• Title/Summary/Keyword: PFM

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INFLUENCE OF COOLING RATE ON THERMAL EXPANSION BEHAVIOR AND FLEXURAL FAILURE OF PFM SYSTEMS (도재 냉각방법의 차이가 금속-도재간 열팽창 양상과 결합력에 미치는 영향)

  • Lim, Ae-Ran;Lim, Ho-Nam;Park, Nam-Soo
    • The Journal of Korean Academy of Prosthodontics
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    • v.28 no.1
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    • pp.165-191
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    • 1990
  • Although a number of studies have been performed to assure that residual stress caused by a mismatch of alloy porcelain thermal expansion can contribute to clinical failure of a ceramometal restoration, the interactive influence of cooling rate on the magnitude of thermal expansion difference and on bond strength between them have not been extensively analyzed. The objective of this study was to determine the influence of cooling rate and the number of firing cycles on the expansion mismatch and the flexural failure resistance of metal porcelain strip. Tested alloys included one Pd-Ag alloy, one Ni-Cr-Be alloy with two kinds of porcelain, Vita and Ceramco. Metal specimens were cast into rods with a height of 13mm and a diameter of 5mm. Subsequently, the castings were subjected to scheduled firing cycles without porcelain. And the porcelain specimens after being fired were trimmed into a bar with a final dimension of $5{\times}5{\times}25mm$. Thermal expansions of the alloys and porcelains were measured by using a push rod or a differential dialometer respecitvely. Porcelain glass transition temperatures and expansion values were derived alloy-porcelain pairs were assessed by comparing expansion values of the components at a porcelain glass transition temperature. Calculations were made using combinations of a Ni-Cr alloy or Pd-Ag alloy with each of two porcelain products. Metal-porcelain strip specimens were subjected to four point loading in an Instron testing machine until crack occured at the metal-cramic interface at the time of sharp decrease of load on recorder. On the basis of this study, the following conclusions may be stated: 1. Regardless of the kinds of ceramometal combinations, both of calculated and experimental data revealed that the double fired specimens exhibited a significantly lower flexural strength. 2. By the rise of the amount of mismatch, bond strength were decreased. 3. Thermal expansion value of Pd-Ag alloys were higher than that of Ni-Cr alloys. 4. Expansion curves of metal were proportional to the increase of temperature and were not affected by the experimental conditions, however porcelains did not show the same magnitude of metal, and a shift of the glass transition temperature to higher temperatures was observed when cooled rapidly 5. Alloy-porcelain thermal compatibility appeared more dependent on the porcelain than the alloy.

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THREE DIMENSIONAL FINITE ELEMENT ANALYSIS OF THE EFFECTS OF ALVEOLAR BONE LOSS ON STRESS DISTRIBUTION IN POST-RECONSTRUCTED TEETH (치조골 흡수가 포오스트로 인한 치근내 응력에 미치는 영향에 관한 삼차원 유한요소법 분석)

  • Lee, Ky-Young;Chang, Ik-Tae
    • The Journal of Korean Academy of Prosthodontics
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    • v.35 no.4
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    • pp.674-696
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    • 1997
  • There're many cases that should be reconstructed with post and core when clinical crown is destructed. But this post and core restoration may cause damaging stress on the teeth. Previous finite element study was restricted to normal bone model relatively close to cemen-toenamel junction. Moreover, the test of a model with diminished bone support was rare. The purpose of this study is to test the effects of alveolar bone loss on the magnitude, stress distribution and displacement of post reconstructed teeth. In this study, it was assumed that the coronal portion of upper incisor was severely destructed. After conventional endodontic treatment, it was restored with post and core. The PFM restoration was made on it. This crown was cemented with ZPC. Alveolar bone was classified by 4 types of bone, such as normal, 2 mm, 4 mm, 6 mm bone, according to the bone loss. Meanwhile, the material of post are divided into 2 types of materials, such as gold, co-cr. Force was applied to two directions. One was fuctional maximum bite force (300 N) applied to the spot just lingual to the incisal edge with the angle of 45 degree to the long axis of the tooth, and the other one was horizontal force (300 N) applied to the labial surface. The results analyzed with three dimensional finite element method were as follows : 1. Stress was concentrated on the adjacent dentin of the post apex, one third portion of the post apex and the labial & lingual mid-portion of the root in all case. The stress of middle third of the root was apparently concentrated on the labial aspect. 2. The stress on adjacent dentin of the post apex and one third of the post apex increased as alveolar bone height moved apically. This increase was dramatic beyond 4 mm bone loss model. 3. The stress of the post apex was spreaded to the middle third of the post and greater than gold post in the case of metal post. 4. The displacement of the neck of post was the greatest in one of the post-cement interface and this increased as alveolar bone height moved apically. Besides the displacement of the metal post is slightly lower than one of the gold post.

