• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.2
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• pp.233-239
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• 2010

Space loss of dental arch can appear when the proper position of teeth within the dental arch changes by a certain cause, because the balance of force makes changes about tooth position as well as alignment. The causes of space loss include proximal caries, early extraction, congenital missing of a tooth and hypodontia, etc. Among those causes of space loss, congenital missing of a tooth is more rarely observed in the primary dentition than in the permanent dentition. Congenital missing in the primary dentition is associated with that in the permanent dentition. Furthermore, it can cause space problem, such as mesial tilting or drift of adjacent teeth, space loss for permanent successors and dental arch constriction, etc. Primary lateral incisors is the most commonly involved, in the maxilla rather than in the mandible, but primary canine is rarely reported. In this patient, who visited the department of pediatric dentistry at Yonsei university dental hospital, it was observed that the maxillary right primary canine was congenitally missing and an odontoma was found insteadly. However, neither the space loss for the congenitally missing primary canine nor midline deviation is remarkable during the 2-year-10-month observation period. In addition, any clinical or radiographical symptom did not occur in spite of odontoma. Therefore, surgical enucleation of odontoma is planned according to the eruption of permanent lateral incisor or canine, unless eruption failure of permanent lateral incisor or canine nor cystic change around the odontoma is occurred. Through further evaluation, space maintainer or orthodontic treatment may be necessary.

• The korean journal of orthodontics
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• v.40 no.1
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• pp.16-26
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• 2010

Objective: The purposes of this study were to evaluate the force and stress depending on the type, deflection and thickness of the materials and to evaluate the mechanical properties of thermoplastic materials after repeated loading. Methods: Four types of thermoplastic products were tested. Force until the deflections of 2.0 mm and the stress when the materials were restoring to its resting position were evaluated. The mechanical properties of thermoplastic materials evaluated after 5 repeated loading cycles. Results: The interaction was observed between the thickness and the deflection (p < 0.05) from the regression equation. Thickness and amount of deflection rather than products and materials showed the largest effect on force and stress. In all products, at least 159 gf of force was required for more than 1.0 mm deflection or when materials with 1.0 mm thickness were deflected. The stress recorded was more than 19 gf/$mm^2$. During repeated loading, each group showed significant difference on the force and the stress (p < 0.01), 10 - 17% reduction of force and 4 - 7% reduction of stress in average. Conclusions: Proper thickness of thermoplastic materials and deflection level of tooth movement should be decided for the physiologic tooth movement. Force decay after repeated loading should be considered for the efficient tooth movement.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.1
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• pp.21-32
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• 2010

The convergence angle of a prepared tooth is a very important factor in the retention and resistance of a crown restoration. But various intraoral environments and clinician's techniques make it difficult to obtain the ideal inclination. Therefore, in this study, clinical convergence angle of a prepared tooth was investigated. The data was collected from the patient models of prosthodontic residents and the patient models of general practitioners. The images of mesiodistal and buccolingual surfaces were taken with a digital camera to evaluate the convergence angle on 'ImageJ' program. The images were classified according to the criteria (1. Clinician group, 2. Position in the dental arch, 3. The purpose of abutment preparation)and then analyzed. The mean convergence angle of a prepared tooth for Korean clinicians was $15.02^{\circ}$ (${\pm}10.13^{\circ}$). 1. It was significant in the convergence angle between the general practitioner group and the prosthodontic resident group(p<0.05). 2. It was significant between the mesiodistal and buccolingual surface in the the prosthodontic resident group(p<0.05). 3. For the general practitioner group, it was significant when anteriors and premolars were compared with molars(p<0.05). For the prosthodontic resident group, it was significant when anteriors and premolars were compared with molars (p<0.05). 4. When divided into upper and lower arches, for the general practitioner group, it showed significant difference in the buccolingual aspect(p<0.05). Also in the prosthodontic resident group, it showed significant difference in the buccolingual aspect(p<0.05). 5. Dividing left and right sides of the arches, there was no significant difference in the general practitioner group and the prosthodontic resident group(p>0.05). 6. In the general practitioner group, it was significant in the mesiodistal axial convergence angle of single crown abutment and 3 unit bridge abutment(p<0.05). In the prosthodontic resident group, it was significant in the mesiodistal and overall axial convergence angle of single crown abutment and 3 unit bridge abutment(p<0.05). Clinical convergence angle of prepared tooth in Korea was included in agreement with other studies investigating convergence angle that ranged from 10 to 22 degrees, achieved in clinical practice.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.4
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• pp.519-525
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• 2010

Ectopic eruption means the eruption of the tooth in an abnormal position due to multiple factors, which found most frequently in maxillary fist permanent molars, mandibular lateral incisors and maxillary permanent canines. Ectopic eruption of the maxillary first permanent molar occurs when the molar erupts with a more mesial angulation than normal, and locks itself in an atypical resorption on the distobuccal root of the second primary molar. The maxillary first permanent molar plays important roles for mastication and occlusion, so ectopically erupted maxillary first permanent molars should be relocated into proper position. Treatment options are separation by insertion of the brass wire or elastic rings, preparation of distal aspect of the maxillary second primary molar, using fixed or removable appliance with finger spring, and placement of space maintainer or space regainer after extraction of the maxillary second primary molar. We report three cases treated of ectopically erupted maxillary first permanent molar by re-setting of stainless steel crowns, placement of brass wire and using active plate. We could find out distal movement of maxillary first permanent molars into proper position and normal occlusion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2360-2367
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• 2013

