• The Journal of Korean Academy of Prosthodontics
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• v.61 no.4
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• pp.275-283
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• 2023

The progressive wear of teeth is a physiologic process of aging, but excessive wear can lead to occlusal disharmony, tooth sensitivity and pulp exposure, decreased masticatory efficiency, and aesthetic problems. It should be treated by evaluating the cause of tooth wear and establishing a stable centric relation with appropriate vertical dimension of occlusion and occlusal plane. The present case report successfully rehabilitated a full-mouth case of a severely worn dentition with the use of digital facebow transfer and virtual articulator.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.4
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• pp.252-259
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• 2017

Purpose: The purpose of this study was to compare and analyze the wear of a prosthesis for 6 months after restoration with implant-supported fixed dental prosthesis made of either zirconia or gold. Materials and Methods: This study was conducted on patients requiring implant-supported fixed dental prostheses on first or second molar from January, 2015 to January, 2016. A total of 47 prostheses and antagonists were examined. Occlusal surface was recorded by impression of each prosthesis and antagonist 1 week and 6 months after prosthesis delivery. The digital files were created by impression scan. Occlusal shapes of 1 week and 6 months were compared and wear of prostheses and antagonists was analyzed. The Mann-Whitney test was used to analyzed the result data underwent normality test using SPSS (Version 23.0, IBM Corporation) Results: Mann-Whitney test revealed that there was no statistically significant difference in the median amount of mean vertical wear for 6 months in zirconia ($50.84{\mu}m$) and gold ($42.84{\mu}m$) prostheses (P > 0.05). When the opposing teeth were natural, the median amount of mean vertical wear of zirconia and gold prostheses was $47.72{\mu}m$ and $41.97{\mu}m$, respectively, and the median amount of mean vertical wear of enamel was $47.26{\mu}m$ and $44.59{\mu}m$, respectively. Statistical analysis showed no significant difference (P > 0.05). Conclusion: Despite the short study period and the small number of experimental groups, zirconia and gold showed no significant difference in wear during the first 6 months. Opposing natural enamel also showed no significant difference in the wear.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.102-109
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• 2009

A retarder, as a supplementary brake system that is not friction-based, is frequently used in heavy-duty vehicles generally to slow the vehicles down on inclines. The electric retarder mainly used in a heavy-duty bus is generally placed between the transmission and the axle. The rotor inside the retarder system is attached to the axle. The operation of the retarder within a driven vehicle generates reverse torque due to coast driving force on hypoid gears in the differential gear system. By the reverse torque, scoring or scuffing on the hypoid gear teeth may directly occur. The scoring may be generated due to excessive contact stresses on the tooth surface. In this study, tooth contact stresses and contact patterns were analysed in order to investigate on the tooth scoring phenomenon using a finite element analysis program T900 in which the Hertzian contact stress formula was taken. Backlash, wear and surface finish were considered in the finite element simulation on the scoring.

• Journal of Korean Society for Quality Management
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• v.30 no.3
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• pp.111-119
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• 2002

Gears are essential elements for mechanical power transmission. Geometric precision is the main factor for characterizing gear grade and qualify. Gear pitch is one of the crucial measurements, which is defined as a distance between two adjacent gear teeth. It is well-known that variability in gear pitches may causes wear-out and vibration noise. Therefore maintaining pitch errors at a low level plays a key role in assuring the gear quality to customers. This paper is concerned with a case study, which presents a computerized system for Inspecting pitch errors in a gear machining process. This system consists of a PC and window-based programs. Although the start and stop is manually accomplished, the process of measuring and analyzing pitch data is automatically conducted in this system. Our purpose lies in reducing inspection cost and time as well as Increasing test reliability. Its operation is briefly illustrated by example. Sometimes a strong autocorrelation is observed from pitch data. We also discuss a process monitoring scheme taking account of autocorrelations.

• Tribology and Lubricants
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• v.7 no.2
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• pp.67-74
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• 1991

The contact characteristics of gear tooth surface were studied by using the gear test rig of power circulation type. The effect of surface treatment conditions and revolutions on the tooth surface roughness parameters, and the relations between the lubrication conditions and tooth surface conditions, in spur gear sets wear considered. The result show that heat treatment of gear have an important effect upon fatigue strength and tooth surface conditions, and surface asperities undergo a circulating process of creation and destruction because of the influnce of plastic deformation. And surface roughness conditions at the tooth tips accompany a great deal of variation in running-in stage. According to the lubrication analysis and the study the tooth surface have a greater effect on surface demage than lubrication conditions, in mixed-lubrication condition.

