• Journal of Technologic Dentistry
• /
• v.25 no.1
• /
• pp.21-28
• /
• 2003

The purpose of this study was to process bio-active glass ceramic composite, reinforced with sapphire fibers, by hot press. Also to study the interface of the matrix and the sapphire fiber, and the mechanical properties. Glass raw materials melted in Pt crucible at 1300$^{\circ}C$ during 3.5 hours. The melt was crushed in ball mill and then crushed material, ground and sieved to $<40{\beta}{\mu}m$. Sapphire fibers cut (30mm) and aligned. Powder and fibers hot pressed. The micrographs show good bonding between the matrix and the fiber and no porosity in the glass matrix. This means ideal fracture phenomena. Glass is fractured before the fiber. This is indication of good fracture strength. EDXS showing aluminum rich phase and crystalline phase. Bright field image of the matrix showing crystalline phase. Also diffraction pattern of TEM showing the crystalline phase and more than one phase. Strength of the samples was determined by 3 point bend testing. Strength of the 10vol% sample was approximately 69MPa, while strength of the control sample is 35MPa. Conclusions through this study as follow: 1. Micrographs show no porosity in the glass matrix and the interface. 2. The interface between the fiber and the glass matrix show no gaps. 3. Fracture of the glass indicates characteristic fiber-matrix separation. 4. Presence of crystalline phase at high processing temperature. 5. Sapphire is compatible with bioactive glass.

• Journal of Technologic Dentistry
• /
• v.29 no.1
• /
• pp.35-48
• /
• 2007

The purpose of this study was to evaluate shade selection using conventional visual assessment in vivo natural teeth and porcelain-fused-to-metal (PFM) crown. Maxillary central incisors, lateral incisors and canines of one hundred twenty four college women were used as vivo natural teeth. Fifty one PFM crown for maxillary central incisor fabricated by dental laboratory were used as experimental materials. Using Vitapan Classical Shade Guides, shade selection of natural teeth was measured by each college woman and shade selection of PFM crown was measured by three ceramists with more than ten years career. Both natural teeth and PFM crown shade selection were measured through Shade Eye-Ex. From the shade selection comparing, following results were obtained. The results were as follows: 1. The shade matching identification of natural teeth between the shade selection using Vitapan Classical Shade Guides and the shade selection using Shade Eye-Ex was 27.4% in maxillary central incisor, 13.7% in lateral incisor and 18.5% in canine. 2. Among the shade selection of PFM crown by three ceramists, the shade evaluation of three ceramists were same only in ten cases. In twenty case, those of two ceramists were same. 3. The shade matching identification of PFM crown between the shade selection using Vitapan Classical Shade Guides and the shade selection using Shade Eye-Ex was 38.6% in average. These results suggest that the shade selection using conventional visual assessment should be dealt with care in clinic and need a credible method for shade matching color.

• Journal of Technologic Dentistry
• /
• v.32 no.1
• /
• pp.17-21
• /
• 2010

This experimental study was to determine the fitness in each cervical margin of reusing porcelain gold alloy. The gold alloy used in this experimental study was a Au-Pt-Pd alloy (BDCG-898, Bukwang Inc, Korea) for the fabrication of porcelain fused to metal crown. Twenty-five copings were divided into the five groups. And the group A, B, C, D and E were cording successively according to the frequency of reuse to five times. Each specimen was reused without adding new metal. The experimental results were as follows: 1. The group A, B, C showed good fitness in each cervical margin. 2. The group D got good fitness in labio and linguo cervical margin, but the mesio and disto cervical margin showed more than $40{\mu}m$ 3. The group E showed worse fitness than the other groups in each cervical margin.

• Journal of Technologic Dentistry
• /
• v.14 no.1
• /
• pp.119-132
• /
• 1992

This paper aims to investigate the effect of B and Si upon the mechanical properties, microstructure and corrosion resistance of Co-Cr base alloy. Ten groups of alloy ingot ingot with various contents of B and Si were remelted by high frequency electrical induction furnace and cast into tensile specimen of ADA Specification No. 14 Tensile and hardness test were carried out by Amsler and Rockwell hardness tester(R-30N), respectively. The microstructures of specimen were observed by SEM. The results obtained are summarized as follows : 1. As B content is increased, tensile strength, yield strength and Rockwell hardness number(R-30N) are also increased significantly, while the elongation is decreased significantly. 2. As Si contect os increased, no significant chang in tensile strength is noticed, yield strength is slightly decreased, but Rockwell hardness number(R-30N) is moderately in creased, Elongation marks maxium value with 1% Si content while with more than 1% Si it is decreased. 3. As B content is increased corrosion resistance is decreased and is at best with 1.5% B content. Corrosion resistance is increased with the increase of Si content and the alloys with Si over 3.0% showed corrosion resistance. 4. As B content increased, precipitates are increased in number at grain boundaries. The grain size tends to become coarse with the increase of Si content. 5. Co rich-Cr alloy is present through matrix whereas at the grain boundaries Cr base precipitates are primarily formed.