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INFLUENCE OF COOLING RATE ON THERMAL EXPANSION BEHAVIOR AND FLEXURAL FAILURE OF PFM SYSTEMS (도재 냉각방법의 차이가 금속-도재간 열팽창 양상과 결합력에 미치는 영향)

  • Lim, Ae-Ran;Lim, Ho-Nam;Park, Nam-Soo
    • The Journal of Korean Academy of Prosthodontics
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    • v.29 no.1
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    • pp.111-137
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    • 1991
  • Although a number of studies have been performed to assure that residual stress caused by a mismatch of alloy porcelain thermal expansion can contribute to clinical failure of a ceramometal restoratoin, the interactive influence of cooling rate on the magnitude of thermal expansion difference and on bond strength between them have not been extensively analyzed. The objective of this study was to determine the influence of cooling rate and the number of firing cycles on the expansion mismatch and the flexural failure resistance of metal porcelain strip. Tested alloys included one Pd-Ag alloy, one Ni-Cr-Be alloy with two kinds of porcelain, Vita and Ceramco. Metal specimens were cast into rods with a height of 13mm and a diameter of 5mm. Subsequently, the castings were subjected to scheduled firing cycles without porcelain. And the porcelain specimens after being fired were trimmed into a bar with a final dimension of 5 x 5 x 25mm. Thermal expansions of the alloys and porcelains were measured by using a push rod or a differential dialometer respectively. Porcelain glass transition temperatures and expansion values were derived alloy- porcelain pairs were assessed by comparing expansion values of the components at a porcelain glass transition temperature. Calculations were made using combinations of a Ni-Cr alloy or Pd-Ag alloy with each of two porcelain products. Metal- porcelain strip specimens were subjected to four point loading in an Instron testing machine until crack occured at the metal-cramic interface at the time of sharp decrease of load on recorder. On the basis of this study, the following conclusions may be stated : 1. Regardless of the kinds of ceramometal combinations, both of calculated and experimental data revealed that the double fired specimens exhibited a significantly lower flexural strength. 2. By the rise of the amount of mismatch, bond strength were decreased. 3. Thermal expansion value of Pd-Ag alloys were higher than of Ni-Cr alloys. 4. Expansion curves of metal were proportional to the increase of temperature and were not affected by the experimental conditions, however porcelains did not show the same magnitude of metal, and a shift of the glass transition temperature to higher temperatures was observed when cooled rapidly. 5. Alloy- porcelain thermal compatibility appeared more dependent on the porcelain than the alloy.

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The Effect of a Au Based Bonding Agent Coating on Non-Precious Metals-Ceramic Bond Strength (비귀금속 합금에 적용한 Au Based Bonding Agent가 금속-도재 결합에 미치는 영향)