• Korean Journal of Computational Design and Engineering
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• v.2 no.3
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• pp.186-194
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• 1997

This paper describes new methods to minimize the cutting time in zigzag milling operation of two dimensional polygonal surfaces. Previous works have been focused on mainly experimental approaches by considering some machining parameters such as, spindle speed, depth of cut, cutter traverse rate, cutter diameter, number of teeth, tool wear, life of tool, and so on. However, in this study, we considered two geometrical factors one by one in order to see the effect separately, which are the length of cut and the number of cutter traverse. In an N-sided concave or convex polygon, an algorithm has been developed which minimize the total length of cut. Also, a heuristic approach was used to minimize the number of cutter traverse.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.579-579
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• 2001

One of the most important factors for the clinical success of adhesive posterior restorations is marginal adaptation. This property is very closely related to mechanical properties and to the shrinkage behavior of composite materials. Most of modem composite materials are light-cured. This is why the first part of this lecture will be confined to our recent research on light curing, such as plasma polymerization, LED polymerization and the power of modem halogen lamps. In the second part of the lecture the shrinkage properties such as dimensional shrinkage and shrinkage forces of different light curing materials and during different curing procedures will be discussed. Finally, in the third part of the lecture, marginal adaptation before and after loading in different cavity classes and by using different restorative techniques and curing procedures will be presented. Data will also be given on wear resistance, abrasiveness against opposing cusps and postcuring of composite materials.(omitted)

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.1
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• pp.207-216
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• 1997

We developed the durability estimation and design systems to minimize the volume, considering the durability, efficiency, and design requirements of worm gears. That is, we consider each kind of factors affecting on durability on the basis of AGMA Standard for the cylindrical and double-enveloping worm gears. We also estimate input power on the basis of wear and durability, bending strength and deflection of worm shaft, and we developed the durability estimation and design systems of power transmission worm gears introducing the optimal design method on the personal computer to be easily used in field. Also, we developed a method which converts the design variables obtained from the optimal design method to integer values(number of worm threads, number of worm threads, number of worm wheel teeth, etc.,) to be used in real design and production. The developed durability estimation and design method can be easily applied to the design of worm gears used as power transmission devices in machineries and is expected to be used for weight minimization of worm gear unit.

• Journal of Technologic Dentistry
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• v.42 no.3
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• pp.298-305
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• 2020

Here, we studied the sports mouse guard as an oral device system, to minimize the sports related facial and dental injuries, jawbone fracture and brain injury, and by layering the hardened sheets for improving the activity performance and stable wearing. By pressuring and layering 2 soft- and 1 hard-layers of ethylene vinyl acetate (EVA) thermoplastic materials, for a category of martial art, record sports and leports, here we introduce a methodology for thickness control of layers to protect the teeth and oral structure. A personally customized mouse guard optimized for sports by layering a mixture of soft and hardened sheets is not easily detached during the sporting activity, easy to breathe through, comforts to wear, and also improves the sporting record. A designed EVA thermoplastic material for individual sports is used as the mouth guard, which is stably attached, easily removed, and convenient for breathing through the mouth.

• The Journal of the Korean dental association
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• v.56 no.6
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• pp.333-338
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• 2018

The mouth guard is a device with elasticity to be installed in the oral cavity. It has a function to reduce the trauma in the oral cavity and to protect the teeth and surrounding tissues from trauma. The purpose of mouth guard is to prevent trauma and concussion. It is mandatory to wear a mouthguard in sports where there is a lot of contact and the possibility of trauma or concussion in the mouth area is high. The mouse guard is divided into a stock type, a mouth formed type, and a custom made type according to the manufacturing method. The custom made type is made on the individual dentition model and has excellent retention because of its excellent fit. Also, the effect of trauma prevention is excellent. It is possible to design and adjust by the dentist and reduce the complaint the athlete has about the mouthguard. In this article, the process of making a dentist-customized mouthguard was described.