• 한국산학기술학회논문지
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• 제16권4호
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• pp.2585-2592
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• 2015

3D 프린팅 기술은 최근 치과용 보철물 제작 기술로 도입이 되었다. 본 연구의 목적은 3D 프린팅 기술에 의해 제작된 금속 코어와 상부 도재와의 전단결합강도를 평가하는 것이다. 본 연구를 위해 30개의 금속 코어를 제작하였다(cast 15개, 3D printing 15개). 금속 코어에 치과용 도재를 축성하여 시편 제작을 완료하였다. 완성된 시편의 전단결합강도는 crosshead speed 1mm/min으로 하중을 가하여 측정하였으며, 두 그룹의 전단결합강도 값 사이에는 통계적으로 유의한지 알아보기 위하여 Mann-Whitney test를 이용하였다(유의수준 0.05). 측정이 끝난 후 시편을 대상으로 파절양상을 분석하였다. 본 연구를 위한 실험 설계, 금속 코어 제작, 도재 축성 등의 시편 제작부터 실험 수행과 수행 후 실험 데이터 분석과 통계 분석 그리고 파절된 시편을 대상으로 한 파절 양상 분석까지 총 6개월이 소요되었다. 실험 결과 cast 50.14, 3D printing 54.36 MPa를 갖는 것으로 조사되었고, 통계적으로도 유의하였다. 파절양상은 두 집단 모두 시편의 대부분이 혼합형 파절양상을 보였다. 이와 같은 결과들로 미루어볼 때 3D 프린팅에 의해 제작된 금속도재관 제작을 위한 금속 코어는 임상적으로 허용이 가능할 것으로 사료된다.

• 대한치과기공학회지
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• 제33권1호
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• pp.15-23
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• 2011

Purpose: Thy yttria tetragonal zirconia polycrystalline(Y-TZP) is a good structural ceramic for dental restoration. But it have a problem that delamination of veneering ceramic from the Y-TZP core materials. The problem generally occur at the interface, thus this study was conducted to evaluate the interface of Y-TZP using scanning electron microscopy(SEM). Methods: To investigate this aspect, high-resolution SEM observations were made of polished and etched (HF content gel) cross-sections of the interface area. Dry and moist veneering porcelain powders were built up on the zirconia base. Results: The extent of this surface faceting is dependent upon the moisture content of the porcelain powder and the firing temperature. More moisture and higher final heating temperature accelerates the observed faceting of the Y-TZP grains at the interface to the veneering ceramic. Conclusion: These changes of the Y-TZP grains indicate that destabilization of the tetragonal phase of zirconia occurs at the interface during veneering with ceramic. It may result in a reduction of the stability of the zirconia and interface.

• 치위생과학회지
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• 제14권3호
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• pp.405-410
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• 2014

본 연구는 심미보철 치료에서 사용되는 금속도재관 제작시 Ni-Cr alloy 하부 구조물에 상부도재를 축성하고 소성하는 과정이 완성된 보철물의 적합도에 미치는 영향을 조사함으로써 임상적 허용을 재확인하기 위함이다. 1차로 lost wax technique으로 제작된 NCC (Ni-Cr alloy core)의 변연 및 내면 적합도를 측정하였고, 2차로 NCC에 상부도재 축성, 소성하여 금속도재관을 최종 완성하여 2차로 측정한 뒤비교한 결과는 다음과 같다. 금속도재관 제작 시 Ni-Cr alloy로 제작된 코어 위에 상부도재를 축성하고 소성하는 과정이 금속 도재관의 적합도를 악화시키는 결과를 보였으며, 부위 별 구분 없이 두 그룹에서 측정된 모든 값의 평균을 비교한 결과 NCC 그룹에서는 $67.1{\pm}23.3{\mu}m$, NMC 그룹에서는 $74.4{\pm}21.9{\mu}m$로 나타났으며 통계적으로 유의한 차이를 보였다(p<0.05). 이와 같은 결과를 토대로 Ni-Cr alloy로 금속도재관 제작 시 상부도재를 축성하는 과정에서 적합도를 악화시킨다는 결론을 얻었으나, 본 실험에서 측정된 결과 값은 임상적 허용 수치($120{\mu}m$)를 넘지 않아 적합도의 기준으로 평가하였을 때 임상적으로 허용 가능할 것으로 생각된다.

