• The korean journal of orthodontics
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• v.41 no.2
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• pp.112-120
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• 2011

Objective: Microscrew implants (MSls) offer many advantages, but some complications are known to occur during their insertion. One of the most commonly reported complications is root injury. Our aim was to identify factors associated with root injury and to evaluate their qualitative and quantitative values. Methods: Thirty-five orthodontists placed MSls (AbsoAnchor$AbsoAnchor^{(R)}$, Dentos Co. Ltd, Daegu, Korea) in the upper jaw of typodonts, labially between the second premolar and the first molar, in low and high vertical positions. Root contacts were counted, and distances between MSI apices and roots were measured. Fear level of the orthodontists was surveyed before and after the experiment. Wilcoxon's test, chi-square test, and Mann-Whitney test were used for statistical analysis. Results: Overall root contact rate of MSI insertion was 23.57%. The root contact rate was significantly higher in MSls inserted at $90^{\circ}$ (45.71%) than at $30^{\circ}$ (1.43%). The distance between the dental root and MSI also increased significantly in MSls inserted at $30^{\circ}$. Mean fear level before MSI insertion (4.6) significantly decreased after insertion (3.2); the causative factors were risk of injury to dental root and maxillary sinus or mandibular canal. Conclusions: Root injury is relatively rare, and oblique angulation reduces the risk of root and MSI contact.

• Animal cells and systems
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• v.13 no.1
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• pp.59-69
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• 2009

This paper documents the defining morphological characteristics of the larval stages of Chionoecetes tanneri Rathbun, 1893, the grooved Tanner crab, from specimens reared in the laboratory. Chionoecetes tanneri larval stages include two zoeae and one megalopa. The first zoea is characterized by: six setae on the posterior margin of the carapace; postero-lateral spines on abdominal somites 3 and 4, extending beyond the posterior margin of adjacent somites and bearing 9-10 spinnules; 12 plumose setae and one stout distal plumose seta present on the margin of the scaphognathite of the maxilla; and one fused lateral spine and one articulated dorso-medial spine on each fork of the telson. The second zoea is characterized by: 9 setae on the postero-lateral margin of the carapace; a serrated mandible molar; a mandibular palp bud; 25-26 plumose setae on the margin of the scaphognathite of the maxilla; pereiopods with well-developed gills and buds; and four pairs of stout setae on the posterior margin of the telson. For the megalopal stage, the distinguishing characteristics include: a rostral spine equal in length to the supraorbital spine; six setae on the exopod of the uropod; and a single spine on the ischium of the second pereiopod. This study allows C. tanneri larvae to be distinguished from the larvae of known sympatric congeners. This information provides a basic taxonomic tool for researchers in fisheries management and zooplankton ecology who are addressing issues related to trophic interactions, metapopulation dynamics and ecosystem impacts in the evolving marine resource management strategies in the North Pacific, and those related to Chionoecetes species in particular.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.38 no.5
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• pp.271-275
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• 2012

Objectives: This study evaluated a range of fixation methods to determine which is best for the postoperative stabilization of a mandibular osteotomy using three-dimensional finite element analysis of the stress distribution on the plate, screw and surrounding bone and displacement of the lower incisors. Materials and Methods: The model was generated using the synthetic skull scan data, and the surface model was changed to a solid model using software. Bilateral sagittal split ramus osteotomy was performed using the program, and 8 different types of fixation methods were evaluated. A vertical load of 10 N was applied to the occlusal surface of the first molar. Results: In the case of bicortical screws, von-Mises stress on the screws and screw hole and deflection of the lower central incisor were minimal in type 2 (inverted L pattern with 3 bicortical repositioning screws). In the case of plates, von-Mises stress was minimal in type 8 (fixation 5 mm above the inferior border of the mandible with 1 metal plate and 4 monocortical screws), and deflection of the lower central incisor was minimal in types 6 (fixation 5 mm below the superior border of the mandible with 1 metal plate and 4 monocortical screws) and 7 (fixation 12 mm below the superior border of the mandible with 1 metal plate and 4 monocortical screws). Conclusion: Types 2 and 6 fixation methods provide better stability than the others.

