All Ceramic Materials in Dentistry: Past, Present and Future: A Review

Fixed partial dentures (FPDs) with high-strength all-ceramicsystems are necessary for replacing missing teeth. Widerange of materials and methods are available to fabricate arestoration outside the mouth and subsequently integratewith a tooth. The traditional methods of ceramic fabricationhave been described to be time-consuming, techniquesensitive, and rather unpredictable due to the many variablespresent which affect the outcome. All-ceramic restorations,has become a segment of dentistry which has experiencedtremendous improvements in the recent years. The increasinguse of polycrystalline alumina and zirconia as frameworkmaterials and the increasing popularity and variety ofcomputer-aided design and computer-aided manufacturing(CAD-CAM) systems seem to be mutually accelerating trendsover the last three decades. This article presents a review ofthe development of all-ceramic restorations, including theevolution and development of materials, technologies andhow to improve the strength of all-ceramic restorations, withrespect to survival, applications, strength, color, and aesthetics.The literature demonstrates that multiple all-ceramic materialsand systems that are currently available for clinical use andconcludes there is not a single universal material or, systemavailable to suit for all clinical situations.

The treatment of an edentulous patient with conventional complete denture and CAD/CAM complete denture / 대한치과보철학회지

In patients with fully edentulous jaw, treatment of complete dentures should be carried out in many stages when following the conventional methods. Therefore there were disadvantages such as multiple visits to dental clinic is inevitable. In addition, errors caused by polymerization shrinkage, which happens during the fabrication of denture, and difficulties in reproduction of damaged or lost denture were considered as disadvantages. But nowadays, computer-aided design and computer-aided manufacturing (CAD/CAM) system is widely used in dentistry and it has begun to expand its spectrum in manufacturing complete dentures. Using CAD/CAM system to fabricate complete dentures can reduce the number of patient's visit and clinical chair time, since taking impression, recording jaw relation, and selection of artificial teeth are performed at the same time during the first visit, and delivering of dentures during the second visit is possible. In addition, because 3D-Printing technology is used, errors by polymerization shrinkage can be reduced. Among the companies that fabricate complete dentures using CAD/CAM system, DENTCA CAD/CAM denture (DENTCA Inc., Los Angeles, CA, USA) is the most commercialized company. In this case, we treated patients of complete dentures using conventional complete denture method and DENTCA CAD/CAM denture system in the same patient. We would like to report this case because we have achieved good results not only in functional aspects of pronunciation, chewing, and swallowing but also in aesthetic aspects.

Clinical effect of resin hybrid ceramic onlay in repairing posterior tooth defects / 口腔疾病防治

Objective@#To investigate the clinical effect of restoration of posterior teeth with machinable CAD/CAM resin hybrid ceramic (VITA Enamic) onlays after root canal treatment. @* Methods @#136 posterior teeth restored after root canal treatment in our hospital were selected as the research subjects. The posterior teeth were restored chairside with CAD / CAM ceramic onlays to recover occlusion relation and protect residual dental tissues. With 68 teeth in each group, one group was restored with a machinable CAD / CAM resin hybrid ceramic (VITA Enamic) while the control group received zirconia-reinforced lithium silicate ceramic (VITA Suprinity). Before bonding, all the onlays were examined for good adjacency, fitness and occlusion, and then the adhesive surface was etched with hydrofluoric acids. After isolating the rubber dams in the mouths, the onlays were bonded with dual-cure resin cements. The patients were followed up for 24 months to compare the degree of prosthesis integrity, marginal fitness, gingival health, dental integrity, color matching and secondary caries. @* Results @#After restoration, all the onlays were in harmony with the surrounding teeth with good aesthetic effect and suitable marginal fit. Two years later, there were no significant differences in the marginal fitness, gingival health, dental integrity or secondary cavities between the two groups (P > 0.05). In terms of restoration integrity, the VITA Enamic onlays (100%) were intact and displayed good retention. The group that received VITA Suprinity had 6 onlay (9.23%) fractures and a success rate of 90.77%; however, the residual dental tissues did not break. The difference of prosthesis integrity between the two groups was statistically significant (χ2= 4.45, P < 0.05). @*Conclusion@#Chairside CAD/CAM resin hybrid ceramic (VITA Enamic) onlays can quickly restore posterior teeth after root canal therapy and better protect the residual dental tissue.