  • Lee, Jung-Hwan;Ahn, Jae-Seok
    • Journal of dental hygiene science
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    • v.9 no.4
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    • pp.405-412
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    • 2009
  • The purpose of this study investigated the effect of Au coating on adhesion between porcelain matrix and metal substructure interface. Titanium, Ni-Cr alloy and Co-Cr alloy are well known as proper metal for the dental restorations. The success of a porcelain fused to metal (PFM) restoration depends upon the quality of the porcelain-metal bond. However, adhesion between dental alloys and porcelain is related to diffusion of oxygen during ceramic firing. The excessive oxidized layers make hard adhesion between dental alloy and ceramic. Ni-Cr and Co-Cr specimens were divided into test and a control group and Titanium specimens were divided into three test groups and a control group. Each group had 20 specimens. The adhesion characteristics of porcelain and metal with Au coating layer and without Au coating layer were observed with scanning electron microscopy(SEM). The adhesion was evaluated by a biaxial flexure test and volume fraction of adherent porcelain was determined by SEM/EDS analysis. Result of this study suggest that Au coating layer is effective barrier to diffuse oxide layer completely protect non-precious alloys from oxidation during the porcelain firing. The SEM photomicrographs of cross-section specimens showed a smooth interface between Au coating layer and metals and porcelain which suggested proper chemical bonding, and no gap, porosity were observed. The mode of failure was mainly adhesive for Ti tested specimens, but mixed failures with adhesive and cohesive were observed in Ni-Cr and Co-Cr specimens. The adhesion between non-precious metals and porcelain would not be improved by Au coating agent. However, It is suggested that the continuous study is required further investigation and development.

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Full mouth rehabilitation using orthodontic treatment and implants in patient with collapsed occlusion: A case report (붕괴된 교합을 가진 환자에서 교정치료와 임플란트를 이용한 전악 수복: 증례보고)

  • Ahn, Ayoung;Koak, Jai-Young;Heo, Seong-Joo;Kim, Seong-Kyun
    • The Journal of Korean Academy of Prosthodontics
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    • v.57 no.4
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    • pp.439-447
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    • 2019
  • The distance between the natural teeth and the implants is an important factor in preserving the periodontal tissues and esthetics. And abnormal positional displacement and tilting of the teeth during restorative procedure may require intentional root canal treatment and may affect masticatory function. This report is to present a successful full mouth rehabilitation of a patient with uneven dentition and collapsed occlusion using orthodontic and implant treatment. The patient had no symptoms or discomfort of temporomandibular joint disorder such as pain or sound. The orthodontic treatment was continued until implant provisional prosthesis delivery. And the vertical height of occlusion was elevated 2mm on anterior basis for anterior teeth protection and esthetics. After the orthodontic treatment, the implant abutments and natural teeth were finally restored with porcelain-fused-to-metal crowns and bridges. Satisfactory function and esthetic outcomes are observed after 6months of follow up.

Rehabilitation of posterior support and vertical dimension in a class 3 malocclusion patient: A case report (III급 부정교합 환자에서 상악 가철성 국소 의치와 하악 임플란트 지지 고정성 보철물을 이용한 구강 회복 증례)

  • Oh, Ji-Hwan;Pyo, Se-Wook;Chang, Jae-Seung;Kim, Sunjai
    • The Journal of Korean Academy of Prosthodontics
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    • v.60 no.2
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    • pp.175-186
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    • 2022
  • A crossed occlusion resulting from the presence of posterior teeth in one arch but no opposing teeth in the opposite arch results in collapse of the vertical dimension. In this case, the patient has a class III malocclusion with crossed occlusion and anterior crossbite. In order to evaluate the proper vertical dimension, provisional denture was used to stabilize the vertical occlusal dimension for 3 months. After, provisional fixed restoration was used for the stabilizing occlusal relationship and aesthetic improvement for lip support. Definitive prosthesis in implants in the mandible and abutments in the maxillary were using Porcelain-fused-to-metal crown (PFM) crown and the maxillary unilateral edentulous area was treated with removable partial dentures. Through this, proper support of the posterior region and normal anterior occlusal relationship were formed, and the patient was able to obtain aesthetically and functionally satisfactory treatment results.

