• The Journal of Korean Academy of Prosthodontics
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• v.41 no.6
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• pp.747-761
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• 2003

Statement of problem. The proper materials of attachments for implant retained overdenture are unknown, such as the correlation between retention and abrasion, as well as the types of materials that are suitable for patrix and for matrix individually. Purpose of this study. The aim of this study was to select a proper clinical attachment system for a successful treatment as well as patient satisfaction. Methods. Retention and abrasion of 14 commercial attachments were measured during 15,000 removes. Results. A retentive part (matrix) which requires elasticity has to be made of gold while the patrix part which does not require elasticity has to be made of titanium. This gold matrix / titanium patrix combination showed the most retentive force and the least retention loss.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.1
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• pp.1-10
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• 2004

Statement of problem : Tooth wear is physiological phenomenon. Ninety-seven percent of normal people have tooth wear and about 7% has pathologic teeth wear. If we know the amount of tooth surface loss caused by pathologic tooth wear, we may restore it ideally Purpose : Recently measurement of tooth wear by using 3D scan has been increasing. Therefore, we need to know how accurate 3D scan is. Past accuracy test on 3D scan was about linear change, but as we know that tooth wear is volume change. Thus, the purpose of this study is to know how accurate 3D scan is. Material and Methods : For accuracy test of 3D scanner volume values measured by 3D scanner and micro-balance were compared. For test I, preliminary, 3 ball samples and 3 circular cones were made with pattern resin. For test II, 10 teeth shape rubber samples were used. Results and Conclusion : 1. The result of the accuracy test on 3D scan with 3 ball samples and 3 circular cones made of pattern resin has no significant difference(p<0.05). 2. The result of the accuracy test on 3D scan with 10 samples of tooth shape rubber has no significant difference (p<0.05). As a result, we may concluded the analysis of quantifying tooth wear used by 3D scan is useful in the clinic.

• Journal of the Korean Society for Railway
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• v.18 no.5
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• pp.410-418
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• 2015

A slider of the pantograph undergoes uneven and abnormal wear due to sliding contact with the catenary. In the case of rain, the loss of lubricant increases the frictional resistance for the reciprocating motion between the catenary and the slider, accelerating local wear. The slider in the winter should have good wear resistance, which can be achieved through alloy design. Uneven and abnormal wear were not observed in the results of a driving test using a wear resistant slider. It was found that the increased density of the slider enhanced the corrosive effects of Fe-Ti, preventing the occurrence of abnormal wear by maintaining the wear and arc resistance in the rainy season. Also, mechanical and electrical wear did not affect the composition of the slider, and this improved the wear resistance. Inaddition, the slider was applied to an entire train and was tested during driving; ananalysis of the correlation of the catenary was performed, including during the rainy season and the winter season.

• Journal of Korea Foundry Society
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• v.16 no.6
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• pp.503-512
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• 1996

Austempered ductile irons(ADI) are characterized by their relatively high retained austenite content which has a significant effect on mechanical properties and performance, such as ductility, toughness, wear resistance and machinability. Austenitising treatment at $900^{\circ}C$ for $1{\sim}2hours$, and austempering treatment within the temperature range $240{\sim}400^{\circ}C$ on ductile cast iron alloyed with Cu and Mo were carried out, and the effects of retained austenite content on the mechanical properties and wear resistance were investigated. In consequence, the amount of retained austenite was found to be 13.5% at the austempering temperature of $240^{\circ}C$, and was increased 28% at $400^{\circ}C$. Tensile strength and hardness of austempered ductile iron were decreased as the retained austenite content increased, but elongation was increased. The retained austenite content at the austenitising time of 2hours was more than at 1hour. The amounts of rolling wear loss were increased as the retained austenite content increased, and the wear surface was become to be rough.

• Elastomers and Composites
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• v.49 no.2
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• pp.149-154
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• 2014

Friction and abrasion behaviors were investigated for SBR rubber compounds reinforced by silica and carbon black. Knife-blade abrader, newly designed based on tearing energy theory, was utilized in order to evaluate the effect of frictional work on the wear rate of the rubber compounds. It was found that the power law relation between frictional work and wear rate worked, in which as the wear rate was increased as frictional work increased. The wear rate could be determined successfully using the knife-blade abrader in which a moving distance of the knife blade in the process of wearing was measured continuously, instead of intermittent measurements of weight loss by wear during experiment.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.1
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• pp.81-90
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• 1994

The purpose of this study is to understand the types of risk consumers feel when they shop at home and to compare their feelings with the perceived risk when they shop at stores and the kinds of clothing frequently purchased at home. For this study, the data were collected through the questionnaire distributed to 692 carried and unmarried women. The analysis was done through the t-test, ANOVA and regression. The results are as follows . 1) Compared to those shopping at stores, at-home shoppers perceived a higher risk in eight kinds of clothing. 2) Compared to shopping at stores, product performance risk, psychological risk and time loss risk increased dramatically Among these, the time loss risk showed the most noticeable increase. 3) When the perceived risk was low for a certain item, it was more often shopped at home. Among the perceived risk types, the lower the financial risk and the time loss risk, the item was more frequently shopped at home. 4) Together with store shopping, the perceived risks when shopping at home differed according the use of clothing. 5) The at-home purchase intentions were higher in the order of at-home wear, casual wear and dress/suit. The higher the price and the more important the fit was, shopping at home was more difficult.

