• The Journal of Advanced Prosthodontics
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• 제11권3호
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• pp.162-168
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• 2019

PURPOSE. The aim of this study was to evaluate the effect of occlusal adjustments on the surface roughness of yttria-tetragonal zirconia polycrystal (Y-TZP) and wear of opposing artificial enamel. MATERIALS AND METHODS. Twenty-five Y-TZP slabs from each brand (Lava, 3M and Bruxzir, Glidewell Laboratories) with different surface conditions (Control polished - CPZ; Polished/ground - GRZ; Polished/ground/repolished - RPZ; Glazed - GZ; Porcelain-veneered - PVZ; n=5) were abraded (500,000 cycles, 80 N) against artificial enamel (6 mm diameter steatite). Y-TZP roughness (in ${\mu}m$) before and after chewing simulation (CS) and antagonist steatite volume loss (in $mm^3$) were evaluated using a contact surface profilometer. Y-TZP roughness was analyzed by three-way analysis of variance (ANOVA) and steatite wear by two-way ANOVA and Tukey Honest Difference (HSD) (P=.05). RESULTS. There was no effect of Y-TZP brand on surface roughness (P=.216) and steatite loss (P=.064). A significant interaction effect (P<.001) between surface condition and CS on Y-TZP roughness was observed. GZ specimens showed higher roughness after CS (before CS - $3.7{\pm}1.8{\mu}m$; after CS - $13.54{\pm}3.11{\mu}m$), with partial removal of the glaze layer. Indenters abraded against CPZ ($0.09{\pm}0.03mm^3$) were worn more than those abraded against PVZ ($0.02{\pm}0.01mm^3$) and GZ ($0.02{\pm}0.01mm^3$). Higher wear caused by direct abrasion against zirconia was confirmed by SEM. CONCLUSION. Polishing with an intraoral polishing system did not reduce the roughness of zirconia. Wear of the opposing artificial enamel was affected by the material on the surface rather than the finishing technique applied, indicating that polished zirconia is more deleterious to artificial enamel than are glazed and porcelain-veneered restorations.

• 대한화학회지
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• 제7권2호
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• pp.153-158
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• 1963

粘土鑛物과 滑石과의 關係에 對한 正確한 報告가 거의 없어. 이에 對한 磁器化溫度範圍 및 電氣的絶緣性과 粘土含量의 關係를 究明하였다. 스테아타이트素地의 製造에 使用한 原料는 國産 滑石, 粘土, 長石, 硅石等이며, 吸水率, 燒成線收縮率을 測定 檢討하고, 또 磁器化된 素地들의 電氣的絶緣性을 測定하였다. 그 結果 磁器化溫度範圍는 재겔錐 1乃至 3番內에 있었으며 $MgCO_3$를 添加함에 따라 燒成收縮은 크게 일어났으나, 粘土含量이 20% 以下였을 때는 磁器化溫度範圍가 增大되었다. 耐熱性은 全般的으로 良好하였으며 粘土量을 增加시킴에 따라 膨脹率, 誘電體力率, 絶線耐性은 增加하고, 體積固有抵抗은 減少하였다.

• 한국세라믹학회지
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• 제16권1호
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• pp.31-37
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• 1979

The middle point of composition within the system $MgO-Al_2O_3-SiO_2$ has been studied for applicability as ceramics dielectrics. A Kyul Sung Tale of high purity, magnesia clinker of Sam-wha chemical company, C.P. aluminium oxide, calcium carbonate, red lead, barium carbonate which was made into frit were used the raw materials. A number of steatite ceramics were prepared under carefully controlled condition and the water absorption, linear shrinkage, power factor, dielectric constant and dielectric loss were measured at elevated temperature. When we used magnesia clinker as flux, the quantity of this flux was 0.05mole, sintering temperature was continued for 2 hrs. at 1, 27$0^{\circ}C$. From this conditions, we could get the data whose power factor was 0.142%, water absorption was zero, linear shrinkage was 8.76%, dielectric constant was 5.63, dielectric loss was 0.00799. When we used red lead as flux, the quantity of this flux was 0.033mole and 0.066mole, sintering temperature was continued for 2hrs. at 1, 26$0^{\circ}C$. From this conditions, we could get the data whose water absorption was zero, linear shrinkage was 8.03%, and 8.48%, power factor was 0.136% and 0.062%, dielectric loss was 0.0072 and 0.0037. When we used barium carbonate made into frit as flux, the quantity of this flux was 0.02mole, sintering temperature was continued for 2hrs. at 1, 27$0^{\circ}C$. From this conditions, we could get the data whose water absoption was zero, linear shrinkage was 8.44%, power factor was 0.138%, dielectric constant was 5.69, dielectric loss was 0.0074.