Three-dimensional evaluation of the machinability of monolithic CAD/CAM-generated posterior crowns by nano-hybrid ceramic / 대한치과재료학회지

The purpose of this study comparatively analyzed the machinability of various dental hybrid blocks manufactured by using the CAD/CAM system. Three hybrid composite blocks (Vita enamic, Lava Ultimate, GC Cerasmart) were used for experimental groups and one conventional ceramic block (Vita Mark II) was used for control. The digital impression of the master model and abutment was taken by using a scanner, and then the CAD software program was used to design restorations. The four-axis milling machine (inLab MCXL; Sirona Dental Systems GmbH, Bensheim, Germany) was used four materials. The digitized data was superimposed with 3D inspection software to quantitatively obtain the machinability of a ceramic crown, and visual differences were confirmed with a color map. The root mean square (RMS) values of ceramic crown group were statistically analyzed with one-way ANOVA (α=0.05). While there was a significant difference in the machinability of the internal surface, among four groups, there was statistically significant difference between conventional (VM group) and hybrid ceramic (VE, LU, GC groups) (p<0.05). Consequently, the machinability of VM is lower than that of other hybrid ceramics, and the machinability of VE is better than that of LU and GC. For ceramics as final restorations, manufacturing of dental restorations using hybrid composite ceramic is recommended.

Accuracy of provisional crowns made using stereolithography apparatus and subtractive technique

PURPOSE: To compare and analyze trueness and precision of provisional crowns made using stereolithography apparatus and subtractive technology. MATERIALS AND METHODS: Digital impressions were made using a master model and an intraoral scanner and the crowns were designed with CAD software; in total, 22 crowns were produced. After superimposing CAD design data and scan data using a 3D program, quantitative and qualitative data were obtained for analysis of trueness and precision. Statistical analysis was performed using normality test combined with Levene test for equal variance analysis and independent sample t-test. Type 1 error was set at 0.05. RESULTS: Trueness for the outer and inner surfaces of the SLA crown (SLAC) were 49.6±9.3 µm and 22.5±5.1 µm, respectively, and those of the subtractive crown (SUBC) were 31.8±7.5 µm and 14.6±1.2 µm, respectively. Precision values for the outer and inner surfaces of the SLAC were 18.7±6.2 µm and 26.9±8.5 µm, and those of the SUBC were 25.4±3.1 µm and 13.8±0.6 µm, respectively. Trueness values for the outer and inner surfaces of the SLAC and SUBC showed statistically significant differences (P < .001). Precision for the inner surface showed significance (P < .03), whereas that for the outer surface showed no significance (P < .58). CONCLUSION: The study demonstrates that provisional crowns produced by subtractive technology are superior to crowns fabricated by stereolithography in terms of accuracy.

Accuracy evaluation of dental models manufactured by CAD/CAM milling method and 3D printing method

PURPOSE: To evaluate the accuracy of a model made using the computer-aided design/computer-aided manufacture (CAD/CAM) milling method and 3D printing method and to confirm its applicability as a work model for dental prosthesis production. MATERIALS AND METHODS: First, a natural tooth model (ANA-4, Frasaco, Germany) was scanned using an oral scanner. The obtained scan data were then used as a CAD reference model (CRM), to produce a total of 10 models each, either using the milling method or the 3D printing method. The 20 models were then scanned using a desktop scanner and the CAD test model was formed. The accuracy of the two groups was compared using dedicated software to calculate the root mean square (RMS) value after superimposing CRM and CAD test model (CTM). RESULTS: The RMS value (152±52 µm) of the model manufactured by the milling method was significantly higher than the RMS value (52±9 µm) of the model produced by the 3D printing method. CONCLUSION: The accuracy of the 3D printing method is superior to that of the milling method, but at present, both methods are limited in their application as a work model for prosthesis manufacture.

