• The Journal of Korean Academy of Prosthodontics
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• 제38권2호
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• pp.242-254
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• 2000

Accurate impression is very important to achieve desirable prosthesis and there are many factors in taking a good impression. For example, types of impression material, types of impression tray, impression taking methods and so on. Recently individual tooth tray technique is accepted as obtaining good impression that can be applied to multiple abutment impression, heavy salivated patient, to minimize the effect of natural teeth s undercuts and to reduce pain during cord packing procedures. The purpose of this study was to compare the accuracy according to materials and forms of the individual tooth tray which is clinically applied nowadays. Used materials in experiment were divided into 3 types (acrylic resin. $Futar^{(R)}$ occlusion. $Blu-mousse^{(R)}$) and forms were divided into 2 types (forming occlusal vent hole or not and forming marginal vent space or not). Stone master model from impression body and metal master model were measured by $X-PLAN360d^{(R)}$ to compare occlusal surface discrepancy and marginal discrepancy. The results were as follows: 1. In comparison of occlusal surface discrepancy and marginal discrepancy according to materials, groups with three materials showed no statistical difference 2. In comparison of occlusal surface discrepancy and marginal discrepancy according to occlusal vent hole, groups with occlusal vent hole showed significantly less marginal discrepancy than groups with no occlusal vent hole(p<0.05). 3. In comparison of occlusal surface discrepancy and marginal discrepancy according to 0.5mm-marginal-vent-space, groups with no 0.5mm-marginal-vent-space showed significantly less marginal discrepancy than groups with 0.5mm-marginal-vent-space (p<0.05). In summary these results suggest that individual tooth tray made of 3 types of materials with occlusal vent hole and individual tooth tray made of acrylic resin with no marginal vent space showed good accuracy of impression. In addition, individual tooth tray which is made of bite registration materials may be more useful because of advantage in facility and timesaving aspect of fabrication.

• The Journal of Korean Academy of Prosthodontics
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• 제28권1호
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• pp.43-61
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• 1990

The laser reflexion method is a new technique which permits precise contactless measurement and observation of tooth mobility as well as tooth movement. The purposes of this study were to clarify the reliability of the laser reflexion method in clinical application and to measure the abutment tooth movement according to clasp design. This study was designed to determine 1) How much a bending movement of the impression plate stand affects the position of the reflexion pattern and how precise the patient bites into plate 2) Which clasp design causes greater movement of the abutment tooth. Under medium and maximum bite forces, tests were performed on central loading position which was 13mm distal to terminal abutment tooth of distal extension removable partial denture. The movement in the mesiodistal and buccolingual directions was measured. The Duncan's New Multiple-Range test was used to compare the means for the four castings under each direction-load combination; and the paired sample t-test was for medium and maximum bite forces. From this experiment, the following results were obtained. 1. The Roach clasp, the combination clasp, the RPI clasp, and the Akers clasp did not significantly differ in their effects on buccolingual movement of the abutment tooth. 2. The direction of abutment tooth movement was not significantly altered by clasp design and all abutment tooth movements were oriented distobuccally. 3. Under medium bite force, the Akers clasp caused greater distal movement of the abutment tooth than did the combination clasp and the RPI clasp. Under maximum bite force, the Akers clasp caused greater distal movement of the abutment tooth than did the RPI clasp. 4. The testing apparatus and procedures used in this study(laser reflexion method) proved to be reliable in clinical application.

• The Journal of Korea Assosiation for Disability and Oral Health
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• 제13권2호
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• pp.95-98
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• 2017