• The Journal of Advanced Prosthodontics
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• v.7 no.4
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• pp.303-311
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• 2015

PURPOSE. The aim of this study was to compare the changes in retentive force of stud attachments for implant overdentures by in vitro 2-year-wear simulation. MATERIALS AND METHODS. Three commercially available attachment systems were investigated: Kerator blue, O-ring red, and EZ lock. Two implant fixtures were embedded in parallel in each custom base mounting. Five pairs of each attachment system were tested. A universal testing machine was used to measure the retentive force during 2500 insertion and removal cycles. Surface changes on the components were evaluated by scanning electron microscopy (SEM). A Kruskal-Wallis test, followed by Pairwise comparison, was used to compare the retentive force between the groups, and to determine groups that were significantly different (${\alpha}$<.05). RESULTS. A comparison of the initial retentive force revealed the highest value for Kerator, followed by the O-ring and EZ lock attachments. However, no significant difference was detected between Kerator and O-ring (P>.05). After 2500 insertion and removal cycles, the highest retention loss was recorded for O-ring, and no significant difference between Kerator and EZ lock (P>.05). Also, Kerator showed the highest retentive force, followed by EZ lock and O-ring, after 2500 cycles (P<.05). Based on SEM analysis, the polymeric components in O-ring and Kerator were observed to exhibit surface wear and deformation. CONCLUSION. After 2500 insertion and removal cycles, all attachments exhibited significant loss in retention. Mechanism of retention loss can only be partially explained by surface changes.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.3
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• pp.239-245
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• 2003

The occurrence and pattern of tooth wear are related to cultural, dietary, occupational, and geographic factors, Excessive occlusal wear can result in pulpal exposure, occlusal disharmony, functional inability. Surface loss can be differentiated into 3 general causal categories: i) mechanical loss, which includes attrition, ii) abrasion chemical loss including erosion, and finally iii) a proposed biomechanical category described as abfraction. Considering that mechanical wear is frequently asymptomatic, patients may have parafunctional habit. Structured clinical decision analysis in fixed prosthodontics, as other branches of dentistry do, allows the practitioner to consider the patient's problems more thoroughly based on the clinical data and extenuation factors. This discipline of decision making is intended to complement the experience level and educational background of the clinician in assisting the patient through the decision process. Additionally, CDA helps the clinician define not only the pre-existing condition of the patient prior to irreversible therapy, but also better treatment strategies for the patient over an extended period. The systematic nature of decision analysis stimulates the dentists to pay further attention to those factors, which is germane to the overall complexity of the case, and exclude factors, which have little influence on its final outcome. Further implementation of computerized databases, procedural outcome probabilities based on clinical and laboratory studies and the clinical experience of those who use it, may provide quite a promising future in the field of structured and formalized clinical decision analysis.

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.407-413
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• 2002

Eutectic high chromium cast irons containing 17%Cr and 26%Cr were produced for this research by making each of them solidify unidirectionally. Abrasion wear test against SiC or $Al_2$O$_3$bonded paper was carried out using test pieces cut cross-sectionally at several distances from the chill face of castings. The wear resistance was evaluated in connection with the parameters such as eutectic colony size($E_w$), area fraction of boundary region of the colony($S_B$) where comparatively large massive chromium carbides are crystallized and, average diameter of chromium carbides in the boundary region($D_c$). The wear rate($R_w$), which is a gradient of straight line of wear loss versus testing time, was influenced by the type and the particle size of the abrasives. The $R_w$ value against SiC was found to be larger than that against A1$_2$O$_3$under the similar abrasive particle size. In the case of SiC, the $R_w$ value increased with an increase in the particle size. The $R_w$ value also increased as the eutectic colony size decreased, and that of the 17%Cr iron was larger than that of the 26%Cr iron at the same $E_w$ value. Both of the $S_B$ and $D_c$ values were closely related to the $R_w$ value regardless of chromium content of the specimens. The $R_w$ values of the annealed specimens were greater than those of the as-cast specimens because of softened matrix structures. As for the relationship between wear rate and macro-hardness of the specimens, the hardness resulting in the minimum wear rate was found to be at 550 HV30.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.120-127
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• 2019

PURPOSE. To determine wear amount of single molar crowns, made from four different restoratives, and opposing natural teeth through computerized fabrication techniques using 3D image alignment. MATERIALS AND METHODS. A total of 24 single crowns (N = 24 patients, age range: 18 - 50) were made from lithium disilicate (IPS E-max CAD), lithium silicate and zirconia based (Vita Suprinity CAD), resin matrix ceramic material (Cerasmart, GC), and dual matrix (Vita Enamic CAD) blocks. After digital impressions (Cerec 3D Bluecam, DentsplySirona), the crowns were designed and manufactured (Cerec 3, DentsplySirona). A dualcuring resin cement was used for cementation (Variolink Esthetic DC, Ivoclar). Then, measurement and recording of crowns and the opposing enamel surfaces with the intraoral scanner were made as well as at the third and sixth month follow-ups. All measurements were superimposed with a software (David-Laserscanner, V3.10.4). Volume loss due to wear was calculated from baseline to follow-up periods with Siemens Unigraphics NX 10 software. Statistical analysis was accomplished by Repeated Measures for ANOVA (SPSS 21) at = .05 significance level. RESULTS. After 6 months, insignificant differences of the glass matrix and resin matrix materials for restoration/enamel wear were observed (P>.05). While there were no significant differences between the glass matrix groups (P>.05), significant differences between the resin matrix group materials (P<.05) were obtained. Although Cerasmart and Enamic were both resin matrix based, they exhibited different wear characteristics. CONCLUSION. Glass matrix materials showed less wear both on their own and opposing enamel surfaces than resin matrix ceramic materials.