Caracterização de sistemas cerâmicos aluminizados infiltrados por vidro / Characterization of glass-infused alumina-based ceramic systems

A realização deste trabalho se deu justamente pela pouca informação sobre sistemas cerâmicos amplamente utilizados no mercado odontológico, sendo o objetivo deste estudo caracterizar e analisar a microestrutura, a composição e as propriedades mecânicas destes materiais, testando a compatibilidade entre os sistemas, além da hipótese de que todos eles apresentam ótimas propriedades. Este estudo caracterizou e comparou os sistemas cerâmicos In-Ceram (Vita Zahnfabrik, Bad Säckingen, Alemanha), Vitro-Ceram (Angelus, Londrina, Brasil) e Alglass (EDG, São Carlos, Brasil) utilizando as seguintes metodologias: 1 ­ Análise da fase vítrea por fluorescência de raios-X; 2 ­ Análise da granulometria da fase cristalina e da fase vítrea; 3 ­ Avaliação da resistência ao ensaio equibiaxial; 4 ­ Análise da microestrutura através de microscopia eletrônica de varredura (MEV). A análise por fluorescência de rx da fase vítrea dos três sistemas mostrou que as suas composições em relação aos elementos principais, como o lantânio (La2O3), alumínio (Al2O3) e silício (SiO2), são semelhantes, diferindo nos aditivos que servem para dar cor e outros ajustes. De acordo com os resultados da granulometria, pode-se observar que o In-Ceram e o Vitro-Ceram apresentam tamanhos de partículas semelhantes, e a alumina do sistema Alglass mostrou uma composição mais heterogênea com grãos maiores que 10 µm e uma grande quantidade de grãos inferiores a 0,6 µm. Isso permite uma maior aglomeração dos grãos, favorecendo a formação de uma estrutura cerâmica mais compacta após a pré-sinterização, o que gera poros de pequeno diâmetro e sem interconexão. Este fato prejudica a infiltração vítrea no compósito cerâmico final, o que pode resultar em um material com mais defeitos e uma redução nas propriedades mecânicas. Além disso, caracterizou-se também o vidro, que não apresentou semelhança entre os três sistemas, porém a sua granulometria elevada facilita seu manuseio e a justaposição sobre as estruturas de alumina pré-sinterizadas, não interferindo na sua infiltração. No ensaio de flexão, os grupos compostos pela alumina do sistema In-Ceram apresentaram as maiores médias, se diferenciando estatisticamente dos demais grupos. Os grupos com a alumina do sistema Vitro-Ceram, por mais que tenham apresentado valores maiores de resistência, não se diferenciaram estatisticamente com relação aos grupos da alumina do sistema Alglass. A infiltração de vidros diferentes em uma mesma alumina não influenciou estatisticamente a resistência mecânica dos materiais. Porém, os grupos que utilizaram a fase vítrea do Alglass apresentaram os maiores valores de resistência. Na análise de validação fractográfica nenhuma das amostras teve de ser descartada por falha na fratura, nos quais 70% dos corpos de prova dos três sistemas cerâmicos estudados tiveram fraturas de baixa força, 30% sofreram fraturas de média força e nenhuma amostra sofreu uma fratura de alta força. Os valores mais baixos encontrados para o sistema cerâmico Vitro-Ceram podem ser justificados pela presença muito maior de bolhas e poros na parte interna do material, consequentemente, esta característica se traduz em perda de resistência mecânica da cerâmica. Por mais que todos os sistemas cerâmicos estejam aptos para utilização clínica, o material In-Ceram de destaca pelas suas características e confiabilidade.

