• Korean Journal of Environmental Biology
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• v.26 no.1
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• pp.36-41
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• 2008

Induction of morphological deformities in Chironomus riparius larvae was assessed after exposure to 0.3, 1, 10 and 30 ${\mu}g\;L^{-1}$ potential endocrine disruption chemicals, Diethylhexyl phtalate (DEHP). We observed and subdivide types of mentum deformities and counted the incidence of mentum deformities. The mortality was not increased according to concentrations of DEHP, while was depend on the exposed days. The incidence of mentum deformities for MLT (median lateral teeth), LT (lateral teeth), and MIX (MLT+LT) of the mentum morphological structure showed MLT (2.8$\sim$11.4%)>LT (2.8$\sim$2.9%)>MIX (2.8$\sim$3.0%). The type of mentum deformities on C. riparius was classified six groups following exposure to DEHP. The incidence rate was occupied following to tooth addition (4.3%), tooth split (2.8%), tooth deletion (2.4%), tooth fusion (1.4%), $K"{o}hn$ gap (0.5%) and abnormal shape (0.5%). Especially tooth split and tooth fusion were observed in DEHP treated conditions.

• Journal of Magnetics
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• v.22 no.1
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• pp.133-140
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• 2017

Split magnetic fluid sealing is a combination of magnetic fluid rotary and plane sealing. Using the theory of equivalent magnetic circuit design as basis, the author theorized the pressure resistance performance of magnetic fluid plane sealing. To determine the pressure resistance of magnetic fluid plane sealing, the author adopted the method of finite element analysis to calculate the magnetic field intensity in the gap between plane sealing structures. The author also analyzed the effect of different sealing gaps, as well as different ratios between the sealing gap and tooth and solt width, on the sealing performance of split magnetic fluid. Results showed that the wider the sealing gap, the lower the sealing performance. Tooth width strongly affects sealing performance; the sealing performance is best when the ratio between tooth width and sealing gap is 2, whereas the sealing performance is poor when the ratio is over 8. The sealing performance is best when the ratio between the solt width and sealing gap is 4, indicating a slight effect on sealing performance when the ratio between the solt width and sealing gap is higher. Theoretical analysis and simulation results provide reference for the performance evaluation of different sealing equipment and estimation of critical pressure at interface failure.

• Journal of Periodontal and Implant Science
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• v.47 no.1
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• pp.41-50
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• 2017

Purpose: The aims of the present study were to compare the image quality and visibility of tooth cracks between conventional methods and swept-source optical coherence tomography (SS-OCT) and to develop an automatic detection technique for tooth cracks by SS-OCT imaging. Methods: We evaluated SS-OCT with a near-infrared wavelength centered at 1,310 nm over a spectral bandwidth of 100 nm at a rate of 50 kHz as a new diagnostic tool for the detection of tooth cracks. The reliability of the SS-OCT images was verified by comparing the crack lines with those detected using conventional methods. After performing preprocessing of the obtained SS-OCT images to emphasize cracks, an algorithm was developed and verified to detect tooth cracks automatically. Results: The detection capability of SS-OCT was superior or comparable to that of trans-illumination, which did not discriminate among the cracks according to depth. Other conventional methods for the detection of tooth cracks did not sense initial cracks with a width of less than $100{\mu}m$. However, SS-OCT detected cracks of all sizes, ranging from craze lines to split teeth, and the crack lines were automatically detected in images using the Hough transform. Conclusions: We were able to distinguish structural cracks, craze lines, and split lines in tooth cracks using SS-OCT images, and to automatically detect the position of various cracks in the OCT images. Therefore, the detection capability of SS-OCT images provides a useful diagnostic tool for cracked tooth syndrome.

• The korean journal of orthodontics
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• v.49 no.6
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• pp.372-380
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• 2019

Objective: To determine the effects of a local injection of leukocyte-platelet-rich plasma (L-PRP) on orthodontic tooth movement in rabbits. Methods: Twenty-three male New Zealand white rabbits were included in a split-mouth design. Tooth movement with a 100-g nickel-titanium closed-coil spring was performed on the maxillary first premolars. L-PRP was injected submucosally at the buccal and lingual areas of the first premolar in one random side of the maxilla and the other side served as the control and received normal saline. The amount of tooth movement was assessed on three-dimensional digital models on days 0, 3, 7, 14, 21, and 28. Histological findings and osteoclast numbers were examined on day 0 as the baseline and on days 7, 14, and 28. Results: The L-PRP group showed significantly greater cumulative tooth movement at all observed periods. However, a significantly higher rate of tooth movement was observed only on days 0-7 and 7-14. The osteoclast numbers were significantly increased in the L-PRP group on days 7 and 14. Conclusions: Local injection of L-PRP resulted in a transient increase in the rate of tooth movement and higher osteoclast numbers.

