• 대한치과보철학회지
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• 제47권4호
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• pp.406-415
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• 2009

연구목적: 본 연구는 유색 및 백색 지르코니아 세라믹으로 제작된 코핑의 디자인에 따른 지르코니아 세라믹 코핑의 파절 하중과 변연 적합성을 평가한 것으로 그 결과를 임상에 응용하는데 도움을 주고자 하였다. 연구재료 및 방법: CAD/CAM system (Everset, KAVO Dental GmbH, Biberach, Germany)을 이용하여, 80개의 상악 제1 소구치 세라믹 코핑을 제작하되, 1그룹은 전체적으로 균일하게 0.3 mm로, 2그룹은 협면 0.3 mm 설면 0.6 mm, 3그룹은 전체 0.6 mm 균일하게, 4그룹은 협면 0.6 mm 설면 1.0 mm로 디자인하고, 유색 (I) 및 백색 (II) 지르코니아 코핑을 각 그룹당 10개가 되게 하였다. 소성직후와 조정 후 코핑의 변연 적합성을 Video Microscope System (sv-35, Sometech, Seoul, Korea)를 이용하여 100배율로 관찰하였고, 금속 주 모형에 코핑을 강화형 글래스아이오노머 시멘트로 합착 후 Universal Testing Machine (Instron 4467, Norwood, MA, USA)을 이용하여 파절 하중을 측정하여, one-way ANOVA test 를 시행하여 결과를 분석하였다. 결과: 1. CAD/CAM 지르코니아 코핑의 파절 하중은 1그룹, 2와 3그룹, 그리고 4그룹간에 유의성있는 차이를 보였으며 I4, II4의 파절 하중값이 가장 컸다. 2. 코핑의 디자인이 같고 색이 다른 그룹간의 비교에서는 전 그룹 모두 파절 하중값의 유의성은 없었다. 3. 소성 직후 변연 오차 측정값은 I2그룹을 제외한 전 그룹에서 협측 측정점에서 변연오차가 가장 큰 경향을 보였다. 4. 소성 직후 변연 오차 측정값은 I 그룹 지르코니아 그룹에서 그룹별 전체적인 변연적합도를 보았을 때 그룹간에 유의한 차이는 없었다 (P>.05). 5. 소성직후 변연 오차 측정값은 백색 지르코니아 그룹에서 그룹별 전체적인 변연 적합도를 보았을때 II1그룹의 변연 오차가 가장 컸다 (P<.05). 6. 소성직후 변연오차 측정값은 디자인이 같은 그룹의 유색, 백색 비교에서, I1와 II1그룹을 제외한 나머지 그룹에서 백색 지르코니아의 변연 적합도가 더 좋았다 (P<.05). 7. 내면 조정 후에는 색상화 및 지르코니아 코어 디자인에 따른 전 그룹간 변연 적합도의 차이는 없었다 (P>.05). 결론: 지르코니아 코핑 디자인과 색상화에 따른 변연 적합성은 소성 직후에는 다소 차이가 있었으나 내면 조정을 하면 임상 사용에는 무리가 없을 것으로 판단되었고, 파절강도 강화를 위해 코핑의 두께는 가급적 두꺼워야 하나, 가시면 (순면, 협면)의 심미성(반투명성)을 고려할 경우 가시면을 0.3 mm로 얇게 해도 파절 강도에 큰 영향을 주지 않는 것으로 사료되었다.

• 대한치과기공학회지
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• 제33권2호
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• pp.129-136
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• 2011

Purpose: The purpose of this study was to investigate the transmittance differences of zirconium core due to thickness within the visible light spectrum. Methods: 36 specimens were divided into 3 groups (0.6mm, 0.8mm, 1.0mm) which have each 12 specimens. The size of specimens was 10mm high and 10mm wide. The transmittance of specimens are measured by spectrophotometer Model Cary 500 that can measure infrared-ray, visible wave and ultraviolet-ray. Results: The results shows that there was no significant difference between specimen's thickness and transmittance. Conclusion: The individual's color perception is personal and there are numerous factors that influence on it. In general, human eye can perceive the color of thing only within visible light spectrum but in this experiment through spectrophotometer there was no big difference between specimen's thickness and transmittance. To sum up, The most important factors were a layed porcelain structure and its thickness rather than core thickness in the porcelain crown.

• 대한치과기공학회지
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• 제33권4호
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• pp.313-321
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• 2011

Purpose: The purpose of this study was to compare color parameters of different fabrication method of Lava ceram powder, Lava DVS blocks, IPS e.max ceram and IPS e.max zirpress. Methods: The three available shades(A1, A2, A3.5) of Lava & Kavo zirconia blocks were examined. For each of three colors, three different thickness were tested, 5 times of measurement frequency. The measurements were made using a spectrophotometer equipped with an integrating sphere using the CIE $L^*$, $a^*$, $b^*$ colorimetric system. Results: Lava build-up group and Lava DVS group showed clinically perceived color difference, on the other hand IPS e.max build-up group and IPS e.max zirpress group did not show clinically perceived color difference to shade allowed on core. When the thickness of porcelain veneer increased from Lava and IPS e.max groups, color differences(${\Delta}E$) were decreased. Conclusion: All-ceramic system has color characteristics that clinicians have to consider when selecting materials. Also, manufacturers of different porcelain systems must make every effort to achieve color reproducibility.

