• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.280-286
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• 2010

Purpose: This study evaluated the detorque values of screws in a multiple implant-supported superstructure using stone casts made with 2 different impression techniques. Material and methods: A fully edentulous mandibular master model and a metal framework directly connected to four implants (Br${\aa}$nemark $System^{(R)}$; Nobel Biocare AB) with a passive fit to each other were fabricated. Six experimental stone casts (Group 1) were made with 6 non-splinted impressions on a master cast and another 6 experimental casts (Group 2) were made with 6 acrylic resin splinted impressions. The detorque values of screws ($TorqTite^{(R)}$ GoldAdapt Abutment Screw; Nobel Biocare AB) were measured twice after the metal framework was fastened onto each experimental stone cast with 20 Ncm torque. Detorque values were analyzed using the mixed model with the fixed effect of screw and reading and the random effect of model for the repeated measured data at a .05 level of ignificance. Results: The mean detorque values were 7.9 Ncm (Group 1) and 8.1 Ncm (Group 2), and the mean of minimum detorque values were 6.1 Ncm (Group 1) and 6.5 Ncm (Group 2). No statistically significant differences between 2 groups were found and no statistically significant differences among 4 screws were found for detorque values. No statistically significant differences between 2 groups were also found for minimum detorque values. Conclusion: In a multiple external hexagon implant-supported prosthesis, no significant differences between 2 groups were found for detorque values and for minimum detorque values. There seems to be no significant differences in screw joint stability between 2 stone cast groups made with 2 different impression techniques.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.3
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• pp.245-252
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• 2012

The purpose of this study was to evaluate the influence of glide path on canal centering ratio after instrumentation with different single file systems; WaveOne and Reciproc. Reciproc R25 (VDW), WaveOne Primary (Dentsply Maillefer) and PathFile #13, 16, 19 (Dentsply Maillefer) were used in this study. In no glide path groups, Reciproc files and WaveOne files used for canal preparation without glide path. In glide path groups, the PathFile were used before canal preparation. Methylene blue dye was introduced into the canal to obtain a clear pre-instrumentation image. Pre-instrumentation images and post-instrumentation images were scanned using Epson Perfection V700 Photo scanner (Epson, Nagano, Japan). Transparencies of post-instrumentation images were changed and superimposed on pre-instrumentation images using Adobe Photoshop CS 3 (Adobe Systems Incorporated, San Jose, CA, USA). The centering ratio was calculated for each instrumented canal using the following formula: CR=|X1-X2|/Y. It was statistically analyzed using two-way ANOVA at 95% confidential level. The centering ratio in glide path groups were significant less than it in no glide path groups at 3, 4, 5 and 6 mm level. Except 1 and 6 mm level, WaveOne groups had significant less centering ration than Reciproc groups. At 6 mm level, there was no significant difference between WaveOne and Reciproc. In the limitation of this study, creation of a previous glide path before reciprocating motion instrumentation in curved canal appears to be appropriate and WaveOne system can be used for preparation of curved canal without severe aberrations.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.3
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• pp.206-214
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• 2014

This study is to evaluate how different bearing surface angles of abutment screw affect the mechanical stability of the joint in the conical seal design implant system. Materials and Methods: Internal connection type regular implants, two-piece cemented type abutments and tungsten carbide/carbon-coated titanium alloy abutment screws were selected. Titanium alloy screws with conical ($45^{\circ}$) and flat ($90^{\circ}$) head designs which fit on to abutment were fabricated. The abutments were tightened to implants with 30 Ncm by digital torque gauge. The loading was applied once to the central axis of abutment. The mean axial displacement was measured using micrometer before and after the tightening and loading (n = 5). The abutment was tightened to implants with 30 Ncm and T-shape stainless steel crown was cemented. Then the change in the amount of reverse-torque was measured after the repeated loading to the central axis, and the place 5 mm away from the central axis. Compressive bending and fatigue strength were measured at the place 5 mm away from the central axis (n = 5). Results: Both groups showed the largest axial displacement when abutment screw tightening and total displacement was greater in the flat head group compared to conical head group (P < 0.05). However, there were no significant differences in reverse torque value, compressive bending and fatigue strength (P > 0.05). Conclusion: Within the limitations of this study, the abutment screw head design had no effect on two groups regarding the joint stability, however the conical head design affected the settlement of abutment resulting in the reduced total displacement.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.355-373
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• 1995