• 한국세라믹학회지
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• 제19권2호
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• pp.139-144
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• 1982

This study has examined closely on the various foundamental conditions for the fitting in steatite porcelain as a industrial porcelain of superior quality, and as a decorated porcelain. The materials consisting of the Kyul Sung talc, and the sea water magnesia clinker power which was produced from Sam Hwa-Hwa Sung, as major constituents have been used, and also used Hyup Jin kaolin as clay minerals to give them plasticity. First, the mixture was made of corresponding in the theoretical composition of enstatite with Kyul sung talc and sea water magnesia clinker, and kaolin was added in various kinds of 1%, 2.5% 5%, 10%, and 20% by weight of the mixture. Next, the mixture was fired at the various temperatures from 1330 to 145$0^{\circ}C$. After we examined closely the physical properties and microstructures, we achieved the results that noted from this study were listed below. 1. The addition amount of kaolin should generally be from 5% to 10% by weight of the mixture to give mixture plasticity in steatite porcelain, but preferably about 20% to consider the firing temperature. 2. The temperature of the optimum firing range is from 1390 C to 142$0^{\circ}C$. 3. A case, which the $A_2$ composition had been fired at 142$0^{\circ}C$, showed a good effect in the strength, but showed a bad result in the absorption. Therefore, the specimens of $A_4$ the composition has excellent in properties of matters when the composition is fired at 142$0^{\circ}C$. Also, we consider that the specimens of the $A_5$ composition, which is fired at 139$0^{\circ}C$, is suitable for the $MgO-SiO_2$ porcelain bodies with respect to the various properties.

• 대한소아치과학회지
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• 제51권1호
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• pp.22-31
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• 2024

The objective of this study was to assess the wear resistance of tooth-colored materials used in crown restoration for primary molars with a chewing simulator. In this study, four groups-three experimental groups and one control group-were included. They consisted of three-dimensional (3D) printed resin crowns (NextDent and Graphy), milled nano-hybrid ceramic crowns (MAZIC Duro), and prefabricated zirconia crowns (NuSmile). Twelve mandibular second molar specimens were prepared from each group. In the wear experiment, 6.0 × 10⁵ cycles were conducted with a force of 50 N, and a 6 mm-diameter steatite ball was used as an antagonist. The amount of wear was calculated by comparing the scan files before and after the chewing simulation using 3D metrology software, and the worn cross-section was confirmed by scanning electron microscopy (SEM). The resin and ceramic groups did not exhibit any statistically significant differences. However, compared to other crown groups, the zirconia crown group demonstrated notably reduced levels of wear (p < 0.05). In SEM images, layers and cracks were observed in the 3D-printed resin crown groups, which differed from those in the other groups.

• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.300-307
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• 2018

PURPOSE. To investigate the fatigue and fracture resistance of computer-aided design and computer-aided manufacturing (CAD/CAM) ceramic molar crowns on dental implants and human teeth. MATERIALS AND METHODS. Molar crowns (n=48; n=8/group) were fabricated of a lithium-disilicate-strengthened lithium aluminosilicate glass ceramic (N). Surfaces were polished (P) or glazed (G). Crowns were tested on human teeth (T) and implant-abutment analogues (I) simulating a chairside (C, crown bonded to abutment) or labside (L, screw channel) procedure for implant groups. Polished/glazed lithium disilicate (E) crowns (n=16) served as reference. Combined thermal cycling and mechanical loading (TC: $3000{\times}5^{\circ}C/3000{\times}55^{\circ}C$; ML: $1.2{\time}10^6$ cycles, 50 N) with antagonistic human molars (groups T) and steatite spheres (groups I) was performed under a chewing simulator. TCML crowns were then analyzed for failures (optical microscopy, SEM) and fracture force was determined. Data were statistically analyzed (Kolmogorow-Smirnov, one-way-ANOVA, post-hoc Bonferroni, ${\alpha}=.05$). RESULTS. All crowns survived TCML and showed small traces of wear. In human teeth groups, fracture forces of N crowns varied between $1214{\pm}293N$ (NPT) and $1324{\pm}498N$ (NGT), differing significantly ($P{\leq}.003$) from the polished reference EPT ($2044{\pm}302N$). Fracture forces in implant groups varied between $934{\pm}154N$ (NGI_L) and $1782{\pm}153N$ (NPI_C), providing higher values for the respective chairside crowns. Differences between polishing and glazing were not significant ($P{\geq}.066$) between crowns of identical materials and abutment support. CONCLUSION. Fracture resistance was influenced by the ceramic material, and partly by the tooth or implant situation and the clinical procedure (chairside/labside). Type of surface finish (polishing/glazing) had no significant influence. Clinical survival of the new glass ceramic may be comparable to lithium disilicate.