• 치위생과학회지
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• 제12권4호
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• pp.368-374
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• 2012

제한된 조건 하에서 수행된 본 연구에서 다음과 같은 결론을 얻었다. 1. 치과용 캐드캠을 이용하여 제작된 지르코니아 코어의 변연 및 내면 적합도보다 전통적인 방식을 이용하여 제작한 금속 코어가 모든 부위에서 우수하였다(p<.001). 2. 두 그룹 모두에서 적합도가 가장 미흡한 부분은 절단부였고, 축벽부가 가장 우수한 것으로 확인되었다. 본 연구 결과를 볼 때 아직까지는 치과용 캐드캠을 이용하여 보철물을 제작하는 것이 기존의 기공 방식을 이용하여 제작된 보철물의 적합도만큼 만족스럽지는 못하였으나 임상적 허용 범위 안에 존재하였다는 점에서 치과용 캐드캠은 임상적으로 사용이 가능한 것으로 판단된다. 앞으로 기계가 개선되고 가공 방식이 지금보다 발전한다면 기존의 기공 방식을 이용하여 제작되는 보철물의 완성도를 능가할 것으로 생각된다.

• 대한치과기공학회지
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• 제35권1호
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• pp.57-64
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• 2013

Purpose: Waste parts of zirconia blocks and powders were remained after CAD/CAM process. In order to make these residual zirconia fit for practical use, zirconia single cores were produced by drain casting process. Methods: Remained zirconia blocks were reduced to powders with zirconia mortar, and screened with 180 mesh sieve. Zirconia slip was prepared from waste parts of zirconia by ball milling. Plaster molds for forming cores by slip casting were also prepared. Formed cores were removed from mold after partial drying. Dried cores were biscuit fired at $1,100^{\circ}C$ for 1hour. Biscuit fired cores were treated with tools to control the fitness and thickness. Finished cores were $2^{nd}$ fired at $1,500^{\circ}C$ for 1hour. Microstructure of cross section of core was observed by SEM. Results: When mill pot was filled with 100g of zirconia and alumina mixed powder, 300g of zirconia ball, and 180g of distilled water, the optimum slip for drain casting was obtained. Gypsum plaster for ceramic forming was more suitable then yellow stone plaster for casting process. SEM photograph showed the microstructure of fully dense with uniform grain size of zirconia and well dispersed alumina grains into the zirconia matrix. Conclusion: Zirconia single cores were produced by drain casting process. Drain casting is useful process to make these residual zirconia fit for practical use. Further study will be focused on the preparation of the bridge type cores by casting.

• 대한치과기공학회지
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• 제35권3호
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• pp.193-200
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• 2013

Purpose: In this study, in order to provide objective standard of the mixed concentration of the zirconia coloring-liquids, compare the shade differences after colored zirconia blocks from different concentrations. Methods: After immersion for 2 minutes zirconia specimen ($1.5{\times}1.5{\times}0.6{\pm}0.01mm$) in coloring-liquids that produced different concentrations, were sintered in furnace dedicated. Then, it was measured in spectrophotometer and Shadepilot. It has been determined mean and standard deviation of the color difference for each group, and verified by one-way ANOVA using the (version12.0) SPSS WIN Program the difference in shade according to the concentration at the significance level of 95% confidence, it conducted a Tukey's multiple range test to post-test. Results: The mean of $L^*$ was decreased toward LN35 group, however the mean of $a^*$ and $b^*$ was increased(p<.05). There is a statistically significant difference in the results of $L^*$ post hoc test of each group was LN15-LN30/LN35, LN20-LN30/LN35, LN25-LN30/LN35, and LN30-LN35 group. The $a^*$ group, it was found that there is a statistically significant difference in all groups for each(p<.05). The $b^*$ group, it was found that there is a statistically significant difference in all groups except the LN25-LN30(p<.05). Conclusion: In order to make effective use of the coloring-liquids of zirconia, the device objective, accurate concentration measurement is required, from the present study, we presented evidence basic to this.

• 대한치과기공학회지
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• 제32권4호
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• pp.327-335
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• 2010

Purpose: The purpose of this study was to investigate the correlation between zirconia core thickness and color tone blocking of discolored tooth and metal post. Methods: For this study, we made 20-porcelain sample and 4-metal sample( liechtenstein IPS e.max) bonded to zirconia core of different thickness with cement(Relyx ARC-3M USA)for produce discolored. We measured the color-spectral characteristics, using Shadepilot equipment(Degudent USA).We measured it with Shadepilot equipment set by automated average mode in 3 times And applied the average value obtained from 2 times of measurement in the middle of each sample. Results: As a result of analysing color-spectral characteristics on zirconia core sample, Depending on the thickness of zirconia core, the value of brightness(${\Delta}L*$:color-spectral characteristic) was increased within limited range, value of ${\Delta}a*$, ${\Delta}b*$ was decrease. Conclusion: Consequently, we obtained the following results: Changes of sample color were observed depending on the thickness of zirconia, but the range of change did not exceed the scope range of shade guide. The case of metal posts, shade guide color D2 were observed in 0.5mm of zirconia core thickness. As a result, in case of porcelain, increasing the zirconia thickness of 0.3mm or more is unnecessary for color blocking effect, in case of metal post, considering the discolored tooth, thickness of zirconia with at least 0.5mm or more is recommended.

