Study on Effect of Welding Parameters and Determination of Suitable Condition at the Horizontal Fillet Welding of FCAW

Welding technology is widely used in the manufacturing industry and its significance is given greater emphasis because welding technology is directly related to the quality and productivity of the product. However, the interest in the welding is very low because it is known as one of the 3D works. Korea has the high consumption of steel ranks and it ranks fifth in the world. It means the higher importance of welding technology compared to other developed or advanced countries. Shipbuilding industry is normally using the traditional DC arc welding machine which is controlled with SCR by analog method. Recently a digital arc welding machine has been developed and its application is growing gradually. The power consumption of digital welding machine can be markedly reduced and its welding quality can be also improved very much. In this study, a lot of welding experiment using digital welding machine were carried out and their results were evaluated by observing arc state and analysing the signal of welding current and voltage. On the basis of this work the relationship of welding parameters and welding results was investigated and the suitable welding condition was proposed for the horizontal fillet FCAW which is most widely used in shipbuilding industries. Finally the DB program was made to easily get the suitable welding conditions.List of Figures Ⅰ List of Tables Ⅱ Abstract Ⅲ 제 1장 서론 1 제 2장 FCAW 2 2.1 용접변수 및 조건 2 2.1.1 원리 및 특징 2 2.1.2 용접전류 3 2.1.3 용접전압 4 2.1.4 와이어 돌출길이 5 2.1.5 용접속도 6 2.1.6 토치방향 6 2.2 용접변수와 비드형상의 관계 7 2.3 용접변수의 상관관계 9 2.4 아크용접로봇 시스템 12 제 3장 실험 14 3.1 실험조건 및 실험방법 14 3.2 실험결과 및 고찰 18 3.3 적정조건 및 실험결과 제시 DB프로그램 28 제 4장 결론 32 참고문헌 3

Anterior open bite with temporomandibular disorders treated with intermaxillary traction using skeletal anchorage system.

OBJECTIVES: The anterior open bite with temporomandibular disorders (TMD) is one of the most challenging cases both orthodontically and surgically. We introduce an intermaxillary traction treatment for patients with anterior open bite and TMD using a skeletal anchorage system (SAS). MATERIALS AND METHODS: This study was comprised of 52 patients with anterior open bite and TMD. A total of four mini-screws were inserted, two screws each into the maxilla and mandible, to obtain a class II pattern of elastic application with 120-200 g force. Adjunctive muscle relaxation treatments, such as splint therapy, medication, and botulinum toxin injection were applied during or before intermaxillary traction. At least one treatment among adjunctive muscle relaxation treatment, mentioned above, was applied to 96.2% of patients. We evaluated the clinical characteristics of patients, TMD symptom changes, amount of open bite improved. The degree of open bite improvement was compared between the open bite-reduced group (21 patients) and not-reduced group (5 patients). RESULTS: TMD symptoms (muscle/joint pain, joint sound, mouth opening) remained or improved in most patients, and worsened in about 10% of patients for each items. Anterior open bite was improved by a mean of 1.75 mm (P<0.01) during treatment. The open bite-reduced group exhibited a significant open bite improvement compared to the not-reduced group (P<0.05), with 37% of open bite improvement occurring during the first 3 months of treatment. CONCLUSION: The intermaxillary traction technique using SAS is a valid modality for correction of anterior open bite and improvement of TMD symptoms.ope

The relationship between mandibular asymmetry and temporomandibular joint disc displacement on MRI

Purpose: This study was aimed to investigate the relationship between the mandibular asymmetry and the internal derangement of temporomandibular joint. Materials and methods: One hundred and sixty eight patients had been assessed through clinical examinations, panoramic radiographs and magnetic resonance imagings (MRIs), were selected. The samples were classified into three subgroups according to the severity of the mandibular asymmetries in the panoramic radiographs and the status of TMJ discs on the MRI were compared among each groups. Results: In an apparent asymmetry group, there was a significant difference in the number of temporomandibular disk displacement without reduction between the long and short side (66.7%, 18/27 joints on the short side) when the ratio of condylar process and coronoid process was used (p<0.05), but there was no statistically significant difference when the ratio of condyle and ramus was used. Conclusion: The probability of the disc displacement without reduction was higher at the side with relatively shorter condylar process on the panoramic radiograph, and also it might be more effective to use ratio of condylar process and coronoid process in the assessment of mandibular asymmetry. Therefore, a careful assessment on the temporomandibular disorders is necessary to diagnose and establish the treatment plans for the patients with a mandibular asymmetry and the panoramic radiograph can be used effectively on that way.ope

Expression of matrix metalloproteinase-1 and -2 mRNA in retrodiscal tissue of the temporomandibular joint

