• The Journal of Advanced Prosthodontics
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• v.7 no.5
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• pp.349-357
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• 2015

PURPOSE. The purpose of this study was to assess the impact of the core materials, thickness and fabrication methods of veneering porcelain on prosthesis fracture in the porcelain fused to metal and the porcelain veneered zirconia. MATERIALS AND METHODS. Forty nickel-chrome alloy cores and 40 zirconia cores were made. Half of each core group was 0.5 mm-in thickness and the other half was 1.0 mm-in thickness. Thus, there were four groups with 20 cores/group. Each group was divided into two subgroups with two different veneering methods (conventional powder/liquid layering technique and the heat-pressing technique). Tensile strength was measured using the biaxial flexural strength test based on the ISO standard 6872:2008 and Weibull analysis was conducted. Factors influencing fracture strength were analyzed through three-way ANOVA (${\alpha}{\leq}.05$) and the influence of core thickness and veneering method in each core materials was assessed using two-way ANOVA (${\alpha}{\leq}.05$). RESULTS. The biaxial flexural strength test showed that the fabrication method of veneering porcelain has the largest impact on the fracture strength followed by the core thickness and the core material. In the metal groups, both the core thickness and the fabrication method of the veneering porcelain significantly influenced on the fracture strength, while only the fabrication method affected the fracture strength in the zirconia groups. CONCLUSION. The fabrication method is more influential to the strength of a prosthesis compared to the core character determined by material and thickness of the core.

• The Journal of Advanced Prosthodontics
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• v.6 no.5
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• pp.372-378
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• 2014

PURPOSE. The porcelain fused to gold has been widely used as a restoration both with the natural esthetics of the porcelain and durability and marginal fit of metal casting. However, recently, due to the continuous rise in the price of gold, an interest towards materials to replace gold alloy is getting higher. This study compared the bond strength of porcelain to millingable palladium-silver (Pd-Ag) alloy, with that of 3 conventionally used metal-ceramic alloys. MATERIALS AND METHODS. Four types of metal-ceramic alloys, castable nonprecious nickel-chrome alloy, castable precious metal alloys containing 83% and 32% of gold, and millingable Pd-Ag alloy were used to make metal specimens (n=40). And porcelain was applied on the center area of metal specimen. Three-point bending test was performed with universal testing machine. The bond strength data were analyzed with a one-way ANOVA and post hoc Scheffe's tests (${\alpha}=.05$). RESULTS. The 3-point bending test showed the strongest ($40.42{\pm}5.72$ MPa) metal-ceramic bond in the nonprecious Ni-Cr alloy, followed by millingable Pd-Ag alloy ($37.71{\pm}2.46$ MPa), precious metal alloy containing 83% of gold ($35.89{\pm}1.93$ MPa), and precious metal alloy containing 32% of gold ($34.59{\pm}2.63$ MPa). Nonprecious Ni-Cr alloy and precious metal alloy containing 32% of gold showed significant difference (P<.05). CONCLUSION. The type of metal-ceramic alloys affects the bond strength of porcelain. Every metal-ceramic alloy used in this study showed clinically applicable bond strength with porcelain (25 MPa).

• Journal of Technologic Dentistry
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• v.30 no.2
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• pp.31-37
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• 2008

A variety of the porcelain fused to gold(PFG) have been developed to which porcelain can be fused. PFG alloys developed for this purposed have a high melting point and do not discolor when combined with porcelain. The design of the compositions of PFG is very important to esthetic restorative materials applying to porcelain. The purpose of this study is on the change of physical and mechanical characteristics in PFG 18K alloy by the small additional elements. Principal results are as follows. The high Au alloy containing 18Karat gold contents is respectively Au(75%), Pd(10%), Pt(4%), Ag(4%), In(2%), Sn(2%), Cu(2%), Ti(1%). These alloys are composed mainly of gold, platinum, silver and palladium with a few percent of the additional elements. By the addition of small amounts of elements such as In, Sn, Ti, the fine grain castings are produced in gold alloy and the small addition of platinum is very effective in increasing of hardness and strength. These gold alloys are representative of the changes to be expected as a result of heat treatment. These changes in strength and hardness values are sufficient to demonstrate a significant difference in performance between a as-casted and a heat-treated. These alloys have mechanical properties characteristics of Type and Type gold alloys. These alloys are useful to porcelain-metal restorations and dental laboratory. Also the porcelain fused to metal(PFM) alloys containing gold are commonly use for dental purposes in dental laboratory.

