• Conservation Science in Museum
• /
• v.14
• /
• pp.29-35
• /
• 2013

In cases, such as white porcelain with openwork lotus scroll design, where the ceramics has intricate form and decorations, we normally use casts to restore the work, in that current restoration materials have short molding time which causes difficulties in delicate work. However, since using a cast for restoration requires longer work-time and uses more materials, we decided to restore in direct. Since the molding time in the restoration material is closely related to the workability, restoration material which secures longer work hours is necessary when directly restoring a complex form of body. Therefore we experimented on the work-time, color variation and workability as time passes by making mixtures of Epoxy putty and Baked clay in different ratios. As a result of the experiment, the mixture ratio of OS8:RQ2 turned out to be the most effective ratio.

• Journal of Technologic Dentistry
• /
• v.24 no.1
• /
• pp.9-18
• /
• 2002

The aim of this study is to propose effective measures for shortage of manpower of dental technology laboratory in Gangwon province by means of examining not only the history of Gangwon association, present condition of transference of members of Gangwon association from 1990, of missing members and annual rate of participation in repair education with setting object of study into Gangwon association under the influence of the Korean Dental Technology Association but also the present condition of opening and closing laboratory, amount of business connection and condition of shortage of manpower and its field with setting object of study into 28 dental technology laboratories. Results from this study are like followings : First, Gagnwon association was established in 1984 as the eleventh in the line of the board, reorganization of board is conducted 8 times up to the eighth in the line of the board in 2001. board is composed of 16 persons including president and operated its term as 3 years. Second, a number of representative and ordinary member of Gangwon association has increased gradually from 1992 to 2001. in aspect of annual rate of participation in repair education, representative's is more higher than ordinary member's overall. the worst rate of whole members' is shown as 47.9% and the its best rate is shown as 92.0%. in addition, 70$\sim$80% rate of participation into repair education is shown most frequently as 8 times of whole 20 times from 1992 to 2001. Third, 29 authorized dental technology laboratories have registered in Gangwon association until march 2002 within 9 cities and counties. in consideration of establishment location. Gangneung city has most amount as 7 laboratories(24.1%), Wonju city has 5(17.2%), Samcheok city and Sokcho city, each has 4(13.8%), Chuncheon city has 3(10.3%), Donghae city and Taeback city, each has 2(6.9%) and Yangyang and Yongwol county, each has 1(3.4%). Fourth, amount of work personnel of laboratory in Gangwon province is 1$\sim$10 persons as the maximum value. 23 laboratories(82.1%) have their own work personnel as amount of 5 and below. in aspect of main business, most of laboratories focus on the Porcelain and Crown. and 16 laboratories(57.1%) have their own expensive equipments such as Milling. its also suggests that 16 laboratories(57.1%) suffer their shortage of working personnel. specifically, 6 laboratories(21.4%) suffer the highest shortage especially in Denture field, Fifth, whole number of Gangwon association is up to 101 members (28 representatives and 73 ordinary members) until December 31th 2001. amount of immune from repair education of Gangwon association until October 2001 is up to 10 persons, and missing members from 1997 is up to 18 persons, suspension of business is up to 4 persons. in aspect of transference from 1990, transfer-in is up to 21 persons and transfer out is up to 16 persons.

• The Journal of Korean Academy of Prosthodontics
• /
• v.49 no.2
• /
• pp.161-167
• /
• 2011

Purpose: The purpose of this study was to evaluate the influence of porcelain re-firing on the formation of surface bubble and on the change in shade of metal-ceramic crown exposed to artificial saliva. Materials and methods: Thirty disk-shaped specimens were made in 10 mm diameter with 0.5 mm metal core thickness and 1 mm ceramic thickness. A spectroradiometer was used to determine the CIE Lab coordinates. The number and size of surface bubble were observed with a stereomicroscope. After the exposure to artificial saliva for 7 days, re-firing was performed at glazing temperature. After re-firing, the CIE Lab were calculated, and the number and size of surface bubble were observed again. The change in shade was expressed with ${\Delta}E$. Statistical analysis was done with paired t-test for the change in the number of surface bubble and student t-test for the change in the size of surface bubble (${\alpha$}=0.05). Results: Shade difference was calculated 2.14 ${\Delta}E$ units. The mean number of surface bubble was $1.33{\pm}1.49$ before re-firing, $3.27{\pm}2.90$ after re-firing. After re-firing, the number of surface bubble was significantly increased (P<.05). The mean size of surface bubble was $81.97{\pm}32.03\;{\mu}m$ before re-firing, $142.94{\pm}47.40\;{\mu}m$ after re-firing. After re-firing, the size of surface bubble was significantly increased (P<.05). Conclusion: Shade change after re-firing was perceptible (${\Delta}E$ < 2.0) and clinically acceptable (${\Delta}E$ < 3.7). The number and size of surface bubble was significantly increased after re-firing. Further investigation to decrease the surface bubble on the extra oral repair of metal-ceramic crown, will be needed in future study.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.22 no.2
• /
• pp.149-159
• /
• 2006

Statement of problem. Porcelain repair mainly involves replacement with composite resin, but the bond strength between composite resin and all-ceramic coping materials has not been studies extensively. Purpose. The objective of this study was to investigate the influence of composite resin and ceramic etching pattern on shear bond strength of Empress2 ceramic and observe the change of microstructure of ceramic according to etching methods. Material and methods. Eighty-five cylinder shape ceramic specimens (diameter 5mm, IPS Empress 2 core materials) embeded by acrylic resin were used for this study. The ceramic were specimens divided into sixteen experimental groups with 5 specimens in each group and were etched with phosphoric acid(37%, 65%) & hydrofluoric acid (4%, 9%) according to different etching times(30s, 60s, 120s 180s). All etched ceramic surfaces were examined morphologically using SEM(scanning electron microscopy). Etched surfaces of ceramic specimens were coated with silane (Monobond-S) & adhesive(Heliobond) and built up composite resin using Teflon mold. Accomplished specimens were tested under shear loading until fracture on universal testing machine at a crosshead speed 1mm/min; the maximum load at fracture(kg) was recorded. Shear bond strength data were analyzed with one way ANOVA and Duncan tests.(P<.05) Results. Maximum shear bond strength was $30.07{\pm}2.41(kg)$ when the ceramic was etched with 4% hydrofluoric acid at 120s. No significant difference was found between phosphoric etchant group and control group with respect to shear bond strength. Conclusion. Empress 2 ceramic surface was not etched by phosphoric acid, but etched by hydrofluoric acid.