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PURPOSE: To evaluate the influence of the thickness and type of computer-aided design and computer-aided manufacturing (CAD-CAM) material on the fatigue resistance and failure mode of endodontically treated teeth (ETT) restored with occlusal veneers (OV). MATERIALS AND METHODS: Seventy-five (N = 75) ETT were restored with Herculite XRV in the endodontic access. Five experimental groups (n = 15) were tested. Four groups had two different thicknesses (0.6-0.7 mm or 1.4-1.6 mm) and two different CAD-CAM materials: zirconia-reinforced lithium-silicate (LS/Celtra Duo) and composite resin (RC/Cerasmart). The fifth group (control) did not have occlusal veneers. All the specimens were subjected to accelerated fatigue (5 Hz frequency) with an occlusal load increasing up to 1800 N and 131,000 cycles. The number of cycles was recorded when the machine stopped or at the completion of the test. Fatigue resistance was analyzed using the Kaplan-Meier survival test (95% significance level, log-rank post hoc pairwise comparisons). The samples were categorized according to failure mode. The CAD-CAM materials were examined through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). RESULTS: No differences were found between the thicknesses, regardless of the type of the CAD-CAM material. The thick LS OV outperformed the RC and control groups. The thin RC OV and control groups showed a higher percentage of repairable and possibly repairable failures than the other groups. LS was more homogeneous under SEM, and the EDS analysis detected Si and Zr, but not Li. CONCLUSIONS: A larger thickness did not improve the resistance of the CAD-CAM materials. Thick LS showed a higher cumulative survival rate to fatigue than the RC and control groups. The direct composite alone (control) survived similarly to the experimental groups, except for the thick LS.

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Introducción: El hidrocloruro de amantadina (I) es conocido como un medicamento antiviral utilizado para prevenir y tratar las infecciones por influenza A. También se utiliza para aliviar los síntomas de la enfermedad de Parkinson en el período inicial. Se han informado varios métodos para la preparación de (I). Estos procedimientos comienzan con adamantano (II) en cuatro o tres pasos de reacción, para producir hidrocloruro de amantadina con rendimientos globales que van del 45 por ciento al 58 por ciento. Objetivo: Mejorar el método para la síntesis de hidrocloruro de amantadina, que puede introducirse a escala industrial. Métodos: La optimización paso a paso para reducir el uso de reactivos, disolventes, así como las condiciones de cada paso, se seleccionaron para ser menos agresivas y más amigables con el medio ambiente. Resultados: Todos los factores relacionados con el rendimiento de la reacción para sintetizar los compuestos intermedios y finales se seleccionaron para obtener el mayor rendimiento de cada etapa. Finalmente, se estableció un procedimiento de dos pasos para la síntesis de (I) a partir de (II), a través de N- (1-adamantil) formamida (III), con un rendimiento global mejorado del 78 por ciento y una pureza del 99,2 por ciento. Se confirmó la estructura del producto por 1H-NMR, 13C-NMR, IR y MS. La síntesis de N- (1-adamantil) formamida (VI) a partir de (II) también se logró con éxito en un solo paso. Este método evita el uso de bromo líquido o ácido sulfúrico gaseoso como reactivos. La conversión posterior de (VI) a (I) se llevó a cabo bajo condiciones de reacción, más suaves sin usar solventes peligrosos. Conclusiones: Se logró la síntesis mejorada del clorhidrato de amantadina (I). Este resultado puede utilizarse en una producción industrialmente conveniente. Las materias primas y reactivos utilizados en esta investigación son baratas y están disponibles. El tiempo total de preparación se redujo significativamente, con ahorro de energía y mano de obra(AU)

Introduction: Amantadine hydrochloride (I) was well-known as an antiviral drug used to prevent and treat influenza A infections. Besides, it also was used to relieve the symptoms of Parkinson's disease in the early period. Several methods for the preparation of I have been reported. These procedures started with adamantane (II) in four or three reaction steps to produce amantadine hydrochloride with overall yields ranging from 45 percent to 58 percent. Objectives: Improving method for synthesis of amantadine hydrochloride could introduce to industrial scale. Methods: Step-by-step optimization to reduce the use of reagents, solvents, as well as the conditions of each step were screened to be milder and more environment-friendly. Results: All factors related to the yield of reaction to synthesize the intermediate and final compounds were screened to give the highest yield of each step. Finally, a two-step procedure for the synthesis of (I) from (II) via N-(1-adamantyl) formamide (III) with improving overall yield of 78 percent and a purity of 99.2 percent was established, and the structure of the product was confirmed by 1H-NMR,13C-NMR, IR and MS. The synthesis of N-(1-adamantyl) formamide (VI) from (II) also was successfully accomplished within only one step. This method avoided the use of liquid bromine or fuming sulfuric acid as reactants. The subsequent conversion of (VI) to (I) was carried out under milder reaction conditions without using hazardous solvents. Conclusions: An improved synthesis for amantadine hydrochloride (I) have been provided. This research can be an industrially convenient production of amantadine hydrochloride. Because the raw materials and reagents used in this research are cheap and available which also were screened to save their use. Moreover, the total preparation time was significantly reduced to save energy as well as labor(AU)

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