Manufacturing and testing of flat-type divertor mockup with advanced materials

  • Nanyu Mou;Xiyang Zhang;Qianqian Lin;Xianke Yang;Le Han;Lei Cao;Damao Yao
    • Nuclear Engineering and Technology
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    • v.55 no.6
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    • pp.2139-2146
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    • 2023
  • During reactor operation, the divertor must withstand unprecedented simultaneous high heat fluxes and high-energy neutron irradiation. The extremely severe service environment of the divertor imposes a huge challenge to the bonding quality of divertor joints, i.e., the joints must withstand thermal, mechanical and neutron loads, as well as cyclic mode of operation. In this paper, potassium-doped tungsten (KW) is selected as the plasma facing material (PFM), oxygen-free copper (OFC) as the interlayer, oxide dispersion strengthened copper (ODS-Cu) alloy as the heat sink material, and reduced activation ferritic/martensitic (RAFM) steel as the structural material. In this study, a vacuum brazing technology is proposed and optimized to bond Cu and ODS-Cu alloy with the silver-free brazing material CuSnTi. The most appropriate brazing parameters are a brazing temperature of 940 ℃ and a holding time of 15 min. High-quality bonding interfaces have been successfully obtained by vacuum brazing technology, and the average shear strength of the as-obtained KW/Cu and ODS-Cu alloy joints is ~268 MPa. And a fabrication route for manufacturing the flat-type divertor target based on brazing technology is set. For evaluating the reliability of the fabrication technologies under the reactor relevant condition, the high heat flux test at 20 MW/m2 for the as-manufactured flat-type KW/Cu/ODS-Cu/RAFM mockup is carried out by using the Electron-beam Material testing Scenario (EMS-60) with water cooling. This paper reports the improved vacuum brazing technology to connect Cu to ODS-Cu alloy and summarizes the production route, high heat flux (HHF) test, the pre and post non-destructive examination, and the surface results of the flat-type KW/Cu/ODS-Cu/RAFM mockup after the HHF test. The test results demonstrate that the mockup manufactured according to the fabrication route still have structural and interfacial integrity under cyclic high heat loads.

Conceptual Design of the Three Unit Fixed Partial Denture with Glass Fiber Reinforced Hybrid Composites (Glass fiber 강화 복합레진을 사용한 3본 고정성 국소의치의 개념 설계 연구)

  • Na, Kyoung-Hee;Lee, Kyu-Bok;Jo, Kwang-Hun
    • Journal of Dental Rehabilitation and Applied Science
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    • v.18 no.3
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    • pp.145-155
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    • 2002
  • The results of the present feasibility study are summarized as follows, 1. The three unit bridge of knitted material and UD fibre reinforcement has both the rigidity and the strength against a vertical occlusal load of 75N. 2. Stress concentration at the junctional area between the bridge and the abutments, i.e. between the pontic and the knitted caps was observed. In the case of the bridge with reinforcement straps, it was partly shown that the concentration problem could be improved by simply increasing the fillet size at the area. Further refining in the surface of the junctional area will be needed to ensure a further improvement in the stress distribution. This will require some trade off in the level of the stress and the available space. A parametric study will help to decide the appropriate size of the fillet. 3. Design refinement is a must to improve the stress distribution and realize the most favourable shape in terms of fabrication. The current straight bar with a constant cross section area can be redesigned to a tapered shape. The curve from the dental arch should also be placed on the pontic design. In accordance with design refinement, the resistance of the bridge frame to other load cases should be evaluated. 4. Although not included in the present feasibility study, it is estimated that bridges of the anterior teeth can be made strong enough with the knitted material without further reinforcement using unidirectional materials. In this regard, a feasibility study on design concepts and stress analysis for 3, 4, 5 unit bridge is suggested. 5. Two types of bridge were analysed in terms of fatigue. The safe life design concept, i.e. fatigue design concept, looks reasonable for the bridge where if cracks should form and propagate there is virtually nothing a dentist to do. The bridge must be designed so that no crack will be initiated during the life span. In the case of crowns, however, if constructed with composite resin with knitted materials, it might be possible to repair them, which in general is impossible for crowns of PFM or of metal. Therefore for composite resin crowns, a damage tolerance design concept can be applied and reasonably higher operational stresses can be allowed. In this case, of course, a periodic inspection program should be established in parallel. 6. Parts of future works in terms of structural viewpoint which need to be addressed are summarized as the following: 1) To develop processing technology to accommodate design concepts; 2) More realistic modelling of the bridge and analysis-geometry and loading condition. Thickness variation in the knitted material, taper in the pontic, design for anterior tooth bridge, the effect of combined loads, etc, will need to be included; 3) To develop appropriate design concepts and design goals for the fibre composite FPD aiming at taking the best advantage of knitted materials, including the damage tolerance design concept; 4) To develop testing method and perform test such as static ultimate load test, fatigue test, repair test, etc, as necessary.