• The Journal of Advanced Prosthodontics
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• v.12 no.5
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• pp.316-321
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• 2020

PURPOSE. The stress distribution and microgap formation on an implant abutment structure was evaluated to determine the relationship between the direction of the load and the stress value. MATERIALS AND METHODS. Two types of three-dimensional models for the mandibular first molar were designed: bone-level implant and tissue-level implant. Each group consisted of an implant, surrounding bone, abutment, screw, and crown. Static finite element analysis was simulated through 200 N of occlusal load and preload at five different load directions: 0, 15, 30, 45, and 60°. The von Mises stress of the abutment and implant was evaluated. Microgap formation on the implant-abutment interface was also analyzed. RESULTS. The stress values in the implant were as follows: 525, 322, 561, 778, and 1150 MPa in a bone level implant, and 254, 182, 259, 364, and 436 MPa in a tissue level implant at a load direction of 0, 15, 30, 45, and 60°, respectively. For microgap formation between the implant and abutment interface, three to seven-micron gaps were observed in the bone level implant under a load at 45 and 60°. In contrast, a three-micron gap was observed in the tissue level implant under a load at only 60°. CONCLUSION. The mean stress of bone-level implant showed 2.2 times higher than that of tissue-level implant. When considering the loading point of occlusal surface and the direction of load, higher stress was noted when the vector was from the center of rotation in the implant prostheses.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.3
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• pp.688-696
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• 1996

Garre's osteomyelitis is a unique form of osteomyelitis characterized rediographically by localized thickening of the periosteum and deposition of laminated subperiosteal bone. The most common inciting factor is a mandibular infection in permanent first molar with necrotic pulp. This disease occurs primarily in children and to date in all instances it has occured only in mandible. It usually results in hard swelling over the jaws, producing facial asymmetry with little or no pain. The overlying skin is normal but can occasionally be inflammed mostly when pain is present. Palpation reveals a usually smooth, bone-hard lesion which feel like an inherent part of the mandible. Unlike other forms of osteomyelitis, there is no marked increase in fever, white bloods cell count, sedimentation rate or alkaline phosphatase value. The treatment of Garre's osteomyelitis usually consist of elimination of the sourses of infection, i.e., either extration of an offending infected teeth or root canal therapy. This treatment almost always results in resolution of the Garre's osteomyelitis. Resistant cases have involved secondary surgery, i.e., decortication and sequestrectomy. This report presents three cases of Garre's osteomyelitis resolved by endodontic treatment. Cliniqtl examination revealed swelling on the face with no tenderness. Periapical radiograph showed deep caries lesion extending into pulp chamber and periapical radiolucency. Occlusal radiograph showed an enlargement of bone and stretching the periosteum. A clinical diagnosis of the Garre's osteomyelitis was made. Endodontic treatment was accomplished with conventional method and restored facial symmetry. Long-term check-ups are necessary to evaluate the results of endodontic treatment.

• Journal of Oral Medicine and Pain
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• v.24 no.1
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• pp.81-94
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• 1999

This study intends to find usefulness of the computer assisted dental identification in mass disaster. The variety of dental characteristics was investigated through the research of dental records of 508 adults. And a computer assisted simulation program was used to evaluate the selectivity of dental identification. Findings were as follows : 1. Combinations of dental characteristics were found 155 types. The most various dental characteristic was showed on the mandibular first molar. 99.0% of subjects had dental characteristics for dental identification. 2. The posterior teeth, in comparison with anterior teeth, showed higher selectivity in dental identification which was enhanced by information on the material, type and cavity of the restoration. 3. The variety of dental characteristics was mainly found on the combinations of missing tooth with the material, type and cavity of the restoration. 4. The computer assisted dental identification program, with informa- tion about one's tooth state, made individual identification possible when there was only a part of the teeth in a corpse. 5. The computer assisted dental identification had considerably high selectivity based on the variety of dental characteristics. And it was also performed faster and preciser than the existing identification methods. Based on the results of this study, there are various combinations of the feature of the tooth itself with dental characteristics caused by a certain type of treatment on the teeth. And using the computer assisted dental identification program based on this, dental identification can be more efficient economically and more useful than any other forensic identification methods.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.1
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• pp.11-20
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• 2013

The prevalence and interest of dental erosion seems to be rising in children all over the world. Thus, This study was performed to investigate the prevalence and severity of dental erosion in the primary molars at terminal stage nearing exfoliation, and associated risk factors. An examination was performed on 788 children using modified Linkosalo & Markkanen system, and questionnaires were gained. Association between dental erosion and the risk factors were statistically analyzed with chi-squared test and logistic regression analysis at a significance level of p < 0.05. As a result, 213 children (27%) showed dental erosion, and the mandibular left first primary molar was the most influenced tooth. According to the analysis of risk factors, frequent intake of carbonated drinks and fruit juices showed significant development of erosion (p < 0.05), and using straw for drinking fruit juices showed significant a reduction of erosion (p < 0.05).

