• Journal of Korean Neurosurgical Society
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• v.30 no.10
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• pp.1210-1219
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• 2001

Introduction : The purpose of this study was to analyze the safety, pullout strength and radiographic characteristics of unicortical and bicortical screws of cervical facet within cadaveric specimens and evaluate the influence of level of training on the positioning of these screws. Methods : Twenty-one cadavers, mean 78.9 years of age, underwent bilateral placement of 3.5mm AO lateral mass screw from C3-C6(n=168) using a slight variation of the Magerl technique. Intraoperative imaging was not used. The right side(unicortical) utilized only 14mm screws(effective length of 11mm) while on the left side to determine the length of the screw after the ventral cortex had been drilled. Three spine surgeons(attending, fellow, chief resident) with varying levels of spine training performed the procedure on seven cadavers each. All spines were harvested and lateral radiographs were taken. Individual cervical vertebrae were carefully dissected and then axial radiographs were taken. The screws were evaluated clinically and radiographically for their safety. Screws were graded clinically for their safety with respect to the spinal cord, facet joint, nerve root and vertebral artery. The grades consisted of the following categories : "satisfactory", "at risk" and "direct injury". Each screw was also graded according to its zone placement. Screw position was quantified by measuring a sagittal angle from the lateral radiograph and an axial angle from the axial radiograph. Pull-out force was determined for all screws using a material testing machine. Results : Dissection revealed that fifteen screws on the left side actually had only unicortical and not bicortical purchase as intended. The majority of screws(92.8%) were satisfactory in terms of safety. There were no injuries to the spinal cord. On the right side(unicortical), 98.9% of the screws were "satisfactory" and on the left side(bicortical) 68.1% were "satisfactory". There was a 5.8% incidence of direct arterial injury and a 17.4% incidence of direct nerve root injury with the bicortical screws. There were no "direct injuries" with the unicortical screws for the nerve root or vertebral artery. The unicortical screws had a 21.4% incidence of direct injury of the facet joint, while the bicortical screws had a 21.7% incidence. The majority of "direct injury" of bicortical screws were placed by the surgeon with the least experience. The performance of the resident surgeon was significantly different from the attending or fellow(p<0.05) in terms of safety of the nerve root and vertebral artery. The attending's performance was significantly better than the resident or fellow(p<0.05) in terms of safety of the facet joint. There was no relationship between the safety of a screw and its zone placement. The axial deviation angle measured $23.5{\pm}6.6$ degrees and $19.8{\pm}7.9$ degrees for the unicortical and bicortical screws, respectively. The resident surgeon had a significantly lower angle than the attending or fellow(p<0.05). The sagittal angle measured $66.3{\pm}7.0$ degrees and $62.3{\pm}7.9$ degrees for the unicortical and bicortical screws, respectively. The attending had a significantly lower sagittal angle than the fellow or resident(p<0.05). Thirty-three screws that entered the facet joint were tested for pull-out strength but excluded from the data because they were not lateral mass screws per-se and had deviated substantially from the intended final trajectory. The mean pull-out force for all screws was $542.9{\pm}296.6N$. There was no statistically significant difference between the pull-out force for unicortical($519.9{\pm}286.9N$) and bicortical($565.2{\pm}306N$) screws. There was no significant difference in pull-out strengths with respect to zone placement. Conclusion : It is our belief that the risk associated with bicortical purchase mandates formal spine training if it is to be done safely and accurately. Unicortical screws are safer regardless of level of training. It is apparent that 14mm lateral mass screws placed in a supero-lateral trajectory in the adult cervical spine provide an equivalent strength with a much lower risk of injury than the longer bicortical screws placed in a similar orientation.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.3
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• pp.290-297
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• 2008