Due to hypodontia, poor oral hygiene, and significantly more prevalent periodontal disease, patients with Down syndrome show higher incidence of edentulism. Oral rehabilitation of such patients is imperative but challenging as high rates of prosthesis failure are reported due to malocclusion, high masticatory force, and parafunctional habits. As CAD/CAM(Computer-Aided Design and Computer Aided Manufacturing) is the recent trend in prosthodontics, this report discusses the application of CAD/CAM in a Down syndrome patient. A 25-year-old patient with Down syndrome was presented to the Department of Pediatric Dentistry, Yonsei University Dental Hospital for oral examination. 5 maxillary teeth were missing, 3 were fully impacted, and 4 had grade III mobility. The patient underwent general anesthesia for extraction of impacted and mobile teeth, implant surgery, and final impression for prosthesis. Afterwards, CAD/CAM was used to design and manufacture a 10-unit zirconia bridge. However the bridge was fractured after 18 months due to the patient's bruxism and high masticatory force. Final impression taking, bite registration, cast fabrication, cast scanning, and prosthesis designing were not needed as CAD/CAM data remained. Previous CAD/CAM design was used to remanufacture the zirconia bridge. Down syndrome patients have malocclusion, high masticatory force, and parafunctional habits which increase the possibility of prosthesis fracture. CAD/CAM is beneficial for Down syndrome patients as previous digital records can be utilized for prosthesis repair or remake. In detail, application of CAD/CAM in remanufacturing decreases patient's discomfort of impression taking, shortens and simplifies dental laboratory procedures, and reduces clinician's effort of taking detailed final impressions or accurate bite registration. In conclusion, oral rehabilitation using CAD/CAM provides not only satisfactory levels of comfort, stability, and esthetics, but also easier repair or remake compared to conventional prostheses.

• Journal of the korean academy of Pediatric Dentistry
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• 제11권1호
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• pp.249-254
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• 1984

This is a case report of Crouzon's disease as a kind of craniofacial dysostosis by premature closure of unilateral coronal suture, showed plagiocephalic skull. 5-year-old boy was visited for the treatment of dental caries and oral examination. Physical examination showed hypertelorism, internal strabismus, and saddle nose. Intraoral radiographs showed congenital missing of upper right and left deciduous and permanent lateral incisors. Cephalometric analysis showed shortening the posterior cranial base length, clockwise growth pattern and class III and open bite tendency. Posterior-anterior and submentovertex view showed multiple radiolucencies-digital impression on inner surface of cranial vault. Maxillo-facial and neuro-surgical treatment was required to improvement of facial esthetics and optic complications. Continuous examination was needed to the growth and development.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• 제23권1호
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• pp.125-136
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• 1993

The geometrically standardized intraoral radiographs using 5 occlusal registration materials were taken serially from immediate, 1 day, 2, 4, 8, 12, and 16 weeks after making the bite blocks. And the resultant images were digitally subtracted using the immediately taken film as reference images. The qualities of those subtracted images were evaluated to check the degree of reproducibility of each impression material. The results were as follows: 1. The standard deviations of the grey scales of the overall subtracted images were 4.9 for Exal1ex, 7.2 for Pattern resin, 9.0 for Tooth Shade Acrylic, 12.2 for XCP only, 14.8 for Impregum. the lesser the standard deviation, the better the quality of the subtracted images. 2. The standard deviation of the grey scales of the overall subtracted images were grossly related to those of the localized horizontal line of interest. 3. Exaflex which showed the best subtracted image quality had 15 cases of straight, 14 cases of wave, 1 case of canyon shape. Impregum which showed the worst subtracted image quality had 4 cases of straight, 8 cases of wave, 18 cases of canyon shape respectively.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제13권1호
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• pp.117-127
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• 1991

When open reduction of maxilla fractures is postponed due to concurrent life-threatening injuries, delayed union may result with malunion or nonunion. If delayed malunion is occurred, significant facial deformity may result, including a dished-out face, irregular retromaxillism with Angle's class III malocclusion, open anterior bite, nasal collapse, telecanthus and malar flattening. The treatment planning for this problem includes cephalometric evaluation anterior and lateral tomograms, dental casts, orthodontic planning, dental planning and use of impression tray to rupture the fibrous tissue casts, orthodontic planning, dental planning and use of impression tray to rupture the fibrous tissue attachment at the fracture site. In this paper, one case presented a 58-year-old female patient with maxilla retrusion after comminuted fracture, who was treated with orthodontic methods of maxillary protraction headgear and Plaster headcap, whereas the other two cases were about male patients who were treated principally with surgically open reduction or Le Fort I-controlled transverse osteotomy with iliac bone graft.

• Journal of Korean society of Dental Hygiene
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• 제13권4호
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• pp.543-552
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• 2013

Objectives : The aim of the study is to investigate job performance expectations according to duration of work and to specify the clinical practice of dental hygienists by career expectations. Methods : The subjects were 310 dental hygienists in Seoul and Incheon. They completed the self-reported questionnaires and 304 data were analyzed except incomplete 6 answers. Results : The tasks performed by dental hygienists were as follows ; SS crown restoration in pediatric dentistry accounted for 25.1%, orthodontics (42.1 %), plaque removal (71.4 %), temporary fillings (60.5%), and impression taking of abutments and bite registration (58.9%). In order to be a skillful dental hygienists, it took two to three years of clinical filed work. Conclusions : On the job training (OJT) is the most important in dental hygiene curricula. So it is necessary to develop the OJT performance skill.

