• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.92-97
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• 2013

PURPOSE. All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident. MATERIALS AND METHODS. Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns. RESULTS. The mean fracture strengths were as follows: $54.9{\pm}15.6$ N for the Lava CAD/CAM zirconia crowns and $87.0{\pm}16.0$ N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (P<.001). Lava CAD/CAM zirconia crowns showed a complete fracture of both the veneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain. CONCLUSION. The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.3
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• pp.246-251
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• 2014

In case of prosthesis fabrication by CAD/CAM, location, area and contour of occlusal contacts can be adjusted so more functional occlusion can be acquired. Also, errors in a manufacturing process is reduced compared to cast metal prostheses and porcelain fused metal prostheses fabricated by conventional methods such as casting and porcelain build up. Therefore, prostheses by CAD/CAM show superior occlusion accuracy. Recently, virtual articulator function has been introduced to CAD/CAM system, which reproduces mandibular movement against maxilla. Thus, it is possible to consider occlusal interference in anterior/lateral movement as well as closing movement. There have been many studies on the marginal and internal fit of prostheses using zirconia but the occlusal fit of zirconia crown fabricated by CAD/CAM has not been researched as much. In this case report, 7 zirconia crowns were designed and fabricated by CAD/CAM for total 5 patients. The models of zirconia crowns before and after occlusal adjustment during intraoral try-in were scanned for occlusal contacts, which were compared to evaluate accuracy of prostheses and understand patterns of occlusal adjustment. Most of the occlusal adjustments were done on functional cusps and slopes of zirconia crown, and the magnitude of occlusal adjustment ranged from $15{\mu}m$ to $60{\mu}m$. In the zirconia crown fabricated with CAD/CAM systems, the occlusal adjustment is a necessary procedure, so additional procedures will be needed for compensating reduced mechanical properties.

• 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.

• Journal of Technologic Dentistry
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• v.30 no.2
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• pp.65-69
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• 2008

Recently, zirconia is widely used in the field of dental ceramics thanks to the proliferation of CAD/CAM systems. Accordingly, different types of zirconia block are being solid in the market. However, there are no precise, objective standards for properties of zirconia. This study concerns the flexural strength of zirconia ceramic for CAD/CAM block. The test specimens used for this study were ZirBlank(Acucera), ZirBlank shade(Acucera), VITA, Cercon(Densply) and Cerasys. The test results suggest that ZirBlank shade block shows the highest flexural strength and density among the zirconia blocks tested. Its flexural strength was $971{\pm}58MPa$ and its density was 99.89%. On the other hand, Cerasys block shows the lowest flexural strength of $576{\pm}36MPa$ and the lowest density of 94.85%. Given all, the density of the specimens is found to be directly proportional to strength and inversely to grain size.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.25 no.1
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• pp.4-14
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• 2016

Although CAD/CAM technology has been used in dentistry for more than decades, the present CAD/CAM dentistry is still quite inefficient or unesthetic. Zirconia restoration has faced with two contradictory words, 'Efficiency' and 'Esthetics'. One can consider monolithic zirconia restoration to be efficient with CAD/CAM. The monolithic zirconia restoration, however, is rarely esthetic due to the current limitations with zirconia. On the contrary, porcelain build-up is almost indispensible in fabricating esthetic restoration, especially in anterior region. In this article, the current status of monolithic zirconia restoration and clinical cases will be presented.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.142-153
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• 2004

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 $S\"{a}ckingen$, Germany), Celay Zirconia(Vita Zahnfabrik, Bad $S\"{a}ckingen$, Germany) and CAD/CAM Zirconia (Adens Zi-Ceram. Seoul , Korea). Material and methods: The four point bending test(ASTM Cl161) 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 (P<0.05). 2. After thermocycling, the average flexural strengths of CAD/CAM Zirconia, Celay Zirconia, In-Ceram Zirconia were 791.2 MPa, 604.2 MPa, 605.4 MPa, respectively. CAD/CAM Zirconia showed statistically significant higher strength(P<0.05). The others showed no significant difference after thermocycling(P>0.05). 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(P<0.05). 4. There was no statistically significant difference in strength of the specimens according to experimental methods except for before and after thermocycling in Celay Zirconia(P>0.05). Conclusion: Besides high esthetic quality, zirconia had sufficiently high mechanical strength.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.3
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• pp.275-283
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• 2006