Sistema CAD-CAM: a tecnologia na confecção de próteses / CAD-CAM System: the technology in the manufacture of prostheses

Introdução: através da introdução na odontologia do sistema CAD- -CAM simplificou-se o sistema de moldagem de próteses, que apresenta uma margem de erro por conter variáveis a serem controladas em relação aos materiais e sua manipulação. Objetivo: este artigo aborda o desenvolvimento do sistema CAD-CAM, como também a engenharia, os programas e as diretrizes de seu funcionamento na confecção de próteses dentárias. Materiais e métodos: o estudo caracterizou-se por uma pesquisa científica e bibliográfica nas plataformas indexadas nas bases de dados PubMED/Medline, Lilacs e Scielo, incluindo artigos originais e de revisão. Utilizou-se os seguintes descritores: Sistema CAD-CAM, CAD-CAM tecnologia no desenvolvimento de próteses, CAD-CAM system. Resultados: tecnologia CAD-CAM surgiu para facilitar o planejamento, o designer e a produção de vários projetos. Quando foi introduzida na odontologia trouxe um marco que revolucionou a forma de confeccionar restaurações, incluindo as protéticas. Sendo desenvolvido por várias empresas, está disponível em diferentes sistemas que, no entanto, se resumem no mesmo funcionamento: digitalização, designer e usinagem, no qual se obtém a imagem através de um escaneamento, manipula-se essa imagem em um software e finalmente converte-se essa imagem em um objeto real, como exemplo em: coroas, pontes, facetas, inlays, onlays e laminados. Conclusão: tendo em vista que essa tecnologia trouxe melhoria para a odontologia protética, na estética, resistência e durabilidade da restauração produzida, melhora a qualidade da saúde bucal oferecida para o paciente e facilita o trabalho do dentista.

Introduction: through the introduction of the CAD-CAM system, the prosthesis molding system has been simplified, which has a margin of error because it contains variables to be controlled in relation to materials and their manipulation. Objective: this article addresses the development of the CAD-CAM system, as well as the engineering, programs and guidelines of its operation in the manufacture of dental prostheses. Methods: this study was characterized by a scientific and bibliographic research in the platforms indexed in PubMED / Medline, Lilacs and Scielo databases, including original and review articles. The following descriptors were used: CAD-CAM system, CAD-CAM technology in prosthesis development, CAD-CAM system. Results: CAD-CAM technology has emerged to facilitate planning, design and production of various projects. When introduced to dentistry brought a landmark that revolutionized the way to make restorations, including prosthetics. Being developed by several companies, it is available in different systems which, however, are summarized in the same operation: digitization, designer and machining, in which the image is obtained through a scan, manipulate that image in a software and finally, this image in a real object, such as: crowns, bridges, facets, inlays, onlays and laminates. Conclusion: since this technology has brought improvement to the prosthetic dentistry, in the esthetics, resistance and durability of the restoration produced, improves the quality of oral health offered to the patient and facilities the work of the dentist.

Accuracy evaluation of metal copings fabricated by computer-aided milling and direct metal laser sintering systems

PURPOSE: To assess the marginal and internal gaps of the copings fabricated by computer-aided milling and direct metal laser sintering (DMLS) systems in comparison to casting method. MATERIALS AND METHODS: Ten metal copings were fabricated by casting, computer-aided milling, and DMLS. Seven mesiodistal and labiolingual positions were then measured, and each of these were divided into the categories; marginal gap (MG), cervical gap (CG), axial wall at internal gap (AG), and incisal edge at internal gap (IG). Evaluation was performed by a silicone replica technique. A digital microscope was used for measurement of silicone layer. Statistical analyses included one-way and repeated measure ANOVA to test the difference between the fabrication methods and categories of measured points (alpha=.05), respectively. RESULTS: The mean gap differed significantly with fabrication methods (P<.001). Casting produced the narrowest gap in each of the four measured positions, whereas CG, AG, and IG proved narrower in computer-aided milling than in DMLS. Thus, with the exception of MG, all positions exhibited a significant difference between computer-aided milling and DMLS (P<.05). CONCLUSION: Although the gap was found to vary with fabrication methods, the marginal and internal gaps of the copings fabricated by computer-aided milling and DMLS fell within the range of clinical acceptance (<120 microm). However, the statistically significant difference to conventional casting indicates that the gaps in computer-aided milling and DMLS fabricated restorations still need to be further reduced.