This work took place because of the very few information available about ceramic systems widely used at the dental market. The aim of this study was to characterize and analyze the microstructure, composition and mechanical properties of these materials, testing the compatibility of the systems and the assumption that they all have excellent properties. This study characterized and compared the In-Ceram ceramic systems (Vita Zahnfabrik, Bad Säckingen, Germany), Vitro-Ceram (Angelus, Londrina, Brazil) and Alglass (EDG, São Carlos, Brazil) using the following methods: 1 - Analysis of the vitreous phase by X-ray fluorescence; 2 - Analysis of the particle size of the crystalline phase and the vitreous phase; 3 - Evaluation of resistance at the equibiaxial test; 4 - Analysis of the microstructure by scanning electron microscopy (SEM). The RX fluorescence analysis of the glass phase of the three systems showed that their compositions in relation to their main elements, such as lanthanum (La2O3), aluminum (Al2O3) and silicon (SiO2), are similar, differing in the additives which serves to give color and other settings. According to the results, it can be seen that Vitro-Ceram and In-Ceram have similar particle size, and the alumina from the Alglass system showed a more heterogeneous composition with grains larger than 10 µm and a large amount of grains below 0,6 µm. This allows a larger agglomeration of the grains, forming a more compact ceramic structure after pre-sintering, which creates pores of small diameter and without interconnection. This fact undermines vitreous infiltration in the final ceramic composite, which can result in a material with more defects and a reduction of the mechanical properties. Also, the glass was also characterized, which showed no similarity between the three systems, but its high grain facilitates its handling and the overlap over the structure of pre-sintered alumina, not interfering in their infiltration. In the bending test, the groups composed by the alumina present at the In-Ceram system had the highest average, being statistically different from the other groups. Despite showing higher values of resistance, the groups with the alumina present at the Vitro-Ceram system did not statistically differ from the groups of Alglass system's alumina. The infiltration of different glasses in the same alumina did not statistically influenced the mechanical strength of the materials. However, groups using the glassy phase of Alglass showed higher resistance. In the fractographic validation analysis none of the samples had to be discarded because of its fracture failure, in which 70% of the specimens of the three studied ceramic systems had low-power fractures, 30% suffered fractures of average strength and no sample suffered a high-strength fracture. Lower values found for the Vitro-Ceram ceramic system can be justified by the presence of much larger blisters and pores inside the material, thus, this feature translates into loss of mechanical strength of the ceramic. As much as all ceramic systems are suitable for clinical use, the In-Ceram material stands out for its features and reliability.

Análise da resistência flexural e microdureza de dois sistemas de cerâmica aluminizada infiltrada por vidro / Analysis of flexural strength and microhardness of two alumina glass infiltrated ceramic systems

O estudo avaliou in vitro a resistência flexural e a microdureza de dois sistemas de cerâmica aluminizada infiltrada por vidro: In-Ceram Alumina (Vita) e Alglass (Celmat). Foram testados corpos de prova em forma de barra, conforme a ISO 6872-1998, foram testados em ensaios de resistência flexural de três pontos e microdureza Vickers, por indentação. Analisou- se a superfície de fratura dos corpos por MEV. In-Ceram Alumina apresentou maior resistência à flexão (441,7 ± 54,1 MPa) que o Alglass (287,8 ± 53,6 MPa). Os sistemas não apresentaram diferença estatística para microdureza: 1210,4 ± 90,0 HV e 1135,6 ± 117,5 HV, respectivamente. In-Ceram Alumina apresentou na superfície de fratura maior homogeneidade e menor número de poros que o Alglass. O Alglass, com custo reduzido comparado ao In-Ceram Alumina, atendeu à ISO 6872-1998 podendo ser empregado clinicamente

The aim of this work was to evaluate, in vitro, the microhardness, mechanical properties and fracture surface morphology of two different systems of glass infiltrated dental ceramic: In-Ceram Alumina (Vita) and Alglass (Celmat) systems. Both materials were used to prepare bar-shaped specimens according to ISO 6872-1998. Three point flexural strength and Vickers microhardness through indentation tests were used to evaluate the samples. The samples surface fracture was achieved through SEM. The Results showed that In-Ceram Alumina presented higher flexural strength values (441.7 ± 54.1 MPa) than Alglass (287.8 ± 53.6 MPa). There was no significant statistic difference in microhardness Vickers results (1210,4 ± 90,0 HV; 1135,6 ± 117,5 HV) between two groups, respectively. In-Ceram Alumina had more homogeneity and less pores at fracture surface than the Alglass. However, Alglass has reduced costs in relation to In-Ceram Alumina and reached the ISO 6872-1998 standard requirements, by this mean this material can be considered to be used clinically used

Standards of teeth preparations for anterior resin bonded all-ceramic crowns in private dental practice in Jordan

OBJECTIVES: To investigate if general dental practitioners (GDPs) in private practice in Jordan follow universal guidelines for preparation of anterior teeth for resin bonded all-ceramic crowns (RBCs). MATERIAL AND METHODS: A sample (n=100) of laboratory models containing 208 tooth preparations for IPS Empress and In Ceram, featuring work from different GDPs, was obtained from 8 commercial dental laboratories. Aspects of preparations were quantified and compared with accepted criteria defined following a review of the literature and recommendations of the manufactures' guidelines. RESULTS: Subgingival margins on the buccal aspect were noticed in 36 percent of the preparations, 54 percent demonstrated overpreparation with a tendency to overprepare the teeth on the mesiodistal plane more than buccolingual plane. Twenty percent of samples presented a shoulder finish line while a chamfer margin design was noticed in 39 percent. Twenty-nine percent and 12 percent of samples had either a feathered or no clear margin design respectively. Incisal underpreparation was observed in 18 percent of dies of each type. Only 17 percent of all preparations were found to follow the recommended anatomical labial preparations while 29 percent of the RBC preparations were found to have the recommended axial convergence angle. In total, 43 percent of preparations were found to have the recommended depth of the finish line. CONCLUSIONS: It was found that relevant guidelines for RBC preparations were not being fully adhered to in private practice in Jordan.

