ABSTRACT
Objective: To study the dimensional accuracy of the Co-Cr crowns prepared by selective laser melting(SLM) technology and to evaluate their internal and marginal fit by "Virtual seating". Methods: The Co-Cr metal crowns were fabricated with 2 different methods(n = 10): milling wax with lost-wax method in the control group and SLM in the test group. After collecting the data of the die and crowns, "virtual seating" was completed by the software of reverse engineering. The gaps between the die and crowns on the 2D cross-sectional were measured by the same software. At last, crowns were cemented on the dies. And the thickness of the crowns and the cement films were measured under a scanning electron microscope. Data were statistically analyzed. Results: The most appropriate pre-set die spacer thickness was 50 μm. The relative errors of the crown thickness of SLM group and the control group were 1. 80％ and 2. 20％ respectively(P＞ 0. 05). No statistically significant difference was found in both internal and marginal fit between the 2 groups (P＞ 0. 05). And there was no statistical difference between the 2 measuring methods (P＞ 0. 05). Conclusion: SLM technique achieves clinically values for internal and marginal fit. "Virtual seating" can be used for evaluate crown dimensional accuracy.
ABSTRACT
La rehabilitación oral en odontología demanda la búsqueda constante de nuevos materiales cada vez más biocompatibles y con apariencia más natural para satisfacer las necesidades actuales de los pacientes. El objetivo de esta investigación fue comparar, en un estudio cuasiexperimental in vitro, el nivel de asentamiento y selle marginal de cofias elaboradas según dos sistemas comerciales totalmente cerámicos, cuando fueron cementadas sobre dientes naturales. Para el estudio se utilizaron 30 dientes naturales extraídos por requerimientos ortodónticos en los cuales se realizaron sendas preparaciones dentarias estandarizadas para prótesis fija según las recomendaciones de ambos fabricantes y se tomaron impresiones estandarizadas en silicona. A partir de los modelos obtenidos mediante estas impresiones se fabricaron y se evaluaron las cofias de los sistemas libres de soporte metálico In Ceram® de la casa VITA y Empress 2® de la casa IVOCLAR simulando una situación clínica. En las 30 cofias obtenidas para los dientes naturales, se aplicaron dos medidas para evaluar el selle marginal y cinco medidas para determinar el grado de asentamiento por medio de la medición directa en el estereomicroscopio de luz, con el cual los resultados se obtuvieron en micras. El análisis de los datos se hizo mediante estadística descriptiva empleando la prueba estadística t de Student, comparando los promedios de los resultados entre los dos grupos experimentales, con una significancia estadística de p<0.05. Los promedios de las medidas de asentamiento se tomaron en los cortes en 5 puntos de referencia en ambos sistemas; en 3 delos 5 puntos los promedios fueron menores en el sistema Empress 2®, que sus correspondientes promedios por punto para el sistema In Ceram®.
Oral rehabilitation procedures constantly demand searching for more biocompatible materials with natural appearance to satisfy patient requirements. The objective of this investigation was to compare the accuracy level of fitness and marginal seal in vitro of abutments made of two commercial totally-ceramic systems on natural teeth. To obtain the pertinent data a quasi-experimental in vitro study was design; 30 natural teeth extracted by orthodontic requirements were experimentally prepared as abutments to receive and support prosthetic dental crowns prepared following the manufacturers recommendations. The reconstructive materials used and evaluated were the totally-ceramic systems In Ceram® (VITA) and Empress 2® (IVOCLAR). Each natural tooth was prepared in a standardized dental preparations for fixed prosthetics, and standardized silicone impressions were built simulating a clinical situation. Thirty abutments for the natural teeth were obtained, evaluating two measures of marginal sealing and five measures of adaptation by direct measuring from light stereomicroscopy in microns. For the data analysis, descriptive statistic was used by means of statistical test t of Student, by comparison between both experimental groups, with a statistical significance of p<0.05. The averages of adaptation levels measured for 5 reference points in cuts made in both systems, were smaller in 3 points for the system Empress 2 ® than those corresponding to in the In Ceram® system. For the marginal seal, the averages of the measures in 2 reference points were considered for both systems, resulting smaller in one point for the Empress 2® system, and equal for the other point. When the averages between both groups were compared, statistically significant differences were found in 3 of the 7 points used as reference. On the other four points there were no significant differences.