Craniofacial region is a musculodentoskeletal system that consists of many anatomical structures ; cranioskeletal structures, dental arches, and formation and functions of masticatory muscles have close correlations. Growth and development of craniofacial region are influenced by not only hereditory factors, but also environmental factors such as craniofacial muscles and surrounding tissues. On the contrary, however, study on changes in functions or adaptations of craniofacial muscles following changes of craniofacial skeletal structures has been somewhat insufficient. The author's purpose was to observe correlations between masticatory muscular functions and change patterns according to cranial skeletal structures and occlusion patterns, for this, comparative study of muscle activity changes of preand post- orthognathic surgery states in skeletal Cl III malocclusion patients was peformed. The selected sample groups were 15 normal male patients, 15 skeletal Cl III pre-orthognatic surgery patients and 15 skeletal Cl III post-orthognatic surgery patients. For each sample groups, cephalometric x-ray taking, masticatory efficiency test and measurements of muscle activities in anterior temporal muscle, masseter and upper lip in rest, clenching, chewing and swallowing were carried out. The following results were obtained : 1. In resting state of mandible, pre-surgery malocclusion group showed higher m. activities in ant. temporalis, masseter and upper lip than post-surgery group. Post-surg. malocc. group showed significantly high m. activity only in upper lip compared to the normal group. 2. In clenching state, post-surg. malocc. group showed higher m. activities in ut. temporalis, masseter and upper lip than pre-surg. malocc. group. 3. In chewing state, post-surg. malocc. group showed higher m. activities in ant. temporalis and masseter than pre-surg. malocc. group, on the other hand, decreased upper lip activity was noticed. 4. In swallowing state, post-surg. malocc. group showed lower upper lip activity than pre-surg. malocc. group but higher than that of the normal group. No significant difference in m. activities of ant, temporalis and masseter was noticed among the three groups. 5. Masticatory efficiency was lower in pre-surg. malocc. group than normal group, masticatory efficiency showed an increase in post-surg. malocc. group compared to the pre-surg. malocc. group. However, both groups showed significant differences compared to the normal group.

• Research in Community and Public Health Nursing
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• v.1 no.1
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• pp.465-502
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• 1989

The purpose of this study was to find out the general characteristics of school health teachers, the status of school health resources and the degrees of self-confident performance for the 124 school health teachers in Pusan City. Data was collected by means of questionaires from Aug. 1986 to Mar. 1987. The data were analyzed by use of percentage, mean, standard deviation, t-test, ANOVA and Pearson-correlation coefficient. The results of this study were as follows: 1 . General Characteristics of School Health Teachers (SHT) 1) The average of age of the SHT was 32.8 years old and 39.5% of them were from 30 to 34 years old. 2) The average for school nursing experience of the SHT was 7.9 years and 37.9% of them were from 5 to 9 years. 3) The 45.2% of them have not the clinical experience. 4) The 74.2% of them were graduated from the 3 years college of nursing. 2. Status of school health resources and nursing activities. 1) The average of student number was 2497.3 and class number was 45.2. 2) The average of school health budget was 1039000 won and 27.7% of school health budget expended on examination cost. 3) Only 29.0% of all schools have organization for school health. 4) The 84.7% of all schools have health clinic separately and 69.1% of schools have less than $33m^2$ sized. 5) The average of clinic visitor number was 2111.8 for 1 year. 6) Major problem was on digestive system. And other problems were skin, respiratory, musculo-skeletal system and dental problem. 7) The number of literal message was 14.4 times for 1 year. 3. The degree of the school health teachers' self-confidence. The school health teachers' self-confidence was deviced into 6 and the maximum degree was 4. 1) Program planning & evaluation; 2.8 2) Clinic management; 2.9 3) Health education, 3.0 4) Management of school environment; 2.7 5) Health care services; 2.7 6) Operating of school health organization; 2.4 4. Significances to the degree of self-confidence on school health nursing activities. 1) There was significant difference between clinical management and Religion (t=2.15 p<.05) 2) There was significant difference between Operating of school health organization and level of school (F=3.588 p<.05) 3) Program planning & evaluation: expending time for clinical management (r=-0.184 p<.05) expending time for health care services (r=0.273 p<.01) 4) Clinical management: use of separate health clinic (r=0.151 p<.05) 5) Health education: use of separate health clinic (r=0.170 p<0.5) 6) Health care services: No. of student (r=-0.144 p<0.5) No. of class (r=-0.160 p<.05) 5. The degree of the school health teachers' self-discipline. The school health teachers' self-discipline was devided into 2 and the maximum degree was 2. 1) Program planning & evaluation:1.8 2) Clinic management: 1.9 3) Health education: 1.9 4) Management of school environment: 1.7 5) Health care services: 1.8 6) Operating of school health organization.: 1.3 6. Significances to the degree of self-discipline on school health nursing activities 1) Program planning & evaluation; Level of nursing education (F=4.309 p<.01) 2) Clinical management: Level of nursing education (F=3.587 p<.05) 3) Operating of school health organization: School health organization (t=-2.68 p<.01) 4) Health care services: School health organization (t=2,58 p<.05) 5) School health performance: School health organization (t=2.32 p<.05) 6) Program planning & evaluation: School health experience (r=0.239 p<.01) Expending time for program planning & evaluation (r=-0.172 p<.05) 7) Clinic management: School health experience (r=0.249 p<.01) Expending time for dinic management (r=0.181 p<.05) No. of student (r=-0.158 p<.05) Expending time of program planning & evaluation (r=-0.199 p<0.5) 8) Health education: School health experience (r=0.234 p<0.1) Expending time of program planning & evaluation (r=-0.193 p<.05) 9) Management of school environment: Age of school health teacher (r=0.142 p<.05) School health experience (r=0.255 p<.01) 10) Operating of school health organization: Medicine Purchase (r=-0.163 p<.05) 11) Health care services: School health experience (r=0.148 p<.05) Medicine purchase (r=-0.229 p<.01) 12) Total school health performance: School health experience (r=0.200 p<.05) Medicine purchase(r=-0.168 p<.05) Based on the above results, the suggestions are as follows: 1) As the SHT take charge of the reasonable number of student, the students will have benefit of the good health service in quality. 2) It is recommended to use the health clinic separately and to arrange adequate place for good school health service. 3) It is necessary that the SHT participate budget for school health. 4) It is required to enhance self-confidence on school health nursing activities through continuous educational programs.

