• Journal of the korean academy of Pediatric Dentistry
• /
• v.38 no.3
• /
• pp.229-236
• /
• 2011

ProRoot MTA(Dentsply Tulsa, U.S.A) which has similar component with Portland cement has setting expansion character and long setting time. Excessive expansion can cause fracture at the apical portion of the root and decreasing of volume stability. And the long setting time makes additional visits for crown restoration and slow setting process of this material can change physical properties itself. In this study, among requirements of root canal filling material(KS P ISO 6876) which is revised at 2008, we investigated the setting time and setting expansion. Objects are recently developed OrthoMTA(BioMTA, Korea), conventional ProRoot white MTA(Dentsply Tulsa, U.S.A) and White portland cement(Union, Korea). The results in setting expansion, OrthoMTA was $0.08{\pm}0.02%$, ProRoot white MTA and White portland cement were each $0.28{\pm}0.06$, $0.80{\pm}0.25%$(p<0.05). The results in setting time, OrthoMTA, ProRoot white MTA, White portland cement were each $307.78{\pm}3.83$ min, $150.44{\pm}2.35$ min, $235.33{\pm}9.07$ min(p<0.05).

• Journal of the Korean Ceramic Society
• /
• v.13 no.2
• /
• pp.3-7
• /
• 1976

Influences of chlorides(CaCl2, MgCl2, NaCl) on the colouring effect of Fe component in white portland cement was investigated. Chlorides enhance the whiteness of the white portland cement owing to volatilization of Fe2O3 and translation of ferrite composition toward C2F. This translation is caused by consumption of alumina at the formation of C12A7, the formation of which is promoted in the presence of chloride. With decrease of p in ferrite composition C6F1-pAp, transfer of Fe3+ from 4 to 6 coordinated cite is occurred, and as a result, whiteness is raised. Hydration process of the cement containing a small amount of chloride differs little from the one without chloride.

• Journal of the Korean Ceramic Society
• /
• v.27 no.8
• /
• pp.1034-1042
• /
• 1990

Investigation for the preparation of high strength hardened cement paste using ordinary portland cement, hydroxypropyl methyl cellulose(HPMC) with various admixtures was carried out. The cement paste was mixed with 0.1 of water cement ratio by twin roll mill and cured 60 days in humidity chamber. When the quartz powder or white cement was added to the paste, the flexural strength was 900∼1000kg/㎠ and the Young's modulus was 8∼9×105kg/㎠. When the silicafume was added, the flexural strength was 800kg/㎠ and the Young's modulus was 6×105kg/㎠.

• Journal of the Korean Ceramic Society
• /
• v.15 no.2
• /
• pp.85-88
• /
• 1978

Influence of cooling atmosphere on the whiteness in white portland cement was studied. The effective composition of gaseous medium of cooling atmosphere is desirable less than 0.5% of $O_2$ and 0.5~1.5% of CO. When theclinker is quenched in nitrogen atmosphere, the color of clinker becomes bright pink. In a weakly reducing gaseous medium or vacuum, the absence of oxygen brings defects in crystal and transformation in the coordination of iron, and as a result, whiteness is raised.

• The Journal of Advanced Prosthodontics
• /
• v.15 no.2
• /
• pp.93-100
• /
• 2023

PURPOSE. The aim of this study is to evaluate the effect of resin cement color, cement thickness, and thermocycling on the final color of monolithic lithium disilicate crowns. MATERIALS AND METHODS. A total of ninety prepared central incisors of typodont teeth were restored with lithium disilicate crowns which have different cement thicknesses (40 ㎛, 80 ㎛, and 120 ㎛) and cement shades (clear, yellow, and white). Color parameters of restorations were measured with a spectrophotometer in three different steps 1) before cementing 2) after cementing and 3) after thermocycling with 10000 cycles. Color differences (ΔE₀₀) were calculated with the CIEDE2000 formula and evaluated according to perceptibility (0.8) and acceptability (1.8) thresholds. The ΔE₀₀ data were analyzed by using two-way ANOVA before and after thermocycling (α = .05). RESULTS. There was no interaction between the cement shade and the cement thickness factors. After cementation, the mean ΔE₀₀ was under the perceptibility threshold in the group of 40 ㎛ cement thickness and clear cement while it was between the perceptibility and acceptability thresholds (0.8 < ΔE₀₀ < 1.8) for all other groups. After thermocycling, the ΔE₀₀ values were between the perceptibility and acceptability thresholds for all experimental groups. Although there were no significant differences among the groups, thermocycling increased the color difference values. CONCLUSION. The cementation of restorations with clear, yellow, and white resin cements resulted in color differences with uncemented restorations except for the group cemented with clear cement in 40 ㎛ cement thickness. All study groups revealed perceptible color change after thermocycling.

