• The korean journal of orthodontics
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• v.18 no.1 s.25
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• pp.79-88
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• 1988

The purpose of this study was to investigate the factors which might be related to mandibular third molar eruption and to predict the possibility of whether or not it will be erupted. The material of this study was lateral cephalometric radiograms, pantomograms and dental casts obtained from 70 patients (19 males, 51 females) ranging in age from 18.0 to 32.1 years. They were devided into erupted group and impacted group of mandibular third molars. For the comparison of each group, a total of 20 measurement items were employed and the data were analyzed by means of computer statistical method. As a result of this study, the following conclusion can be made; 1. The longer mandibular body length and narrower mandibular ramus width, the higher eruption tendency of the lower third molar, but the degree of genial angle was not related to mandibular third molar eruption. 2. The lower percentage of posterior mandibular body height to anterior mandibular body height, the higher eruption tendency of the lower third molar. 3. The total tooth size, including the lower second molar, appeared to be larger in the impacted group than in the erupted group of the lower third molar. 4. The arch length discrepancy of the impacted group was more severe in contrast with the erupted group of the lower third molar.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.24-30
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• 2020

The high speed of an engine balance box may cause significant additional gear noise. Gear accuracy is the most useful key to reduce gear noise, but the small tooth width and thin-walled anti-backlash gear introduce challenges to the manufacturing process. In order to reduce the gear noise caused by gear pitch error, this paper investigates the correlation between influencing factors and gear pitch error by analyzing the processing technology, tooling fixture, and equipment accuracy. By improving the process and optimizing the gear design, the gear machining accuracy was improved and the processing cost was saved.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.5
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• pp.8-16
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• 2021

This study develops a shaft analysis model for the optimization of the power transmission system. The finite element method was used for the shaft analysis model. The shaft and gear were assumed Timoshenko beams. Strength was evaluated according to DIN 743, and gear misalignment was calculated through ISO 6336 and the coordinate system rotation. The analysis software for a power transmission system was developed using Visual Studio 2019. The analysis results of the developed program were compared with those of commercial software (MASTA, KISSsoft, and Romax). We confirmed that the force, deformation, and safety factors at each node were the same as those of the commercial software. The absolute value of the gear misalignment of the developed program and commercial software was different. However, the gear misalignment tended to increase with increasing the displacement in the tooth width direction.

• Journal of Species Research
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• v.11 no.2
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• pp.98-101
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• 2022

The genus Tripylina Brzeski, 1963 is a group of terrestrial nematodes that inhabit soil and semi-wet biomes, most of which have been reported from Europe, Asia, America, Africa, and New Zealand. Tripylina stramenti (Yeates, 1971) Tsalolikhin, 1983, belonging to the family Trischistomatidae Andrassy, 2007, is newly discovered from Korea. The specimens were collected from the edge of the valley of Ulleung-gun, Gyeongsangbuk-do, South Korea. Tripylina stramenti described herein shows typical morphological characters of the genus Tripylina, including six and four setae in a single whorl, present dorsal tooth and subventral teeth, prodelphic reproductive system of female, absence post-uterine sac, narrow sickle-shaped spicule of male and generally S-shaped tail. The specimens differ in their body width (from the New Zealand populations), outer labial setae length, cuticles thickness(from the West African populations), and nerve ring position (from Indian populations). This species is distinguished from other Tripylina species by its relatively large body, two anterior and subventral teeth, and single cervical seta. In this study, morphological characteristics and morphometric information of the Korean T. stramenti isolate are described, illustrated, and compared with the same species from other geographic origins.

• Proceedings of the KACD Conference
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• 2008.05a
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• pp.177-183
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• 2008

It was reported that esthetic composite resin restoration reinforces the strength of remaining tooth structure with preserving the natural tooth structure. However, it is unknown how much the strength would be recovered. The purpose of this study was to compare the fracture resistance of three types of undermined cavity filled with composite resin with that of non-cavitated natural tooth. Forty sound upper molars were allocated randomly into four groups of 10 teeth. After flattening occlusal enamel. undermined cavities were prepared in thirty teeth to make three types of specimens with various thickness of occlusal structure (Group $1{\sim}3$). All the cavity have the 5 mm width mesio-distally and 7 mm depth bucco-lingually. Another natural 10 teeth (Group 4) were used as a control group. Teeth in group 1 have remaining occlusal structure about 1 mm thickness, which was composed of mainly enamel and small amount of dentin. In Group 2, remained thickness was about 1.5 mm, including 0.5 mm thickness dentin. In Group 3, thickness was about 2.0 mm, including 1 mm thickness dentin. Every effort was made to keep the remaining dentin thickness about 0.5 mm from the pulp space in cavitated groups. All the thickness was evaluated with radiographic Length Analyzer program. After acid etching with 37% phosphoric acid, one-bottle adhesive (Single $Bond^{TM}$, 3M/ESPE, USA) was applied following the manufacturer's recommendation and cavities were incrementally filled with hybrid composite resin (Filtek $Z-250^{TM}$, 3M/ESPE, USA). Teeth were stored in distilled water for one day at room temperature, after then, they were finished and polished with Sof-Lex system. All specimens were embedded in acrylic resin and static load was applied to the specimens with a 3 mm diameter stainless steel rod in an Universal testing machine and cross-head speed was 1 mm/min. Maximum load in case of fracture was recorded for each specimen. The data were statistically analyzed using one-way analysis of variance (ANOVA) and a Tukey test at the 95% confidence level. The results were as follows: 1. Fracture resistance of the undermined cavity filled with composite resin was about 75% of the natural tooth. 2. No significant difference on fracture loads of composite resin restoration was found among the three types of cavitated groups. Within the limits of this study, it can be concluded the fracture resistance of the undermined cavity filled with composite resin was lower than that of natural teeth, however remaining tooth structure may be supported and saved by the reinforcement with adhesive restoration, even of that portion consists of mainly enamel and a little dentin structure.