Statement of problem. There have been many studies about marginal discrepancy of single restorations made by various systems and materials. However most of the statistical inferences are not definite because of sample size, measurement number, measuring instruments, etc, and there have been few studies about the marginal fit of the Digident CAD/ CAM zirconia ceramic crowns. Purpose. The purpose of this study was to compare the marginal fit of the anterior single restorations made by using the Digident CAD / CAM zirconia ceramic crowns with metal-ceramic restorations and to obtain more accurate information by using a large enough sample size and by making sufficient measurements per specimen. Material and Methods. The crowns were made from one extracted maxillary central incisor pre-pared with a 1mm shoulder margin and $6^{\circ}$ taper walls by milling machine. The in vitro marginal discrepancies of the digident CAD / CAM zirconia ceramic crowns and control groups(metal ceramic crowns) were evaluated and compared. Twenty crowns per each system were fabricated. Measurements of a crown were recorded at 50 points that were randomly selected for marginal gap evaluation. Parametric statistical analysis was performed for the results. Conclusion. Within the limitations of this in vitro study, the following conclusions were drawn: 1. Mean gap dimensions and standard deviations at the marginal opening for maxillary incisal crowns were $88{\pm}10{\mu}m$ for the control (metal-ceramic crowns), $92{\pm}4{\mu}m$ for Digident CAD / CAM zirconia ceramic crowns. 2. Marginal gap between Digident CAD / CAM zirconia ceramic crowns and metal ceramic crowns did not show significant difference (P>.05). 3. The Digident CAD/ CAM zirconia ceramic crowns and metal ceramic crowns showed clinically acceptable marginal discrepancy.

• Journal of Korean society of Dental Hygiene
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• v.14 no.5
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• pp.617-622
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• 2014

With the explosive increase of esthetic demands by patients, many dental materials for the esthetic restoration have been introduced. Recently, zirconia based restorations are using for the cases of single crown, bridges, implant prostheses etc. Zirconia have superior mechanical properties and biocompatibility. Owing to the properties of high strength, zirconia has to be manufactured by CAD/CAM system. Dental CAD/CAM system is a futuristic treatment and technical system which makes it possible to produce the precision and uniform prosthesis and also standardize the treatments. This article introduces the characteristics of zirconia, fabrication procedure using CAD/CAM system and procedure for the cementation of zirconia based restoration.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.4
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• pp.352-358
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• 2014

They have been recently introduced many aesthetic implant prosthesis using with zirconia and CAD/CAM. However, there are many limitations in their gingival and occlusal region. In this case, submucosal zirconia implant prosthesis were fabricated with CAD/CAM system. The connection of these screw cement retained prosthesis and titanium abutment was designed to 1mm above the fixture. The clinical results were satisfactory on the aesthetics and function.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.2
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• pp.205-212
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• 2020

The purpose of this study is to evaluate the validity of primary anterior zirconia crown made with Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) technology by analyzing fracture strength and translucency parameter. Zirconia crown was designed with CAD software, using 3D scanned data of #61 tooth model. Crown fabrication was performed with CAM machine using zirconia block. Zirconia crowns were divided into 3 groups according to thickness(0.3, 0.5, and 0.7 mm), and fracture strength was compared with 1.0 mm thickness of resin strip crown. The compressive force was applied with universal testing machine at 30° along the incisal edge at increments of 1 mm/min. For translucency evaluation, 0.3, 0.5, and 0.7 mm thickness of zirconia specimens were fabricated and translucency was measured with spectrophotometer. Among zirconia groups, there was a significant increase in fracture strength as thickness increased (p < 0.05). The fracture strength of zirconia crown was significantly higher than resin strip crown in all groups (p < 0.05). Translucency parameter was highest in 0.3 mm group, and significantly decreased as thickness increased to 0.5 and 0.7 mm (p < 0.05). Thin primary anterior zirconia crown can be designed and fabricated according to individual needs by using CAD/CAM. Restoration with thin crown would reduce the amount of tooth reduction, risk of pulp exposure, and make more esthetic restoration possible.