• The korean journal of orthodontics
• /
• v.21 no.3
• /
• pp.603-614
• /
• 1991

To study the possibility of attraction magnetic forces to expand maxillary arch, we used 2 big adult dogs, 2 small puppies, 1 small adult dog as experiments, and 1 small adult dog as a control. We measured the intercanine width and intermolar width and histologically observed in the suture and cervical and apex region of teeth and took occlusal X-rays to observe separation of suture line in the maxilla. The results were as follows: 1. Expansion velocities of intercanine (0.25mm/day) and intermolar widths (0.23mm/day) in puppies were faster than those (0.135mm/day, 0.09mm/day) in adults. 2. In all experiments in adults (0.135mm/day) and puppies (0.25mm/day), expansion velocity of intercanine widths were faster than those (0.09mm/day, 0.23mm/day) of intermolar width. 3. In all experiments ectatic changes were observed and cellularities of fibroblast increased in the suture line. Only in adults dogs the separations of palatal suture were observed in the occlusal X-ray view. 4. In the puppies bony deposition was particularly observed in the suture line and micro-bony fragments were often observed. 5. In the all experiments no root resorption was observed in the cervical and root area, but normal root resorption due to eruption of permanent teeth was observed in the puppies.

• Geomechanics and Engineering
• /
• v.34 no.1
• /
• pp.103-113
• /
• 2023

This study focused on understanding the relationship between the design of a tunnel boring machine disc cutter ring and its rock-breaking efficiency, as well as the applicable conditions of different cutter ring types. The discrete element method was used to establish a numerical model of the rock-breaking process using disc cutters with different ring types to reveal the development of rock damage cracks and variation in cutter penetration load. The calculation results indicate that a sharp-edged (V-shaped) disc cutter penetrates a rock mass to a given depth with the lowest load, resulting in more intermediate cracks and few lateral cracks, which leads to difficulty in crack combination. Furthermore, the poor wear resistance of a conventional V-shaped cutter can lead to an exponential increase in the penetration load after cutter ring wear. In contrast, constant-cross-section (CCS) disc cutters have the highest quantity of crack extensions after penetrating rock, but also require the highest penetration loads. An arch-edged (U-shaped) disc cutter is more moderate than the aforementioned types with sufficient intermediate and lateral crack propagation after cutting into rock under a suitable penetration load. Additionally, we found that the cutter ring wedge angle and edge width heavily influence cutter rock-breaking efficiency and that a disc cutter with a 16 to 22 mm edge width and 20° to 30° wedge angle exhibits high performance. Compared to V-shaped and U-shaped cutters, the CCS cutter is more suitable for soft or medium-strength rocks, where the penetration load is relatively small. Additionally, two typical case studies were selected to verify that replacing a CCS cutter with a U-shaped or optimized V-shaped disc cutter can increase cutting efficiency when encountering hard rocks.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.31 no.4
• /
• pp.569-578
• /
• 2004

The purpose of this study was to clarify the palatal arch length, width and height in the primary and permanent dentition. Samples were consisted of normal occlusions both in the primary dentition(50 males and 50 females) and in the permanent dentition(50 males and 50 females). With their upper plaster casts were used and through 3-dimensional laser scanning(3D Scanner, DS4060, LDI, U.S.A.), cloud data, polygonization, section curve and loft surface, fit and horizontal plane were based to measure the palatal arch length, width and height(Surfacer 10.0, Imageware, U.S.A.). T-tests were applied for the statistical analyze of the data. The results were as follows : 1. In the measurement values, the values of the male were higher than those of the female except primary anterior palatal height. There were not only statistically significant differences in anterior palatal width(p<0.05) and posterior palatal width(p<0.01) in primary dentition but palatal width(p<0.05), anterior palatal length(p<0.01), middle and posterior palatal length(p<0.05) in permanent dentition between male and female. 2. In the indices of palate, there were statistically significant differences in height-length index(p<0.05) and width-length index(p<0.01) between male and female in primary dentition. In permanent dentition, there was statistically difference between male and female. 3. In the measurement values, posterior palatal width was increased most greatly. Posterior palatal height, anterior palatal width and anterior palatal length were followed by descending order. On the other hand, anterior palatal height and posterior palatal length were decreased. 4. In the indices of palate, the height-length index, the width-length index and posterior height-width index were increased, but the others were decreased.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.28 no.4
• /
• pp.356-364
• /
• 2006

Transverse mandibular deficiency has a many problem in growing patients. Therefore, Mandible symphysis widening is recommended. A new surgical technique has been developed to widen the mandible. The purpose of this study is to report the effect of mandibluar symphyseal distraction osteogenesis by use of bone-borne type distractor. The surgical procedure was accomplished under general anaesthesia with step-line osteotomy. Bone-borne type distractor was used to generally widen the mandible. The expansion achieved in the mandible was 8.31mm at the device, 6.32mm at the canines, 4.06mm at the first molars. The symphyseal distraction gaps were bridged by new bony regeneration. Mandibular symphseal distraction osteogenesis increased mandibular arch width, stabilized occlusion, and corrected dental crowding.

• The Journal of Korean Academy of Prosthodontics
• /
• v.36 no.6
• /
• pp.867-877
• /
• 1998

The purpose of this study was to investigate the ideal locations and dimensions of bristles for the patients who were installed with fixed prostheses and severely involved periodontitis. The models of 16 pts were analysed and the resullts were as follows: 1. There were no tooth brushes in the market, which were proper for the patients who were installed with fixed prostheses and had severely periodontally involved teeth. 2. The neck portion of the tooth brush should be narrow as possblly. 3. The size of tooth brush should be analyzed by the size of arch. 4. The width of tooth brush should be analyzed by the degree of bone recession. 5. The custom made tooth brush may be ideal, if possible.

