Simulated Porcelain Firing Research Articles

Ni–Cr dental alloys - porcelain firing impact on corrosion properties and surface characteristics

Biocompatibility is a critical aspect of the use of materials in the human body. The use of base metal alloys in dentistry is primarily regulated by health and safety standards set by regulatory authorities in various countries. The porcelain-fused-to-metal (PFM) process applied to Ni-Cr dental alloys can alter their properties, particularly in terms of corrosion and surface characteristics. This study aimed to assess the effect of the heat processing used for dental porcelain firing on these properties. The two casted alloys: Ceramic N and Ivoclar Vivadent 4all, used in the study were characterized by analyzing the microstructure by scanning electron microscopy (SEM), composition with energy dispersive x-ray spectroscopy (EDS), hardness, surface profile and electrochemical corrosion resistance (Ecorr, jcorr, polarization curve, Ebr and electrochemical impedance spectroscopy (EIS) results), as well as ions release before and after the simulated porcelain firing. Based on the conducted research the following conclusions can be drawn: Analyzes of the material characteristics before and after the simulation showed that the discussed process, although it does not cause the formation of chemical impurities on the surface of the alloys, results in changes in the chemical composition and structure of surface oxides, increases roughness and reduces hardness. The results of the corrosion examinations showed a deterioration in anti-corrosion properties after the simulation. The statistically significant decrease in corrosion resistance may result from the increased heterogeneity of the surface oxide layers and partial changes in their composition.

Does Simulated Porcelain Firing Influence Corrosion Properties of Casted and Sintered CoCr Alloys?

The aim of the study was to evaluate how heat processing used for dental porcelain firing influences the surface properties of sintered and casted CoCr alloy. Two CoCr alloys, Soft Metal LHK (milling in soft material and sintering) and MoguCera C (casting), were used for the study. The samples were examined using SEM–EDS before and after heat treatment. Next, corrosion examinations (Ecorr, jcorr, polarization curve, Ebr) were performed. Finally, the samples were evaluated under SEM. Based on the results, the following conclusions might be drawn: 1. Thermal treatment (porcelain firing) did not cause chemical impurities formation on the surface of CoCr alloy; 2. The sintered metal exhibited significantly higher corrosion resistance than the casted one due to its homogeneity of structure and chemical composition; 3. Heat treatment (porcelain firing) decreased the resistance of casted and sintered CoCr alloy to electrochemical corrosion. The reduction in corrosion resistance was significantly higher for the casted alloy than for the sintered alloy; 4. The corrosion resistance decrease might be due to an increased thickness and heterogeneity of oxide layers on the surface (especially for the casted alloy). The development of corrosion process started in the low-density areas of the oxide layers; 5. The sintered metal seems to be a favourable framework material for porcelain fused to metal crowns.

Effect of cooling rate on hardness and microstructure of Pd–Ag–In–Sn−Ga alloy during porcelain firing simulation

This study examined the effect of the cooling rate on the hardness and its effect on the microstructure during porcelain firing simulation of a Pd–Ag–In–Sn−Ga metal-ceramic alloy. In practice, after each firing step for porcelain bonding, the prosthesis is cooled to room temperature before proceeding to the next firing step. The cooling step is known to allow the hardness of the metal substructure to increase. The aim of the study was to determine whether controlling the cooling rate after each porcelain-firing step increases the hardness of the Pd–Ag-based metal-ceramic alloy. The results showed that the hardness of specimens cooled at a higher cooling rate increased after each firing step compared to specimens cooled at a lower cooling rate (p < 0.05). During cooling after the firing simulation the InPd3–based phase of tetragonal structure precipitated from the Pd–Ag-rich matrix of the face-centered cubic structure. Hardening by cooling at a higher cooling rate after firing was the result of the coherency strains that formed at the interface of the Pd–Ag-rich matrix and the metastable phase based on the InPd3 phase. . The reduced hardness obtained in the specimen cooled at a lower cooling rate after firing resulted from the loss of coherency strains as the fine metastable phases based on the InPd3 phase were transformed into the coarser stable phase with decreased (c/a) of 0.88. This finding revealed that controlling the cooling rate during porcelain firing simulation improves the hardness of the Pd–Ag–In–Sn−Ga metal-ceramic alloy without an additional heat treatment of the alloy.

