Selle marginal y asentamiento en dos sistemas cerámicos in-vitro / Marginal sealing and bonding in two ceramic systems in vitro

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.

Comparative study of fracture strength depending on the thickness of some all ceramic cores / 대한치과보철학회지

STATEMENT OF PROBLEM: The increased awareness of esthetics in dentistry has brought the esthetic consideration in prosthetic restorations. Dental ceramics offer better esthetics for use of prosthetic restorations. Unfortunately, dental ceramic materials are not always the most suitable candidate materials since their inherently brittle nature. In recent years, basic research in ceramic science has led to the recognition of several approaches to strengthen and to enhance esthetics of ceramics. Several all ceramic systems use ceramic core and porcelain build up structures. Ceramic cores influence to strength of all ceramic crowns. So the strength of ceramic cores is important to all ceramic crowns. PURPOSE: The purpose of this study is to estimate the flexural strength of ceramic cores in some all ceramic systems. Material and method : A biaxial flexure test was conducted on three groups(Cergo, Empress 2, In-Ceram). Each group consisted of 30 discs of nearly identical dimension with a 0.5mm, 1.0mm, 1.5mm thickness and 12mm in diameter. The fracture load was recorded by Instron. Analysis of variance(ANOVA) and Tukey's tests were performed using SAS statistical software. RESULTS: 1.5mm thickenss of specimens were significantly stronger than 0.5mm and 1.0mm thickness of specimens in Cergo and In-Ceram. But each sepecimen group of Empress 2 was no significantly strength by thickness. In order of In-Ceram, Empress 2 and Cergo has significantly stronger strength in the same thickness. CONCLUSION: In-Ceram is the strongest ceramic material in 3 materials. All the materials can be used according to the required characters.

Surface hardness and pressing accuracy of reused IPS empress 2 / 대한치과보철학회지

STATEMENT OF PROBLEM: IPS Empress2 system was developed and used in prosthodontic treatment, but the cost of ingot is expensive for wide application. PURPOSE: This study was to investigate the possibility on recycling of IPS Empress 2 ceramic for wide application of IPS Empress 2 ceramic in prosthodontic treatment. MATERIAL AND METHOD: 1st, 2nd and 3rd pressed disc-shaped(10x1.5mm) IPS Empress 2 specimens were made with IPS Empress ingot(200, Ivoclar, Liechtenstein) and pressing furnace(IPS Empress EP 500, Ivoclar, Liechtenstein). Vicker's surface hardness and fracture toughness, acid resistance, and pressing accuracy of IPS Empress 2 ceramic were measured and analyzed. Surface hardness was measured by microhardness tester(MTX 70, Matsuzawa, Japan). before and after surface treatment with 0.5% hydrofluoric acid and carbonic acid(Coca cola) for evaluation of acid resistance. RESULTS: The surface hardness of 1st pressed specimen was the higher(5.11 GPa) than those of 2nd pressed( 4.89 GPa) and 3rd pressed specimen(4.86 GPa). and the fracture toughness of 1st pressed (1.58 MPam1/2)and 2nd pressed specimen(1.51 MPam1/2) were higher than that of 3rd pressed specimen(1.39 MPam1/2). The changes of surface hardness of 1st, 2nd, and 3rd pressed specimens after treatment with fluoric acid were 0.17, 0.06, 0.05(GPa) respectively, and those of 1st, 2nd, and 3rd pressed specimens after treatment with carbonic acid were 0.07, 0.00, 0.05(MPa) respectively. The pressing accuracy of 1st, 2nd and 3rd specimen were 77.22%, 85.681%, and 75.05%. The pressing accuracy of 2nd pressed specimen was higher than that of the 3rd specimen. CONCLUSION: The changes of physical properties according to recycling of IPS Empress 2 from this study were insignificant. Therefore the possibility of recycling of IPS Empress 2 can be suggested from the results.

Flexure strength and color change of reused IPS Empress 2 / 대한치과보철학회지

Development of new ceramic and esthetic need of patient increased the use of ceramic restorations. The purpose of this study was to confirm the possibility of recycling for IPS Empress2 which has a lot of advantages in esthetics. 1st, 2nd and 3rd pressed disc-shaped(10x1.5mm) IPS Empress 2 specimens were made with IPS Empress ingot(shade 200, Ivoclar, Liechtenstein) and pressing furnace(IPS Empress EP 500, Ivoclar, Liechtenstein). Flexure strength was measured with universal testing machine(Zwick 145641, Zwick, Germany), and color change and staining resistance of specimens were evaluated with colorimeter (Model TC-6FX, Tokyo Denshoku Co., Japan). The followings were drawn from this study : 1. Flexure strength of the 1st, the 2nd, and the 3rd pressed specimens showed 236.78 MPa, 247.16MPa, and 220.72MPa, respectively. Flexure strength of the 2nd pressed specimens was higher than others, but there's no statistical difference between them. 2. The color difference between the 1st and the 2nd pressed specimens was 3.25, and that between the 1st and the 3rd pressed specimens was 3.63(P<0.05). 3. The color change after staining of the 1st, the 2nd, and the 3rd pressed specimens were 1.43, 2.64, and 1.45, respectively. In this study, reused IPS Empress 2 specimens showed insignificant change of flexure strength and stain resistance, but they showed some color change according to reuse. From this results, the limited possibility of reuse for IPS Empress 2 could be considered.