• Restorative Dentistry and Endodontics
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• v.33 no.3
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• pp.177-183
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• 2008

It was reported that esthetic composite resin restoration reinforces the strength of remaining tooth structure with preserving the natural tooth structure. However, it is unknown how much the strength would be recovered. The purpose of this study was to compare the fracture resistance of three types of undermined cavity filled with composite resin with that of non-cavitated natural tooth. Forty sound upper molars were allocated randomly into four groups of 10 teeth. After flattening occlusal enamel, undermined cavities were prepared in thirty teeth to make three types of specimens with various thickness of occlusal structure (Group $1{\sim}3$). All the cavity have the 5 mm width mesiodistally and 7 mm depth bucco-lingually. Another natural 10 teeth (Group 4) were used as a control group. Teeth in group 1 have remaining occlusal structure about 1 mm thickness, which was composed of mainly enamel and small amount of dentin. In Group 2, remained thickness was about 1.5 mm, including 0.5 mm thickness dentin. In Group 3, thickness was about 2.0 mm, including 1 mm thickness dentin. Every effort was made to keep the remaining dentin thickness about 0.5 mm from the pulp space in cavitated groups. All the thickness was evaluated with radiographic Length Analyzer program. After acid etching with 37% phosphoric acid, one-bottle adhesive (Single $Bond^{TM}$, 3M/ESPE, USA) was applied following the manufacturer's recommendation and cavities were incrementally filled with hybrid composite resin (Filtek $Z-250^{TM}$, 3M/ESPE, USA). Teeth were stored in distilled water for one day at room temperature, after then, they were finished and polished with Sof-Lex system. All specimens were embedded in acrylic resin and static load was applied to the specimens with a 3 mm diameter stainless steel rod in an Universal testing machine and cross-head speed was 1 mm/min. Maximum load in case of fracture was recorded for each specimen. The data were statistically analyzed using one-way analysis of variance (ANOVA) and a Tukey test at the 95% confidence level. The results were as follows: 1. Fracture resistance of the undermined cavity filled with composite resin was about 75% of the natural tooth. 2. No significant difference in fracture loads of composite resin restoration was found among the three types of cavitated groups. Within the limits of this study, it can be concluded the fracture resistance of the undermined cavity filled with composite resin was lower than that of natural teeth, however remaining tooth structure may be supported and saved by the reinforcement with adhesive restoration, even if that portion consists of mainly enamel and a little dentin structure.

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.17-27
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• 1998

Study on growth change of dental arch is considered to both an important data in orthodontic diagonsis and treatment planning as well as analysis of treatment results , also, arch form is important in anthropology and dentistry, even more so in prosthodontics and orthodontics. In the field of orthodontics, studies on the functional aspect of upper and lower teeth and maintenance of stability of dentition and occlusion were carried out from the early days. Some of the early studies include explanation of growth change in dental arch from measuring directly fom human stroll, and afterwards, cephalometrics x-rays were introduced; accordingly, studies using cephalometric measurement and linear measurements of study models were often performed. By this method, arch width, arch depth and perimeters were measured, and growth change or dental arch was studied. The subject ror this study were sn children(boys and girls or ages from 3 yens to 12 years from Kang-won district and Seoul, who has no history of orthodontic treatment and who show healthy status and normal growth and development. Cephalometric x-ray, panoramic x-ray, and study model were taken for each subject consecutively for 2 years, and the subjects are still followed up. 400 pairs of study models from the past two years were used in this study; mesio-distal diameater of each tooth, intercanine width, intermolar width, canine depth, molar depth and arch perimeters were measured. Afterwards, mean value and each standard deviation of each age group and each gender were obtained, and representation graph were drawn. The following conclusion were obtained. 1. Intercanine width showed gradual increase until the age of 10-years and after that, showed no increase. 2. Intermolar width in upper arch showed gradual increase : intermolar width in lower arch showed no significant chang, and after the age of 9-years, showed increase. 3. Cainine arch depth showed relatively rapid increase after the age of 6-years, and this pattern was more obvious in lower arch. 4. Molar arch depth increased gradually in both archs and it decrease after the age of 10-years : this phenomenon was more prominent in the lower arch. 5. Arch perimeter showed gradual inerease and convert to plateau at the age of 10-years, after that, it decreased. this pattern was more prominent in lower arch.