Accuracy evaluation of metal copings fabricated by computer-aided milling and direct metal laser sintering systems

PURPOSE: To assess the marginal and internal gaps of the copings fabricated by computer-aided milling and direct metal laser sintering (DMLS) systems in comparison to casting method. MATERIALS AND METHODS: Ten metal copings were fabricated by casting, computer-aided milling, and DMLS. Seven mesiodistal and labiolingual positions were then measured, and each of these were divided into the categories; marginal gap (MG), cervical gap (CG), axial wall at internal gap (AG), and incisal edge at internal gap (IG). Evaluation was performed by a silicone replica technique. A digital microscope was used for measurement of silicone layer. Statistical analyses included one-way and repeated measure ANOVA to test the difference between the fabrication methods and categories of measured points (alpha=.05), respectively. RESULTS: The mean gap differed significantly with fabrication methods (P<.001). Casting produced the narrowest gap in each of the four measured positions, whereas CG, AG, and IG proved narrower in computer-aided milling than in DMLS. Thus, with the exception of MG, all positions exhibited a significant difference between computer-aided milling and DMLS (P<.05). CONCLUSION: Although the gap was found to vary with fabrication methods, the marginal and internal gaps of the copings fabricated by computer-aided milling and DMLS fell within the range of clinical acceptance (<120 microm). However, the statistically significant difference to conventional casting indicates that the gaps in computer-aided milling and DMLS fabricated restorations still need to be further reduced.

Evaluation of different approaches for using a laser scanner in digitization of dental impressions

PURPOSE: This study aimed to investigate the potential clinical application of digitized silicone rubber impressions by comparing the accuracy of zirconia 3-unit fixed partial dentures (FPDs) fabricated from 2 types of data (working model and impression) obtained from a laser scanner. MATERIALS AND METHODS: Ten working models and impressions were prepared with epoxy resin and vinyl polysiloxane, respectively. Based on the data obtained from the laser scanner (D-700; 3Shape A/S, Copenhagen, Denmark), a total of 20 zirconia frameworks were prepared using a dental CAD/CAM system (DentalDesigner; 3shape A/S, Copenhagen, Denmark / Ener-mill, Dentaim, Seoul, Korea). The silicone replicas were sectioned into four pieces to evaluate the framework fit. The replicas were imaged using a digital microscope, and the fit of the reference points (P1, P2, P3, P4, P5, P6, and P7) were measured using the program in the device. Measured discrepancies were divided into 5 categories of gaps (MG, CG, AWG, AOTG, OG). Data were analyzed with Student's t-test (alpha=0.05), repeated measures ANOVA and two-way ANOVA (alpha=0.05). RESULTS: The mean gap of the zirconia framework prepared from the working models presented a narrower discrepancy than the frameworks fabricated from the impression bodies. The mean of the total gap in premolars (P=.003) and molars (P=.002) exhibited a statistical difference between two groups. CONCLUSION: The mean gap dimensions of each category showed statistically significant difference. Nonetheless, the digitized impression bodies obtained with a laser scanner were applicable to clinical settings, considering the clinically acceptable marginal fit (120 microm).

Comparison of compressive strength and fracture mode between four kinds of CAD/CAM zirconia / 医用生物力学

Objective To analyze the compressive strength and fracture mode between four kinds of dental zirconia CAD/CAM ceramic materials by Hertzian contact test. Methods Four CAD/CAM ceramic materials including Cercon smart, Lava, Porcera, and CEREC 3 were selected. Six zirconia sectioned flat specimens were prepared in each group. The critical load and fracture load as well as the fracture mode for each specimen were analyzed with digital image correlation (DIC) technique. Results It was found that cracks were initiated at the middle level of the veneer below the contact zone and propagating along an arc curve into the core/veneer interface, which eventually caused the debonding of the core/veneer layers. For the four ceramic systems, there were no significant differences in the critical load（P＞0.05）, while there were significant differences in the fracture load（P＜0.05）. Conclusions The compressive strength of the four zirconia CAD/CAM ceramic materials could substantially meet the clinic requirement for oral functions regarding the maximum occlusal load. Crack initiation and complete fracture only occurred in the veneer, which indicated that the strength of the veneer should be further reinforced.