STATEMENT OF PROBLEM: Implant-supported fixed cantilever prostheses are influenced by various biomechanical factors. The information that shows the effect of implant number and position of cantilever on stress in the supporting bone is limited. PURPOSE: The purpose of this study was to investigate the effect of implant number variation and the effect of 2 different cantilever types on stress distribution in the supporting bone, using 3-dimensional finite element analysis. MATERIAL AND METHODS: A 3-D FE model of a mandibular section of bone with a missing second premolar, first molar, and second molar was developed. $4.1{\times}10$ mm screw-type dental implant was selected. 4.0 mm height solid abutments were fixed over all implant fixtures. Type III gold alloy was selected for implant-supported fixed prostheses. For mesial cantilever test, model 1-1 which has three $4.1{\times}10$ mm implants and fixed prosthesis with no pontic, model 1-2 which has two $4.1{\times}10$ mm implants and fixed prosthesis with a central pontic and model 1-3 which has two $4.1{\times}10$ mm implants and fixed prosthesis with mesial cantilever were simulated. And then, 155N oblique force was applied to the buccal cusp of second premolar. For distal cantilever test, model 2-1 which has three $4.1{\times}10$ mm implants and fixed prosthesis with no pontic, model 2-2 which has two $4.1{\times}10$ mm implants and fixed prosthesis with a central pontic and model 2-3 which has two $4.1{\times}10$ mm implants and fixed prosthesis with distal cantilever were simulated. And then, 206N oblique force was applied to the buccal cusp of second premolar. The implant and superstructure were simulated in finite element software(Pro/Engineer wildfire 2.0). The stress values were observed with the maximum von Mises stresses. RESULTS: Among the models without a cantilever, model 1-1 and 2-1 which had three implants, showed lower stress than model 1-2 and 2-2 which had two implants. Although model 2-1 was applied with 206N, it showed lower stress than model 1-2 which was applied with 155N. In models that implant positions of models were same, the amount of applied occlusal load largely influenced the maximum von Mises stress. Model 1-1, 1-2 and 1-3, which were loaded with 155N, showed less stress than corresponding model 2-1, 2-2 and 2- 3 which were loaded with 206N. For the same number of implants, the existence of a cantilever induced the obvious increase of maximum stress. Model 1-3 and 2-3 which had a cantilever, showed much higher stress than the others which had no cantilever. In all models, the von Mises stresses were concentrated at the cortical bone around the cervical region of the implants. Meanwhile, in model 1-1, 1-2 and 1-3, which were loaded on second premolar position, the first premolar participated in stress distribution. First premolars of model 2-1, 2-2 and 2-3 did not participate in stress distribution. CONCLUSION: 1. The more implants supported, the less stress was induced, regardless of applied occlusal loads. 2. The maximum von Mises stress in the bone of the implant-supported three unit fixed dental prosthesis with a mesial cantilever was 1.38 times that with a central pontic. The maximum von Mises stress in the bone of the implant-supported three-unit fixed dental prosthesis with a distal cantilever was 1.59 times that with a central pontic. 3. A distal cantilever induced larger stress in the bone than a mesial cantilever. 4. A adjacent tooth which contacts implant-supported fixed prosthesis participated in the stress distribution.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.1
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• pp.77-94
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• 2021

The purpose of this study was to investigate the three-dimensional characteristics of mesiodens using Cone-beam Computed Tomography(CBCT) and analyze the factors affecting complications and anesthetic methods of extraction. This study evaluated 602 mesiodens of 452 patients who underwent extraction of mesiodens at the department of Pediatric Dentistry in Seoul National University Dental Hospital between 2017 and 2019. The ratio of mesiodens patients over total patient per year was gradually increased over the past 20 years. Mesiodens with labio-palatally horizontal direction while root directing labial were the most common among the mesiodens with horizontal direction. Mesiodens were the most common at the cervical side of the adjacent teeth(37.0%) and mesiodens located in the near-palatal side were observed about 3.83 times higher than the far-palatal side. Most of the mesiodens(82.1%) were in contact with adjacent permanent teeth on all three sides of the CBCT and 46.2% of mesiodens had curved roots. The patient's age, vertical position, presence of complications, and proximity showed a significant difference in the selection of general anesthesia among anesthetic methods. The direction and vertical position of mesiodens had a significant effect on complications. These results provide a better understanding of mesiodens for establishing an accurate diagnosis and treatment plan.