• 대한치과기공학회지
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• 제31권2호
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• pp.45-52
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• 2009

Esthetic restorations have been widely used in dental practice, although many studies have focused on the development and improvement of all ceramic restorations. The success of esthetic restorations depends primarily on an optimal bond strength between various veneered ceramics and core materials for esthetic restorations. The purpose of this study was to compare the shear bond strength between various veneered ceramics and core materials for esthetic restorations. 30 metal cores and 20 zirconia cores were fabricated and divided into five groups according to veneered ceramic materials such as Creation porcelain powder, Cercon Ceram Kiss, and IPS e.max ZirPress. Thirty spacimens were prepared using Creation porcelain powder, veneered 3mm height and 3mm in diameter, over the metal cores (n=10). Twenty specimens were prepared using Cercon Ceram Kiss and Zirpress, veneered 3mm height and 3mm in diameter, over the zirconia cores (n=10). The shear bond strength test was performed in a universal testing machine with a crosshead speed of 1mm/min. Ultimate shear bond strength data were analyzed with One-way ANOVA and the Scheffe's test (p=.05). Within the limits of this study, the following conclusions were drawn: The mean shear bond strengths (MPa) were: 18.44 for Uni metal VH/Creation (NCUC); 18.72 for Heraenium/Creation (NCHC); 16.23 for Wirobond C/Creation (NCWC); 13.88 for Zirconia core/$110{\mu}m$ $Al_2O_3$ sandblasting/Cercon Ceram Kiss (ZS110P); 14.61 for Zirconia core/No surface treatment/IPS e.max ZirPress (ZNTH). The mean shear bond strength for NCUC (Uni metal VH/Creation), NCHC (Heraenium/Creation) and NCWC (Wirobond C/Creation) were significantly superior to ZS110P (Zirconia core/$110{\mu}m$ $Al_2O_3$ sandblasting/Cercon Ceram Kiss) and ZNTH(Zirconia core/No surface treatment/IPS e.max ZirPress) (p<0.05).

• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.179-186
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• 2013

PURPOSE. One of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting. MATERIALS AND METHODS. The 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (${\alpha}$=.05). RESULTS. In both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown). CONCLUSION. Although the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range.

• 대한치과의사협회지
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• 제27권1호통권236호
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• pp.15-18
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• 1989

"62번 보다는 좀 어둡게" 또는 "62번과 65번 사이 정도로"라는 이러한 지시들이 만족스러운 결과를 가져오는가? "선생님, 제 앞니가 이젠 너무 희고 자연스럽지 않아요. 남들이 보면 해 넣은건지 금방 알아요." Porcelain fused to metal crown은 그 심미적 장점 때문에 전치부 수복에 있어 사용이 보편화되어 왔다. 하지만 두께의 제한과 세련되지 못한 일률적인 수복물은 일반적으로 너무 밝고 흰(높은 명도와 낮은 채도) 까닭에 인공적인 것을 쉽게 식별할 수 있으며, 환자들도 하여금 보다 개성화가 요구되어 오고 있다. 이러한 심미적 요구와 함께 최근 우수한 심미성과 높은 강도의 도재전장관들, 즉 Dircor이나 Cera Pearl, Alumina 또는 Magnesia core porcelain등이 연구 개발되어 왔다. 도재 축성술에 있어서도 내장된 첨색효과(internal characterization)나 다층축성법(layer build up)등 많은 방법들이 발전되어 왔다. 자연스러운 도재관을 재현하여 주기 위해서는 먼저 자연치아의 색조에 관한 치과의사의 충분한 인식과 판단이 앞서야 한다. 인식된 색조에 대한 정보가 체계적으로 기록되어 기공사에게 전달되고 재현되어야 한다.

• 대한치과기공학회지
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• 제34권2호
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• pp.95-103
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• 2012

Purpose: Fracture strength of all-ceramic 3-unit fixed partial dentures manufactured by CAD/CAM and copy-milling systems were evaluated. Methods: Zirconia cores were made by milling the pre-sintered zirconia block by CAD/CAM or copy milling method followed by subsequent sintering. By building-up the corresponding porcelains on the core, all-ceramic bridges were fabricated, and those were evaluated in comparison with PFM fixed partial denture. Results: During the flexural test of the 3-unit PFM bridge, the porcelain started to chip or break at 507.28(${\pm}62.82$)kgf and the metal framework did not break until the maximum load level of 800kgf which was set in the testing instrument of this study. However, among all-ceramic restoration test groups, Everest(EV) group showed a peeling off or breakage of the porcelain from 365.64(${\pm}64.96$)kgf and the core was broken at 491.77(${\pm}55.62$)kgf. Those values of Zirkonzahn(ZR) were 431.03(${\pm}58.47$)kgf and 602.74(${\pm}48.44$)kgf, respectively. The break strength of the porcelain of PFM(PM) group was significantly higher than that of EV (p<0.05) group and there was no significant difference when comparing to that of ZR (p>0.05). ZR group showed higher break strength than that of EV group however there was no significant difference (p>0.05). The break strength of cores were in the increasing order of EV < ZR < PM (p<0.05). Conclusion: We could find that even though the PM group fractured at much higher value than all-ceramic cores, the breakage values of the porcelain of PM group with crack formation or delamination, which will be regarded as clinical failure, was significantly higher than that of EV group and not significantly higher than that of ZR group at p-values of 0.05. The break strength of ZR group was higher than that of EV group at an insignificant level(p>0.05).