Pd-Ag-In-Ga계 금속-세라믹용 합금의 모의 소성과 냉각에 따른 경도 및 미세 구조의 변화

본 실험에서는 조성이 49.5Pd-40Ag-9In-1Ga(wt.%)인 합금을 이용하여, 모의 소성 시 합금의 경화에 가장 효과적인 냉각 속도를 알아내고, 모의 소성의 각 단계에서 합금의 경화에 가장 효과적인 냉각 속도로 냉각하거나 급랭하여 소성 과정과 그 후의 냉각 과정에 따른 합금의 경도 및 이와 관련된 미세 구조의 변화를 관찰하였다. 이를 위하여, 합금을 모의 소성한 후 경도 시험, 미세 구조, 결정 구조 및 원소 분포의 변화를 조사하여 다음과 같은 결과를 얻었다. 본 실험에 사용된 합금은 주조 후 산화 처리에 의해 균질화가 진행되어 합금이 연화 되었고, 그 후 냉각됨에 따라 경화 되었다. 합금의 산화 처리 후 냉각 시 최고의 경화 효과를 나타내는 냉각 속도는 Stage 0이었다. 모의 소성 진행 시 각 단계별 냉각 속도를 Stage 0으로 통일하여 최종 소성 단계인 Glaze 단계까지 진행하여도 최종 모의 소성을 완료한 후 얻어진 금속 하부 구조물의 최종 경도는 주조 직후의 합금의 경도보다 낮았다. 모의 소성 과정에 따른 경도의 하강은 석출물이 조대화됨에 따라 면심정방(face-centered tetragonal) 구조의 석출물과 면심입방(face-centered cubic) 구조의 기지 사이의 계면의 면적이 감소되어 격자 뒤틀림이 해소된 것에 기인하였다.

Simulated Porcelain Firing of CO-CR Alloy

Simulated Porcelain Firing of CO-CR Alloy

Effect of ice quenching after oxidation with or without vacuum on the hardness of Pd–Ag–Au–In alloy during porcelain firing simulation

This study examined the effect of ice-quenching after oxidation treatment with or without vacuum, on the change in the hardness of a Pd–Ag–Au–In metal–ceramic alloy during porcelain-firing simulation. The aim of the present study is to determine whether ice quenching after oxidation renders a Pd–Ag metal–ceramic alloy soft enough for easy processing without the need for an additional solution treatment and whether it affects the final hardness of the Pd–Ag metal–ceramic alloy after porcelain firing simulation. The oxidation treatment resulted in the as-cast specimen becoming homogenized, which was progressed further by vacuuming. The bench-cooling to room temperature after the oxidation resulted in precipitation. From the next firing step, the precipitation occurred during the firing process as well as subsequent bench-cooling; this was owing to the presence of a phase boundary wherein the single phase is separated into two phases between the temperatures of the oxidation treatment (1010 °C) and post-oxidation treatment (~960 °C). During the firing process until main bake, the specimen that was ice-quenched after oxidation maintained a higher hardness than the bench-cooled specimen, particularly for the oxidation treated specimen with vacuum (p < 0.05). The mechanism of ice-quenching after oxidation with vacuum to induce further hardening during the firing process involved more active precipitation; this was attributed to the further progress of homogenization during the oxidation. The precipitation reaction in the present study corresponded to the Pd–In binary phase diagram, illustrating that as the firing proceeded, the Pd3(In,Sn,Ga) phase was precipitated from the Pd–Ag–Au–rich matrix. The findings revealed that ice quenching after oxidation makes the alloy soft enough for easy processing without an additional heat treatment and does not affect the final hardness of the Pd–Ag metal–ceramic alloy after porcelain firing simulation.

Effects of second heat treatment on softening of a Pd-Au-Ag metal-ceramic alloys during simulated porcelain firing

Effects of second heat treatment on softening of a Pd-Au-Ag metal-ceramic alloys during simulated porcelain firing

Promoting porcelain–zirconia bonding using different atmospheric pressure gas plasmas

