• Journal of dental hygiene science
• /
• v.14 no.1
• /
• pp.29-34
• /
• 2014

The purpose of this study was to evaluate the influence of low temperature degradation (LTD) on the bonding strength of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). The push-shear bond test method was used to investigate the core-veneer bonding strength of industrially manufactured Y-TZP core ceramic and manufacturer recommended veneering ceramic. Four groups from ceramic-zirconia specimens (n=28; n=7 per group) were assigned into four experimental aging conditions, namely storage in an autoclave at $134^{\circ}C$ for 0, 3, 5, 10 hours. Bonding strength was obtained using a universal testing machine with crosshead speed 0.5 mm/min. Data were statistically analyzed using one-way ANOVA and Tukey's test (${\alpha}=0.05$). In bonding strength test, the group which was treated with LTD showed lower bonding strength than no treated group. The ceramic-zirconia bonding strength was affected by LTD (p<0.05). Digital microscope examination of the fracture surface showed mixed failures with adhesive and cohesive types in LTD with treated Y-TZP groups.

• The Journal of Korean Academy of Prosthodontics
• /
• v.34 no.4
• /
• pp.746-754
• /
• 1996

The purpose of this study was to evaluate the fracture strength of porcelain laminate veneer with various lingual extention length when incisal restoring. Sixty recently extracted, intact maxillary incisors were used and stored in a physiologic saline solution from the time of extraction. Seating form was preparation at the labial surface of each tooth with a water-cooled round diamond bur. Standard block was formed with 32 gauge and 24 gauge wax at tooth labial and lingual surface. Lingual extention length differed according to each group. (group I : 0.5mm, group II : 1 mm, group III : 2mm, group IV : 0mm) All tooth specimens were impressioned with examix(GC Inc., Japan). Refractory cast were maked with refractory die material(Ceramco Inc., U.S.A.) Laminate porcelain (Ceramco II Veneer porcelain, Ceramco Inc., U.S.A.) was condensed in refractory die cast and baked according to the manufacturer's recommendations. Each surface was contoured with low speed diamond bur according to guide block. All porcelain specimens were sandblasted and ultrasonically cleaned in distlled water for 3 minutes. Then, all porcelain specimen were etched with 8% hydrofluoric acid for 5 minutes. Sixty specimens were bonded with composite resin cement(Choice Porcelain Veneer System, Bisco Inc., U.S.A.) according to manufacture's directions. The fracture loads of the specimen were measured by Instron universal testing machine. The mean values of fracture loads for the groups were statistically compared by Duncan's multiful range test. The result were as follows : Mean fracture strengths of each group were 86.95Mpa in no lingual extention group, 44.98Mpa in 0.5mm lingual extention group, 27.47Mpa in 1mm lingual extention group, 19.61Mpa in 2mm lingual extention group. There was a statistically significant difference between all group(p<0.01).

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.30 no.4
• /
• pp.81-92
• /
• 2012

The purpose of this study is to compare values, characteristics and the world heritage listed tendency of walls in East Asia. Walls in East Asia are similar by the geographically adjacent, type, form and materials, etc. Thus to demonstrate the differentiation is not easy, but walls heritage of a tentative list or listed on the UNESCO World Heritage were discriminated by the evaluation criteria of world heritage. Hidden problems are not to be described the differences by the consistent manner. So we need efforts to separate the distinction and originality of walls according to the characteristics of each heritage. As the method of this study, we reviewed the terminology associated with the wall and then have examined the following four aspects as the characteristics of each heritage category. 1) Classification according to the function and purpose, 2) Classification according to the type and size of the walls(the length of wall), 3) Classification according to the location and topography, 4) Classification according to materials and technology(construction method). And we have analyzed the tendency of OUV(Outstanding Universal Value) of the world heritage listed wall. Also we examined the value basis of the differences and similarities presented by each heritage. In the future, we should complement the following two aspects of the wall heritage in East Asia for comparing the exact value. first, we ought to come up with a system that we can easily compare the similarities and differences of similar walls heritage. Second, we have to make every effort to describe the walls heritage by considering OUV evaluation criteria to be able to share with people all around the world.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.34 no.3
• /
• pp.115-123
• /
• 2016