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.1-12
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• 2009

The objective of this study was to test the effects of crown material, cement type, the direction in which stress is applied and distribution of luting cement that might lead to cement microfracture using 2D Finite Element Method. Twenty three finite element models with a chamfer margin configuration were generated for a mandibular first molar. Crown models exhibited four crown materials: type 3 gold alloy, Ni-Cr alloy, ceramic and composite resin, and two luting cements: zinc phosphate and glass ionomer cements with a thicknesses of $70{\mu}m$. Modeled crowns were loaded axially or obliquely at unit load of 1 N. Areas and levels of stress concentrations within the cement were determined. Stress in the cement layer at the margins of crowns were higher than those in the area away from the margin. Stress under oblique loads were much higher than under axial load. The stiffer crown material produced higher stress and similarly, higher stress were found in cements with the greater Young's modulus.

• Journal of Technologic Dentistry
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• v.40 no.2
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• pp.63-69
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• 2018

Purpose: The purpose of this study is to investigate the non-precious metal core materials used in the dental laboratory to fabricate the implant superstructure by CAD / CAM method. And to observe and compare the morphology and distribution of the osteoblasts in relation to implant osseointegration. Methods: In this study, the mandibular right first molar tooth model was selected as an international standard to produce a single core. Using this model, the impression was made with the silicone rubber, the tooth model was scanned, and a single core was designed and 5-axis milling was performed. The materials used were Cobalt-Chromium and Nickel-Chromium, and the cores for dental implant top structures were fabricated according to the procedures of the dental labs. After the fabrication, the marginal area of the core was separated and cell culture experiment was performed. The osteoblast cells used MC3T3-E1, which is currently widely used. For morphological analysis of osteoblasts, cells were posttreated and observed using CLSM (Confocal Laser Scanning Microscope) and compared. Results: The cell adhesion behavior of the specimen surface measured by CLSM was uniformly distributed in specimen A (Cobalt-Chromium) than in specimen B (Nickel-Chromium). The distribution and changes of the cells were different in the two specimens. Conclusion : It is possible to confirm that specimen A (Cobalt-Chromium) is suitable for the living body through adhesion and proliferation of osteoblasts related to implant osseointegration in the non-precious metal superstructure used after implantation. It is considered that it is preferable to use Co-Cr when fabricating the superstructure.

• The korean journal of orthodontics
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• v.46 no.3
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• pp.137-145
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• 2016

Objective: The purpose of this study was to investigate the characteristics of orthodontic patients at Yonsei Dental Hospital from 2008 to 2012. Methods: We evaluated Angle's classification from molar relationships, classification of skeletal malocclusion from the A point-nasion-B point angle, facial asymmetry, and temporomandibular joint disorders (TMDs) from the records of 7,476 patients who received an orthodontic diagnosis. The orthognathic surgery rate, extraction rate, and extraction sites were determined from the records of 4,861 treated patients. Results: The patient number increased until 2010 and gradually decreased thereafter. Most patients were aged 19-39 years, with a gradual increase in patients aged ${\geq}40years$. Angle's Class I, Class II divisions 1 and 2, and Class III malocclusions were observed in 27.7%, 25.6%, 10.6%, and 36.1% patients, respectively, with a gradual decrease in the frequency of Class I malocclusion. The proportion of patients with skeletal Class I, Class II, and Class III malocclusions was 34.3%, 34.3%, and 31.4%, respectively, while the prevalence of facial asymmetry and TMDs was 11.0% and 24.9%, respectively. The orthognathic surgery rate was 18.5%, with 70% surgical patients exhibiting skeletal Class III malocclusion. The overall extraction rate among nonsurgical patients was 35.4%, and the maxillary and mandibular first premolars were the most commonly extracted teeth. Conclusions: The most noticeable changes over time included a decrease in the patient number after 2010, an increase in the average patient age, and a decrease in the frequency of Angle's Class I malocclusion. Our results suggest that periodic characterization is necessary to meet the changing demands of orthodontic patients.