ObjectivesTo evaluate the effects of different atmospheric-pressure plasma (APP) on the physicochemical properties of yttria-stabilized zirconia, and promoting the adhesion of veneering porcelain. MethodsCercon base zirconia disks were prepared to receive different treatments: as-polished, three APPs (oxygen, OP; argon, AP; and CF4, CP), and grit-blasted (GB). Their surface roughness and hydrophilicity were measured, and surface morphology was examined either after treatments, after simulated porcelain firing, or additional thermal etching. X-ray photoelectron spectroscopy (XPS) analysis characterized the surface chemical compositions. Shear bond strength (SBS) tests examined the adhesion between veneering porcelain and zirconia either before or after thermocycling. The layered ceramic disks were also sectioned to inspect the porcelain–zirconia interfaces. Statistical analysis was performed with one-way ANOVA and post hoc Duncan’s test. ResultsGrit-blasting caused surface damage and increased roughness. All APP-treated disks exhibited deeper grain boundaries and enlarged grain sizes after thermal etching, while CP disks revealed additional particle dispersions. Three APPs rendered the zirconia surface superhydrophilic. XPS spectra of three APP groups revealed increased hydroxyl groups and reduced C–C contents, and CP group especially showed the existence of Z–F bonds. CP exhibited the highest SBS both before and after thermocycling, while AP and GB also showed improved SBSs compared to the as-polished. OP presented reduced SBS, and its cross-sections showed increased microporosities in the veneering porcelain. SignificanceAPP did not change surface morphology but enhanced wettability. CP and AP improved porcelain–zirconia SBSs, primarily through surface hydroxylation. OP induced the microporosities in porcelain and adversely affected the adhesion.

금속-세라믹용 Pd-Cu-Ga-Zn계 합금의 산화처리 시 냉각 속도가 모의 소성 후 후열처리에 따른 경도 변화에 미치는 영향

금속-세라믹용 Pd-Cu-Ga-Zn계 합금의 산화처리 시 냉각 속도가 모의 소성 후 후열처리에 따른 경도 변화에 미치는 영향을 조사하여 다음과 같은 결과를 얻었다. 산화처리 시 급랭하여 모의 소성한 시편에서는 후열처리에 의한 경도의 상승효과가 나타나지 않았으나 산화처리 시 서냉하여 모의 소성한 시편에서는 25분간의 후열처리가 경도 상승에 효과적인 것으로 나타났다 (p0.05). 산화처리 시 급랭하여 모의 소성한 시편에서 후열처리 과정 동안 경도가 크게 하강한 것은 기지와 판상형 석출물 내부에 생성된 미세한 석출물의 조대화에 기인하였다. 산화처리 시 서냉하여 모의 소성한 시편에서 25분간의 후열처리 과정 동안 경도가 상승한 것은 석출경화에 기인하였다. 이상으로부터 산화처리 시 냉각 속도가 모의 소성 후 후열처리에 따른 경도 변화에 영향을 미치는 것을 알 수 있었으며, 이러한 결과는 산화처리시 냉각 속도를 달리한 두 시편에서 생성된 상은 동일하였으나 냉각 속도에 따라 석출물의 조대화 정도가 차이 나는 것에 기인하였다. 이러한 결과로부터 Pd-Cu-Ga-Zn계 합금은 산화처리 시 냉각 속도를 느리게 하는 것이 모의 소성 후 후열처리에 따른 합금의 경도 상승에 유효함을 알 수 있었다.

다목적용 Ag-Pd-Zn-In-Sn계 합금의 모의소성 시 냉각속도의 조절이 소성 및 후열처리에 따른 경도변화에 미치는 영향

본 연구에서는 소성 시 냉각속도를 조절하는 것과 동시에 소성 후 추가적인 후열처리를 시행하는 것이 후열처리를 시행하지 않는 것보다 합금의 경도 상승에 더욱 효과적인지 알아보고자, 다목적용 Ag-Pd-Zn-In-Sn계 합금을 이용하여 모의소성 시 냉각속도의 조절이 소성 및 후열처리에 따른 합금의 경도변화에 미치는 영향을 조사하여 다음과 같은 결과를 얻었다. 다목적용 Ag-Pd-Zn-In-Sn계 합금의 모의소성 시 냉각속도를 조절함에 따라 합금의 연화가 억제되었다. Stage 0(4단계의 냉각속도 중 가장 빠른 속도; 소성로 챔버가 소성 종료 즉시 전체가 열린 상태로 냉각되는 단계)으로 냉각속도를 조절하여 합금을 소성한 경우, 모의소성 과정에서 합금이 연화되었으며, 적절한 시간동안의 후열처리가 경도상승에 효과적이었다. Stage 3(4단계의 냉각속도 중 가장 느린 속도; 소성로 챔버가 소성완료 후 닫혀진 상태로 냉각되는 상태)으로 냉각속도를 조절하여 합금을 소성한 경우, 모의소성 과정에서 합금이 연화되지 않았으며, 추가적인 후열처리는 합금의 경도를 하강시켰다. Stage 0으로 모의소성 된 합금에서 30분간의 후열처리에 의해 경도가 크게 상승한 원인은 소성에 의해 기지 내로 고용되었던 석출물이 다시 기지 밖으로 활발하게 석출된 것에 기인하였다. Stage 3으로 모의소성 된 합금에서는 후열처리에 의해 석출물이 기지 내로 다시 고용되었고, 새로운 석출상의 생성이 미미하여 후열처리가 경도 상승에 기여하지 못하였다.