• Restorative Dentistry and Endodontics
• /
• v.35 no.3
• /
• pp.149-151
• /
• 2010

Since its introduction in 1993, Mineral Trioxide Aggregate (MTA) has been shown to be superior to others in sealing, biocompatibility, and many other aspects of clinical endodontics. MTA is primarily Portland cement with bismuth oxide as a radiopacitifier. Although some studies suggested that the reasonable-priced Portland cement could be used instead of MTA, but MTAs are different from Portland cement in its composition, especially in heavy metal contents. Therefore, clinicians should be meticulous adapting the Portland cement as a MTA substitute.

• The Journal of the Korean dental association
• /
• v.12 no.8
• /
• pp.613-617
• /
• 1974

The authors have studied the marginal leakage of various dental cements; Fynal cement (Caulk), Zinc cement (S.S. White) Carbo cement (Shofu, Poly-carboxylate cement), EBA cement (Opotow alumina cement), Propac (G-C's zinc oxide euginol cement), and Super cement (Shofu oxyphosphate zinc cement), by means of penetration of 2% methylene blue solution between orden crown restorations and human teeth in 150 cases. The result revealed as follow 1. None of the cements tested were free from dye penetration. 2. There was a wide difference in dye penetration among the trade brands of dental cement when immersed in dye solution before setting of cements. 3. EBA cement and Carbo cement showed comparatively low grade of dye penetration at the restorative margins.

• Current Photovoltaic Research
• /
• v.6 no.2
• /
• pp.62-67
• /
• 2018

Multi-wire busbar-type bifacial n-type Si solar cells have been used for the fabrication of monofacial and bifacial photovoltaic (PV) module, where bifacial module was equipped with transparent backsheet while monofacial module was prepared using white backsheet. The comparison of six-day accumulated power production obtained from outdoor test under gray cement ground conditions using 60cell monofacial and bifacial PV modules suggested the bifacial gain of over 20% could be achieved. Furthermore, the outdoor evaluation tests of bifacial modules with different ground conditions such as cement (reference), green paint, white paint and green artificial grass, were performed. It turned out white paint showed the best albedo and thus the highest power production, while green paint and artificial grass showed less power generation than cement ground.

• International Journal of Concrete Structures and Materials
• /
• v.1 no.1
• /
• pp.75-81
• /
• 2007

The concrete pavement of the Seohae Highway in Korea has suffered from serious distress, only four to seven years after construction. Deterioration due to Alkali-Silica Reaction (ASR) has seldom been reported per se in Korea, because the aggregate used for the cement concrete has been considered safe against alkali-silica reaction so far. The purpose of this study is to examine the deterioration caused by an alkali-silica reaction of concrete pavement in Korea. The investigation methods included visual inspection and Automatic Road Analyzer (ARAN) analysis of surface cracks, coring for internal cracks, stereo microscopic analysis, scanning electronic microscope (SEM) analysis, and electron dispersive X-ray spectrometer (EDX) analysis. The results are presented as follows: the crack pattern of the concrete pavement in Korea was longitudinal cracking, map cracking or D-cracking. Local areas of damage were noticed four to five years after construction. The cracks started from edges or joints and spread out to slabs. The most intensive cracking was observed at the intersection of the transverse and longitudinal joints. Where cracking was the most intense, pieces of concrete and aggregate had spalled away from top surface and joint interface area. The progress of deterioration was very fast. The reaction product of alkali-silica gel was clearly identified by its generally colorless, white, or very pale yellow hue seen through a stereo optical microscopy. The typical locations of the reaction product were at the interface between aggregate and cement paste in a shape of a rim, within aggregate particles in the cracks, and in the large void in the cement paste. Most of the white products were found at interface or internal aggregates. SEM and EDX analysis confirmed that the white gel was a typical reaction product of ASR. The ASR gel in Korea mainly consisted of Silicate (Si) and Potassium (K) from the cement. The crack in the concrete pavement was caused by ASR. It seems that Korea is no longer safe from alkali-silica reaction.

• Journal of the Korean Ceramic Society
• /
• v.24 no.4
• /
• pp.329-334
• /
• 1987

Diffusion of SO4-- ion in hardened cement paste with slag and siliceous powders such as silica fume and white carbon was investigated. Ca(OH)2 from hardenend cement paste was dissolved by sea-water and then gypsum was formed from the reaction of Ca++ in hardenend cement paste and SO4-- ions in MgSO4 solution. A part of the gypsum by reaction with calcium aluminate hydrates formed ettringite. Amounts of SO4-- ions passed through hardened cement paste was less than that of Cl- ions(Dcl-) in hardened cement paste were 0.1∼0.6${\times}$10-11$\textrm{cm}^2$/sec and 1∼4${\times}$10-8$\textrm{cm}^2$/sec respectively.