bile duct are often suspected in patients with abnormal serum hepatic enzyme levels and obstruction of the biliary system. Although cross-sectional imaging can provide evidence for biliary obstruction and a malignancy arising from the bile duct, a definitive diagnosis is often obtained through the use of endoscopic procedures. Endoscopic retrograde cholangiopancreatography (ERCP), the most commonly performed procedure for cholangiocarcinoma, can provide a tissue diagnosis through brush cytology of the bile duct. Relief from biliary obstruction can be provided with temporary plastic stenting or permanent metal stenting. Photodynamic therapy guided by ERCP may provide improved palliation from biliary obstruction in the future. Endoscopic ultrasonography complements the role of ERCP and may provide a tissue diagnosis through fine-needle aspiration and staging through ultrasound imaging. High-resolution ultrasound images can provide detailed information regarding the relationship between a mass and the bile duct wall. Despite these advances in endoscopic techniques and imaging of the bile duct, a tissue diagnosis often remains elusive in many patients. In the future, molecular markers will be employed to improve the sensitivity for the detection of malignancy in bile duct samples obtained through brushing, aspiration, and biopsy.