Effect of ice-quenching after oxidation treatment on hardening of a Pd-Cu-Ga-Zn alloy for bonding porcelain.

This study examined the effect of ice-quenching after oxidation treatment on hardness change of a Pd-Cu-Ga-Zn metal-ceramic alloy during porcelain firing simulation. Although not statistically significant, the alloy was softened slightly during porcelain firing simulation with conventional slow cooling rate. On the other hand, the hardness increased significantly by ice-quenching instead of the slow cooling after oxidation (p<0.001). The gap in the final hardness depending on ice-quenching occurred in the matrix and plate-like precipitates but not in the particle-like structure without plate-like precipitates (p<0.05). The mechanism of ice-quenching after oxidation to prevent softening and induce hardening during porcelain firing simulation involved the more active precipitation and retardation of microstructural coarsening. In conclusion, for practical work on Pd-Cu-Ga-Zn alloys, the oxidation treatment followed by ice-quenching instead of slow cooling is recommended for the simultaneous oxidation and hardening effects on the alloy.

금속-세라믹용 Pd-Cu-Ga-Zn계 합금의 모의 소성 시 냉각 속도가 석출 경화에 미치는 영향

금속-세라믹용 Pd-Cu-Ga-Zn계 합금의 모의 소성 시 냉각 속도가 석출 경화에 미치는 영향

금속-세라믹용 Pd-Ag-Sn-Au계 합금의 모의소성 시 산화처리 후 급랭에 의한 경화 효과

금속-세라믹용 Pd-Ag-Sn-Au계 합금의 모의소성 시 산화처리 후 급랭에 의한 경화 효과

Potentiodynamic polarization study of the corrosion behavior of palladium-silver dental alloys

Statement of problemAlthough palladium-silver alloys have been marketed for over 3 decades for metal-ceramic restorations, understanding of the corrosion behavior of current alloys is incomplete; this understanding is critical for evaluating biocompatibility and clinical performance. PurposeThe purpose of this in vitro study was to characterize the corrosion behavior of 3 representative Pd-Ag alloys in simulated body fluid and oral environments and to compare them with a high-noble Au-Pd alloy. The study obtained values of important electrochemical corrosion parameters, with clinical relevance, for the rational selection of casting alloys. Material and methodsThe room temperature in vitro corrosion characteristics of the 3 Pd-Ag alloys and the high-noble Au-Pd alloy were evaluated in 0.9% NaCl, 0.09% NaCl, and Fusayama solutions. After simulated porcelain firing heat treatment, 5 specimens of each alloy were immersed in the electrolytes for 24 hours. For each specimen, the open-circuit potential (OCP) was first recorded, and linear polarization was then performed from –20 mV to +20 mV (versus OCP) at a rate of 0.125 mV/s. Cyclic polarization was subsequently performed on 3 specimens of each alloy from –300 mV to +1000 mV and back to –300 mV (versus OCP) at a scanning rate of 1 mV/s. The differences in OCP and corrosion resistance parameters (zero-current potential and polarization resistance) among alloys and electrolyte combinations were compared with the 2-factor ANOVA (maximum-likelihood method) with post hoc Tukey adjustments (α=.05). ResultsThe 24-hour OCPs and polarization resistance values of the 3 Pd-Ag alloys and the Au-Pd alloy were not significantly different (P=.233 and P=.211, respectively) for the same electrolyte, but significant differences were found for corrosion test results in different electrolytes (P<.001 and P=.032, respectively). No significant interaction was found between the factors of alloy and electrolyte (P=.249 and P=.713, respectively). The 3 Pd-Ag silver alloys appeared to be resistant to chloride ion corrosion, and passivation and de-alloying were identified for these alloys. ConclusionsThe Pd-Ag alloys test results showed excellent in vitro corrosion resistance and were equivalent to those of the high-noble Au-Pd alloy in simulated body fluid and oral environments. Passivation, de-alloying, and formation of a AgCl layer were identified as possible corrosion mechanisms for Pd-Ag alloys.