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.

The study of flexural strength of various zirconia ceramics / 대한치과보철학회지

STATEMENT OF PROBLEM: Increasing demand of esthetic restorations made lots of kinds of ceramic materials. Among them, zirconia has been being focused by many dentists. But, mechanical properties of zirconia were still unclear. PURPOSE: The purposes of this study were to analyze the flexural strength of various zirconia ceramics which had been currently used for clinic i.e., In-Ceram Zirconia(Vita Zahnfabrik, Bad Sa ckingen, Germany), Celay Zirconia(Vita Zahnfabrik, Bad Sa ckingen, Germany) and CAD/CAM Zirconia(Adens Zi-Ceram, Seoul, Korea). MATERIAL AND METHODS: The four point bending test(ASTM C1161) was used to measure the flexural strength of a specimen before and after circular heat treatment and fatigue loading. RESULTS: 1. The average value of flexural strengths of CAD/CAM Zirconia, Celay Zirconia, In-Ceram Zirconia in dry condition were 806.5 MPa, 669.9 MPa, 605.6 MPa, respectively. There was a statistically significant difference in strength among the types(P0.05). 3. After fatigue loading in wet condition, the average flexural strengths of CAD/CAM Zirconia, Celay Zirconia, In-Ceram Zirconia were 806.0 MPa, 674.9 MPa, 601.7 MPa, respectively. There was a significant difference in strength among the types(P0.05). CONCLUSION: Besides high esthetic quality, zirconia had sufficiently high mechanical strength.

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.

On the marginal fidelity of all-ceramic core using CAD/CAM system / 대한치과보철학회지

Novel methods producing supplementary and prosthetic material by cutting or discharge processing via computer design have been proposed as alternatives for traditional casting methods and are being utilized for commercial purposes. The CAD/CAM system used in dentistry can be classified into three-dimensional input of target values, restoration design, and material processing. The marginal fidelity in production of In-Ceram core has important clinical implications and is a key consideration issue in CAD/CAM production as well. Through this research, the author arrived at the following conclusion after conducting comparison analysis of marginal fidelities between the In-Ceram core produced via CAD/CAM and that produced through the traditional method: 1. In the cases of mesial, distal, and lingual margins, the core margins via CAD/CAM produced lower values than those via the traditional method, but the differences were found to be statistically insignificant. 2. In the case of labial flange, the core margins via CAD/CAM produced lower values than those via the traditional method and the differences were found to be statistically significant. (p<0.05) 3. In comparision with overall marginal fidelity, the core margins via CAD/CAM produced lower values than those via the traditional method, but the differences were found to be statistically insignificant. 4. Among the core margins produced via the traditional method did not have statistically significant differences but for those produced via CAD/CAM had statistically significant differences between labial and lingual sides and between labial and mesial sides. (p<0.05)

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.

Influence of repeated infiltrating firing on the micro-structure of In-Ceram alumina substrate / 实用口腔医学杂志

Objective: To investigate the influence of repeated infiltrating on the microstucture of In-Ceram alumina substrate. Methods:6 disks of aluminum oxide with the height of 3 mm and diameter of 12 mm were perpared and infiltrated with infiltrating glass for 0～5 times for each disk respectively.The fractured surfaces of the samples were observed by scanning elctron microscope. Results:After sintering,a net -shaped porous coping of alumina was formed. The glass infiltration resulted in a dense ceramic mass. The porous coping matrix was infiltrated with low-viscosity glass in void.3-time-infiltration resulted in the best results. Conclusion: With repeated infiltrating firing,the micro-stucture of In-Ceram alumina substrate may become a dense mass.