• 대한치과기공학회지
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• 제34권2호
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• pp.75-81
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• 2012

Purpose: All ceramic crown, made from zirconia instead of metal for core material, is recognized the best esthetical prosthesis. Recently, high-priced zirconia blocks and expensive CAD/CAM machines come into use for making zirconia core. In this study, slip casting process is adapted to evaluate the possibility of the recycling the remained parts of zirconia block after machining. Methods: Remained zirconia blocks were reduced to powders with zirconia mortar, and screened with 180 mesh sieve. Passed powders were ball milled under various conditions to obtain the optimum zirconia slip for casting. Solid casting method was used for casting the specimens with plaster mold. Formed specimens were dried and biscuit fired at $1,000^{\circ}C$ for 1 hour. Biscuit fired specimens were finished with exact shape of square pillar. Finished specimens were fired from $1,200^{\circ}C$ to $1,550^{\circ}C$ at $50^{\circ}C$ intervals for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM. Results: Above examinations indicated that the optimum firing temperture was $1,500^{\circ}C$, and when fired at this temperature for 1 hour, apparent porosity was 0% and flexural strength was 680MPa. SEM photomicrographs showed uniform 200~300nm grain size, which is equal with microcture of sintered commercial zirconia block. when compare 24% linear shrinkage of cast specimen with 20% linear shrinkage of CAD/CAM machined block, it was estimated that the size controlling of cast core was not so difficult. Conclusion: According to the all of this experimental results, the cast zirconia core produced from the remained parts of zirconia block was possible to use for all ceramic denture.

• 대한치과기공학회지
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• 제42권3호
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• pp.213-219
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• 2020

Purpose: This study aimed to identify the impact of physical surface roughing with a polishing tool onto the pre-sintering yttria-stabilized tetragonal zirconia polycrystals (TZP) core and liner treatment for chemical bonding on the bond strength of TZP core and veneering ceramic. Methods: Overall, 80 specimens were classified into two groups (non-liner, NL; and usingliner, UL ) depending on the use of liner, and these two groups were then subclassified into four groups depending on the polishing tool used. (1) Non-liner groups: NS, non-liner+stone point; NC, non-liner+carbide bur; NP, non-liner+paper cone point; NT, non-liner+silicon point. (2) Using-liner groups: US, using-liner+stone point; UC, using-liner+carbide bur; UP, usingliner+paper cone point; UT, using-liner+silicon point. The pre-sintering surface roughing values and shapes were observed, and after burning up the veneering ceramic, the shear bond strength was measured using a universal testing machine. For significance testing, a one-way analysis of variance and Tukey's multiple comparison test were conducted. An optical microscope was used to observe the fracture plane, and the following results were obtained. Results: Surface roughness NP (4.09±0.51 ㎛) represented a higher value than other groups (p<0.001). In shear bond strength, NS (35.21±1.44 MPa) of the NL group showed the highest bond strength (p<0.001). The UL group did not show a statistically significant difference between groups (p=0.612). Conclusion: Our study findings reveal that the bond strength of TZP core and veneering ceramic was improved by pre-sintering physical surface treatment than by chemical bonding with liner surface treatment.

• 대한치위생과학회지
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• 제5권1호
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• pp.13-19
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• 2022

Background: In this study, zirconia copings were fabricated by setting clinically acceptable inner values for prostheses using computer-aided design/computer-aided manufacturing (CAD/CAM). The processed copings were evaluated for the marginal and internal fit of each abutment shape with a CAD program using the silicone replica technique. Methods A total of 20 copings was produced by selecting models commonly used in clinical practice. After injecting the sample, the minimum thickness, internal adhesion interval, and distance to the margin line were set to 0.5, 0.05, and 1.00 mm using a dental CAD program, respectively. It was measured using a 2D section function in a three-way program of the silicon replication technology. Although the positions and number of measurements of the anterior and posterior regions differed, nine parts of each pre-tube were designated and measured by referring to a previous study to compare the two samples. Results As a result, the average margin of the mesial, distal, and buccal (labial) surfaces was 59.90 ㎛ in the anterior region and 60.40 ㎛ in the posterior region. The mean axial wall margin was 67.25 ㎛ in the anterior region and 69.25 ㎛ in the posterior region. In occlusion, the anterior teeth (77.70 ㎛), posterior teeth (77.60 ㎛), and both anterior and posterior regions were within the clinically acceptable range. Conclusion The edge and inner fit of zirconia coping manufactured using the CAD/CAM system showed clinically applicable results. To reduce errors and increase accuracy, materials and machine errors that affect the manufacture of prosthetics should be investigated. Based on our results, the completeness of prosthetics could increase if the inner value and characteristics of the material are adjusted when applied in clinical practice.