In this study, the landscape characteristics of the sacred Dangsan forests at Singi-ri, Namwon-si were investigated as an agricultural heritage, and the management scheme for revitalization of the village was introduced. FAO established the term of 'GIAHS' (Globally Important Agricultural Heritage Systems) for conservation of each country's farmland, unique agricultural landscape, and cultural diversity. The Ministry of Agriculture, Food and Rural Affairs of Korea evaluates that the Agricultural Heritage is a new means and potential for rural development. Dangsan forest, a traditional village forests of rural Korea is a representative 'agricultural heritage' with a history of more than several hundred years of Dangsan ritual. The Dangsan forests were closely linked with paddy fields. This forest was composed of two Dangsan forests, and one Bibo forest. Especially, the Dangsan forest 2 was established on the mounding with 395m in length and 15m in width. Although, most of Dangsan forests do not have accurate records about forest establishment, this forest has retained a stone monument that illustrated the history of the forest. These aspects of Singi-ri's Dangsan forest indicated clear difference and characteristics compared to other ones. This Dangsan forest has been left alone from the public attention. The Dangsan forest at Singi-ri need to be recognized for their valuable landscape characteristics. By linking the Dangsan forest with 'Jirisan trail', the trail path will lead people to the agricultural heritage at Singi-ri. Enhancing the management scheme will contribute to revitalize the village.

• Journal of the Korea Concrete Institute
• /
• v.23 no.5
• /
• pp.683-692
• /
• 2011

In piloti-type low-rise RC residential buildings, severe damages have been usually concentrated at piloti stories under the earthquake. In this study, a piloti story was retrofitted by installation of buckling-restrained braces (BRB's) to increase strength and stiffness of piloti story and by application of fiber reinforced polymer (FRP) sheet on columns to avoid the brittle shear and axial failure of columns. To verify this retrofit performance, reversed cyclic lateral load tests were performed on 1:5 scale bare and retrofitted frames. The test results showed that yield strength (43.2 kN) appeared to be significantly larger than design value (30 kN) due to the increase of strength in the compression side, but the stiffness value (11.6 kN/mm) turned out to be approximately one-half of the design value (24.2 kN/mm). The reasons for this difference in stiffness were due to slippage at joint between the frame and the BRB's, displacement and rotation at footing. The energy absorption capacity of the retrofitted frame was 7.5 times larger than that of the bare frame. The change of the number of load cells under the footing from 2 to 1 reduced lateral stiffness from 11.6 kN/mm to 6 kN/mm, which was only three times larger than that of the bare frame (2.1 kN/mm).

• Journal of the Korean GEO-environmental Society
• /
• v.7 no.3
• /
• pp.5-19
• /
• 2006

The secondary consolidation settlement of soft clay is generally very little compared to the total settlement and occurs very slowly during long-term period. However the secondary consolidation settlement is comparatively large amount in organic and heavily compressed clay and is a very important engineering factor. In order to reduce residual settlements in reclaimed soft ground, the preloading method is often used. In this study, in order to determine reasonable long-term settlements of large reclaimed site, laboratory incremental loading consolidation tests and surcharging consolidation tests are performed. Sampling was done at Incheon area of west coast and Gwangyang area of south coast in Korea. The characteristics of secondary consolidation have obtained through laboratory tests and analyzed systematically to predict long-term settlements. Additionally, the location data and laboratory test results are correlated by using GIS(geographic information system). The secondary consolidation settlement of the site was predicted based on D/B and the operation technique and estimation technique of space of GIS.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.20 no.2
• /
• pp.109-120
• /
• 2004

INTRODUCTION: The build-up method has been used for application of porcelain powder on the metal framework to make final tooth shape conventionally. This method takes time and need skill to mimic final shade and shape of porcelain fused to metal crown. The purpose of this study was to develop standard shape and shade laminating porcelain forms to reduce build-up time. METHODS: To make tooth form porcelain paste, several liquid organic compounds were added to conventional feldspathic porcelain. The amount of additives and rheologic property were tested to find out best composition. Comparison of mixing methods to reduced porosity, proper heating schedule, and measurement of shrinkage amount and residual organic materials were performed to set-up standard procedures. Finally, biaxial flexural strength and color of preformed laminated paste porcelain were compared with those of porcelain which fabricated by the conventional build-up method. RESULTS: There was no significant difference in physical properties and color stability between two fabrication methods after various testing methods. Conclusion: This new build-up method can be applied to fabricate the PFM crown and bridge without any loss of strength and optical properties.