• The korean journal of orthodontics
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• v.31 no.4 s.87
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• pp.467-477
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• 2001

This investigation was designed to determine the effects of wire size, bracket width and the number of bracket on bracket-wire dynamic frictional resistance during simulating arch wire-guided tooth movement in vitro. For simulation of an arch wire-guided tooth movement, we simulated tooth, periodontal ligament and cancellous bone. Maxillary premolar and 1st molar were simulated as real sized resin teeth, the simulated resin teeth which its root was coated by polyether impression material which its elastic modulus is similar to periodontal ligament were embedded in steel housing with inlay wax which its elastic modulus is similar to cancellous bone. Stainless steel wires in four wire size (0.016, 0.018, $0.016\;{\times}\;0.022,\;0.019\;{\times}\;0.025$ inch) were examined with respect to three (stainless steel) bracket widths (2.4, 3.0, 4.3mm) and the number of medium bracket(one, two, three) included in the experimental assembly under dry condition. The wires were ligated into the brackets with elastomeric module. The results were as follows : 1. In all the brackets, frictional resistance increased with increase in wire size. But, statistically similar levels of frictional resistance were observed between 0.018 inch and $0.016\;{\times}\;0.022$ inch wires in narrow bracket and also between 0.016 inch and 0.018 inch wire in wide backet. 2. The frictional forces produced by 0.016 inch wire were statistically similar levels in all the brackets. In 0.018 inch round wire, wide bracket was associated with lower amounts of friction than both narrow and medium brackets. In $0.016\;{\times}\;0.022,\;0.019\;{\times}\;0.025$ inch rectangular wire, wide bracket produced target friction than both narrow and medium brackets. In all the wirer, narrow and medium bracket demonstrated no statistical difference in levels of frictional resistance. 3. Frictional resistance increased with increase In number of medium bracket. 0.016 inch round wire demonstrated the greatest increment in frictional resistance, followed by $0.019\;{\times}\;0.025,\;0.016\;{\times}\;0.022$ inch rectangular wire which were similar level in increment of frictional resistance, 0.018 inch wire demonstrated the least increment. The increments of frictional resistance were not constantly direct proportion to number of bracket.

• The korean journal of orthodontics
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• v.36 no.1 s.114
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• pp.45-54
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• 2006

Recent beauty trends have caused an increase in the number of bialveolar protrusion patients seeking treatment of lip protrusion. But studies of these patients are not common. Studies using their dental models are especially rare. Dental models have been measured manually or through a computer by digitizing two dimensional images of models. Nowadays, we are able to study dental models more easily and accurately by utilizing the three-dimensional (3-D) laser scanner in dentistry. An investigation was carried out to evaluate the characteristics of the dental arch in a bialveolar protrusion group in comparison with a normal group using 3-D digital models. The normal group was composed of 20 subjects who were selected from students of the School of Dentistry, Kyungpook National University. The bialveolar protrusion group was composed of 20 subjects who visited for treatment at the Department of Orthodontics, Kyungpook National University Hospital. Tooth size, arch width and arch length were measured digitally, and arch shape and the shape of the palate were drawn. Based on the results of this study, the differences of the arch characteristics in the bialveolar protrusion group were that the size of the teeth was larger, mandibular canine width and 1st premolar width were wider, and arch length was longer than in the normal group. And there were differences in the arch shape and the shape of palate between the bialveolar protrusion and normal groups.

• Korean Journal of Environment and Ecology
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• v.30 no.1
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• pp.39-47
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• 2016

Recently, it has been reported that morphologically and genetically different two Siberian roe deer (Capreolus pygargus, Pallas, 1771), in Mainland and in Jeju island. Until now, this roe deer has not been clearly taxonomy of Siberian roe deer in Korean peninsula. So, the aim of this study was to compare the skull morphometrics of mainland and Jeju roe deer to obtain more information on the species status of C. pygargus and study the distribution of roe deer subspecies in this region. A total of 50 skulls of adult roe deer was compared and analyzed. The maximum skull length, condylo-basal length, basilar length, maximum skull width, cheek-bone width, interorbital width, rostrum length, length of upper tooth row from the Siberian roe deer in Jeju island were significantly smaller than those of the deer in mainland. Length of the skull was the principal factor of interpopulational variability in roe deer. Variation was not distributed along latitude, longitude, or elevation, but those factors did influence the variation through effects on primary production, which in turn caused isolated differences in skull morphology apparently related to types of forage selected by roe deer in various geographic areas. According to the analysis results of the skull characters, Mainland roe deer was more similar to C. p. tianschanicus which is a subspecies of Siberian roe deer. In addition, Jeju roe deer showed distinct differences compared to European roe deer, 3 subspecies of Siberian roe deer, so it appeared that they could be a unique native species inhabited only in Jeju Island. Because Siberian roe deer in Jeju Island can be classified at subspecies level in this study.