A comparison of the fidelity of various zirconia-based all-ceramic crowns fabricated with CAD/CAM systems / 대한치과보철학회지

STATEMENT OF PROBLEM: The interest in all-ceramic restorations has increased as more techniques have become available. With the introduction of machinable dental ceramics and CAD/CAM systems there is a need to evaluate the quality levels of these new fabrication techniques. PURPOSE: This study is to evaluate the crown fidelity (absolute marginal discrepancy and internal gap) of various zirconia-based all-ceramic crowns fabricated with different CAD/CAM (computer-assisted design/computer-assisted manufacturing) systems and conventional cast metal-ceramic crowns. MATERIAL AND METHODS: A resin tooth of lower right second premolar was prepared. After an impression was taken, one metal master die was made. Then 40 impressions of metal master dies were taken for working dies. 10 crowns per each system were fabricated using 40 working dies. Metal-ceramic crowns were cast by using the conventional method, and Procera, Lava, and Cerec inLab crowns were fabricated with their own CAD/CAM manufactruing procedures. The vertical marginal discrepancies and internal gaps of each crown groups were measured on a metal master die without a luting agent. The results were statistically analyzed using the one-way ANOVA and Tukey's HSD test. RESULTS: 1. Vertical marginal discrepancies were 50.6 +/- 13.9 micrometer for metal-ceramic crowns, 62.3 +/- 15.7 micrometer for Procera crowns, 45.3 +/- 7.9 micrometer for Lava crowns, and 71.2 +/- 2.0 micrometer for Cerec inLab crowns. 2. The Internal gaps were 52.6 +/- 10.1 micrometer for metal-ceramic crowns, 161.7 +/- 18.5 micrometer for Procera crowns, 63.0 +/- 10.2 micrometer for Lava crowns, and 73.7 +/- 10.7 micrometer for Cerec inLab crowns. CONCLUSION: 1. The vertical marginal discrepancies of, 4 crown groups were all within the clinically acceptable range (120 micrometer). 2. The internal gaps of LAVA, Cerec inlab, and metal-ceramic crowns were within clinically acceptable range except Procera crown (140 micrometer).

A comparison of the fidelity between various cores fabricated with CAD/CAM systems / 대한치과보철학회지

STATEMENT OF PROBLEM: Recently, various all-ceramic crowns fabricated with CAD/CAM systems have come into wide use in dental clinic. However, there are only few domestic studies on CAD/CAM restorations. PURPOSE: Purpose of this study was to compare the fidelity (absolute marginal discrepancy and internal gap) between various cores fabricated with different CAD/CAM systems (Procera system, Lava system, Cerec inLab system) and conventional metal cast core. MATERIALS AND METHODS: 10 cores per each system were fabricated. The absolute marginal discrepancies were measured using measuring microscope and digital counter. The internal gaps were calculated using a silicone paste. The results were statistically analyzed using the one-way ANOVA test and Tukey's HSD test. RESULTS: Within the limits of this study the results were as follows. 1. The absolute marginal discrepancies were 32.5+/-3.7 micrometer for metal cast core, 72.2+/-7.0 micrometer for Procera core, 40.8+/-5.4 micrometer for Lava core, and 55.3+/-8.7 micrometer for Cerec inLab core. The internal gaps were 38.4+/-5.7 micrometer for metal cast core, 71.4+/-5.3 micrometer for Procera core, 45.9+/-7.3 micrometer for Lava core, and 51.8+/-6.2 micrometer for Cerec inLab core. 2. The fidelity of metal cast core showed the smallest gaps, followed by Lava core, Cerec inLab core, and Procera core. CONCLUSION: The fidelities of 4 core groups were all within the clinically acceptable range (120 micrometer).