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.173-180
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• 2007

There was a great problem about the deposition between materials of a different kind at the beginnings of the introduction of porcelains, however, thereafter the deposition efficiency was settlded to the sufficient level of all user thanks to effort to have studied by many scholars and clinical authorities. But in a clinical process, as the difference of designs has an effect on fractures of porcelains, this researcher divided them into 4 groups of A: 1 mm, B: 2 mm, C: 3 mm, and D: 4 mm, and made 40 pieces to each 10 as the test samples to consider a length axis of tooth for studies in accordance with a position of a finishing line to meet between porcelain and metal at the contact point at the adjacent side to a metal porcelain. The sample materials are those to be use at the open market and the test samples wer completed by the same manufacturing technique to that of existent metal porcelain tube. s a result of the strength test on fractures, the average value is as in the following, A: 1 mm - 8.5bar, B: 2 mm - 10.5bar, C: 3 mm - 14.3bar, and D: 4 mm - 15.0bar. In case of the metal porcelain tube, the more faraway to process parts of metal and porcelain from the contact point of adjacent side has the stronger strength of fractures, Accordingly, the research shows that it had better to keep off more than 3 to consider a ledngth axis of tooth.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.67-84
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• 1991

This study was carried out to investiagate the residual stress caused by the mismatch of thermal expansion and the bond failure resistance of alloy-porcelain specimens. The thermal expansions of alloys and porcelains were measured by using a straight push-rod dilatometer. Porcelain glass transition temperatures, thermal expansion coefficients, and thermal compatibility indices were derived from length-versus-temperature curves. Strain gauges were used to experimentally determine the Young's moduli of porcelains, the residual stresses of porcelain surface, and tensile bond strengths of the specimens of simulated porcelain metal crown. The obtained results were as follows: 1. The coefficients of thermal expansion for alloys were the minimum of $13.53\mu/^{\circ}C$ and the maximum of $20.11\mu/^{\circ}C$ in the range of $100\sim600^{\circ}C$ and those for porcelains were the minimum of $7.72\mu/^{\circ}C$ and the maximum of $31.24\mu/^{\circ}C$ in the range of $100\sim500^{\circ}C$. 2. The glass transition temperature of porcelains exhibited the same value without my relation to the healing rate, and the thermal disharmony of porcelain and alloy was more affected by porcelains than by the alloys. 3. The Young's moduli of body porcelains were larger than those of opaque porcelains(P<0.01) 4. It seemed that the residual stresses of porcelain surfaces in the porcelainalloy systems were more affected by porcelains than by alleys. 5. The bond strengths of the procelain-base metal alloy systems were larger than those of the porcelain-precious metal alloy systems. The fracture strengths of porcelain surfaces showed significant difference between porcelains (P<0.05).

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.2
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• pp.191-200
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• 2012

The patients' demand for treatment of unesthetic anterior teeth is steadily growing. Accordingly, several treatment options such as porcelain laminate veneers(PLV) have been proposed to restore the esthetic appearance of the dentition. Porcelain laminate veneers are considered minimally invasive, but they also require removal of sound enamel. One critical step in the porcelain laminate veneer technique is the achievement of sufficient ceramic thickness, and several different strategies for tooth preparation can be found in the literature. This clinical report describes a step-by-step protocols for preparation of these restorations used with the silicone index from diagnostic wax-up and the acrylic resin mock-up. Conservative use of porcelain laminate veneers provided satisfactory esthetic outcomes and preserved sound tooth structure.

• The Journal of Advanced Prosthodontics
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• v.4 no.4
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• pp.179-186
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• 2012

