• Journal of Dental Rehabilitation and Applied Science
• /
• v.28 no.2
• /
• pp.119-126
• /
• 2012

State of problem: Cement-retained implant-supported prostheses are routinely used in dentistry. The use of high strength cements has become more popular with the increasing confidence in the stability of the implant-abutment screw connection and the high survival rates of osseointegrated implants. No clinical data on retention of metal copings using CAD/CAM. To evaluate retention of metal copings using CAD/CAM system bonded to short titanium abutment with four different cements and compare retentive strength of metal copings with sandblasting or without sandblasting before cementation. Forty titanium abutment blocks were fabricated and divided into 4 groups of 10 samples each. Forty metal copings with occlusal hole to allow for retention testing were fabricated using CAD/CAM technology. The four cements were Fujicem(Fuji, Japan), Maxcem Elite(Kerr, USA), Panavia F2.0(Kurarary, Japan) and Superbond C&B(Sunmedical, Japan). The copings were cemented on the titanium abutment according to manufacture's recommendation. All samples were stored for 24h at 37oC in 100% humidity and tested for retention using universal testing machine(Instron) at a crosshead speed of 1.0mm/min. Force at retentive failure was recorded in Newton. The mode of failure was also recorded. Means and standard deviations of loads at failure were analyzed using ANOVA and Paired t-test. Statistical significance was set at P<0.05. Panavia F2.0 provided significantly higher retentive strength than Fujicem, Maxcem Elite(P<0.05). Sandblasting significantly increased bond strength(P<0.05). The mode of failure was cement remaining principally on metal copings. Within the limitation of this study, Panavia F2.0 showed significantly stronger retentive strength than Fujicem, Maxcem Elite(p<0.05). The Ranking order of the cements to retain the copings was Panavia F2.0, Fujicem = Maxcem Elite. Sandblasting significantly increased bond strength(P<0.05). The retentive strength of metal copings on implant abutment were influenced by surface roughness and type of cements.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.28 no.4
• /
• pp.673-682
• /
• 2001

The use of resin composites has continued to increase over the last several years. In spite of their growing popularity, composites continue to exhibit a number of undesirable characteristics. One of the major deficiencies of composite restorative resins is their inadequate resistance to wear. Of the multitude of factors that have been associated with wear, subsurface degradation within the restoration is considered to be one. The aim of this study was to evaluate the resistance to degradation of four commercial composite resins in an alkaline solution. This solution with a high concentration of hydroxyl ions is a convenient medium for accelerated degradation of silane coupling and filler particles. The brands studies were Definite($Degussa-H\ddot{u}ls$ AG, Germany), Prodigy(Kerr, USA), Pyramid(Bisco, USA) and Synergy(Coltene, Swiss). Preweighed discs of each brand were exposed to 0.1N NaOH solution at $60^{\circ}C$. After 14 days they were removed, neutralized with HCl, washed with water and dried. Resistance to degradation was evaluated on the basis of following parameters : (a) mass loss(%)-determined from pre-and post-exposed specimen weights : (b) Si loss(ppm)-obtained from ICP-AE analysis of solution exposed to specimens; and (c) degradation $depth({\mu}m)$-measured microscopically (SEM) from polished circular sections of exposed specimens. The results were follows: 1. Mass loss of Synergy was $1.24{\pm}0.002%$, it was the highest, there was no significant difference among the materials. 2. The degree of degradation layer depth of Synergy was $107.83{\pm}2.52{\mu}m$, it was the highest, there was no significant difference among any other materials than Synergy. 3. There was no difference among the four materials in Si loss. 4. The correlation coefficient between mass loss and degradation depth was relatively high(r=0.06, p<0.05). 5. There was no coefficient correlation between Si loss and mass loss, the degree of degradation layer depth and Si loss. 6. When observed with SEM, destruction of bonding is observed between resin matrix and filler.

• Journal of the Korean Magnetics Society
• /
• v.27 no.2
• /
• pp.41-48
• /
• 2017

Recent study shows that ordered alloy of $L1_2$ $XPt_3$ (M = V, Cr, Mn, Co, and Fe) exhibits various magnetic phases such as ferromagnetic-to-antiferromagnetic transition at the $MnPt_3$ surface. Moreover, it has been argued that $CrPt_3$, in particular, possess large magnetocrystalline anisotropy and Kerr rotation with possible violation of Hund's rule. As such, we extend our work to thickness dependence of the magnetic structure of $CrPt_3$ thin film using density functional theory. Magnetic ground state of the bulk $CrPt_3$ turns out to be ferromagnetic (FM), where other magnetic phases such as A-type (A-AF), C-type (C-AF), and G-type antiferromagnetic (G-AF) state have higher total energies than FM by 0.517, 0.591, and 0.183 eV, respectively, and magnetic moments of Cr in bulk are respectively 2.807 (FM), 2.805 (A-AF), 2.794 (C-AF) and $2.869_{{\mu}_B}$ (G-AF). We extend our study to $CrPt_3$(001) thin films with CrPt-and Pt-termination. The thickness and surface-termination dependences of magnetism are investigated for 3-9 monolayers (ML), where different magnetic phases from bulk emerge: C-AF for CrPt-terminated 3 ML and G-AF for Pt-terminated 5 ML have energy difference relative to FM by 8 and 54 meV, respectively. Furthermore, thickness- and surface-termination-dependent magnetocrystalline anisotropies of the $CrPt_3$(001) films are discussed.

• Korean journal of food and cookery science
• /
• v.18 no.6
• /
• pp.644-654
• /
• 2002

Brown color characteristics and antioxidizing activities were investigated for Doenjang under different processing conditions. Doenjang A was prepared directly from Meju and saline solution whereas Doenjang B was Prepared after separating soy sauce by soaking for 45 days. Both Doenjangs were aged for up to 180 days. Antioxidizing activity was studied in relation to the brown color characteristics using fat-soluble extract and water-soluble extract of Doenjang. The intensity of brown color was higher in the water-soluble Doenjang extract than the fat-soluble Doenjang extract. In the UV-VIS scanning spectra, water-soluble Doenjang extracts showed significant changes as the aging proceeded, but fat-soluble Doenjang extract did not. Antioxidizing activity of fat-soluble Doenjang extract increased as the aging period extended; however, no significant difference was detected in the water-soluble extract. Overall, Doenjang A showed higher contents of amino acids, reducing sugar, brown color, and antioxidizing activity, and the antioxidizing ability was higher in water-soluble Doenjang extract rather than in the fat-soluble Doenjang extract.

• Korean journal of food and cookery science
• /
• v.18 no.6
• /
• pp.557-561
• /
• 2002

The changes in some chemical and physical properties of fresh or rancid soybean oil by the treatment with sweet potato, potato, burdock, and carrot were investigated. The results of the study were as follows: The specific gravity of the soybean oil increased by heating and decreased by the addition of sweet potato, burdock and carrot into the oil. The chromaticity of soybean oil increased by heating and treatment with above vegetables having antioxidant activity. To investigate the antioxidant effects of above vegetables during heating, anisidine value (AV) and DPPH (1,1-diphenyl-2-picrylhydrazyl) electron donating ability were measured. The AV of oil decreased by heating with sweet potato in fresh or rancid oil. The DPPH value decreased by heating with sweet potato and carrot, of which the antioxidant activity were similar to that of 0.02 ∼ 0.05 mg of dl-${\alpha}$ -tocopherol.