• Journal of Periodontal and Implant Science
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• v.35 no.3
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• pp.563-575
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• 2005

The aim of present study is to evaluate the influence of adjacent tooth to the microbiology of clinically healthy implant. Control group included patients who had clinically healthy implant and tooth with healthy $periodontium(PD{\leq}3mm)$, test group was composed of patients who had clinically healthy implant and tooth with periodontal pocket(PD>3mm). The criteria of clinically health implant are no pain or discomfort, the restorative suprastructure provide satisfactory fit and function, and the tissue around the fixtures were firm and probing with standard periodontal probe with a rounded tip 0.5mm in diameter resulted in penetration of no more than 5mm when using a force of 0.5N at any location. 38 patients, partially edentulous subjects with endosseous root-form implants were selected. All subjects were medically healthy and had not taken systemic antibiotics and professional plaque control 3 months before sampling. Number of control group is 25(mean age $52{\pm}13$, 26 teeth, 34 implants) and test group is 13(mean age $60{\pm}13$, 13 teeth, 17 implants). All teeth and implants of each patient were examined probing depth(PD), bleeding on probing(BOP), and plaque index(PI), and samples of subgingival plaque were obtained at each site with sterile curet or fine paper points, then the plaque transferred to PBS. Obtained samples were examined for the presence of P. gingivalis, T. forsythensis, and T. denticola by the polymerase chain reaction(PCR). The relationship among clinical parameters and the colonizations by the 3 bacterial species from natural teeth and implants region were analyzed by student t-test. The results of this study were as follows: 1. PD was different in teeth between 2 groups(p<0.05), but the other parameters were not. 2. Statistically significant difference was not found in clinical parameters of implants between 2 groups. 3. All bacterial prevalences of teeth were higher in test group than in control group, and prevalence of T. forsythensis had statistically significant difference between 2 groups(p<0.05). 4. Prevalences of P. gingivalis and T. forsythensis are higher in test group than control group, and that of T. denticola is higher in control group than in test group. But there were no statistically significant differences between 2 groups. In conclusion, there is no statistically significant difference in prevalence of implant microbiology between 2 groups. But if the number of samples increased, it will be possible to find out statistical significance in prevalence of P. gingivalis. It seems that pocket of adjacent tooth influences prevalence of P. gingivalis. These results mean that improvement of the periodontal condition before implantation is very important.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.8 no.1
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• pp.10-17
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• 1999

Replacements for natural dentition must fulfil many criteria. An important aspect, especially for the patient, is aesthetic consideration. The shape and colour can be important factors in the aesthetic success of an anterior restoration. In order to allow for proper shape; the outline form, the spatial position of individual teeth and the surface characteristics must be considered. For the colour; translucency, value, chroma and hue must be expressed exactly. The dentist and technicians should catch up these very specific characteristics of the patient and convert them accurately to the restorations with the simplest way.

• Tribology and Lubricants
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• v.24 no.1
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• pp.44-48
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• 2008

The wear characteristics of the gold alloy dental prosthesis have been investigated. The wear tests were performed by using a pin-on-disk wear tester at room temperature. Vickers hardness and fracture toughness measurement of dental materials were preformed. Microscopic observations on worn surfaces of specimens were conducted by microscope. The friction coefficient of the gold alloy dental prosthesis was investigated according to weight and slinging velocity. The hardness of the gold alloy dental prosthesis were similar and a half of the enamel of natural teeth.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.583.2-583
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• 2001

In these days, as the patients requirements on ethetics are getting greater, so the restorative materials which match well with natural teeth colors are being developed. One of those materials is the composite resin. When we fill the composite resin into the prepared cavity, it makes some clinical problems because it shrinks during the polymerization. To resolve these problems, first we must have sufficient understandings on the polymerization of composite resin.(omitted)

• Journal of Technologic Dentistry
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• v.31 no.1
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• pp.23-36
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• 2009

The goal of esthetic restoration is to achieve morphologic, optical, and biologic acceptance. Creation of a natural looking ceramic restoration, which blends harmoniously with surrounding dentition, is not always achieved. A successful color match is an important aspect of any esthetic dental restoration. Since natural enamel has inherent translucency, it is important that ceramic restorations reproduce the translucency and color of the natural teeth. However, the final color match of porcelain crowns to adjacent natural dentition remains some problem. Difficulties related to color matching arise from the structural differences that exist between metal ceramic crowns and natural teeth, the limited range of available ceramic shades, inadequate shade guides, different types of metal alloys, repeated firing, the condensation technique, and varying compositions of ceramic materials. Many factors contribute to the esthetic success of dental restoration: optical properties such as color and its elements of hue, value, and chroma; translucency and opacity; light transmission and scattering; and metamerism and fluorescence. The purpose of this study was to determine the color changes of metal-ceramic system with different veneering porcelain powder after repeated firing. The objectives of this in vitro study were to measure the lightness($L^*$), chromaticity($a^*$), chromaticity($b^*$), chroma($C^*$), hue(h), reflectance(%), color difference(${\Delta}E$). The following conclusions were obtained: 1. An increase in the number of firings resulted in decrease in lightness($L^*$) but increase in chromacticity($a^*$) with all porcelain. After the second sintering resulted in decrease in chromacticity($b^*$) with opaque-dentin porcelain and dentin porcelain but in increase with enamel porcelain and translucency porcelain. And after the second sintering resulted in decrease in chroma($C^*$) with opaque-dentin porcelain and dentin porcelain, but on the whole side in decrease with enamel porcelain and translucency porcelain. 2. After the second firing, a increase in the number of firings resulted in decrease reflectance(%) in all wavelength. 3. There were noticeable color differences(${\Delta}E$) between first sintering and multiple firings(dentin porcelain: 5.29~8.15, opaque-dentin porcelain: 4.83~8.2, enamel porcelain: 8.93~13.15, translucency porcelain: 9.37~12.91), but the color difference(${\Delta}E$) after second sintering were down to 4.87 in all porcelain. 4. Given the NBS Criteria, a 'trace' was not found this study but a 'slight' was found 2-3, 3-5 in dentin porcelain, 2-3 in opaque-dentin porcelain, 3-5, 5-10 in enamel porcelain and translucency porcelain, a 'noticeable' was 2-5, 3-10, 5-10 in dentin porcelain and opaque-dentin porcelain, 2-3, 2-5, 3-10 in enamel porcelain 2-3, 3-10 in translucency porcelain, an 'appreciable' was 1-2, 1-3, 2-10 in dentin porcelain 1-2, 1-3, 2-10, 3-10 in opaque-dentin porcelain, 2-10 in enamel porcelain, 2-5, 2-10 in translucency porcelain, a 'much' was 1-5, 1-10 in dentin porcelain and opaque-dentin porcelain, 1-2, 1-3, 1-5 in enamel porcelain 1-2, 1-3, 1-5, 1-10 in translucency porcelain, a 'very much' was 1-10 in enamel porcelain.