• Journal of Chest Surgery
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• v.30 no.5
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• pp.471-478
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• 1997

Introduction: The use of rabbits as a cardiopulmonary bypass(CPB) animal model is extremely dif%cult mainly due to technical problems. On the other hand, deep hypothermic circulatory arrest(CA) is used to facilitate surgical repair in a variety of cardiac diseases. Although steroids are generally known to be effective in the treatment of cerebral edema, the protective effects of steroids on the brain during CA are not conclusively established. Objectives of this study are twofold: the establishment of CPB technique in rabbits and the evaluation of preventive effect of steroid on the development of brain edema during CA. Material '||'&'||' Methods: Fifteen New Zealan white rabbits(average body weight 3.5kg) were divided into three experimental groups; control CA group(n=5), CA with Trendelenberg position group(n=5), and CA with Trendelenberg position + steroid(methylprednisolone 30 mglkg) administration group(n=5). After anesthetic induction and tracheostomy, a median sternotomy was performed. An aortic cannula(3.3mm) and a venous ncannula(14 Fr) were inserted, respectively in the ascending aorta and the right atrium. The CPB circuit consisted of a roller pump and a bubble oxygenator. Priming volume of the circuit was approximately 450m1 with 120" 150ml of blood. CPB was initiated at a flow rate of 80~85ml/kg/min, Ten min after the start of CPB, CA was established with duration of 40min at $20^{\circ}C$ of rectal temperature. After CA, CPB was restarted with 20min period of rewarming. Ten min after weaning, the animal was sacrif;cod. One-to-2g portions of the following tissues were rapidly d:ssected and water contents were examined and compared among gr ups: brain, cervical spinal cord, kidney, duodenum, lung, heart, liver, spleen, pancreas. stomach. Statistical significances were analyzed by Kruskal-Wallis nonparametric test. Results: CPB with CA was successfully performed in all cases. Flow rate of 60-100 mlfkgfmin was able to be maintained throughout CPB. During CPB, no significant metabolic acidosis was detected and aortic pressure ranged between 35-55 mmHg. After weaning from CPB, all hearts resumed normal beating spontaneously. There were no statistically significant differences in the water contents of tissues including brain among the three experimental groups. Conclusion: These results indicate (1) CPB can be reliably administered in rabbits if proper technique is used, (2) the effect of steroid on the protection of brain edema related to Trendelenburg position during CA is not established within the scope of this experiment.

• The korean journal of orthodontics
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• v.37 no.1 s.120
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• pp.44-55
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• 2007

Objective: Previous studies have reported that morphological features of the first cervical vertebra (atlas) have been associated with mandibular growth direction. The purpose of this study was to show the possible positional and morphological changes of the Atlas from activator treatment in Class II malocclusion patients. Methods: Lateral cephalometric radiograph tracings were made at initial, middle and final stages of treatment. Angular and linear measurements of skeletal and morphological features were measured on the anatomical landmarks and reference planes. Results: The skeletal effects of activator treatment on Class II malocclusion patients were evident on ramal height, body length, effective body length, ANB, and overjet. Clockwise rotation of the long axis of the Atlas was found in Group 1, but there was no inclination change of the Atlas in groups 2 and 3. There was no significant correlation between anterior and posterior positions of the atlas or morphological change in all groups. - except for posterior movements of the Atlas found in group 1. Conclusion: Clockwise rotation of the atlas axis resulted from activator treatment in Cl II malocclusion patients. Change in atlas axis can be thought of as an indicator for success of activator treatment.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.4
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• pp.446-454
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• 2017