Comparative study in marginal adaptation of zirconia cores fabricated with 3 different CAD/CAM systems / 대한치과보철학회지

STATEMENT OF PROBLEM: There have been many studies about marginal adaptation of Zirconia core fabricated with various CAD/CAM systems. But, the comparative study has not been conducted much. PURPOSE: This study was to compare marginal adaptations of zirconia cores fabricated with 3 different CAD/CAM systems. MATERIAL AND METHODS: The in vitro marginal adaptations of zirconia cores fabricated with 3 different CAD/CAM systems(Adens(R) system, Lava(R) system, and Cerasys(R) system) were evaluated and compared. In this study 30 zirconia cores were fabricated(10 zirconia cores per each system). The measurements of the marginal adaptatioin were carried out using microscope L-150A(R)(Nikon, Japan). Measurements were recorded at 50 points. The measurements were analyzed using Kruskal-Wallis test and Wilcoxon rank sum test. RESULTS: Within the limits of this study, the results were as follows. 1. Mean marginal gap values obtained were 284.5+/-152.9 micrometer in Adens(R) system, 99.0+/-73.0 micrometer in Lava(R) system, and 153.5+/-85.7 micrometer in Cerasys(R) system. 2. Zirconia core made by Lava(R) system showed the smallest marginal gap(P<0.05). CONCLUSION: In the limitation of this study, we concluded that Lava(R) System was superior than other systems(Adens(R) system and Cerasys(R) system) in the marginal adaptation.

Comparative study in fracture strength of zirconia cores fabricated with three different CAD/CAM systems / 대한치과보철학회지

PURPOSE: The purpose of this study is to compare three different CAD/CAM systems through the fracture strength of zirconia core and to evaluate the clinical availability of each system. MATERIAL AND METHODS: The following three groups of 30 maxillary mesial incisor core for all-ceramics(each group 10) were fabricated as follows: group 1. Adens(R) CAD/CAM system, group 2. Cerasys(R) CAD/CAM system, group 3. 3M LAVA(R)CAD/CAM system. All specimens were manufactured consistently thickness 0.5mm and relief 40 micrometer. Specimens were subjected to compressive loading on the lingual area by Z250/SN5S(R). Each group's mean and standard deviation were calculated and Kruskal Waillis test, Wilcoxon Rank Sum test were utilized to find out the relationship among the groups. RESULTS: The results were as follows: 1. The mean fracture strength of Adens(R) system was 615.89+/-156.1N, the Cerasys(R) system was 863.98+/-151.5N, and the 3M LAVA(R) system was 1143.1+/-286.6N. 2. The fracture strength of the systems showed the significant statistical differences in order of 3M LAVA(R) system, Cerasys(R) system, Adens(R) system. CONCLUSION: In this study, in spite of the differences among the groups, every group showed clinically useful results. It is necessary to study further clinical experiments on a long term basis.

Fracture strength between different connector designs of zirconia core for posterior fixed partial dentures manufactured with CAD/CAM system / 대한치과보철학회지

Statements of problem: Zirconia core is used for posterior fixed partial dentures because it's good mechanical properties. Stress is concentrated on connectors in fixed partial dentures, so the proper design of connector areas is needed for adequate mechanical long-term properties of any prosthesis. The area of connector is critical, but tooth size and surrounding soft tissue limit the connector design. PURPOSE: The purpose of this study is to compare fracture strengths between different connector designs of zirconia core for posterior fixed partial dentures manufactured with CAD/CAM system and determining the optimal connector design satisfying strength and hygiene. MATERIAL AND METHOD: The following four groups of 40 posterior fixed partial denture specimens(each group 10) were fabricated as followed; group 1, vertical height of connector is 3mm(control group, all groups have the same condition); group 2, lingual vertical 1mm reinforcement on connector; group 3, lingual vertical 2mm reinforcing on connector and group 4, lingual vertical 3mm reinforcing on connector. Specimens were subjected to compressive loading on the central fossa of pontic by instron. SEM was used to identify the initial crack and characterize the fracture mode. RESULTS: The results were as follows: 1. The mean fracture load of the non-lingual reinforcing group was 1212N and the lingual vertical 1mm reinforcing group was 1510N, the lingual vertical 2mm reinforcing group was 1882N, the lingual vertical 3mm reinforcing group was 1980N. 2. The reinforcing groups were statistically significant compared to non-reinforcing groups(P0.05) 4. Fractures were initiated in gingival embrasures of connectors and processed to the loading site. CONCLUSION: In this study, lingual reinforcement of connector for improved strength of zirconia based fixed partial denture is nessasary. And long-term study for clinical application is required.