• Journal of the Korean Society of School Health
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• v.12 no.2
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• pp.295-303
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• 1999

The purpose of this study was to evaluate the effect of systemic oral health education on the improvement of knowledge levels and patient hygiene performance(PHP) for elementary school students. The randomly selected 1st and 5th grade students in a public elementary school of Taegu city were divided by education group(118 students) and non-education group(122 students). The oral health education lesson was systematically held on the education group once a month for 4 months. The questionnaire queried all the subjects about their knowledge and attitudes before and after oral health education, and PHP was also tested at the same time. Corresponding p-values were significantly considered at values less than 0.05. The obtained results were as follows: Due to the oral health education lesson, the education group of both 1st and 5th grade students came to have a higher knowledge level than the non-education group. There was high improvement of items such as toothbrushing time, toothbrushing method, cause of dental caries, treatment after tooth damage, and tongue-brushing. Therefore, these items should be educated to all the elementary school students. By increaseing the knowledge level of oral health after education, the PHP index in the education group was significantly decreased in comparison to the non-education group and hence the capability of oral health management improved. From the above results, a systematically and periodically oral health education system for elementary school students can improve the knowledge level and capability of oral health management. Further study will be required to develop an easy and acceptable systemic oral health education program for elementary schools.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.528-543
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• 2005

Statement of problem: Repeated delivery and removal of abutment cause some changes such as wear, scratch or defect of hexagonal structure. It may increase the value of rotational freedom(RF) between hexagonal structures. Purpose: The purpose of this study was to evaluate surface changes and rotational freedom between the external hexagon of the implant fixture and internal hexagon of abutment after repeated delivery and removal under SEM and toolmaker's microscope. Materials and methods: Implant systems used for this study were 3i and Avana. Seven pail's of implant fixture, abutment and abutment screws for each system were selected and all fixtures were perpendicularly mounted in liquid unsaturated polyesther with dental surveyor. Each one was embedded beneath the platform of fixture. Surfaces of hexagonal structure before repeated closing and opening of abutment were observed using SEM and rotational freedom was measured by using toolmaker's microscope. Each abutment was secured to the implant future by each abutment screw with recommended torque value using a digital torque controller and was repeatedly delivered and removed by 20 times respectively. After experiment, evaluation for the change of hexagonal structures and measurement of rotational freedom were performed. Result : The results were as follows; 1. Wear of contact area between implant fixture and abutment was considerable in both 3i and Avana system. Scratches and defects were frequently observed at the line-angle of hexagonal structures of implant fixture and abutment. 2. In the SEM view of the external hexagon of implant fixture, the point-angle areas at the corner edge of hexagon were severely worn out in both systems. It was more notable in the case of 3i systems than in that of Avana systems. 3. In the SEM view of the internal hexagon of abutment, Gingi-Hue abutment of 3i systems showed severe wear in micro-stop contacts that were machined into the corners to prevent rotation and cemented abutment of Avana systems showed wear in both surface area adjacent to the corner mating with external hexagon of implant fixture. 4 The mean values of rotational freedom between the external hexagon of the implant fixture and internal hexagon of abutment were 0.48$\pm$0.04$^{\circ}$ in pre-tested 3i systems and 1.18$\pm$0.25$^{\circ}$ after test, and 1.80$\pm$0.04$^{\circ}$ in pre-tested Avana systems and 2.61$\pm$0.16$^{\circ}$ after test. 5. Changes of rotational freedom after test shouted statistical)y a significant increase in both 3i and Avana systems(P<0.05, paired t-test). 6. Statistically, there was no significant difference between amount of increase in the rotational freedom of 3i systems and amount of increase in that of Avana ones(P>0.05, unpaired t-test). Conclusion: Conclusively, it was considered that repeated delivery and remove of abutment by 20 times would not have influence on screw joint stability. However, it caused statistically the significant change of rotational freedom in tested systems. Therefore, it is suggested that repeated delivery and remove of abutment should be minimal as possible as it could be and be done carefully Additionally, it is suggested that the means or treatment to prevent the wear of mating components should be devised.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.83-94
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• 2009