Recently, there have been many studies on bulk-fill resin composites. However, studies on the proper materials for pediatric patients are rare. The aim of this study was to compare the cavity wall adaptation of bulk-fill resin composites with conventional resin composite in class II cavities of primary molars using microcomputed tomography (micro-CT). Standardized class II slot cavities were prepared in 80 exfoliated primary molars and randomly divided into 4 groups. The control group was restored with conventional resin composite, Filtek Z-350 XT (FZ), and the three groups were restored with bulk-fill resin composites, Filtek bulk-fill posterior (FB), Tetric N-Ceram Bulk Fill (TNC), Filtek bulk-fill flowable (FBF). All specimens were thermocycled and then immersed in 50% silver nitrate ($AgNO_3$) solution. Micro-CT was used to measure the penetration volume of the total silver nitrate and the degree of cervical marginal leakage and the number, size, and position of the voids were evaluated. The results revealed that the volume of silver nitrate were significantly different between FB and FZ (p < 0.05). The results also revealed that the penetration length of silver nitrate FBF showed statistically lower than the FZ and FB (p < 0.05). There was no significant difference between the groups in number and size of voids. In conventional resin composite, most of the voids were present inside the restoration (83.3%), but the voids in the bulk-fill resin composites incidence were higher in the gingivoaxial angle. The cavity wall adaptation demonstrated in class II restorations of primary molar by new bulk fill resin composites was similar to conventional incremental technique. Bulk-fill resin composites might be an clinical option for a faster restoration in deciduous teeth.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.1
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• pp.11-18
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• 2004

The eruption of permanent teeth represents the movement in the alveolar bone before appearance in oral cavity, to the occlusal plane after appearance in oral cavity, and additive movement after reaching th the occlusal plane. Tooth eruption is mostly controlled by genetic signals. The eruption stage is divided to preeruptive alveolar stage, alveolar bone stage, mucosal stage according to the process of growth and development. If the disturbance is occured in any stage of eruption, tooth does not erupt. The cause of eruption disturbance are ectopic position of the tooth germ, obstruction of the eruption path and defects in the follicle or PDL. In the treatment of eruption disturbance, surgical procedures are commonly used. There are three kind of surgical procedure ; surgical exposure, surgical repositioning, surgical exposure and traction Surgical exposure is basic procedure. This involves removal of mucosa, bone, lesion that are surrounding the teeth, dental sac when necessary to maintain a patent channel between the crown and the normal eruptive path into the oral cavity. To ensure this patency, many techniques including cementation of a celluloid crown, packing with gutta-percha or zinc oxide-eugenol, or a surgical pack, are used. When surgical exposure is conducted, operators should not expose any part of cervical root cement and not injure periodontium or root of adjunct tooth. After surgical exposure, tooth should be surrounded by keratinized gingiva. There is direct relationship between the extent of development of pathophysiologic aberrations and the intensity of the manipulative injury inflicted on the tooth by surgical treatment, so operator should consider this thing. In these cases, surgical exposure is conducted on Maxillary 1st milars that have a eruption disturbance and improve the eruption disturbance effectively.

• Radiation Oncology Journal
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• v.26 no.4
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• pp.271-279
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• 2008

Purpose: To evaluate the efficacy of a belly-board device (BBD) in reducing the volume of small bowel during four-field pelvic irradiation. Materials and Methods: Twenty-two cancer patients (14 uterine cervical cancer, 6 rectal cancer, and 2 endometrial cancer) scheduled to receive pelvic irradiation were selected for this study. Two sets of CT images were taken with and without the belly-board device using the Siemens 16 channel CT scanner. All patients were set in the prone position. The CT images were transferred to a treatment planning system for dose calculation and volume measurements. The external surfaces of small bowel and the bladder were contoured on all CT scans and the 4-pelvic fields were added. The dose-volume-histogram of the bladder and small bowel, with and without the BBD, were plotted and analyzed. Results: In all patients, the total small bowel volume included in the irradiated fields was reduced when the BBD was used. The mean volume reduction was 35% (range, $1{\sim}79%$) and was statistically significant (p<0.001). The reduction in small bowel volume receiving $10{\sim}100%$ of the prescribed dose was statistically significant when the BBD was used in all cases. Almost no change in the total bladder volume involved was observed in the field (<8 cc, p=0.762). However, the bladder volume receiving 90% of the prescribed dose was 100% in 15/22 patients (68%) and $90{\sim}99%$ in 7/22 patients (32%) with the BBD. In comparison, the bladder volume receiving 90% of the prescribed dose was 100% in 10/22 patients (45%), $90{\sim}99%$ in 7/22 patients (32%), and $80{\sim}89%$ in 5/22 patients (23%) without the BBD. When the BBD was used, an increase in the bladder volume receiving a high dose range was observed Conclusion: This study shows that the use of a BBD for the treatment of cancer in the pelvic area significantly improves small bowel sparing. However, since the BBD pushed the bladder into the treatment field, the bladder volume receiving the high dose could increase. Therefore it is recommended to be considerate in using the BBD when bladder damage is of concern.