• The Journal of Korean Academy of Prosthodontics
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• 제35권4호
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• pp.767-780
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• 1997

One of the most common problems of implant prosthesis is the screw loosening of abutment screws. This brings on discomfort in mastication, inflammation in the peri-implant tissue due to poor oral hygiene and fracture of prosthesis or loss of osseointegration. To prevent screw loosening, appropriate implantation to direct the occlusal force to the long axis of the implant, accurate design of the superstructure, decrease of the occlusal table, and adequate torque on the abutment screw are necessary. In this study the screw loosening torque was evaluated in implants with dimples or flutes in the internal surface of abutment screw holes. The abutments were fastened with slot type and hexagonal type abutment screws and were sealed with vinyl poly siloxane impression and bite registration material respectively. The screw loosening torque was evaluated after 1,800 and 12,600 times loading under a loading machine. The results were as follows. 1. The flute form group showed significantly higher loosening torque compared to the dimple form group and the group with no inner surface treatment (p<0.05). 2. There was no statistical difference in loosening torque according to the sealing materials. 3. The loosening torque according to the types of abutment screw showed no significant difference. 4. The loosening torque was significantly higher after 1800 times loading compared to 12600 times loading(p<0.05). From the above results. it is thought that formation of a flute in the internal surface of the screw hole decreases the chance of screw loosening, but the sealing materials and types of abutment screw did not show significant difference in prevention of screw loosening.

• The Journal of Korean Academy of Prosthodontics
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• 제39권3호
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• pp.273-281
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• 2001

Digital subtraction radiography may be one of the most precise and noninvasive methods for assessing subtle density changes in peri-implant bone, providing additional diagnostic information on implant tissue integration in overall maintenance. The aims of this study were to evaluate density changes after first, second surgery of dental implant and to measure the amount of marginal bone loss 9 months after second surgery using digital subtraction radiography. Bone change around 30 screw-shaped implants in 16 patients were assessed on radiographs. 17 Branemark implants of 3.75mm in diameter(Nobel Biocare, Goteborg, Sweden), 2 Branemark implants of 5.0mm in diameter, 11 $Replace^{TM}$ implants of 4.3mm in diameter(Nobel Biocare, Goteborg, Sweden) were used. To standardize the projection geometry of serial radiographs of implants, customized bite block was fabricated using XCP film holder(Rinn Corporation, Elgin, IL.) with polyether impression material of Impregum(ESPE, Germany) and direct digital image was obtained. Qualitative and quantitative changes on radiographs were measured with Emago software(The Oral Diagnostic System, Amsterdam, Netherlands). The results were as follows: 1. The peri-implant bone density of 69.2% implants did not change and the peri-implant bone density of 30.8% implants decreased after 3 months following first surgery. 2. The crestal bone density of 53.9% implants decreased first 3 months after second surgery. The crestal bone density of 58.8% implants increased 9 months after second surgery. No density change was observed around the midportion of the implants after second surgery, 3. The amount of marginal bone loss between different kinds of implants showed no statistically significant differences (p>0.05). 4. More than 90% of total marginal bone loss recorded in a 9-month period occurred during the first 3 months.

• Journal of Korean society of Dental Hygiene
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• 제21권6호
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• pp.793-803
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• 2021

Objectives: The purpose of this study was to investigate the current status of dental hygiene curricula related to clinical practice in Korea. Methods: Clinical work included the categories 'history taking, infection control, oral prophylaxis, preventive treatment, education/counseling, radiography/reading, assisting/cooperation, impression/bite registration, anesthesia, etc.', and 66 works were finally selected based on the frequent tasks of dental hygienists. The subjects were made to answer nine questionnaires. Results: It was found that the theory and practice of the main works operated quite differently in lectures and practice in each school. All types of practice were applied to all schools in the case of 'scaling'. The evaluation of clinical practice was also found to be very different from school to school. Conclusions: For dental hygienists to establish expertise in clinical practice and promote quality improvement, it is necessary to develop a core curriculum focusing on clinical practice. The standardized curriculum should be improved to an efficient and competency-centered one defining clearly the role of dental hygienists considering the needs and importance of clinical practice.