Effect of fatigue loading and failure mode of different ceramic implant abutments.

STATEMENT OF PROBLEM: Currently many options are available for restoring a dental implant, although the ideal implant abutment for withstanding the occlusal load and the restorative material for fulfilling the esthetic need remains unclear. Zirconia (Zir) abutments offer good esthetics, but concerns still remain regarding their fracture strength, complex fabrication, and higher cost as compared with those of titanium (Ti) base abutments offering lower cost, acceptable esthetics, and a straightforward procedure. PURPOSE: The purpose of this in vitro study was to evaluate the fracture strength and failure mode of single-tooth Zir and Ti base implant abutments with fatigue loading. MATERIAL AND METHODS: Forty restorations were included using 4 different types of abutment-restorations. Zir abutments with lithium disilicate crowns (ZirLd); titanium base abutments with custom Zir abutments and lithium disilicate crowns (TiZirLd); titanium base abutments with monolithic lithium disilicate abutment-crowns (TiLd); titanium base abutments with monolithic polymer-infiltrated ceramic abutment-crowns (TiEn). Specimens were subjected to a progressive cyclic loading by using a custom-made mastication simulator at a frequency of 1.4 Hz starting with a load of 88 N followed by stages of 170, 210, 250, and 290 N for a maximum of 20 000 cycles each or until fracture occurred. The number of cycles, maximum load, and failure modes were recorded. Statistical analysis was done by using the Mann-Whitney U test (α=.05). RESULTS: Group TiEn showed a lower resistance to fatigue, with a mean ±standard deviation of 5054 ±123.3 cycles subjected to a mean force of 170 N. Groups ZirLd and TiLd resisted higher forces without fracture 13452.6 ±7094.3 cycles, and load of 178 ±16.9 N, followed by the TiLd group with a mean ±standard deviation of 25798.6 ±5498.7 cycles, and load of 202 ±16.9 N, while the TiZirLd group showed a mean of 48235.4 cycles subjected to a mean force of 258 N. The failure mode observed in the TiEn occurred only in the ceramic, whereas in the ZirLd and TiLd group, it was above the shoulder level of the Ti base abutment. Even though the TiZirLd group was able to withstand higher loads and a higher number of cycles, the failures were catastrophic and presented fractures of the titanium-base abutment and prosthetic screw. CONCLUSIONS: The TiZirLd, ZirLd, and TiLd abutment-restorations have the potential to withstand the average physiological occlusal forces that occur in the anterior region. The group with the higher fatigue resistance was TiZirLd, although care should be taken with patients presenting parafunctional habits since the failure mode can be catastrophic. Also, polymer-infiltrated ceramic is not suitable for a Ti base abutment when subjected to oblique loading.

Inhomogeneous Broadening of Photoluminescence Spectra and Kinetics of Nanometer-Thick (Phenethylammonium)2PbI4 Perovskite Thin Films: Implications for Optoelectronics.

An outstanding potentiality of layered two-dimensional (2D) organic-inorganic hybrid perovskites (2DHPs) is in the development of solar cells, photodetectors, and light-emitting diodes. In 2DHPs, an exciton is localized in an atomically thin lead(II) halide inorganic layer of sub-nanometer thickness as in a quantum well sandwiched between organic layers as energetic and dielectric barriers. In previous years, versatile optical characterization of 2DHPs has been carried out mainly for thin flakes of single crystals and ultrathin (of the order of 20 nm) polycrystalline films, whereas there is a lack of optical characterization of thick (hundreds of nanometers) polycrystalline films, fundamentals for fabrication of devices. Here, with the use of photoluminescence (PL) and absorption spectroscopies, we studied the exciton behavior in ∼200 nm polycrystalline thin films of 2D perovskite (PEA)2PbI4, where PEA is phenethylammonium. Contrary to the case of ultrathin films, we have found that peak energies and line width of the excitonic bands in our films demonstrate unusual extremely weak sensitivity to temperature in 20-300 K diapason. The excitonic PL band is characterized by a significant (∼30 meV) Stokes shift with respect to the corresponding absorption band as well as by a full absence of the exciton fine structure at cryogenic temperatures. We suggest that the observed effects are due to the large inhomogeneous broadening of the excitonic PL and absorption bands resulting from the (PEA)2PbI4 band gap energy dependence on the number of lead(II) halide layers of individual crystallites. The characteristic time of the exciton energy funneling from higher- to lower-energy crystallites within (PEA)2PbI4 polycrystalline thin films is about 100 ps.