• Journal of Acupuncture Research
• /
• v.29 no.5
• /
• pp.187-195
• /
• 2012

Objectives : Amyotrophic lateral sclerosis(ALS) is a progressive and incurable disease that causes degeneration of the motor neurons of the brain stem and spinal cord. The purpose of this study was to report the effectiveness of Sa-am acupuncture treatment on ALS patient. Methods : Following the stabilization period, a ALS patient respiratory figures(Et $C_{O2}$, Sp $_{O2}$, RR, pulse) were measured by using capnography & pulse oximetry for 30 minutes before acupuncture treatment. Acupuncture treatment such as lung tonification($SP_3(+){\cdot}LU_9(+){\cdot}HT_8(-){\cdot}LU_{10}(-)$), heart tonification($HT_9(+){\cdot}LR_1(+){\cdot}SI_8(-){\cdot}KI_{10}(-)$), liver tonification ($KI_{10}(+){\cdot}LR_8(+){\cdot}LU_8(-){\cdot}LR_4(-)$) were conducted for 5 days. Each Sa-am acupuncture treatment conducted at AM 7 : 00, AM 11 : 00, PM 4 : 30 of the day. During acupuncture treatment, the patient respiratory figures were measured equally for 30 minutes. The patient was treated by using Dong-bang acupuncture needles($0.30{\times}4.0$) and also stimulated using infra red. Results : The value of Et $C_{O2}$ has decreased more after Sa-am acupuncture lung tonification treatment than others. The value of pulse has decreased more after Sa-am acupuncture heart tonification treatment than others. The value of raspiration rate has decreased more after Sa-am acupuncture liver tonification treatment than others. And the value of Sp $O_2$ has increased more after Sa-am acupuncture liver tonification treatment than others. Conclusions : Although this study was subject to a few limitations, but it shows that Sa-am acupuncture treatment for ALS patients has a meaningful effect. This study needs to be developed further using a larger sample size to obtain more valuable and meaningful data.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.28 no.3
• /
• pp.253-268
• /
• 2012

Full-mouth reconstruction of a patient using dental implants is a challenge if there is vertical and horizontal bone resorption, since this includes the gingival area and restricts the position of the implants. however, hard- and soft-tissue grafting may allow the implants to be placed into the desired position. Although it is possible to regenerate lost tissues, an alternative is to use fixed detachable prostheses that restore the function and the esthetics of the gingiva and teeth. Various material combinations including metal/acrylic, metal/ceramic, and zirconia/ceramic have been used for constructing this type of restoration. Other problems include wear, separation or fracture of the resin teeth from the metal/acrylic prosthesis, chipping or fracture of porcelain from the metal/ceramic or zirconia/ceramic prosthesis, and fracture of the framework in some free-end prostheses. With virtually unbreakable, chip-proof, life-like nature, monolithic zirconia frameworks can prospectively replace other framework materials. This clinical report describes the restoration of a patient with complete fixed detachable maxillary and mandibular prostheses made of monolithic zirconia with dental implants. The occluding surfaces were made of monolithic zirconia, to decrease the risk of chipping or fracture. The prostheses were esthetically pleasing, and no clinical complications have been reported after two years.

• Journal of dental hygiene science
• /
• v.13 no.4
• /
• pp.487-492
• /
• 2013

This study aimed to illuminate the correlatives between the surface processing of Zirconia core and the shear bond strength. The specimens were made by precipitating for two minutes in color liquid and drying to produce a colored Zirconia core following the manufacturer's instructions. The specimens were divided into 4 subgroups according to the surface treatment-sandblasted+liner treatment, SLT group; sandblasted treatment, ST group; liner treatment, LT group; non treatment (control), NT group. The specimens were put on the device with regard to ISO/TS 11405, then tested the shear bond strength with 1 mm shearing speed per minute using the Instron multi-purpose tester. The collected data was analysed by one way ANOVA and t-test. After applying the liner and sandblast to the Zirconia core, shear bond strength value were SLT (23.19 MPa), ST (21.17 MPa), LT (20.53 MPa) and NT (16.46 MPa) in the order. There was a significant difference in the surface roughness between NT and ST group (p<0.001), and in the compressive shear bond strength between NT and SLT group (p<0.05). Therefore, sandblasted plus liner treatment on pre-sintered substructure increased the bond strength of veneering ceramic, compared with other surface treatments.