Effect of ice-quenching on the change in hardness of a Pd-Au-Zn alloy during porcelain firing simulation.

This study examined the effect of ice-quenching after degassing on the change in hardness of a Pd-Au-Zn alloy during porcelain firing simulations. By ice-quenching after degassing, the specimens were softened due to homogenization without the need for an additional softening heat treatment. The lowered hardness by ice-quenching after degassing was recovered greatly from the first stage of porcelain firing process by controlling the cooling rate. The increase in hardness during cooling after porcelain firing was attributed to the precipitation of the f.c.t. PdZn phase containing Au, which caused severe lattice strain in the interphase boundary between the precipitates and matrix of the f.c.c. structure. The final hardness was slightly higher in the ice-quenched specimen than in the specimen cooled at stage 0 (the most effective cooling rate for alloy hardening) after degassing. This was attributed to the more active grain interior precipitation during cooling in the ice-quenched specimen after degassing.

Pd-Au-Ag계 금속-도재용 합금의 탈가스 처리 후 급냉 처리가 모의소성과정에서 경도변화에 미치는 영향

본 연구에서는 Pd-Au-Ag계 금속-도재용 합금의 탈가스 처리(degassing) 후 급냉 처리가 모의소성과정에서 경도변화에 미치는 영향을 관찰하여 다음과 같은 결과를 얻었다.BR 1. 탈가스 후 급냉에 의해 경도는 하강하였고, 이는 급냉에 따른 합금의 균질화에 의해 유도되었다.BR 2. 탈가스 후 급냉하여 낮아진 경도는 나머지 모의소성 과정의 첫 단계인 1st opaque 단계에서 완전히 회복되었으며, 이는 석출에 의해 유도되었다.BR 3. 탈가스 후 급냉 처리는 이후 모의소성과정 동안 시편의 경도변화에 아무런 영향을 미치지 않았다.BRBR 이상의 결과로부터 금속-도재용 합금을 탈가스 후 급냉 처리한다면 최종 보철물의 내구성에 영향을 미치지 않고 금속하부구조물에 대한 도재 소성 전처리 작업을 효과적으로 할 수 있을 것으로 생각되었다.

금속-세라믹용 Pd-Au-Ag-Sn계 합금의 모의 소성에 따른 경도변화에 미치는 냉각 속도의 영향

금속-세라믹용 Pd-Au-Ag-Sn계 합금의 모의 소성에 따른 경도변화에 미치는 냉각 속도의 영향

Pd-Ag-In-Au계 금속-세라믹 합금의 모의소성에 따른 경도 및 미세구조의 변화

Change in hardness and microstructure during porcelain firing simulation in a Pd-Ag-In-Au metal-ceramic alloy was examined by observing the change in hardness, crystal structure and microstructure. In the as-cast specimen, the matrix was composed of the Pd3Ga phase(f.c.t.), and the particle-like structures were composed of the Pd-Ag-based phase(f.c.c.). The precipitates which covered the particle-like structures were composed of the Pd3In phase(f.c.t.). Specimen which was cooled by ice quenching after oxidation was softened due to homogenization of the microstructure, and then it was hardened due to precipitation during the simulated firing stages. The decrease in hardness by subsequent firing schedule was resulted from reduction of precipitates in the particle-like structures.

Hardening by cooling rate control and post-firing heat treatment in Pd-Ag-Sn alloy for bonding porcelain.

The aim of this study was to determine the hardening effect by controlling the cooling rate during the porcelain firing process and performing an additional post-firing heat treatment in a Pd-Ag-Sn alloy. The most effective cooling rate for alloy hardening was determined by cooling the specimens at various cooling rates after oxidation treatment. A subsequent porcelain firing simulation followed by cooling at the selected cooling rate was performed. A post-firing heat treatment was then done at 600°C in a porcelain furnace. The hardening mechanism was characterized by a hardness test, X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Alloy softening occurred during the porcelain firing process followed by cooling at a controlled cooling rate. A post-firing heat treatment allowed apparent precipitation hardening. It is advisable to perform a postfiring heat treatment at 600°C in a porcelain furnace by annealing metal substructure after porcelain fusing.

Effect of softening-heat treatment on hardness change of an Au-Pd-Zn-In-Sn metal-ceramic alloy during porcelain firing simulation

Effect of softening-heat treatment on hardness change of an Au-Pd-Zn-In-Sn metal-ceramic alloy during porcelain firing simulation