Frecuencia de nefrotoxicidad y su severidad en niños de unidad de cuidados intensivos e intermedios pediátricos, expuestos a medio de contraste intravenoso, para realización de tomografía computarizada / Frequency and Severity of Nephrotoxicity in Children of Intensive and Intermediate Pediatric Care Unit, Exposed to Intravenous Contrast Media for Computerized Tomography

Introducción: El objetivo de este artículo es estimar la frecuencia y severidad de la nefrotoxicidad en población pediátrica expuesta a medio de contraste intravenoso, para realización de tomografía, en unidad de cuidados intensivos e intermedios de un hospital. Métodos: Estudio descriptivo prospectivo. El medio de contraste utilizado fue iodado monómero no iónico de baja osmolalidad en pacientes con edades entre 30 días y 18 años. Se realizó recolección de datos previa y posterior a la aplicación del contraste. Se definió como nefrotoxicidad si después de la aplicación del medio de contraste y hasta 72 horas posteriores se cumplía cualquier estadio de los criterios RIFLE pediátricos (Riesgo, Lesión o Falla) o un aumento mayor del 25 % de la creatinina de base. Resultados: Se realizaron 68 tomografías con aplicación de medio de contraste intravenoso y se analizaron 40 eventos. De estos, 4 cumplieron la definición de nefrotoxicidad (10 %). Ninguno requirió terapia de reemplazo renal ni falleció durante su estancia en unidad de cuidados intensivos. Conclusiones: La frecuencia de nefrotoxicidad por medio de contraste en niños de unidad de cuidados intensivos e intermedios pediátricos se encuentra dentro de lo reportado en la literatura en la población general, a pesar de las múltiples comorbilidades que presentan estos pacientes. El estricto seguimiento hemodinámico que se les realiza a los pacientes pediátricos en unidades de cuidado crítico, hace que su estado de hidratación sea adecuadamente regulado, medida que ha sido demostrada como la mejor nefroprotección en múltiples estudios.

Introduction: The purpose of this article is to estimate the frequency and severity of nephrotoxicity in a pediatric population exposed to intravenous contrast medium, in order to perform computerized tomography in Intensive and Intermediate care unit of a pediatric hospital. Methods: The descriptive prospective study. The contrast medium used was iodinated monomer nonionic of low osmolality, in patients between the ages of 30 days to 18 years. Data was collected before and after the application of the contrast medium. It was defined as nephrotoxicity if, after applying the contrast medium, any stage of the RIFLE (Risk, Injury, or Failure) pediatric criteria or an increase greater than 25% of baseline creatinine was met up to 72 hours later. Results: 68 CT scans with application of intravenous contrast and 40 events were analyzied.in patients in intensive and intermediate pediatric care units. Forty events were analyzed. Of these, four events met the definition of nephrotoxicity (10%). None of the four required renal replacement therapy or died during their stay in intensive care unit. Conclusion: The frequency of nephrotoxicity by contrast medium in children intensive and intermediate pediatric care unit is met within that reported in the literature in the general population, despite the multiple comorbidities in these patients. The strict hemodynamic monitoring, which is undergo pediatric patients in critical care units, it makes the hydration status of these patients, it is properly regulated, as has been proven as the best nephroprotection in multiple studies.

[Retroperitoneal bronchogenic cyst: Report of one case]. / Quiste broncogénico retroperitoneal: Caso clínico.