• The Journal of Advanced Prosthodontics
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• v.16 no.1
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• pp.12-24
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• 2024

PURPOSE. This study aimed to evaluate the maximum vertical wear, volume wear, and surface characteristic of antagonist enamel, opposing monolithic zirconia or lithium disilicate crowns. MATERIALS AND METHODS. The study comprised 24 participants (n = 12), who were randomly allocated to receive either a 5 mol% Y-TZP or a lithium disilicate crown in positions which would oppose the natural first molar tooth. The contralateral first molar along with its antagonist was considered as the enamel opposing natural enamel control. Data collection was performed using an intraoral scanner and polyvinylsiloxane impression. The means of the maximum vertical loss and the volume loss at the occlusal contact areas of the crowns and the various natural antagonists were measured by 3D comparison software. A scanning electron microscope was subsequently used to assess the wear characteristics. RESULTS. The one-year results from 22 participants (n = 11) indicated no significant differences when comparing the zirconia crown's antagonist enamel (40.28 ± 9.11 ㎛, 0.04 ± 0.02 mm³) and the natural enamel wear (38.91 ± 7.09 ㎛, 0.04 ± 0.02 mm³) (P > .05). Also, there is no significant differences between lithium disilicate crown's antagonist enamel (47.81 ± 9.41 ㎛, 0.04 ± 0.02 mm³) and the natural enamel wear (39.11 ± 7.90 ㎛, 0.04 ± 0.02 mm³) (P > .05). CONCLUSION. While some studies suggested that monolithic zirconia caused less wear on opposing enamel than lithium disilicate, this study found similar wear levels to enamel for both materials compared to natural teeth.

• The Journal of the Korean dental association
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• v.9 no.4
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• pp.151-157
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• 1971

Freshly extracted permant teeth were examined by electron microscope according to the Filmy replica method. Preparatory method with hydrochloric acid or proteolytic enzyme treatment was used in order to injure the structural composition of enamel surface to compare between the natural carious defects and the etched samples used in this study. The natural carious defects were chalky white or brown discolored portions at the smooth enamel surface without having visible loss of enamel substances. The findings were as follows: 1. The first caries attact initiated from the mineralized portion of rod sheath which is located at the top of enamel rod. 2. The caries developed downward along the rod sheath interprismatic substances and enamel rods subsequently. However, the caries involvement of interprismatic substances and enamel rods occured almost at the same time. 3. The rod sheath attached to the remineralized smooth emael surface was located at the top of enamel rod.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.803-806
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• 1995

The vibration and nosic of gears is causeed by manufacting error,alignment error in assembly, and thr meshing stiffness of gears which changes periodically as the meshing of teeth process. On a pair of power transmission helical gears with profile error, the relation between the characteristics of gear vibration and the profile error type have been investigated by simulating the vibrational acceleration level and calculating the natural frequency. The results show that the profile error decrease the natural frequency by reducing the tool stiffness and that the concave error type increase the vibrationsl level. And this paper describes the effect of the tip relief on the vibrational acceleration level which a pair of helical gears with concave error generates.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.137-143
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• 2012

This study analyzes flywheel through the analyses of stress, fatigue and vibration. Maximum equivalent stress is 15.271MPa at the mid round shape and maximum deformation is 0.02264mm at the outer teeth. Among the cases of nonuniform fatigue loads, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of -$10^4$MPa and the amplitude stress of 1000 to 2900MPa, the possibility of maximum damage becomes 30%. This stress state can be 20 times greater than the damage possibility of 'SAE bracket history' or 'SAE transmission'. The range of natural frequencies becomes 200 to 820Hz and the values of these deformations are not more than 10mm. The structural result of this study can be effectively utilized with the design of flywheel by investigating prevention and durability against its damage.

• Animal Systematics, Evolution and Diversity
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• v.35 no.4
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• pp.168-181
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• 2019

Two cirolanid isopods, Eurydice longiantennata Nunomura and Ikehara, 1985 and Metacirolana japonica (Hansen, 1890), are newly reported based on the materials collected from the subtidal zone around Jeju Island. Eurydice longiantennata can be distinguishable from its congeners by the following features: body length is 5 mm; antennule is not extending beyond the cephalon; flagellum of the antenna is consisted of 31 flagellar articles; and pleotelson has eleven teeth and twelve setae distally. Metacirolana japonica is distinguished from its related species by the following characteristics: body is not ornament; pleonite 1 is entirely visible dorsally in male; pleotelson is gradually tapering distally; and uropodal rami have serrate margins.