The purpose of this study was to improve the paramedics skills to manage advanced airway by comparing speed and success rate between endotracheal intubation and laryngeal mask airway(LMA) insertion in a moving ambulance. Sixty subjects were randomly recruited and samely divided into control group and experimental group. And they were asked to join a practical experiment using dummy model. Data analysis was done by SPSS WIN 14.0 Version. As a result of this research, in terms of difference in speed according to patient's intubation posture, the speed of control group was indicated to be good in sniffing position(t=-4.038, p<.001). There was no difference in speed between two groups in neutral position. In the neutral posture given the endotracheal intubation, tooth fracture occurred in 16 people(53.3%). There was no difference in success rate between two groups. As for a change in self-confidence before and after experiment, the post self-confidence was indicated to have been enhanced in both groups. In conclusion, it is effective to use LMA in the traumatic patient who is unable to receive endotracheal intubation in sniffing position. It is very important for the paramedics to receive the continuous training of the airway management skills.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.2
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• pp.259-271
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• 1992

This study was designed to investigate the criteria of the perfect smile that was necessary to improve the esthetic problem in oral and maxillo-facial region and treating the anterior tooth region. The author took the facial straight photograph of 240 university students(male : 129, female : 111) in a resting and a smiling position, measured and analized the lip pattern and the relation between the lip and the teeth when they were smiling. Besides, 10 members of committee for appraisal (dentist : 5 persons, professor of the college of fine arts : 5 persons) estimated the smiling pattern. After that the author have compared and analyzed the obtained results. The results obtained were as follows : 1. In the shape of the upper lip, when the upper lip curved downward, it was 42.92% , straight was 45.00% and curved upward was 12.08%. The group in which the upper lip curved upward was the most esthetic. 2. In the relation between the upper lip and the teeth, high smile was 29.17%, average smile was 55.83% and low smile was 15.00%. The group of average smile was the most esthetic. 3. In the parallel relation between the lower lip and maxillary anterior incisal curvature, the group of paralled was 60.42%, the group of straight was 34.17% and the group of reverse was 5.41%. The group of parallel was the most esthetic. 4. In the relationship between maxillary anterior incisor and lower lip, the group of the maxillary anterior incisor were slightly covered by the lower lip was 10.42%, the group of the maxillary anterior teeth touched to the lower lip was 35.83%, and the no-touching was 53.75%. The group of the maxillary anterior teeth touched to the lower lip was the most esthetic. 5. In the teeth displayed in a smile, displayed to the canine was 0.84%, displayed to the first premolar was 19.17%, displayed to the second premolar was 57.92%, displayed to the first molar was 20.00% and displayed to the second molar was 2.08%. The group of displayed to the first molar was the most esthetic. 6. At smiles, the width of the mouth corner was 0.46 times of the full face width, 0.95 times of the interpupillary distance, and 1.23 times of the resting position. 7. At smiles, the lengh of the upper lip was 0.71 times and lower lip was 0.93 times of the length in the resting position.

• Restorative Dentistry and Endodontics
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• v.24 no.3
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• pp.465-472
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• 1999

The aim of this study was to determine the shear bond properties of four dentin bonding systems to internal cervical dentin, and to investigate the effect of the pretreatment for removing smear layer and position of dentin on shear bond strength of dentin bonding agents. The materials tested in this study were consisted of four commercially available dentin bonding systems[Allbond 2(AB), Clearfil Linerbond 2(CL), Optibond FL(OP), Scotchbond Multi-purpose(SB)], a restorative light-cured composite resin[Z100]J and a chelating agent[RC-prep(RC)]. Fifty-six freshly extracted human molars were used in this study. Dentin specimens were prepared by first cutting the root of the tooth 1mm below the cementoenamel junction with a diamond bur in a high speed handpiece under air-water coolant, and then removing occlusal part at pulp horn level by means of a second parallel section, The root canal areas were exposed by means of cutting the dent in specimens perpendicular to the root axis. Dentin specimens were randomly assigned to two groups(pretreated group, not-pretreated group) based on the pretreatment method of dentin surface. In pretreated group, RC was applied to dentin surface for 1minute and then rinsed with NaOCl. In not-pretreated group, dentin surface was rinsed with saline Each groups were subdevided into four groups according to dentin bonding systems. Four dentin bonding systems and a restorative resin were applied according to the directions of manufacturer. The dentin-resin specimens were embedded in a cold cure acrylic resin, and were cut with a low speed diamond saw to the dimension of $1{\times}1mm$. The cut specimens were divided into three groups according to the position of internal cervical dentin. The shear bond properties of dentin-resin specimens were measured with Universal testing machine (Zwick, 020, Germany) with the cross head speed of 0.5mm/min. From this experiment. the following results were obtained : 1. In case of shear bond strength, there was no significant difference among dentin bonding systems in not-pretreated groups, whereas in pretreated groups, the shear bond strengths of AB and of SB were statistically significantly higher than those of CL and of OP. 2. The shear bond strengths of AB and of SB in pretreated groups were significantly higher than those in not-pretreated groups. 3. The shear bond strengths of radicular layer of OP were higher than those of occlusal layer of OP in not-pretreated groups, and of AB in pretreated groups. The shear bond strengths of radicular layer of AB and of CL in not-pretreated groups were higher than those in pretreated group.