• Korean Journal of Veterinary Research
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• v.38 no.1
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• pp.147-159
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• 1998

A survey of the internal parasites in 115 fishes of Ophicephalus argus was carried out in Kyungpook province during the period from January 1995 to November 1997. A species of trematode from the stomach and a species of nematode from the caeca of the fishes was discovered respectively. The trematode was identified as Azygia hwangtsinyi (Tsin, 1993) and the nematode as Pingus sinensis ($Hs\ddot{u}$, 1993). The fluke was pressed at thick of 0.1mm~0.2mm between slide glasses and fixed in 70% ethyl alcohol solution. The fluke was washed with tap water after fixation and stained with hematoxylin-carmin and mounted in balsam through routine methods. The nematode was fixed in 5% formalin solution and mounted with lactophnol or glycerine jelly. Morphology : Arygia hwantsinyi ; The fluke is elongate body with approximately parallel margins and rounded extremities in pressed preparations(Fig 1). The cuticle is unarmed. The oral sucker is ventro-subterminal in position. The ventral sucker is slightly smaller than oral sucker and positioned at 14.2% of body length from the oral sucker. The cirrus sac and genital pore is in mid-ventral line, slightly anterior to the ventral sucker. The oral sucker is succeeded by a well developed muscular pharynx. It is succeeded by a short inverted Y-shaped oesophagus. The inner wall of oesophagus is consisted of many fine folded membrane. The fine tubes of esophagus pass into the intestinal heads which are distended and presented a marked borderline between the fine tube and intestinal heads. The Intestinal heads start at level of pharynx and pass caudad in a zigzag course to end quite near caudal margin. The uterine coils occupy the intercecal area between the level of the cephalic margin of the ovary and about the level of the ventral sucker. The uterus is filled with many eggs. The testes are round or oval and placed one behind the other generally a little diagonally. The posterior testis is placed at level of 75.1% of body length. The ovary is oval, placed ahead the anterior testis. The shell gland not discernible outline is contacted with ovary ahead it. The vitelline glands are consisted of small oval vesicles. The vesicles occupy extracecal regions and between a little posterior of the ventral sucker and near caudal margin. Pingus sinensis : Female ; The cuticle is smooth and the cervical alae are well developed. The mouth opening is small, triangular, and without lips. The anterior end bears four sub-medial papillae. The oesophagus is divided into a muscular and glandular portion. The nerve ring is situated just at the junction of the muscular and glandular portions of the oesophagus. The vulva which has a prominent flap, is placed behind the middle of the body about one-third of the length of the worm from the posterior extremity. The vagina is strongly muscularised and after running anteriorly about $68{\mu}$, divides itself into two broad uterine tubes with an anterior and a posterior one. There are a few eggs in the uterine tubes. The tail is slender, straight and pointed. The ovary extends almost to the posterior extremity. Male : Male is smaller than female. The tail is pointed, curved and carrying well-developed caudal alae. A prominent muscular precloacal sucker is characteristic. The spicules are equal and short. There are four pairs of pedunculated pre-anal papillae, of which the most anterior pair are situated just at the level anterior to the muscular sucker. Two pairs of pedunculated papillae are present before the anus. There are five pairs of post-anal papillae of which the most anterior pair and the second counted from the posterior end are ventral and more marked than the ones which are situated laterally.