• 대한치과보철학회지
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• 제31권3호
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• pp.317-349
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• 1993

This study investigated the effect of filler particle size and weight% on mechanical properties of dental core porcelain. In alumina, variation in particle size and weight% and in zirconia, variation in weight%, all specimens were tested three-point bending strength, transmittance, thermal expansion coefficient, porosity and shrinkage and observed with SEM and analysed with X-ray diffractometer. In order to develop shrink-free porcelain, after firing alumina only, glass wasinfiltrated. And aluminum was added to alumina with the expanding character of aluminum oxidize into alumina, and was followed by second firing of glass infiltration procedure. Then mechanical properties were observed. The results of this study were obtained as follows. 1. The bending strength of zirconia was higher than that of alumina, and $5{\mu}m$ alumina had highest strength in variation of particle size of alumina. Except for $5{\mu}m$ alumina, increased with weight%, bending strength increased up to 80% and decreased at 90%. In case of glass infiltration, bending strength was slight higher than 80% and 90% of $5{\mu}m$ alumina. 2. Transmittance increased with increase of shrinkage, decrease of porosity, and with increase of filler size and had no direct correlation with weight%. 3. Thermal expansion coefficient of alumina group was $7.42\sim8.64\times10^{-6}/^{\circ}C$ and that of zirconia group was $9.83\sim12.11\times10^{-6}/^{\circ}C$ and the latter was higher than the former. 4. In x-ray diffraction analysis, alumina group and zirconia group increased $Al_2O_3$ peak and $t-ZrO_2$ peak with increase of weight%. The second phase(cristobalite peak) was observed in zirconia 40% group. 5. Porosity of zirconia was lower than that of alumina and $5{\mu}m$ alumina group had many pores with SEM. In case of low filler content, fracture occurred in glass and high filler content, in glass and filler. In case of aluminum addition to alumina, small oxidised aluminum was observed. 6. Zirconia group had high shrinkage than alumina group, and mixed group of alumina group had high shrinkage. In case of glass infiltration, shrinkage decreased and aluminum addition to alumina group was almost shrink-free.

• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.187-197
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• 2013

PURPOSE. The purpose of this study was to evaluate various core designs on stress distribution within zirconia crowns. MATERIALS AND METHODS. Three-dimensional finite element models, representing mandibular molars, comprising a prepared tooth, cement layer, zirconia core, and veneer porcelain were designed by computer software. The shoulder (1 mm in width) variations in core were incremental increases of 1 mm, 2 mm and 3 mm in proximal and lingual height, and buccal height respectively. To simulate masticatory force, loads of 280 N were applied from three directions (vertical, at a $45^{\circ}$ angle, and horizontal). To simulate maximum bite force, a load of 700 N was applied vertically to the crowns. Maximum principal stress (MPS) was determined for each model, loading condition, and position. RESULTS. In the maximum bite force simulation test, the MPSs on all crowns observed around the shoulder region and loading points. The compressive stresses were located in the shoulder region of the veneer-zirconia interface and at the occlusal region. In the test simulating masticatory force, the MPS was concentrated around the loading points, and the compressive stresses were located at the 3 mm height lingual shoulder region, when the load was applied horizontally. MPS increased in the shoulder region as the shoulder height increased. CONCLUSION. This study suggested that reinforced shoulder play an essential role in the success of the zirconia restoration, and veneer fracture due to occlusal loading can be prevented by proper core design, such as shoulder.

• 한국치위생학회지
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• 제13권2호
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• pp.361-368
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• 2013

Objectives : The purpose of this in vitro study was to evaluate the effect of firing cycles on the marginal and internal fit of metal ceramic crown. Methods : Ten same cases of stone models (abutment teeth 11) were manufactured. Ten cobalt-chrome cores were made per each models and the marginal and internal fit was evaluated through a silicone replica technique. The marginal and internal fit of specimens was measured twice. The first measurement was done after manufacturing cobalt-chrome alloy core and the second measurement was done after porcelain firing. T-test of paired sample for statistical analysis was executed with SPSS 12.0K for Windows (${\alpha}$=0.05). Results : Mean(SD) marginal and internal fit were 77.1(23.3) ${\mu}m$ for the cobalt-chrome alloy core group and 84.4(21.9) ${\mu}m$ for the metal-ceramic crown group. They were statistically significant differences between groups for marginal and internal fit (p<.05). Conclusions : All metal ceramic crowns showed marginal and internal fit ranged within the current clinical recommendations.