RESUMEN
PURPOSE: Conventional resin-bonded fixed partial dentures (RBFPDs) are usually made with a two-retainer design. Unlike conventional RBFPDs, cantilever resin-bonded fixed partial dentures (Cantilever RBFPDs) are, for their part, made with a single-retainer design. The aim of this study was to compare the effect of tooth surface preparation on the bond strength of zirconia cantilever single-retainer RBFPDs. The objective is to evaluate the shear bond strength of these single-retainer RBFPDs bonded on 3 different amount of tooth surface preparation. MATERIALS AND METHODS: Thirty extracted bovine incisors were categorized to 3 groups (n=10), with different amounts of tooth surface preparations. Teeth were restored with single-retainer RBFPDs with different retainer surfaces: large retainer of 32 mm²; medium retainer of 22 mm²; no retainer and only a proximal connecting box of 12 mm². All RBFPDs were made of zirconia and were bonded using an adhesive system without adhesive capacity. Shear forces were applied to these restorations until debonding. RESULTS: Mean shear bond strength values for the groups I, II, and II were 2.39±0.53 MPa, 3.13±0.69 MPa, and 5.40±0.96 MPa, respectively. Statistical analyses were performed using a one-way ANOVA test with Bonferroni post-hoc test, at a significance level of 0.001. Failure modes were observed and showed a 100% adhesive fracture. CONCLUSION: It can be concluded that the preparation of large tooth surface preparation might be irrelevant. For zirconia single-retainer RBFPD, only the preparation of a proximal connecting box seems to be a reliable and minimally invasive approach. The differences are statistically significant.
Asunto(s)
Adhesivos , Dentadura Parcial Fija , Dentadura Parcial Fija con Resina Consolidada , Incisivo , DienteRESUMEN
La evaluación del umbral de desfibrilación (UDF) es una práctica habitual en la mayoría de los implantes de cardiodesfibriladores implantables (CDI). La práctica estándar busca obtener una desfibrilación exitosa de la fibrilación ventricular. En pacientes con umbrales de desfibrilación elevados en los cuales esto no resulta posible se da inicio a una serie de maniobras tendientes a corregir la situación. En esta presentación se describe un caso en el que se recurrió a una estrategia de uso poco frecuente para mejorar resultados durante la falla del UDF. Se trata de un paciente de 78 años, de sexo masculino, con antecedentes de miocardiopatía dilatada, que fue derivado al laboratorio de electrofisiología para el implante de un CDI para prevención primaria. Durante el procedimiento, el CDI falló en desfibrilar al paciente aun luego de haber posicionado el cable en diferentes áreas del ventrículo derecho y de haber optimizado la onda de choque. El paciente finalmente recibió el implante de un electrodo de desfibrilador en la vena ácigos, lo que permitió la reorientación del vector de desfibrilación hacia el eje posterior, con el resultado de una desfibrilación exitosa de la fibrilación ventricular por el CDI.
The evaluation of the defibrillation threshold (DFT) is common after the implantation of implantable cardioverter defibrillator (ICD) devices. The goal of this standard of care is to achieve successful defibrillation of ventricular fibrillation. In patients with elevated defibrillation thresholds, alternative techniques are required to correct the situation. We describe a case in which an uncommon strategy was used to improve DFT after failed defibrillation. A 78-year old man with a history of dilated cardiomyopathy was referred to the electrophysiology laboratory to have an ICD implanted as primary prevention strategy. During the procedure, the ICD failed to defibrillate the patient even after the lead was placed in different areas of the right ventricle and after optimizing the shock wave. A defibrillation lead was implanted in the azygos vein, and the shock vector was directed towards the posterior axis; a successful defibrillation was thus achieved.
RESUMEN
OBJECTIVES: Titanium dioxide (TiO2), a common nanoparticle widely used in industrial production, is one of nano-sized materials. The purpose of this study was to determine the acute and chronic toxicity of TiO2 using different size and various concentrations on Daphnia magna. METHODS: In the acute toxicity test, four concentrations (0, 0.5, 4, and 8 mM) for TiO2 with 250 or 500 nm and five concentrations (0, 0.25, 0.5, 0.75, and 1 mM) for TiO2 with 21 nm were selected to analyze the toxic effect to three groups of ten daphnia neonates over 96 hours. In addition, to better understand their toxicity, chronic toxicity was examined over 21 days using 0, 1, and 10 mM for each type of TiO2. RESULTS: Our results showed that all organisms died before the reproduction time at a concentration of 10 mM of TiO2. In addition, the exposure of anatase (21 nm) particles were more toxic to D. magna, comparing with that of anatase (250 nm) and rutile (500 nm) particles. CONCLUSIONS: This study indicated that TiO2 had adverse impacts on the survival, growth and reproduction of D. magna after the 21days exposure. In addition, the number of test organisms that were able to reproduce neonates gradually were reduced as the size of TiO2 tested was decreased.