THE INFLUENCE OF SURFACE TREATMENTS ON THE SHEAR BOND STRENGTH OF RESIN CEMENTS TO IN-CERAM CORE / 대한치과보철학회지

An increasing demand for esthetic restorations has led to the development of new ceramic systems. In-Ceram, a glass-infiltrated alumina ceramic has three to four times greater flexural strength than other ceramic glass material. Because of its high strength, In-Ceram has been suggested as inlay, crown, laminate veneer and core material for resin bonded fixed partial dentures. This clinical application requires a stable resin bond to In-Ceram core. The purpose of this study was to evaluate the shear bond strength between In-Ceram core and resin cements according to various surface treatments and storage conditions. The surface of each In-Ceram core sample was subjected to one of the following treatments and then bonded to Panavia 21 or Variolink II resin cement. ; (1) sandblasting with 110 micrometer aluminum oxide powder, (2) sandblasting and silanization, (3) sandblasting and Siloc treatment, (4) sandblasting and Targis link application. Each of eight bonding groups was tested in shear bond strengths after the following storage times and thermocycling. ; A) 24 hours storage in distilled water at 371C, B) 5 weeks storage in dis tilled water at 37 C, C) 5 weeks storage in distilled water at 371C and thermocycled 2,000 ther mocycling for every 10 days(totally 10,000 thermocycling) in 51C - 551C bath. The bond failure modes were observed with scanning electron microscope (SEM). The results were as follows : 1. The shear bond strengths of sandblasting group were significantly lesser than the other groups after 24 hours water storage. 2. No significant difference of bonding strengths was found between storage time conditions (24 hours and 5 weeks). The shear bond strengths showed a tendency to decrease in Variolink II bonding groups and to increase in Panavia 21 bonding groups. 3. After thermocycling, the shear bond strengths of all groups were significantly decreased (p<0.01) and Targis link group exhibited significantly greater strengths than the other groups(p<0.05). 4. Panavia 21 bonding groups exhibited significantly greater bonding strengths in sandblasting group(p<0.01) and silane group(p<0.05) than Variolink II bonding groups. 5. In observation of bond failure modes, Targis link group showed cohesive failure in resin part and silane group and Siloc group showed complex failure and sandblasting group showed adhesive failure between In-Ceram and resin.

TENSILE BOND STRENGTH OF ALUNMINA CORE TREATED BY ION ASSISTED REACTION / 대한치과보철학회지

This study was undertaken to evaluate the tensile bond strength of In-Ceram alumina core treated by ion assisted reaction(IAR). Ion assisted reaction is a prospective surface modification technique without damage by a keV low energy ion beam irradiation in reactive gas environments or reactive ion itself. 120 In-Ceram specimens were fabricated according to manufacturer's directions and divided into six groups by surface treatment methods of In-Ceram alumina core. SD group(control group): sandblasting SL group: sandblasting + silane treatment SC group: sandblasting + Siloc treatment IAR I group: sandblasting + Ion assisted reaction with argon ion and oxygen gas IAR II group: sandblasting + Ion assisted reaction with oxygen ion and oxygen gas IAR III group: sandblasting + Ion assisted reaction with oxygen ion only For measuring of tensile bond strength, pairs of specimens within a group were bonded with Panavia 21 resin cement using special device secured that the film thickness was 80micrometer. The results of tensile strength were statistically analyzed with the SPSS release version 8.0 programs. Physical change like surface roughness of In-Ceram alumina core treated by ion assisted reaction was evaluated by Contact Angle Measurement, Scanning Electron Microscopy, Atomic Force Microscopy; chemical surface change was evaluated by X-ray Photoelectron Spectroscopy. The results as follows: 1. In tensile bond strength, there were no statistically significant differences with SC group, IAR groups and SL group except control group(P<0.05). 2. Contact angle measurement showed that wettability of In-Ceram alumina core was enhanced after IAR treatment. 3. SEM and AFM showed that surface roughness of In-Ceram alumina core was not changed after IAR treatment . 4. XPS showed that IAR treatment of In-Ceram alumina core was enabled to create a new functional layer. A keV IAR treatment of In-Ceram alumina core could enhanced tensile bond strength with resin cement. In the future, this ion assisted reaction may be used effectively in various dental materials as well as in In-Ceram to promote the bond strength to natural tooth structure.

