• The Journal of Korean Academy of Prosthodontics
• /
• v.46 no.4
• /
• pp.420-430
• /
• 2008

Statement of problem & Purpose: Articulators are very important for education and overall clinical situation in the field of prosthodontics, however preexisting articulators are designed and built based on maxillofacial structures and mean values of mandibular movement of Western people. Purpose of this research is to find out a adequate basis for applicating these articulators, presently used for clinical education, for Korean. Material and methods: 59 Korean adults (41 males, 18 females), aged between 24 to 41, where selected for this study. Two pairs of both maxillary and mandibular models were made for each examinee. These models where attached to both KaVo PROTARevo 7 and Hanau Modular semiadjustable articulators by using facebow transfer, than sagittal condylar inclination, occlusal plane inclination and position of mandibular on the articulator where measured. Result and conclusion: 1. Mean sagittal condylar inclination for KaVo PROTAR semiadjustable articulator was $33.75^{\circ}$(standard deviation $12.46^{\circ}$) meanwhile Hanau Modular semiadjustable articulator showed $40.72^{\circ}$(standard deviation $12.09^{\circ}$) for mean sagittal condylar inclination. 2. Mean occlusal plane inclination for KaVo PROTAR semiadjustable articulator was $-2.76{\circ}$(standard deviation $3.63^{\circ}$) meanwhile Hanau Modular semiadjustable articulator showed $11.87^{\circ}$ (standard deviation $3.63^{\circ}$) for mean occlusal plane inclination. 3. On the average center of the mandibular dentition were in the range of 5 to 7 mm of the central position of the articulator. Both anterior and posterior dentition were positioned at the center of the articulator vernacularly for KaVo PROTAR semiadjustable articulators, meantime for Hanau Modular semiadjustable articulator, anterior dentition was positioned 5 mm downwards and 3mm upwards for posterior dentition from vertically central position of the articulator.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.26 no.3
• /
• pp.221-239
• /
• 2010

Bone loss may occur depending on the loading conditions. careful treatment planning and prosthetic procedures are very important factors for the proper distribution of stress. Evaluate the stress distributions according to numbers and location of implants in three-unit fixed partial dentures. A mandible missing the right second premolar, first molar and second molar was modeled. Using the CT data. we modeled a mandible with a width of 15mm, a height of 20mm and a length of 30mm, 2mm-thickness cortical bone covering cancellous bone mallow. An internal type implant and A solid type abutment was used. A model with 3 implants placed in a straight line, offset 1.5 mm buccally, offset 1.5 mm lingually and another model with 3 implants offset in the opposite way were prepared. And models with 2 implants were both end support models, a mesial cantilever model and a distal cantilever model. Three types of loading was applied; a case where 155 N was applied solely on the second premolar, a case where 206 N was applied solely on the second molar and a case where 155 N was applied on the first premolar and 206 N was applied on the first and second molar. For all the cases, inclined loads of 30 degrees were applied on the buccal cusps and vertical loads were applied on the central fossas of the teeth. Finite element analysis was carried out for each case to find out the stress distribution on bones and implants. This study has shown that prostheses with more implants caused lower stress on bones and implants, no matter what kind of load was applied. Furthermore, it was found out that inclined loads applied on implants had worse effects than vertical loads. Therefore, it is believed that these results should be considered when placing implants in the future.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.27 no.4
• /
• pp.343-358
• /
• 2011

As implant treatment has become popular, lots of different shapes and materials of the implant upper component have been supplied. And there are also diverse reports about failures including loosening of the abutment screw which is one of the most common reason. Purpose : The purpose of this study is to find out how different screw tightening orders and methods influence on screw loosening according to the different connection systems. The upper component was fabricated by casting method. After fabricating master models that are precisely attached to the upper component, 5 experimental models each for the external connection system and internal connection system were fabricated using splinting impression technique. First, to find out the influence of the screw tightening order, screws were tightened in 3 orders; 1-2-3-4, 2-3-1-4, 2-4-3-1. After tightening, removal torque values (RTV) of each group was measured. And also to find out the influence of screw tightening method, a model with 2-3-1-4 screw tightening order was tightened with 30 Ncm at one time(1-step method) and the RTV was compared with the same order group (2-3-1-4) in the 2 step method. In the external connection system, RTV appeared significantly lower in group 2-3-1-4 than group 2-4-3-1 (p<0.05). And also in the internal connection system, the RTV of group 2-3-1-4 appeared significantly lower than that of group 2-4-3-1 and 1-2-3-4 (p<0.05). When comparing the tightening number of the screw without considering the screw tightening order, the first tightened screw appeared significantly higher RTV than the second one in the external connection system (p<0.05), however there was no significant difference from the first tightened screw to the last tightened screw in the internal connection system. And there was no statistically significant difference between the two screw tightening methods in both internal and external connection system. In the comparison of external and internal connection system, each RTV appeared 16.27 Ncm and 14.25 Ncm and appeared as a statistically significant difference (p<0.05). There was a significant difference in RTV measured according to the screw tightening order. The lowest RTV appeared in the groups started tightening from the middle. There was also a significant difference in RTV between the two connection system groups. A further study is needed to find out the influence factors in RTV and also a study is required related to the load condition.

