• Journal of Technologic Dentistry
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• v.33 no.3
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• pp.219-224
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• 2011

Purpose: The current study focused on investigating color change of dental zirconia block with respect to the block coloring time. Methods: Three types of dental zirconia blocks(Zirtooth, Pearl-HT, D-Max) were tinted with coloring agent under four different time condition (0 minutes, 1 minutes, 10 minutes, 30 minutes). The quantitative evaluation of the tinted dental zirconia blocks was conducted with spectrophotometer. Results: The Zirtooth and D-Max blocks showed lower H value. The Pearl-HT blocks showed poor reflectivity(L value). Conclusion: The study of color change of zirconia block, which consists the substructure of all ceramic Crown, is applicable for deciding appropriate coloring condition when fabricating one layer ceramic Crown or double layer ceramic Crown.

• Journal of Korean Dental Science
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• v.10 no.2
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• pp.74-81
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• 2017

This report describes two cases of complete arch implant-supported restorations. The first patient had seven dental implants in each arch with monolithic zirconia frameworks. At four weeks' follow-up, the one-piece maxillary framework was fractured, which was re-designed and re-fabricated using laser-sintered cobalt-chrome alloy. The second patient had four implants in the mandible only. A mandibular monolithic zirconia framework and a maxillary conventional complete denture were fabricated and delivered. At five years' follow-up, the patient reported no significant discomfort. Careful consideration and monitoring of the status of antagonistic arches and stress distribution on zirconia frameworks were suggested for complete arch implant-supported fixed restorations.

• Journal of Technologic Dentistry
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• v.38 no.3
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• pp.135-142
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• 2016

Purpose: The aim of this research was to evaluate the influence of different surface treatments on the shear bond strength of zirconia ceramic to composite resin. Methods: Seventy two cylinder-shape (diameter: 5 mm; height: 12 mm) blocks of experimental industrially manufactured Y-TZP ceramic were abraded with $125{\mu}m\;Al_2O_3$ particles and randomly divided into 4 groups. All the materials were categorized as group Gc(control group - composite resin veneering on zirconia surface), Gr - composite resin veneering after surface treatment of Rocatec system (3M ESPE, Seefeld, Germany) group; Gz - composite resin veneering after surface treatment of Zirconia primer (Z-primer, Bisco, U.S.A) group; Gm - composite resin veneering after surface treatment of zirconia primer (Monobond plus, ivoclar vivadent AG, Liechtenstein) group. Two different zirconia primers and Rocatec system were used to zirconia cylinders (n=16) onto the zirconia surface. Zirconia specimens, polished and roughened, were pretreated and composite bilayer cylinders bonded using conventional adhesive techniques. Results: Shear bond strengths were analyzed using single-factor ANOVA(p<0.05). Bond strength values achieved after airbone particle abrasion and zirconia surface pre-treatments(p<0.05). Conclusion: Shear bond strength tests denmonstrated that zirconia primer is a viable method to improved bond strength between zirconia ceramic core and veneering composites.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.24 no.2
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• pp.101-121
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• 2015

Zirconia polycrystalline (Y-TZP) showed better mechanical properties and superior resistance to fracture than other conventional dental ceramics. Zirconia-based ceramics have been successfully introduced into the clinic to fabricate fixed dental prostheses (FDPs), along with a dental computer-aided/computer-aided manufacturing (CAD/CAM) system. It has been clinically available as an alternative to the metal framework for fixed dental prostheses (FDPs). The most frequent clinical complication with zirconia-based FDPs was chipping of the veneering porcelain that was affected by many factors. Another option was full-contour zirconia FDPs using high translucent zirconia. Full-contour zirconia FDPs has many clinical advantages but it caused concern about the wear of antagonist enamel, because the hardness of Y-TZP was over double that of porcelain. However, many articles demonstrates that highly polished zirconia yielded lower antagonist wear compared with porcelains. In this article (1) advantages of full zirconia restorations, (2) clinical applications of zirconia restorations, (3) abutment preparation, (4) surface finish of zirconia restoration and antagonist enamel wear, (5) bond of zirconia with resin-based luting agents, (6) communication in clinical & lab.procedures for full zirconia restorations are reviewed.

• The Journal of the Korean dental association
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• v.49 no.5
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• pp.260-264
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• 2011

Zirconia ($ZrO_2$) is a crystalline dioxide of zirconium. Dental zirconia blocks for CAD/CAM are usually fabricated with powders of tetragonal zirconia polycrystals (TZP) stabilized with 3mol% yttria. Because of its mechanical properties similar to those of metals and color similar to tooth, it is evaluated to attain the two purposes at a time, strength and aesthetic in prosthetic dentistry. The ability of transformation of Y-TZP from tetragonal to monoclinic helps to prevent crack propagation and contributes the increase of strength and fracture toughness. Two different types of blocks, soft and hard, are used to prepare the zirconia frameworks. The fuzzy-sintered block is difficult in machining, so pre-sintered soft 3Y-TZP block is usually used to mill by computer aided machining.

• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.41-47
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• 2008

This study was to evaluate the biaxial flexural strength of zirconia ceramics after glass-infiltration on zirconia core. The zirconia specimens were made with diameter-15mm, thickness-0.6mm using zirconia block which divided into 1) sintered group, 2) heat - treated group, 3) Glass - infiltrated group and experimented fracture strength by each 10 specimens in experimental group. The biaxial flexural test was performed at crosshead speed of 0.1${\beta}\;{\AE}$ min. The experiment result average fracture strength was shown 541.0${\beta}\acute{A}$ in sintered group and glass-infiltrated group as 662.2${\beta}\acute{A}$ river of 22.4% rise appear. Weibull coefficient sintered group is 3.462 and glass-infiltrated group improved believability about fracture strength from melting permeation processing of glass by 4.716.

• Journal of Technologic Dentistry
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• v.33 no.2
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• pp.137-145
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• 2011

Purpose: To evaluate the accuracy of zirconia copings in terms of clinical verified for the clinical application of CAD/CAM. Methods: Zirconia copings (n=5) were prepared using CAD/CAM system and were sintered using the relevant electrical induction furnace, which uses a 2h sintering program with a maximum temperature of $1500^{\circ}C$. The copings placed at the models and the interval values were measured. Results: The meas interval values between the die and the zirconia copings were $44.14{\mu}m$(A), $44.57{\mu}m$(B), $44.72{\mu}m$(C). 51.05 ${\mu}m$(D). Conclusion: The maximum interval values between the die and the zirconia copings were $51.3{\mu}m$ which is acceptable for clinical use. ${\mu}m$ Proper understanding of the test conditions will help enhancing the accuracy of zirconia coping.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.456-461
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• 2014

PURPOSE. Translucency and colour stability are two most important aspects for an aesthetic dental restoration. Glass ceramic restorations are popular amongst clinicians because of their superior aesthetic properties. In the last decade, zirconia has generated tremendous interest due to its favorable mechanical and biological properties. However, zirconia lacks the translucency that lithium disilicate materials possess and therefore has limitations in its use, especially in esthetically demanding situations. There has been a great thrust in research towards developing translucent zirconia materials for dental restorations. The objective of the study was to evaluate and compare the transmittance of a translucent variant of zirconia to lithium disilicate. MATERIALS AND METHODS. Two commercially available zirconia materials (conventional and high translucency) and 2 lithium disilicate materials (conventional and high translucency) with standardized dimensions were fabricated. Transmittance values were measured for all samples followed by a microstructural analysis using a finite element scanning electron microscope. One way analysis of variance combined with a Tukey-post hoc test was used to analyze the data obtained (P=.05). RESULTS. High translucency lithium disilicate showed highest transmittance of all materials studied, followed by conventional lithium disilicate, high translucency zirconia and conventional zirconia. The difference between all groups of materials was statistically significant. The transmittance of the different materials correlated to their microstructure analysis. CONCLUSION. Despite manufacturers' efforts to make zirconia significantly more translucent, the transmittance values of these materials still do not match conventional lithium disilicate. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.

• Journal of Technologic Dentistry
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• v.41 no.2
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• pp.93-100
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• 2019

Purpose: This study is making a dog dental prosthesis using digital dental technology. The mechanical strength of the prosthetic material was observed in terms of compressive strength and fracture pattern. Methods: The experiment was performed using dog mandibular molars. The teeth were scanned and modeled. The specimens were made of zirconia, PMMA and Ni-Cr. The specimens were subjected to a vertical compression test with an artificial cancellous bone in UTM tester. Vertical compressive strength and fracture behavior of specimen were observed. Results: The result of observing the compressive load between specimen and artificial bone were $184.8{\pm}5.7N$ in the zirconia specimen, $185.6{\pm}8.9N$ in the PMMA specimen, and $184.4{\pm}4.0N$ in the Ni-Cr alloy specimen. Compression marks of artificial bones were observed. The fracture strength of specimen was observed. The fracture strength of the zirconia specimen was an average of 1,381.4N. The fracture strength of the PMMA specimen was an average of 572.2N. Conclusion: The crown made of three kinds(zirconia, PMMA, Ni-Cr alloy) of materials has the strength to chew about the artificial bone. zirconia and PMMA have vertical compressive strength applicable to medium dog dental prosthetic materials.

• Journal of Technologic Dentistry
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• v.33 no.4
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• pp.283-289
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• 2011

Purpose: The purpose of this study was to evaluate flexural strength of full zirconia crown using block after clinical work. Methods: The three point bending test was used to measure the flexural strength of zirconia block. Statistical analysis was done using the Statistical Package for Social Sciences version 19.0 for Windows. As for the analysis methods, the study used analysis of variance, Tukey's test. Results: The ave Rage value of flexural strengths of WIELAND, Zirkonzahn, Hass, D-MAX were 516.2 MPa, 612.6MPa, 566.2MPa, 744.6MPa. The ave Rage value of Surface Roughness of WIELAND, Zirkonzahn, Hass, D-MAX were 0.39Ra, 0.33Ra, 0.33Ra, 0.47Ra. Conclusion: Flexural strength of zirconia block decreased after clinical work. Flexural strength of zirconia block is equal to or higher than flexural strength of dental metal, so zirconia block can be used as dental material.