Matrix metalloproteinases (MMPs) play an important role in the normal morphogenesis, maintenance, and repair of matrix and also have important functions in pathologic conditions characterized by excessive degradation of extracellular matrix, such as rheumatoid arthritis, osteoarthritis, periodontitis and in tumor invasion and metastasis. In this study, expression of MMP-1 and -2 mRNA in retrodiscal tissue of the temporomandibular joint (TMJ) was examined and compared with magnetic resonance imaging (MRI) and surgical findings. MMP mRNAs in the retrodiscal tissue samples were detected by reverse transcription - polymerase chain reaction. TMJ internal derangement (ID) was categorized as normal disc position, disc displacement with reduction, early stage of disc displacement without reduction (DDsR) and late stage of DDsR. TMJ osteoarthrosis (OA) was classified with normal, mild and advanced OA. The amount of synovial fluid collection was divided into not detected, small, large and extremely large amount on MR T2-weighted imaging. Perforation and adhesion were examined during open surgery of the TMJ. Six out of 37 samples were excluded because of little amount of extracted total mRNA. MMP-2 mRNA was detected whole joints, and so the MMP-2 mRNA seems to be expressed normally in retrodiscal tissue. However, MMP-1 mRNA was expressed in 8 of 31 joints. Frequencies of MMP-1 mRNA expression according to the TMJ IDs, amount of synovial fluid and surgical findings made no significant difference. MMP-1 mRNA was detected more frequently in OA groups (7/16 joints, 43.8%) than in normal bony structure group (1/15 joints, 6.7%). Expression of MMP-1 mRNA in retrodiscal tissue might be related with OA of the TMJ.ope

Alloplastic total temporomandibular joint replacement using stock prosthesis: a one-year follow-up report of two cases

Alloplastic total replacement of the temporomandibular joint (TMJ) was developed in recent decades. In some conditions, previous studies suggested the rationale behind alloplastic TMJ replacement rather than reconstruction with autogenous grafts. Currently, three prosthetic products are available and approved by the US Food and Drug Administration. Among these products, customized prostheses are manufactured, via computer aided design/computer aided manufacturing (CAD/CAM) system for customized design; stock-type prostheses are provided in various sizes and shapes. In this report, two patients (a 50-year-old female who had undergone condylectomy for the treatment of osteochondroma extending to the cranial base on the left condyle, and a 21-year-old male diagnosed with left temporomandibular ankylosis) were treated using the alloplastic total replacement of TMJ using stock prosthesis. The follow-up results of a favorable one-year, short-term therapeutic outcome were obtained for the alloplastic total TMJ replacement using a stock-type prosthesis.ope

Relationship between stress levels and treatment in patients with temporomandibular disorders

OBJECTIVES: Stress may have an impact on treatment types that patients receive for temporomandibular disorders (TMDs). This study sought to investigate the relationship between the stress index and type of treatments in patients with TMD. MATERIALS AND METHODS: The psychosocial well-being index-short form (PWI-SF) was used to evaluate stress levels in ninety-two patients with TMD. Treatment types were classified into two groups: one group received counseling, physical therapy or medication, while the second group received splint therapy or surgical intervention. RESULTS: The high-risk group (PWI-SF> or =27, the higher the points, the more severe the stress level) was more frequently treated by splint therapy than the low-risk group (PWI-SF<27). Female TMD patients reported higher PWI-SF scores than male TMD patients. CONCLUSION: This study suggests a relationship between stress levels and treatment types for patients with TMD. Thus, the appropriate evaluation and management of stress could be an important factor in treating TMD.ope

The cephalometric analysis of the soft tissue changes at the middle face in the skeletal class III patients with the orthognathic 2-jaw surgery

Considering the skeletal class III malocclusion that complains of mandibular prognathism, there have been some studies of the mandibular change for comparing the changes of pre operative with post operative state. Nowadays it is common to do the orthognathic 2-jaw surgery for the correction of the maxillary deficiency, the post operative stability and the esthetics. We compare and analyze the changes of soft tissue around the nose and the lip with the changes in the direction and the amount of maxilla. Patients who were diagnosed as maxillofacial deformity and received orthognathic surgery of both jaws at Yongdong Severance hospital from 2001 through 2003 were included in this study. Their lateral cephalograms were analyzed, and the post operative change of hard tissue and soft tissue were studied. Upon analyzing the preoperative cephalograms and 6 month post operative cephalograms, there were significant in the vertical change of Labialis superius(Ls) and Stomion(Stm) in soft tissue in relation to the vertical change of skeletal landmarks (Anterior Nasal Spine, Subspinale, Prosthion, Incision Superious). In addition, there were no significance in horizontal movement of the skeletal landmarks among groups. In terms of hard tissue landmarks, group 3(maxillary posterior impaction and advancement surgery group) showed significantly greater change in the vertical movement of Anterior Nasal Spine(ANS), Subspinale(A), Prosthion(Pr), and Incision Superious(Is) compared with other groups. In terms of soft tissue change, group 3 showed more significant change in the vertical movement of Ls and Stm. This study calculated the changes of the skeletal and soft tissue landmarks in order to act as a guide in planning and performing the surgery and as a reference in predicting the postoperative change of facial appearance.ope