• The korean journal of orthodontics
• /
• v.31 no.1 s.84
• /
• pp.25-38
• /
• 2001

The purpose of this study was to compare the force, the displacement and the stress distribution on the maxillary first molars altered by the application of various asymmetric head-gear. For this study, the finite element models of unilateral Cl II maxillary dental arch was made. Also, the finite element models of asymmetric face-bow was made. Three types of asymmetric face-bow were made : each of the right side 15mm, 25mm and 35mm shorter than the left side. We compared the forces, the displacement and the distribution of stress that were generated by application of various asymmetric head-gear, The results were as follows. 1. The total forces that both maxillary first molars received were similar in all groups. But the forces that mesially positioned tooth received were increased as the length of the outer-bow shortened, and the forces that normally positioned tooth received were decreased as the length of the outer-bow shortened. 2. In lateral force comparison, the buccal forces that normally positioned tooth received were increased as the length of the outer-bow shortened, and the buccal fortes that mesially positioned tooth received were decreased as the length of the outer-bow shortened. Though the net lateral force moved to the buccal side of normally positioned tooth as the length of the outer-bow shortened, both maxillary first molars received the buccal force. That showed 'Avchiai Expansion Effect' 3. The distal forces, the extrusion forces and the magnitudes of the crown distal tipping that mesially positioned tooth received were increased as the length of the outer-bow shortened, and the forces that normally positioned tooth received were decreased as the length of the outer-bow was shortened. 4. The magnitude of the distal-in rotation that normally positioned tooth received were increased as the length of the outer-bow was shortened. But, mesially positioned tooth show two different results. For the outer-bow 15mm shortened, mesially positioned tooth showed the distal-in rotation, hut for the outer-bow 25mm and 35mn shortened, mesially positioned tooth showed the distal-out rotation. Thus, the turning point exists between 15mm and 25mm. 5. This study of the initial stress distribution of the periodontal ligament at slightly inferior of the furcation area revealed that the compressive stress in the distobuccal root of the normally positioned tooth moved from the palatal side to the distal side and the buccal side successively as the length of the outer-bow shortened. 6. This study of the initial stress distribution of the periodontal ligament at slightly inferior of the furcation area revealed that the magnitudes of stress were altered but the total stress distributions were not altered in the mesiobuccal root and the palatal root of normally positioned tooth, and also three roots of mesially positioned tooth as the length of the outer-bow shortened.

• The korean journal of orthodontics
• /
• v.28 no.1 s.66
• /
• pp.99-111
• /
• 1998

The purpose of this study was to evaluate the positioning errors according to the method of bonding lingual brackets. Dental models of twenty orthodontic patients with malocclusion were selected for this study. The positioning errors were measured on each model that brackets were bonded to. Three different bonding methods were used. For the first method the bracket was bonded intimately to the lingual surface of the model. For the second method, the bracket was bonded intimately to the lingual surface after setting up using articulator. The passive bracketing, bonding the bracket ligated first to ideal archwire, was used after setting up as the last method. The results were as follows: 1. The brackets bonded without setting up showed greater angulation errors in the upper 1st premolar and the lower canine than those in other bonding methods. The brackets bonded without passive bracketing showed greater positioning errors in upper central incisor, lower 1st and End premolars. 2. The brackets bonded without setting up showed greater torque error in lower 2nd premolar than those in other bonding methods. The brackets bonded without passive bracketing showed greater torque errors in all upper teeth, lower 1st and 2nd premolars. 3. The brackets bonded without passive bracketing showed greater rotation errors between upper central incisors, lower central incisors, lower lateral and central incisor, lower canine and lateral incisor. 4. The brackets bonded without setting up showed greater in-out errors between upper canine and lateral incisor than those in other bonding methods. The brackets bonded without passive bracketing showed greater in-out errors between upper central incisors, upper central and lateral incisors, upper 1st and 2nd premolars, lower lateral and central incisors, lower canine and lateral incisor. These results suggest that there is a large amount of positioning error in lingual brackets even by an indirect bonding technique, and it may be reduced by passive bracketing.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.45 no.3
• /
• pp.271-279
• /
• 2018