• Imaging Science in Dentistry
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• v.33 no.2
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• pp.79-83
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• 2003

Purpose : To assess the relationship between the direction of the indicating rod of the radiographic stent for ideal prosthetic design and the actual possible path of implant fixture placement when residual ridge resorption is considered. Materials and Methods: The study materials consisted of 326 implant sites (male 214 cases and female 112 cases) from a total of 106 patients (male 65 patients and female 41 patients) who desired implant prostheses. Computed tomography of patients were taken and reformatted using ToothPix/sup (R)/ software. Bony defects, bony sclerosis, the change of the direction of indicating rod, and root proximity of the adjacent teeth were examined on the CT-derived images. Results: The rate of the irregular crestal cortex was relatively high on premolar and molar area of maxilla. Mandibular molar area showed relatively high rate of focal sclerosis on the area of implant fixture insertion. The position of the indicating rods were relatively acceptable on the molar areas of both jaws. However, the position of the indicating rods should be shifted to buccal side with lingual rotation of the apical end on maxillary anterior teeth and premolar area. Conclusion: Clinically determined rod direction and position of the indicating rod for implant placement was not always acceptable for insertion according to the reformatted CT images. The pre-operative treatment plan for implant should be determined carefully, considering the state of the alveolar bone using the reformatted CT images.

• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.54-59
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• 2022

This paper is a purpose to study and analyze the failure examples for timing belt, camshaft position sensor and ignition coil of LPG automotive engine. The first example, whe the service man install the front case bracket of engine, he excessively tightened up a 12mm bolt for being fixed of brackct. As a results, the bolt was separated from joint part so that it was put in between the crankshaft sprocket. Therefore the belt was broken off because of interference between timing belt and sprocket tooth. The second example, it verified the disharmony phenenomen of engine that the gap of the camshaft position sensor and camshaft senseing point assembled on cylinder head part was small more than iregular value so that the it was generated senseing damage phenomenon by pulse signal misconduct. The third example, it was found the engine disharmony phenomenon that the fire in the ignition coil was leaked by inner damage of Number 2 ignition coil.Therefore, the the manager of a car throughtly have to inspect not in order to arise the failure symptoms.

• The korean journal of orthodontics
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• v.33 no.5 s.100
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• pp.339-350
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• 2003

The purpose of this study was to investigate the micro-implant height and anterior hook height to prevent maxillary six anterior teeth from lingual tipping and extruding during space closure. We manufactured maxillary dental arch form, bracket and wire, using the computer aided three-dimensional finite element method. Bracket was $.022'{\times}.028'$ slot size and attached to tooth surface. Wire was $.019'{\times}.025'$ stainless steel and $.032'{\times}.032'$ stainless steel hook was attached to wire between lateral incisor and canine. Length of hook was 8mm and force application points were marked at intervals of In. Four micro-implants were implanted on alveolar bone between second premolar and first molar. The heights of them were 4, 6, 8, 10mm starting from wire. We analyzed initial displacement of teeth by various force application point applying force of 150gm to each micro-implant and anterior hook. The conclusions of 4his study are as the following : 1. When the micro-implant height was 4m and the anterior hook height was 5mm and below, anterior teeth were tipped lingually. When the anterior hook height was 6mm and above, anterior teeth were tipped labially. 2. When the micro-implant height was 6mm and the anterior hook height was 6mm and below, the anterior teeth were tipped lingually. When the anterior hook height was 6m and above, the anterior teeth were tipped labially. But lingual tipping of anterior teeth decreased and labial tipping Increased when the micro-implant height was 6mm, compared with 4mm micro-implant height. 3. When the micro-implant height was 8mm and the anterior hook height was 2mm, the anterior teeth were tipped lingually. When the anterior hook height was 3mm and above, labial tipping movement of the anterior teeth increased proportionally. 4. When the micro-implant height was 10mm and the anterior hook height was 2mm and above, labial tipping of the anterior teeth increased proportionally. 5. As the anterior hook height increased, aterior teeth were tipped more labially. But extrusion occurred on canine and premolar area because of the increase of wire distortion. 6. Movement of the posterior teeth was tipped distally during maxillary six anterior teeth retraction using micro-im plant because of the friction between bracket and were Based on the results of this study, we could predict the pattern of the tooth movement according to position of micro-implant and height of anterior hook. It seems that we can find the force application point for proper tooth movement in consideration of inclination of anterior anterior teeth, periodontal condition, overjet and overbite