Retroperitoneal cystic tumors are uncommon. More than two thirds are malignant. Benign lesions include lipomas and leiomyomas, among others. Bronchogenic cysts are congenital anomalies that result from an abnormal budding of the primitive foregut, and are most commonly found in the mediastinum. Occasionally they can be seen in the skin, subcutaneous tissue, in the pre-sternal and pericardial areas, but those located under the diaphragm are extremely rare. We report a 24 year-old female who consulted for abdominal pain. An abdominal ultrasound disclosed a retroperitoneal cystic lesion, that was confirmed with a CAT scan. The patient was operated, finding a cyst that was adhered to the pancreas. A distal pancreatectomy and cyst excision were done. The pathological examination of the lesion showed a bronchogenic cyst. The patient was discharged ten days after surgery.

Quiste broncogénico retroperitoneal: Caso clínico / Retroperitoneal bronchogenic cyst: Report of one case

Retroperitoneal cystic tumors are uncommon. More than two thirds are malignant. Benign lesions include lipomas and íeiomyomas, among others. Bronchogenic cysts are congenital anomalies that result from an abnormal budding of the primitive foregut, and are most commonly found in the mediastinum. Occasionally they can be seen in the skin, subcutaneous tissue, in the pre-sternal andpericardial areas, but those located under the diaphragm are extremely rare. We report a 24 year-old female who consulted for abdominal pain. An abdominal ultrasound disclosed a retroperitoneal cystic lesion, that was confirmed with a CAT scan. The patient was operated, finding a cyst that was adhered to the pancreas. A distal pancreatectomy and cyst excision were done. The pathological examination of the lesion showed a bronchogenic cyst. The patient was discharged ten days after surgery.

[Liver transplantation in adults: a caseload from Clínica Alemana de Santiago, Chile]. / Trasplante hepático en adultos: casuística de Clínica Alemana de Santiago.

BACKGROUND: The success of orthotopic liver transplantation (OLT) has resulted in its widespread use for different liver diseases. AIM: To report our 8 years experience with adult OLT at Clinica Alemana de Santiago. PATIENTS AND METHODS: In all transplantations done at the center, we recorded patient's overall data and survival, postoperative medical and surgical complications and causes of death. RESULTS: Between November 1993 and September 2001, 51 consecutive OLT were performed in 44 patients (22 females, median age 45 years old). Thirty eight patients presented with chronic and 6 with acute or sub-acute liver failure. Cryptogenic cirrhosis and hepatitis C infection were the most common causes for OLT. Postoperative bleeding and extrahepatic biliary complications were seen in 17.6 and 21.5% of cases respectively. Acute rejection, bacterial infections, CMV infection or disease and post OLT hemodialysis were the most common medical complications (51, 31, 19.6 and 19.6% of cases respectively). The overall 1 and 5 years survival rates were 80% and 73% respectively. Considering exclusively the last 22 OLT performed since January 1999, the 1 year survival rate has improved to 91%. CONCLUSIONS: Liver transplantation in Chile provides a good long term survival with acceptable morbidity, due to a multidisciplinary approach management. The survival rates have improved over the last few years probably due to better surgical techniques, ICU care and immunosuppression. These overall results are comparable with those from other Centers in developed countries.

Drenajes en cirugía abdominal / Drainage in abdominal surgery

En Cirugía el uso de los drenajes intraabdominales es un tema controvertido en lo que se refiere a indicaciones, rendimiento, normas de adecuado manejo y complicaciones potenciales. Las publicaciones al respecto son muy numerosas y sus resultados y conclusiones muy diversas. El uso de drenajes data desde la época de Hipócrates y la experiencia acumulada hasta la fecha no ha permitido aclarar algunos aspectos que siguen siendo discutidos. Se han intentado múltiples sistemas y materiales, algunos de los cuales, si bien han mejorado el rendimiento de los anteriores, no han solucionado por completo el problema. Los trabajos experimentales y clínicos son numerosos; están dirigidos a investigar algunos aspectos del tema y han permitido obtener conclusiones importantes. Los tipos de drenaje existentes son múltiples, y obviamente, el que se escoja, depende de los objetivos perseguidos. Las indicaciones, normas de manejo y complicaciones potenciales deben necesariamente ser conocidas para obtener resultados que justifiquen su uso. El objetivo de esta revisión es proporcionar información actualizada pero resumida, relacionada con los diversos problemas que plantean los drenajes intraabdominales en Cirugía, de manera de promover su adecuado manejo práctico