• Journal of Technologic Dentistry
• /
• v.8 no.1
• /
• pp.51-55
• /
• 1986

The castability of base metal alloys for dental casting in influenced by burn-out temperature and recent percentage. Burn-out temperatures for casting are set at 200$^{\circ}F$ interval from 1000$^{\circ}F$ to 1800$^{\circ}F$. According to recast metal percent in new cast alloy metal alloys are tested. The results are as followings: 1. In the new alloy(100%), the castability is the most. 2. The burn-out temperature in 1600$\sim$1800$^{\circ}F$, castability of 100% new alloy was more four times than of 50% new alloy plus 50% recast alloy. The using of 50% new alloy and 50% recast alloy, therefore, was unlike in castability. 3. The burn-out temperature in 1600$^{\circ}F$, castability of 100% new alloy was more than four times in soaking 20 minutes, but there was no any difference at 18700$^{\circ}F$. 4. It is investigated that the optimal burn-out temperature is 1600$^{\circ}F$ for the C & B alloy.

• International Journal of Advanced Culture Technology
• /
• v.6 no.4
• /
• pp.52-57
• /
• 2018

The purpose of this paper is to develop simulations that can be used for virtual education in dentistry. The virtual education to be developed will be developed with clinical training and actual case data of tooth extraction. This development goal is to allow dental students to learn the necessary surgical techniques at the point of their choice, not going into the operating room, away from time, space, and physical limits. I want to develop content using VR. Oculus Rift HMD, Optical Based Outside-in Tracking System, Oculus Touch Motion Controller, and Headset as Input / Output Device. In this configuration, the optimization method is applied convergent, and when the operation of the VR contents is performed, the content data is extracted from the interaction analysis formed in the VR engine, and the data is processed by the content algorithm. It also computes events and dental operations generated within the 3D engine programming and generates corresponding events through data processing according to the input signal. The visualization information is output to the HMD using the rendering information. In addition, the operating room environment was constructed by studying lighting and material for actual operating room environment. We applied the ratio of actual space to virtual space and the ratio between character and actual person to create a spatial composition at a similar rate to actual space.

• Journal of Technologic Dentistry
• /
• v.31 no.2
• /
• pp.31-38
• /
• 2009

In recent year, the population for sports has been increased and lots of wounded patients at the oral & facial portion were troubled with the accidents. So, it was needed to protect them from the sports accident, by the use of the mouthguard appliance. This study was done as ae guide for selection of the mouthguard materials. Such mouthguards classified as E.V.A., PE, silicone as material, Scheu(Germany), Tru-Tain(U.S.A.), Dreve(Germany) as companies, 1.5mm, 3.0mm, and 4.0mm as thickness and single sheet, soft double sheet, hard double sheet methods were selected for experiment to compare the fracture protect test. The obtained results are as follows. 1. All types of mouthguards, whatever differences there are in material, production company, procedure and the thickness, were effective for fracture protect effect. 2. The most effective one for fracture protection was recommended as E.V.A. in material, and Tru-Tain in company. 3. More thick, and soft & hard multi sheets productions were more effective for fracture protection.

• Journal of Technologic Dentistry
• /
• v.6 no.1
• /
• pp.11-14
• /
• 1984

The auther performed this experimental study on cervical margin distortion in preheating method during soldering. 1. In soldering methods, the method using the furnace has less distortion than the method using open-flame and longer the bridge spon, the larger the distortions. 2. Table Ⅰ Showed that buccal margin, lingual margin, mesial margin and distal margin had respectively 0.01mm, 0.02mm, 0.03mm, 0.03mm closer adaptation in 3 unit bridge than in 5 unit bridges. 3. Table II showed that buccal margin, lingual margin, mesial margin and distal margin had respectively 0.06mm, 0.07mm, 0.11mm, 0.05mm closer adaptation in 3 unit bridge than in 5 unit bridges.

• Journal of Technologic Dentistry
• /
• v.31 no.1
• /
• pp.17-21
• /
• 2009

This experimental study was to determine the fitness on each cervical margin of recast using crown base metal alloy. The alloy used in this experimental study was a Ni-Cr alloy(Wirolloy, Bego, Germany) for the fabrication of full cast crown prosthesis. Twenty-five copings were divided into the five groups. And the group A, B, C, D and E were cording successively according to the frequency of recast to five times. Each specimen was recasted without adding new metal. The experimental results were as follows: 1. The group A and B showed good fitness had subtle differences in each cervical margin adaptation, in other words, the mesio and disto cervical margin showed worse adaptation than the bucco and linguo cervical margin. 2. The group C got good fitness in bucco and linguo cervical margins, but the mesio and disto cervical margin showed inaccurate fitness. And I could not get good casting bodies without adding new metal. 3. The group D and E showed bad fitness for each cervical margin. Therefore the group D and E lost its function as a dental restoration.

• Journal of Technologic Dentistry
• /
• v.23 no.2
• /
• pp.95-103
• /
• 2002

For this study, self curing resin and heat curing resin used for existing usual resin denture base in the denture industry were chosen by manufacturer. Curing tests for 30-minute, I-hour, 2-hour and 3-hour were conducted to know the strength of the resins and conduct analysis to get other necessary information. The results obtained are as follows: 1. Heat curing resins show a little differences among the manufacturers. However 30-minute curing resin shows great difference as shown in the fracture strength test. 2. The effect from the granularity of the resins on the fracture strength was found insignificant which means there is no difference between coherence and strength. 3. To summarize the results from each time level, the longer the time is, the more the minute cracks on the surface, which is the cause of reduced strength. From this test, it was identified that in making the denture base for patients in dental clinics, 30-minute curing is most efficient and effective in reducing discoloration and monomers, although long-time curing has been considered to be the principal.