A STUDY ON THE MARGINAL FIT OF ALL-CERAMIC CROWN USING CCD CAMERA / 대한치과보철학회지

The purpose of this study was to evaluate marginal fit of four all-ceramic crown systems 1) conventional In-Ceram, 2) copy-milled In-Ceram using Celay system, 3) IPS Empress, 4) OPC(Optimal Pressable Ceramic). All ceramic crowns were made on epoxy dies. The fabricated crowns were sandblasted, cleaned with ultrasonic cleansing, silanated, and cemented with Bistite composite resin cement. The selected marginal areas of the crowns were the labial, lingual, mesial, and distal surface. Each selected area of surface was 0.6Xl.6mm in dimension. The image of each marginal area was captured to computer files using DT-55 Frame Grabber and light microscope connected CCD camera. The marginal gaps were measured every 70mm using computer image analysis program. The results obtained were summarized as follows : 1. The marginal fit of four all-ceramic crowns were significantly different from each other(p<0.01), and mean marginal fit values obtained were 31.42 +/- 16.52mm in conventional In-Ceram, 55.45 +/- 27.90mm in copy-milled In-Ceram using Celay-system, 44.36 +/- 24.59mm in IPS Empress, 47.21 +/- 20.42mm in OPC. 2. In the marginal fit of conventional In-Cerani and copy-milled In-Ceram crowns using Celay-system there was no significant difference between mesiodistal and buccolingual surface. but in the marginal fit of IPS Empress and OPC crowns, there was significant difference between mesiodistal and buccolingual surface(p <0.01). 3. The marginal fit of four hinds of all-ceramic crowns was clinically acceptable.

THE CLINICAL STUDY ON SHORT TERM PROGNOSIS OF IN-CERAM ALUMINA BRIDGE RESTORATION / 대한치과보철학회지

All ceramic restorations except In-Ceram Alumina system gave a good esthetics and an exellent marginal fidelity. The flexural strength of them had about 150MPa, so the indication is only single crown. By using In-ceram Alumina System(450MPa), it is thought to be possible to construct bridge for its high flexural strength. But the prognosis is unclear. The purposes of this study are to clear short term prognosis of In-Ceram bridge restorations, to elucidate its clinical significance. Among 22 In-Ceram Bridge restored in our department, 11 In-Ceram bridges with follow up were used. The period of placement is from 1 to 18 months. The results were as follow : 1. Among follow up 11 bridges, 2 bridges were fractured. One is 4 unit in maxillary lateral incisors, the other is 3 unit bridge in maxillary canine and premolar. Including 11 bridge without follow up, failure rate is very low(2/22). 2. The fracture sites are connector areas between abutment and pontic. To maintain In-Ceram bridge for long term period, it is needed to remove the nonphysiologic occlusal force and to have sufficient thickness of alumina core. For estabilishing clinical use of In-Ceram bridges, it is thought to need clinical research during long term period.

THE PHYSCIAL PORPERTIES OFY Y2O3-CONTAINING GLASS INFILTRATED ALUMINA CORE MADE BY PRESSURELESS POWDER PACKING METHOD / 대한치과보철학회지

The objective of this study was to characterize the mechanical properties of Y2O3-containing glass infiltrated ceramic core material, which was made by pressureless powder packing method. A pure alumina powder with a grain size of about 4micrometer was packed without pressure is silicon mold to form a bar shaped sample, and applied PVA solution as a binder. Samples were sinterd at 1350degrees C for 1 hour. After cooling, Y2O3-containing glass (SiO2, Y2O3, B2O3, Al2O3, ect) was infiltrated to the sinterd samples at 1300degrees C for 2 hours and cooled. Six different proportions Y2O3 of were used to know the effect of the mismatch of the thermal expansion coefficient between alumina powder and glass. The samples were ground to 3x3x30 mm size and polished with 1microneter diamond paste. Flexural strength, fracture toughness, hardness and other physical properties were obtained, and the fractured surface was examined with SEM and EPMA. Ten samples of each group were tested and compared with In-Ceram(TM) core materials of same size made in dental laboratory. The results were as follows : 1. The flexural strengths of group 1 and 3 were significantly not different with that of In-Ceram, but other experimental groups were lower than In-Ceram. 2. The shrinkage rate of samples was 0.42% after first firing, and 0.45% after glass infiltration. Total shrinkage rate was 0.87%. 3. After first firing, porosity rate of experimental groups was 50%, compared with 22.25% of In-Ceram. After glass infiltration, porosity rate of experimental groups was 2%, and 1% in In-Ceram. 4. There was no statistical difference in hardness between two materials tested, but in fracture toughness, group 2 and 3 were higher than In-Ceram. 5. The thermal expansion coefficients of experimental groups were varied to 4.51~5.35x10-6/degrees C according to glass composition, also the flexural strengths of samples were varied. 6. In a view of SEM, many microparticles about 0.5microneter diameter and 4microneter diameter were observed in In-Ceram. But in experimental group, the size of most particles was about 4microneter, and a little microparticles was observed. The results obtained in this study showed that the mismatch of the thermal expansion coefficients between alumina powder and infiltrated glass affect the flexural strength of alumin/glass composite. The Y2O3-containing glass infiltrated ceramic core made by powder packing method will takes less time and cost with sufficient flexural strength similar to all ceramic crown made with slip casting technique.