Fracture strength between different connector designs of zirconia core for posterior fixed partial dentures manufactured with CAD/CAM system / 대한치과보철학회지

Statements of problem: Zirconia core is used for posterior fixed partial dentures because it's good mechanical properties. Stress is concentrated on connectors in fixed partial dentures, so the proper design of connector areas is needed for adequate mechanical long-term properties of any prosthesis. The area of connector is critical, but tooth size and surrounding soft tissue limit the connector design. PURPOSE: The purpose of this study is to compare fracture strengths between different connector designs of zirconia core for posterior fixed partial dentures manufactured with CAD/CAM system and determining the optimal connector design satisfying strength and hygiene. MATERIAL AND METHOD: The following four groups of 40 posterior fixed partial denture specimens(each group 10) were fabricated as followed; group 1, vertical height of connector is 3mm(control group, all groups have the same condition); group 2, lingual vertical 1mm reinforcement on connector; group 3, lingual vertical 2mm reinforcing on connector and group 4, lingual vertical 3mm reinforcing on connector. Specimens were subjected to compressive loading on the central fossa of pontic by instron. SEM was used to identify the initial crack and characterize the fracture mode. RESULTS: The results were as follows: 1. The mean fracture load of the non-lingual reinforcing group was 1212N and the lingual vertical 1mm reinforcing group was 1510N, the lingual vertical 2mm reinforcing group was 1882N, the lingual vertical 3mm reinforcing group was 1980N. 2. The reinforcing groups were statistically significant compared to non-reinforcing groups(P0.05) 4. Fractures were initiated in gingival embrasures of connectors and processed to the loading site. CONCLUSION: In this study, lingual reinforcement of connector for improved strength of zirconia based fixed partial denture is nessasary. And long-term study for clinical application is required.

Three-dimensional analysis of the normal dentition and edentulous maxilla of Koreans / 대한치과보철학회지

STAEMENT OF PROBLEM: In Korea, the preliminary impression trays for dental and edentulous maxillae are manufactured on the base of the statistical value of Westerners. There had been less study on the dental and edentulous arches of Koreans. PURPOSE: The purpose of this study was to evaluate an average dental cast, preliminary impression trays, three-dimensional relation of dental and edentulous maxilla of Koreans. MATERIAL AND METHODS: The subjects for this study were 173 dental casts of maxilla (dental: 52, edentulous: 146) with ages 18~60 years old. Each of the master casts was measured 69 measuring points on the dental cast of maxilla, and 46 measuring points on the edentulous cast of maxilla with three-dimensional digital measuring machine. Each measuring points were analysed and were overlapped, that three dimensional dental graphic manufactured by CAD/CAM system. RESULTS: 1. A standard of distribution to alveolar bone were width between left and right buccal border lines of the standard 3/4 line. The mean value of dental and edentulous casts were 67.27mm, 63.49mm, respectively. 2. Morphological classification of dental casts were divided into three groups of V-shape, O-shape, U-shape, that proportion of distribution were 17%, 16%, 67%, respectively. Dimensional classification of the dental casts were divided into five groups of less than 63mm, 63 up to 65mm, 65 up to 67mm, 67 up to 69mm, more than 69mm, respectively. 3. Morphological classification of edentulous casts were divided into three groups of V-shape, O-shape, U-shape, that proportion of distribution were 18%, 17%, 65%, respectively. Dimensional classification of the edentulous casts were divided into five groups of less than 57mm, 57 up to 61mm, 61 up to 65mm, 65 up to 69mm, more than 69mm, respectively. 4. Mean dental and edentulous cast of maxilla were overlapped, the proportion of bone resorption to alveolar bone is higher than that of palatal bone, its difference were higher anterior 2/4 area than posterior 3/4 area. CONCLUSION: It obtains information of preliminary impression trays for dental and edentulous maxilla of Koreans.

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)