Differences in serum ferritin and vitamin D levels of Korean women with obesity and severe obesity (비만과 고도비만 한국 여성의 혈청 페리틴과 비타민 D 수준의 비교)

  • Kang, Nan Hui;Park, Ji Sook;Lee, Hongchan;Yim, Jung-Eun
    • Journal of Nutrition and Health
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    • v.53 no.4
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    • pp.381-389
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    • 2020
  • Purpose: This study examined the relationships among serum ferritin, vitamin D, folate, iron, and vitamin B12 as indicators of obesity. The results provide the basic data for the prevention and treatment of obese and severely obese people. Methods: This study selected 44 people from 18 years of age or older to 59 years. This study used the indicators of the body mass index (BMI) to analyze obesity as the obesity group (BMI of 25.0-29.9 kg/㎡) and as the severe obesity group (BMI ≥ 30.0 kg/㎡). Of the 44 subjects, 23 and 21 subjects were in the obesity and severe obesity groups, respectively. Their height, weight, body fat, skeletal muscle mass measured using bioimpedance analysis, and measured serum nutrients and biochemical parameters. Results: The obesity group showed a significantly lower age, body weight, BMI and body composition, body fat mass, and body fat percentage, and the height was significantly lower in the severe obesity group. The results of the biochemical parameters of the subjects showed that the levels of aspartate transaminase, alanine transaminase, hemoglobin A1c, total cholesterol, and triglyceride were within the normal range, and there was no significant difference between the 2 groups. The levels of folate, vitamin B12, 25-hydroxyvitamin D3, iron, and ferritin were almost normal, and there was no significant difference between the 2 groups. Conclusion: This study revealed an association with the serum nutrients and obesity, but there was no difference between the obesity group and severe obesity group. Observations of the nutrient levels in not only the blood in obesity and severe obesity but also in red blood cells and tissues will be necessary.

Effect of Pentoxifylline Concentration on Sperm Quality in Jeju Crossbred Horses (Jeju Crossbred Horses 정액 생산 시 Pentoxifylline 농도가 정자 성상에 미치는 영향)

  • Park, Seol-Hwa;Shin, Sang-Min;Yang, Byoung-Chul;Kim, Nam-Young;Woo, Jae-Hoon;Shin, Moon-Cheol;Yoo, Ji-Hyun;Son, Jun-Kyu
    • Journal of Embryo Transfer
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    • v.33 no.1
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    • pp.17-22
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    • 2018
  • This study was conducted to determine the effect of pentoxifylline levels on sperm motility, survival rate, sperm membrane integrity of frozen semen and fresh-extended equine semen in Jeju cross-bred horses. As a result of sperm characteristic comparison depending on pentoxifylline levles at 30 minutes post-thaw, the progressive motilities were $53.25{\pm}2.87$ (4mM pentoxifylline) and $50.28{\pm}2.14$ (8mM pentoxifylline) and significantly higher compared to the control group($40.09{\pm}5.15$) and other treatment group (16mM pentoxifylline, $41.27{\pm}2.82$). The progressive fast motility were $22.44{\pm}1.62$ (4mM pentoxifylline,) and $22.74{\pm}3.07$ (8mM pentoxifylline) and significantly higher compared to the control group ($13.47{\pm}1.48$) and other treatment group (16mM pentoxifylline, $14.66{\pm}3.68$) (p<0.05). As a result of sperm characteristic comparison depending on pentoxifylline levles at 30 minutes post-thaw were $68.96{\pm}1.64$ (4mM pentoxifylline) and $67.90{\pm}6.72$ (8mM pentoxifylline) and significantly higher compared to the control group ($53.48{\pm}4.84$) and other treatment group (16mM pentoxifylline, $58.14{\pm}2.65$) (p<0.05). In conclusion, these results suggest that treatment groups with 4mM and 8mM pentoxifylline were higher compare to equine seperm mobility and the control group and treatment groups with more than 16mM pentoxifylline has a negative effect on sperm characteristics. After thawing, the total motility in post-thawed equine sperm has increased by 10 percent for 1 hour. these results suggest that pentoxifylline contributes to the improvement of the equine sperm motility and characteristics in post-thawed semen.