PURPOSE. The aim of this study was to evaluate the efficiency of manual polishing over autoglazed and overglazed porcelain and their effect on plaque accumulation. MATERIALS AND METHODS. Thirty-six porcelain discs were fabricated out of which 18 each was subjected for autoglazing and overglazing. Half surface of the discs was left intact; the remaining half was roughened with medium grit diamond bur. Roughened surfaces were repolished by porcelain polishing kits (Shofu, DFS, Eve). All the surfaces were evaluated by the perthometer and SEM. Six discs from each sample were placed in human volunteer's mouth for 72 hours to evaluate the plaque accumulation. Acquired data was subjected to ANOVA comparative evaluation. RESULTS. Roughened surfaces had average roughness value of $2.88{\pm}0.1935{\mu}m$. The repolished surfaces by porcelain correction kits Shofu, DFS and Eve, average roughness value reduced to $0.6250{\pm}0.1036$, $0.9192{\pm}0.0953$, $0.9017{\pm}0.1305$ respectively. Autoglazed and overglazed surfaces showed the mean roughness value (Ra) of $0.4217{\pm}0.0685$, $0.3450{\pm}0.0729$. SEM study showed the improved surfaces when subjected for polishing. Plaque accumulation percentage was the highest on roughened surface ($93.83{\pm}6.2552%$), followed by porcelain discs polished by commercial kits. Autoglazed surfaces found to be the best surfaces with the least plaque accumulation ($0.5237{\pm}0.4209%$). CONCLUSION. All the polishing kits used in the study reduced the average roughness by approximately 77%. Corrected porcelain surfaces should ideally be reglazed, alternatively, polish the surfaces before final cementation.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.2
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• pp.96-103
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• 2015

Purpose: The purpose of this study was to spectrophotometrically evaluate the influence of porcelain layer thickness and substructure. Materials and Methods: Four groups of porcelain specimens (metal and ceramic substructure) was prepared for analysis. Color parameters were measured with spectrophotometer and color difference (${\Delta}E*$) were calculated. T-test and one-way ANOVA test were used to find out significant difference and Tukey test was used to identify where the difference ware. Results: Increasing the thickness of porcelain decreased values (P < 0.05). Increasing the thickness of porcelain on ceramic substructure decreased the $a^*$ (P < 0.05) but, the $b^*$ were not statistically different. Total color difference (${\Delta}E*$) were below 1 when the difference of porcelain thickness were 0.5 mm. Conclusion: The thickness of porcelain are the factor effecting on color. This study will help the color are controlled by changing the thickness of porcelain clinically.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.3
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• pp.348-355
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• 2009

Statement of problem: Although the use of colorimeter to improve the accuracy of tooth color measurement has increased, it is real situation that there is almost no comparative study about the accuracy among various colorimeters. Purpose: The purpose of this study is to compare the accuracy of porcelain color reproducibility using ShadeEye-Ncc dental chroma meter (Shofu Inc., Kyoto, Japan) and Shadepilot$^{TM}$ system (Degudent Inc., Hanau, Germany). Material and methods: Color of 2M2 and 3M2 shade tap of Vitapan 3D Master shade guide were measured using the above two colorimeters. Porcelain specimens were fabricated through this data. The porcelain systems used were Vintage Halo Porcelain system with ShadeEye-Ncc dental chroma meter, and VitaOmega900 Porcelain system with Shadepilot$^{TM}$ system. Colors of shade tap models and porcelain specimen were measured with spectrophotometer, and calculated delta E based on the results. Results: The following results were obtained. 1. Shadepilot$^{TM}$ system showed more suitable porcelain color reproducibility compared to ShadeEye-Ncc dental chroma meter (P <.05). 2. The result showed the difference of porcelain color reproducibility according to shade of Shade tap which is model. More suitable porcelain color reproducibility was shown at 3M2 shade tap than at 2M2 shade tap (P <.05). 3. The average of ${\Delta}E*$ of porcelain specimens which was made by the two colorimeters was 4.44-6.14, so the difference of shade was shown through the naked eye. Conclusion: Shadepilot$^{TM}$ system showed more suitable porcelain color reproducibility. When using ShadeEye-Ncc dental chromameter, it will be necessary to improve accuracy through coloring various parts of the whole tooth.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1461-1470
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• 2012

This paper reports the contamination performance of transmission line porcelain insulators tested under five different contaminant conditions - clean and ESDD (equivalent salt deposit density) level (A, B, C, and D) through measurement of their leakage current under drop of potential method. To estimate the contamination for transmission line porcelain insulators, leakage current waveform and its maximum value were measured under step-up power test. In the clean insulators test, % distortion factors decreased with increasing step-up power, and as the ESDD level increased, some characteristics such as frequency analysis, harmonics and % distortion facotor could be used for contamination diagnosis of the transmission line porcelain insulators.