Mechanical Properties Of Reused Lithium Disilicate Glass-Ceramic Of Ips Empress 2 System / 대한치과보철학회지

This investigation was designed to estimate the biaxial flexure strength and fracture toughness of lithium disilicate glass-ceramics of IPS Empress 2 system pressed with as-received ingots and their sprue buttons. Two groups of the lithium disilicate glass-ceramics were prepared as follows: group 1 is ingot-pressed group; group 2 is sprue button-pressed group. A ball-on-three-ball test was used to determine biaxial flexure strength (BFS) of disks in wet environment. Scanning electron microscopy(SEM) analysis was conducted to observe the microstructure of the ceramics. Unpaired t-test showed that there were no differences in the mean biaxial flexure strength (BFS) and KIC values between group 1 and 2 (p>0.05). Two groups showed similar values in the KIC and the strength at 5% failure probability. The SEM micrographs of the IPS Empress 2 glass-ceramic showed a closely packed, multi-directionally interlocking pattern of numerous lithium disilicate crystals protruding from the glass matrix. The lithium orthophosphate crystals could not be observed on the fracture surface etched. There was no a marked difference of the microstructure between group 1 and 2. Although there were no tests including color stability, casting accuracy, etc., the results of this study implied that we could reuse the sprue button of the pressed lithium disilicate glass-ceramic of IPS Empress 2 system.

Marginal Fit of Celay/in-Ceram, Conventional In-Ceram And Empress 2 All-Ceramic Single Crowns / 대한치과보철학회지

There have been many studies about marginal discrepancy of single restorations made by various systems and materials.But many of statistical inferences are not definite because of sample size,measurement number,measuring instruments,etc. The purpose of this study was to compare the marginal adaptations of the anterior single restorations made by different systems and to consider more desirable statistical methods in analysing the marginal fit.The in vitro marginal discrepancies of three different all-ceramic crown systems(Celay In-Ceram,Conventional In-Ceram,IPS Empress 2 layering technique)and one control group (PFM)were evaluated and compared.The crowns were made from one extracted maxillary central incisor prepared with a 1mm shoulder margin and 6 taper walls by milling machine.10 crowns per each system were fabricated.Measurements of a crown were recorded at 50 points that were randomly selected for marginal gap evaluation.Non-parametric statistical analysis was performed for the results. Within the limits of this study,the following conclusions were drawn: 1.Mean gap dimensions and standard deviations at the marginal opening for the maxillary incisor crowns were 98.2+/-40.6 mu m for PFM,83.5+/-18.7 mu m for Celay In-Ceram,104.9+/-44.1 mu m for conventional In-Ceram,and 45.5+/-11.5 mu m for IPS Empress 2 layering technique.The IPS Empress 2 system showed the smallest marginal gap (P<0.05).The marginal openings of the other three groups were not significantly different (P<0.05). 2.The marginal discrepancies found in this study were all within clinically acceptable standards(100 150 mu m). 3.When the variable is so controlled that the system may be the only one,mean value is interpreted to be the marginal discrepancy of a restoration which is made by each system and standard deviation is to be technique-sensitivity of each one. 4.From the standard deviations,the copy-milling technique (Celay/In-Ceram)was not considered to be technique-sensitive in comparison with other methods. 5.Parametric analysis is more reliable than non-parametric one in interpretation of the mean and standard deviation.The sample size of each group has to be more than 30 to use parametric statistics. The level of clinically acceptable marginal fit has not been established.Further studies are needed.

FLEXURE STRENGTH AND MICROSTRUCTURE OF IPS EMPRESS 2 GLASS-CERAMIC ON HEAT PRESSING AND HEAT TREATMENTS / 대한치과보철학회지

This investigation was designed to determine whether heat-pressing and/or simulated heat treatments affected the flexure strength and the microstructure of the lithium disilicate glassceramic in the IPS Empress 2 system. Four groups of the specimens were prepared as follows group 1 - as-received material ; group 2 - heat-pressed material ; group 3 - heat pressed and simulated initial heat-treated material ; group 4 - heat-pressed and the simulated heat-treated material with full firings for a final restoration. The three-point bending test and the scanning electron microscope (SEM) analysis was conducted for the purpose of this study. The flexure strength of group. 2 was significantly higher than that of group 1. However, there were no significant differences in strength among group 2, 3, and 4, and between group 1 and 4. The SEM micrographs of the lithium disilicate glass-ceramic showed the closely packed, multi-directionally interlocking microstructure of numerous lithium disilicate crystals protruding from the glass matrix. The crystals of the heat-pressed materials (group 2, 3, and.4) were a little denser and about two times bigger than those of the as-received material (group 1). This change of microstructure is more obviously exhibited particularly between group 1 and 2. However, there was no a marked difference among group 2, 3, and 4 after the heat pressing procedure. Although there were significant increase of the strength and some changes of the microstructure after the heat-pressing operation, the conr bination of the heat-pressing and the simulated subsequent heat treatments did not produce the increase of strength of IPS Empress 2 glass-ceramic.