• Acta Via Serica
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• 제6권2호
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• pp.91-116
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• 2021

India has had a rich and diverse textile tradition since the 3rd millennium BCE. The origin of Indian textiles can be traced back to the Harappan period. Owing to the hot and humid climate in most parts of India, cotton has remained India's favourite choice of fabric for normal use. Thus, India is supposed to be the first nation to have grown, woven, and patterned cotton fabrics. Moreover, India is one of the leading cotton-growing countries in the world. The earliest occurrence of cotton thread in India is roughly datable to 4000 BCE and of dyed fabrics to about 2500 BCE. Large numbers of needles and spindle-whorls found in Harappa and other early historic sites in India reveal the prosperous state of textile production and its trade in the early period. The textile producers used a wide range of skills to process raw materials and make regionally idiosyncratic dyes, weaves, prints, and embroideries. Additionally, the silk from wild indigenous forms of silkworms was known in the Indian sub-continent roughly contemporary with the earliest clear archaeological evidence for silk in China. The analysis of thread fragments found inside a copper bangle and ornament from Harappa and steatite beads from Chanhu-daro, have yielded silk fibers dating to 2500-2000 BCE. Apart from other products, cotton and silk textiles were important export materials from India right from the Harappan period. Actually, the sea-borne trade had played an important role in the economic growth and prosperity of the Harappan civilization. Several ancient seaports in the entire coastline of India played a vital role in the maritime trade during the Harappan period and cotton and silk textiles of Indian origin have been found in various countries. The contemporary writings and epigraphy have also attested to the vast maritime trade network of India and the export of textile materials. The paper discusses in detail the origin and development of cotton and silk textile production in India through the ages and its role in maritime trade networks.

• 대한치과보철학회지
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• 제57권2호
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• pp.110-117
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• 2019

목적: 본 연구의 목적은 적층 가공(additive manufacturing)법, 절삭 가공(subtractive manufacturing)법, 전통적인 방법에 따른 임시 수복용 레진의 마모 저항성을 조사하는 것이다. 재료 및 방법: 제작방법에 따라 4개의 군으로 나누었으며, 각 군은 전용의 임시 수복용 레진을 사용하였다: S3P군, Stereolithography apparatus (SLA) 3D 프린터 및 전용의 광경화성 수지로 제작한 군; D3P군, Digital Light Processing (DLP) 3D 프린터 및 전용의 광경화성 수지로 제작한 군; MIL군, Milling machine 및 밀링용 레진 블록으로 제작한 군; CON군, 전통적인 방법 및 자가중합형 레진으로 제작한 군. 한편, 3D 프린팅된 레진 시편을 제작함에 있어 적층 각도와 층 두께를 각각 $0^{\circ}$와 $100{\mu}m$로 설정하였다. 구강내 환경을 재현하기 위하여 열순환 처리와 수평, 수직운동이 가능한 2축 chewing simulator를 사용하였으며, 하부에는 한쪽면이 편평하게 제작된 임시 수복용 레진을, 상부에는 끝이 3 mm 직경을 가지는 원뿔형의 steatite를 고정하여 마모시험 진행하였다(5 kg, 30,000회, 0.8 Hz, $5^{\circ}C/55^{\circ}C$). 임시 수복용 레진의 마모량은 마모 전후의 Standard Triangulated Language (STL) 파일과 전용의 CAD software를 이용하여 부피를 계산하였고, 주사전자현미경으로 마모 양상을 비교하였다. 결과: S3P군, D3P군, MIL군의 마모량은 CON군보다 유의하게 작았으며 (P < .05), S3P군, D3P군, MIL군 사이에는 통계학적으로 유의한 차이가 없었다 (P > .05). 주사전자현미경으로 마모면을 관찰한 결과, S3P군과 D3P군에서는 대합치의 운동 방향에 대해 수직적으로 갈라진 흔적이 발견되었다. MIL군에서는 전반적으로 균일한 마모면이 보인 반면, CON군에서는 대합치 운동 방향으로의 뚜렷한 마모 흔적과 다수의 기포가 관찰되었다. 결론: 본 연구의 한계 내에서, 3D 프린팅된 임시 수복용 레진은 치과용으로서 적절한 마모저항성을 보였다.