Previous studies to elucidate the etiology of cyclosporine(Cs)-induced gingival overgrowth in children have not completely excluded all factors that may cause differences among individuals. This study examined the effect of cyclosporine on the metabolism of type 1 collagen(CoL-I) in experimental models that controlled the effects of biological variations on individuals. Five 5-week-old male Sprague-Dawley rats were administered Cs by gastric feeding for 6 weeks. Gingival specimens were harvested from the mandibular posterior area before beginning Cs administration and at 2, 4, and 6 weeks thereafter. Gingival fibroblasts were cultured from all the 20 biopsies collected from the gingiva. Half of the fibroblasts collected prior to the Cs administration were designated as Control. The other half of the fibroblasts were treated with Cs in vitro and called in vitro test group(Tt). The fibroblasts collected 2, 4, and 6 weeks after the Cs administration were called in vivo test groups : T2, T4, T6, respectively. Immunofluorescence microscopy was used to detect CoL-I in all the fibroblasts. CoL-I was analyzed at both the gene and protein expression levels by real-time polymerase chain reaction and western blotting. Changes in CoL-I before and after Cs treatment were evaluated from the gingiva of each rat. There was no significant difference in gene expression of CoL-I in the control and test groups. CoL-I protein expression levels of fibroblasts increased in in vitro Cs treatment for each individual, and also increased in in vivo Cs treatment. In this study, the experimental method that control biological variations that can occur due to differences among individuals was useful. Subsequent studies on other factors besides CoL-I and in-depth studies in humans are needed.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.36 no.2
• /
• pp.70-79
• /
• 2020

Purpose: The purpose of this study was to evaluate the effect of attachments and palatal coverage on stress distribution in maxillary implant overdenture using finite element analysis. Materials and Methods: Four maxillary overdenture 3-D models with four implants placed in the anterior region were fabricated with computer-aided design. 1) Ball-F: Non-splinted ball attachment and full palatal coverage, 2) Ball-P: Non-splinted ball attachment and U-shaped partial palatal coverage, 3) Bar-F: Splinted milled bar attachment and full palatal coverage, 4) Bar-P: Splinted milled bar attachment and U-shaped partial palatal coverage. Stress distribution analysis was performed with ANSYS workbench 14. 100 N vertical load was applied at the right first molar unilaterally and maximum stress was calculated at the implant, peri-implant bone and mucosa. Results: The use of the ball attachment showed lower maximum stress on implant and peri-implant bone than the use of the milled bar attachment. But it showed contrary tendency in the mucosa. Regardless of attachment, full palatal coverage showed lower maximum stress on implant, peri-implant bone and mucosa. Conclusion: Within the limitation of this study, ball attachment improved stress distribution on implant and peri-implant bone rather than milled bar attachment in maxillary implant overdenture. Also, full palatal coverage is more favorable in stress distribution.

• The korean journal of orthodontics
• /
• v.29 no.6 s.77
• /
• pp.649-661
• /
• 1999

The goals of this study were 1) to present pre-surgical naso-alveolar molding (PNAM) appliance for bilateral cleft lip and palate treatment and 2) to evaluate the effects of the PNAM appliance on the alveolar molding of the premaxilla and the lateral segments. Subjects consisted of 8 bilateral cleft lip and palate infants (7 males and 1 female, mean age at first visit = 61.6 days after birth) who were treated with PNAM appliances in Department of Orthodontics, Seoul National University Dental Hospital. Average alveolar cleft gap between the premaxilla and the lateral segment was $8.09{\pm}5.03mm$ and average duration of alveolar molding treatment was $8.8{\pm}3.1$ weeks. These patients' models were obtained at initial visit (T0) and after alveolar molding (T1). 20 linear and 14 angular variables were measured by using photometry and digital caliper, All statistical analyses were performed by Microsoft Excel 97 program. Paired t-test was used to discriminate the effect of alveolar molding by PNAM appliance. 1. Closure of the alveolar cleft gap in bilateral cleft cases by molding therapy was completed successfully, 2. Alveolar molding inhibited outward growth of lateral segments and produced inward bending of lateral segments. 3. By bending the anterior part of the vomer, the premaxilla could be rotated and moved. posteriorly via alveolar molding. Conclusion This appliance can be applied to bilateral cleft lip and palate infants with satisfactory results before cheiloplasty.

