Objetivo: Comparar in vitro la adaptación marginal de coronas unitarias de porcelana vitrocerámica elaboradas con tres sistemas de procesado. Materiales y métodos: El presente estudio fue de tipo experimental in vitro. La muestra estuvo conformada por 69 coronas de porcelana vitrocerámica fabricadas con los sistemas: CAD-CAM, inyección de porcelana y condensación sobre muñón refractario. Para la evaluación de la discrepancia marginal vertical se realizó un registro fotográfico con una cámara digital y un lente macroscópico de 100 milímetros. Las imágenes fueron medidas digitalmente (ImageJ) y se utilizaron 52 puntos aleatorios de discrepancia marginal vertical alrededor de las coronas para obtener el promedio de cada una de ellas. Se utilizó la prueba de Kruskal-Wallis para realizar la comparación entre los grupos de estudio con un nivel de significancia estadística de p<0.05. Resultados: El presente estudio encontró diferencias estadísticamente significativas al comparar los tres sistemas de procesado (<0.001). El sistema CAD-CAM tuvo una discrepancia marginal vertical menor (53 µm) en comparación con el sistema de inyección de porcelana (85 µm) y el de condensación sobre muñón refractario (113 µm). Conclusiones: Se encontraron diferencias estadísticamente significativas entre los tres grupos de estudio. Asimismo, el sistema CAD-CAM tuvo una mayor adaptación marginal en comparación con los otros dos métodos de fabricación. Finalmente, los tres sistemas de confección utilizados tuvieron una discrepancia marginal vertical por debajo del límite establecido por la Asociación Americana de Odontología (<120 µm). / Objective: To compare in vitro the marginal adaptation of ceramic glass porcelain single crowns made with three processing systems. Materials and methods: The present study was experimental in vitro. The sample consisted of 69 glass ceramic porcelain crowns manufactured with the following three systems: CAD-CAM, porcelain injection and powder condensation. For de measurement of the vertical marginal discrepancy, the crowns were photographed using a digital camera with a macroscopic lens of 100 millimeters. The images were imported into image processing software (ImageJ) and 52 points were randomly selected around the crown to measure the vertical marginal discrepancy. For each crown, the 52 measurements were combined into a single average marginal discrepancy. Kruskal-Wallis was used to test differences in the observed marginal discrepancies between the study groups. (p <0.05) Results: This study found statistically significant differences when comparing the three different processing systems (<0.001). The CAD-CAM system had a smaller vertical marginal discrepancy (53 µm) compared to the porcelain injection (85 µm) and the powder condensation techniques (113 µm). Conclusions: Statistically significant differences were found between the three study groups. Also, the CAD-CAM system had a greater marginal adaptation compared to the other two manufacturing techniques. Finally, the three fabrication methods used in this study had a vertical marginal discrepancy within the limit established by the American Dental Association (<120 µm). / Tesis

Indiana University-Purdue University Indianapolis (IUPUI) / Background: Elucidating the lithium disilicate system like the popular IPS e.max® CAD (LS2), made specifically for Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM), as a function of temperature unravels new ways to enhance material properties and performance. Objective: To study the effect of various thermal processing on the crystallization kinetics, crystallite microstructure, and strength of LS2. Methods: The control group of the LS2 samples was heated using the standard manufacturer heating-schedule. Two experimental groups were tested: (1) an extended temperature range (750-840 °C vs. 820-840 °C) at the segment of 30 °C/min heating rate, and (2) a protracted holding time (14 min vs. 7 min) at the isothermal temperature of 840 °C. Five other groups of different heating schedules with lower-targeted temperatures were evaluated to investigate the microstructural changes. For each group, the crystalline phases and morphologies were measured by X-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. Differential scanning calorimeter (DSC) was used to determine the activation energy of LS2 under non-isothermal conditions. A MTS universal testing machine was used to measure 3-point flexural strength and fracture toughness, and elastic modulus and hardness were measured by the MTS Nanoindenter® XP. A one-way ANOVA/Tukey was performed per property (alpha = 0.05). Results: DSC, XRD, and SEM revealed three distinct microstructures during LS2 crystallization. Significant differences were found between the control group, the two aforementioned experimental groups, and the five lower-targeted-temperature groups per property (p<0.05). The activation energy for lithium disilicate growth was 667.45 (± 28.97) KJ/mole. Conclusions: Groups with the extended temperature range (750-840 °C) and protracted holding time (820-840 °C H14) produced significantly higher elastic-modulus and hardness properties than the control group but showed similar significant flexural-strength and fracture-toughness properties with the control group. In general, explosive growth of lithium disilicates occurred only when maximum formation of lithium metasilicates had ended.