• The korean journal of orthodontics
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• v.48 no.3
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• pp.200-211
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• 2018

The aim of this systematic review was to evaluate the effectiveness and complications of corticotomy and piezocision in canine retraction. Five electronic databases (PubMed, SCOPUS, Web of Science, Embase, and CENTRAL) were searched for articles published up to July 2017. The databases were searched for randomized control trials (RCTs), with a split-mouth design, using either corticotomy or piezocision. The primary outcome reported for canine retraction was either the amount of tooth movement, rate of tooth movement, or treatment time. The secondary outcome was complications. The selection process was based on the PRISMA guidelines. A risk of bias assessment was also performed. Our search retrieved 530 abstracts. However, only five RCTs were finally included. Corticotomy showed a more significant (i.e., 2 to 4 times faster) increase in the rate of tooth movement than did the conventional method. For piezocision, both accumulative tooth movement and rate of tooth movement were twice faster than those of the conventional method. Corticotomy (with a flap design avoiding marginal bone incision) or flapless piezocision procedures were not detrimental to periodontal health. Nevertheless, piezocision resulted in higher levels of patient satisfaction. The main limitation of this study was the limited number of primary research publications on both techniques. For canine retraction into the immediate premolar extraction site, the rate of canine movement after piezocision was almost comparable to that of corticotomy with only buccal flap elevation.

• The Journal of the Korean dental association
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• v.12 no.5
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• pp.351-352
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• 1974

This is a case report on split tooth which the author experienced. Fine hairline fracture of right 1st molar was detected by means of staining dye stoff under illumination. The patients complained sensitive to temperature change and to biting force.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.2
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• pp.208-219
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• 2001

To study the effect of dentin permeability on a tooth with wear from tooth brushing after application of desensitizing agent, extracted teeth free from caries were chosen. Coronal dentin discs with thickness of 1mm were prepared. Using the split chamber device developed by Pashely, hydraulic conductance, scanning electron microscope images(SEM) and atomic force microscope images(AFM) were compared and contrasted before and immediately after the application of desensitizing agent and after equivalent tooth brushing of 1 week, 2 weeks, and 6 weeks. Four commercially available desensitizing agents were used in this study ; they were Gluma, Seal & Protect, All-Bond 2 and MS Coat. The results of this study are as follows. 1. On all specimens, the hydraulic conductance decreased after the application of tooth desensitizing agent. 2. Except the specimens treated with MS Coat, the remaining specimens had an increase in dentin permeability after tooth brushing for 1 and 2 weeks but a decrease after 6 weeks. 3. The specimens treated with MS Coat had statistically significant increase in the dentin permeability regardless with the duration of tooth brushing. 4. On examination of SEM and AFM, the dentinal tubule diameter had decreased after treatment of desensitizing agents. The specimens other than those treated with MS Coat, smear layers were noted after tooth brushing. It is not always consistant but the hydraulic conductance correlated with the images from SEM and AFM.

• The korean journal of orthodontics
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• v.48 no.6
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• pp.405-411
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• 2018

Objective: This study was performed to investigate the rate of tooth movement and histological characteristics of extraction sockets those were subjected to corticotomy. Methods: A split-mouth randomized controlled trial experiment was designed. Thirty-two adult, male Wistar rats were divided into 2 groups: healing extraction socket (H) and recent extraction socket (R); these groups were randomly classified into 4 subgroups (0/7/21/60 days). The first maxillary molar was extracted on 1 side and 2 months were allowed for complete bone healing; then, the corresponding molar was extracted on the other side and surgical intervention was performed at the mid-alveolar point of the first maxillary molar. Ten grams of continuous force was applied. The outcomes measured were rate of tooth movement, percentage of periodontal space and histological evaluation. The rate of tooth movement was calculated as the measured distance divided by the duration of molar movement. Histomorphometric evaluations were performed on the second and third maxillary molars. The Wilcoxon signed rank test was used to compare differences between the two groups. Results: There were no significant differences in the rates of tooth movement between H and R groups at any of the 4 time points. The histological appearance and percentage of periodontal space between the R and H groups also demonstrated no significant differences. Conclusions: The rates of orthodontic tooth movement into recent and healed socket sites did not differ between the groups. Histological analysis of tooth movement revealed regional acceleration during every time period.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.241-243
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• 1996

This papar presents an analysing method of radial force densities acting on each stator tooth of an induction motor with skewed slots. Two-dimensional finite element method is used for electromagnetic Held analysis of an induction motor, and skew effects are considered by coupling several disks cut by planes perpendicular to the shaft. Radial force densities as a source of vibration are calculated along the surface elements of each stator tooth and its time harmonics are examined by discrete Fourier decomposition.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.3
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• pp.73-78
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• 2011

This study contains to theory and analysis research for the stress and the translation of an expand disk that fix a ring gear for tooth profile machining. The stress of the expand disk is analysed by the finite element method(FEM) to calculate design parameters. From the analysis results, the stress of the expand shows a linear tendency under various fixing force. This results show that the expand disk have a elastic characteristics as a disk spring. The maximum stress was observed on under side in split section of the expand disk. It is verified that the analysis results are useful to calculate design parameters of the expand disk.