• The Journal of the Korean dental association
• /
• v.9 no.1
• /
• pp.43-48
• /
• 1971

The purpose of this study is to evaluate the influence of genetics of the dimensions of dental arches in twins. Thirty-four pairs of Korean twins, of which twenty-three were monozygotic and eleven dizygotic, participated in the study. The twins ranged in age from 6 years to 12 years with mixed dentition. The results were as follows: 1) No significant differences were observed between male and female in mean interpair diffenences of monozygotic twins. 2) Mean interpair differences of monozygotic twins were lesser than these of dizygotic twins. 3) Highly significiant zygotic differences were observed in the mean interpair differences of the width of upper and lower dental arch. This suggest that there is a significant component of hereditary variability.

• The Journal of the Korean dental association
• /
• v.25 no.8 s.219
• /
• pp.783-788
• /
• 1987

The authors observed the two cases of Rieger's syndrome in 21-year-old male and 13-year-old female with a chief complaint of Partial anodontia of permanent teeth on both jaws. We had done the laboratory and ophthalmic examinations and had taken radiographs. Final diagnosis was established as Rieger's syndrome. We obtained the results as follows, 1. There was no peculiar hereditary tendency in them. 2. The patients had no disturbance of general physical activity and mentality. 3. The male patient had pseudoprogenathism, concave profile, congenital missing on upper anterior and second premolar teeth, and conical shaped crown of upper len celral incisor. The female patient had also pseudoprognathism, concave profile, thickened upper labial frenum, decreased upper dental arch width, congenital missing on upper anterior teeth, and delayed eruption of second premolars. 4. The ophthalmic symptoms that were ins abnormalities, decreased visual acuity, and increased intraocular pressure were present. 5. The abnormalities except dental and ophthalmic abnormalities were not round.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.30 no.6
• /
• pp.516-525
• /
• 2004

Mandibular symphyseal distraction osteogenesis is an alternative approach for correcting mandibular transverse deficiencies and dental crowding. The traditional approaches for these are extraction of teeth and arch expansion with traditional orthodontic treatment. Also extractions are usually unavoidable in patients with severe crowding. The purpose of this study is to evaluate the effect of mandibular symphyseal distraction osteogenesis by use of tooth-borne expansion appliance. All of 12 patients had been performed distraction osteogenesis. The surgical procedures were accomplished under local anesthesia and intravenous sedation in an ambulatory surgical setting using a routine distraction protocol. The latency period was 5 days or 7 days after symphyseal osteotomies. The rate & rhyth is a intermittent, 0.75mm or 1.0 mm per day and stabilized for 6, 8 weeks after distraction. The time of orthodontic tooth movement after distraction was variable from 2 weeks to 8 weeks (mean 3 weeks). All patients had been evaluated with study casts, plain periapical films, panorama radiograms before & after surgery. Mandibular symphyseal distraction osteogenesis increased mandibular arch width and corrected dental crowding, with paralleling tooth-borne movement, without proclination of the mandibular incisors.

• The korean journal of orthodontics
• /
• v.45 no.4
• /
• pp.190-197
• /
• 2015

Objective: The aim of the study was to analyze the prevalence and distribution of ectopic eruption of the permanent maxillary first molar (EEM) in individuals scheduled for orthodontic treatment and to investigate the association of EEM with dental characteristics, maxillary skeletal features, crowding, and other dental anomalies. Methods: A total of 1,317 individuals were included and randomly divided into two groups. The first 265 subjects were included as controls, while the remaining 1,052 subjects included the sample from which the final experimental EEM group was derived. The mesiodistal (M-D) crown width of the deciduous maxillary second molar and permanent maxillary first molar, maxillary arch length (A-PML), maxillomandibular transverse skeletal relationships (anterior and posterior transverse interarch discrepancies, ATID and PTID), maxillary and mandibular tooth crowding, and the presence of dental anomalies were recorded for each subject, and the statistical significance of differences in these parameters between the EEM and control groups was determined using independent sample t -tests. Chi-square tests were used to compare the prevalence of other dental anomalies between the two groups. Results: The prevalence of maxillary EEM was 2.5%. The M-D crown widths, ATID and PTID, and tooth crowding were significantly greater, while A-PML was significantly smaller, in the EEM group than in the control group. Only two subjects showed an association between EEM and maxillary lateral incisor anomalies, which included agenesis in one and microdontia in the other. Conclusions: EEM may be a risk factor for maxillary arch constriction and severe tooth crowding.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.3 s.49
• /
• pp.113-123
• /
• 2006

An experimental investigation on the behavior of reinforced concrete coupling beams is presented. The test variables are the span-to-depth ratio, the ratio of flexural reinforcements and the ratio of shear rebars. The distribution of arch action and truss action which compose the mechanism of shear resistance is discussed. The increase of plastic deformation after yielding transforms the shear transfer by arch action into by truss action. This study proposes the deformation model for reinforced concrete coupling beams considering the bond slip of flexural reinforcement. The strain distribution model of shear reinforcements and flexural reinforcements based on test results is presented. The yielding of flexural reinforcements determines yielding states and the ultimate states of reinforced concrete coupling beam are defined as the ultimate compressive strain of struts and the degradation of compressive strength due to principal tensile strain of struts. The flexural-shear failure mechanism determines the ultimate state of RC coupling beams. It is expected that this model can be applied to displacement-based design methods.