EXPRESSION OF ESTROGEN RECEPTORS IN RETRODISCAL TISSUE OF THE TEMPOROMANDIBULAR JOINT DISORDER PATIENTS

Those composing temporomandibular joint (TMJ) complex such as the temporal bone, the disc and the mandibular condyle perform their own functions with organic relation. The retrodiscal tissue is the main area of pain induction and contributes to compositional change of synovial fluid. If displacement of the disc lasts long time, not only adaptive changes, but also destructive or degenerative changes may happen. It was reported that these changes and symptoms appear mostly to female rather than male and especially, in the case of patients suffering from TMJ disorder, a large quantity of female sex hormone is found in the joint synovium. And that may play a role in bone resorption and inflammation. Also, the frequency and the intensity of pain perception for female is reported to be much more than for male. In this study, we investigated the expression extents of estrogen receptors (ER) and progesteron receptors (PR) in retrodiscal tissue with immunohistochemistry among the patients received TMJ surgery and compared with MRI findings and surgical findings. We report the relations between the expression of ER in retrodiscal tissue and the pathological change in TMJ, such as inflammation, internal derangement and osteoarthritisope

A radiographic study of changes of upper respiratory airway space after orthognathic surgery of both jaws in patients with skeletal class III malocclusion

PURPOSE: The aim of this study is the changes of upper respiratory airway space in patients with mandibular prognathism after 2-jaw orthognathic surgery in patients with skeletal classs III malocclusion. METHOD: We measured the lines between selected upper airway landmarks on lateral cephalometric xray films of skeletal class III 64 persons who had not been operated yet, were 6 months after operation. The test subjects were divided into 3 groups according to maxillary movement, as follows; maxillary advancement (MA) group, maxillary posterior impaction (MPI) group, maxillary posterior impaction and superior repositioning (MPI+MSR) group. RESULT: In this study, nasopharyngeal airway space in MPI+MSR group was significantly increased after operation (p<0.05). Oropharygeal and hypopharyngeal airway space in MA group and MPI group were significantly decreased after operation (p<0.05). From hyoid bone to anterior mandible point distance in MA group and MPI group were significantly decreased after operation (p<0.05). CONCLUSION: Oropharygeal and hypopharyngeal airway space were influenced more by mandibular setback than maxillary movement. Maxillary movement surgery as well as mandibular setback surgery should be taken into consideration in order to minimize symptoms related to obstructive sleep apnea syndrome after operation.ope

CEPHALOMETRIC NORMS OF THE HARD TISSUES OF KOREAN FOR ORTHOGNATHIC SURGERY

This study was performed to evaluate hard tissue cephalometric norms for Korean adults which can be implemented in surgical orthodontic treatment planning using selected horizontal reference plane especially for Koreans (Male: SN−7.5 ∘ SN−7.5∘ , Female: SN−9.0 ∘ SN−9.0∘ ) and a simplified analytical method. 70 males and 70 females consisting of freshmen of Yonsei University from 1996 to 1997 and students from the Dental College of Yonsei University were chosen according to clinical examination and cephalometric analysis. The samples had normal profiles, normal anteroposterior skeletal relationship(ANB angle of 0 ∘ 0∘ to 4 ∘ 4∘ and Wits appraisal of -4.0mm to 0mm), and Class I molar and canine relationship. They had no missing or supernumerary teeth and had no experience of orthodontic or prosthetic treatment. After the selection of 23 landmarks and the construction of horizontal and vertical reference lines, 22 skeletal and 12 dental measurements were taken. These consisted of vertical and horizontal linear measurements and angular measurements. The results were as follows. 1. Mean and standard deviation of the measurements were calculated for males and females. 2. Most of the skeletal vertical measurements, and maxillary and mandibular length were bigger in males than females. Whereas anterior facial height ratio(N-ANS/ANS-Me) as well as maxillary and mandibular antero-posterior position in relation to the vertical reference line(N-perpendicular) showed no signigicant difference between sexes. 3. Maxillary and mandibular dental antero-posterior position in relation to the vertical reference line(N-perpendicular) showed no significant difference between sexes. 4. The upper incisor show(U1-Stms) was 2.1±1.7mm 2.1±1.7mm in males and 3.3±1.7mm 3.3±1.7mm in females. In this study, hard tissue cephalometric norms of Korean adults for orthognathic surgery were obtained.ope