• Korean Journal of Health Education and Promotion
• /
• v.5 no.2
• /
• pp.26-40
• /
• 1988

This survey was conducted to find out the present status of health education program being provided in primary schools focusing its planning, operation, contents and attitude of school nurses in September, 1988. Total 413 school nurses who are presently working in Seoul city was surveyed by mail and 167 school nurses who responded to the questionnaire were finally ana lysed. The following results were obtained. 1. The general charcteristics of the school nurses′ surveyed. As for age distribution, 30-40 age group was 60.4％ the highest and the mean age was 30. 13. As for educational attainment, junior nursing college was 71.9％. 68.3％ of the surveyed was married and 43.1％ of them has 5-10 years of working experiences. As for schools where school nurses are presently working, 31.7％ has 2,000-3,000 students, 22.8％ has 50-60 classes and 5 schools have more than 80 classes. 2. Planning of a school health education School health education was planned every semester in 55.7％, which was the highest. As for utilization status of the materials for planning of a school health education as a referance, 86.8％ of the total respondants utilized the guidelines published by Seoul city School nurses′ Association, and the administrative guidelines for school health, textbooks, school health statistics and articles related to school health in order. It was tried whether the number of referances being utilized was related to the working experiences. It was found that the shorter the experiances, the more materials were utilized. It was answered that teaching plan for health education was prepared by school-nurses themselves (95.2％), and was differentiated as three levels as the first and second grades, the third and fourth grades, and the fifth and sixth grades 3. The contents of the school health education 16 subjects offered to 6 grades of students were surveyed as follows. As for fifth and sixth grades, contents on growth and development was most widely provided as 54.5％, and 68.9％, respectively. And the next to this subject, dental health education was also frequently offered to the second, third and fourth grades as 50.9％, 68.9％, and 47.3％, respctively. 4. The operation of school health education Health education provided by school nurses was conducted formallu in 36.6％, and formally of informally accordin to grades in 43.9％. It was answered that 50.3％ of the surveyed school had started health education from 1987, when the plan for activation of school health was ordered from. Educational Committee. Teaching hours of school nurses was 6 in 32.9％, which was the highest. The lesson was provided for class unit in 77.2％, and sex education was sometimes offered to male and female students separately. As for support of health personnels out of school for health education, 79.0％ did not receive any support. If there were any aids out of school, 62.9％ received them from other related agencies and 74.3％ anwered that it was once in a semester. As for expenses for health education, 57.3％ did not input any expenses alloted to school health program as a whole. As audio-visual materials, slides were utulized most frequently and models, and charts in order. 5. Awareness of school nurses on the operation of school health education School nurses evaluated their educational quality as a health educator subjectively, 60-70％ of them answered to be average in 4 domains such as knowledge, educational skill, ability to prepare teaching plan, and cooperation. As for the awareness on the support and cooperation of the higher institutions, 46.4％ -61.8％ answered that "so and so" toward Ministry of Education and Ministry of Affairs, and 13-37％ "not supportive" Teachers of the corresponding schools were answered to be "so and so" in 55.9％-56.7％, and "very supportive" in 33.34％. There was a significant difference in formality of the lesson according to the support of the superintendent.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.26 no.1
• /
• pp.1-12
• /
• 2010

The purpose of this study was to compare the strain on the alveolar ridge in the centric, eccentric and protrusive position according to the occlusal scheme (bilateral balanced occlusion with 33 degree anatomical teeth, group B; monoplane occlusion with non-anatomical teeth, group M; lingualized occlusion with 33 degree anatomical teeth and non-anatomical teeth, group L; of complete dentures. Experimental dentures were set bilateral balanced occlusion, lingualized occlusion and monoplane occlusion. They are analysed through T-Scan II(Tekscan, Boston, U.S.A) and 1.5mm thick layer was removed from the denture-supporting surface of resin model and then replaced with silicone to simulate resilient edentulous ridge mucosa. A $4{\times}6$ linear strain gauge is attached to the $1^{st}$ premolar and $1^{st}$ molar area. The strain values are recorded according to the occlusal scheme in the centric, eccentric and protrusive position after uniformly applying 50 N and 150 N force through a Universal Testing Machine(instron$^{(R)}$ 5567, Bluehill 2.0 software ,U.S.A.) with the models mounted in the articulator. When performing centric and protrusive occlusion, the three groups of occlusal scheme were compared in the anterior region and in the posterior region. The strains of each group were also compared in the working side and in the non-working side during eccentric excursion. It was observed that the strain in the bilateral balanced occlusion showed a higher value than the lingualized occlusion and monoplane occlusion in every position except the non-working side. However, during the eccentric movement the strain value in the non-working side showed the lowest value in the bilaterally balanced occlusion. The strain change amount from the working side or centric occlusion to non-working side and also the strain variation rate within the non-working side showed the highest value in bilateral balanced occlusion.