The aim of this study was to investigate the shear bond strength between zirconia ceramic and resin cement according to various surface treatments. The surface of each zirconia ceramic was subjected to one of the following treatments and then bonded Rely X Unicem or Rely X ARC resin cement; (1) Rocatec system and $50{\mu}m$ surface polishing, (2) No treatment and $50{\mu}m$ surface polishing, (3) Rocatec system and $1{\mu}m$ surface polishing, (4) No treatment and $1{\mu}m$ surface polishing. Each of eight bonding group was tested in shear bond strengths by universal testing machine(Z020, Zwick, Ulm, Germany) with crosshead speed of 1mm/min. The results were as follows; 1. Rocatec treatment groups showed greater bonding strengths than No Rocatec groups. There was significant difference of among groups(P<0.001) 2. For Rocatec groups, $50{\mu}m$ surface roughness groups showed greater bonding strengths than $1{\mu}m$ surface roughness groups.(P<0.001) But for No Rocatec groups, There was no significant difference of among groups(P>0.05) 3. Rely X Unicem groups showed greater bonding strengths than Rely X ARC groups. There was significant difference of among groups(P<0.01) Within the conditions of this study, Rocatec treatment was an effective way of increasing zirconia bonds to a resin cement, even in the case of self-adhesive resin cement.

• Journal of Periodontal and Implant Science
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• v.27 no.3
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• pp.533-547
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• 1997

In periodontics, much progress was made in the understanding of periodontal disease from 1960s to 1980s and in prevention and management of periodontal disease since the end of 1980s. This presentation will discuss about the prevalence of periodontal disease, treatment need, and provision of periodontal treatment in Korea, and how we could manage the periodontal disease efficiently in the future. According to an epidemiological study in Korea, periodontal disease(including gingivitis) was present in 82% of general population and periodontitis in 30-40% in adult population over 30y and juvenile periodontitis in 0.1% of adolescents. If we consider that at least 17% of these patients may have recurrent or refractory forms, there is obviously an abundance of disease that needs treatment, As a result of increase in life expectancy, senile population over 65 y will be increased from 6% in 1996 to 6.9% in 2000, and tooth retention rate and periodontal treatment need are expected to increase. Periodontists need all the help they can get from the general dentists to control periodontal disease. As for provision, postgraduate course in periodontics started in 1957 in Korea and produced over 700 specialized dentists in periodontics. One report indicated that the periodontists as well as general practitioners did periodontal therapy on only a few periodontal patients, because of specific control by current medical insurance system in Korea. Comprehensive periodontal examination is rarely done in local dental clinic. Therefore, enhancement of periodontal care in medical insurance system and education of simplified periodontal examination such as Periodontal Screening & Recording will make dentists diagnose and manage the management of adult patients is based on the recognition that there are multiple diseases, including gingivitis, chronic adlt periodontitis, and other more aggressive forms of periodontitis, and requires the earliest possible recognition of these three disease categories. In this presentation, we discuss practical approach using PSR to diagnose, manage and refer the patients, to facilitate the separation of the simple from the complex and the predictable from the unpredictable form of periodontal diseases and to integrate diagnostic and therapeutic techniques into private practice today.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.148-155
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• 2009

Statement of problem: The interest in all-ceramic restorations has increased as more techniques have become available. With the introduction of machinable dental ceramics and CAD/CAM systems there is a need to evaluate the quality levels of these new fabrication techniques. Purpose: This study is to evaluate the crown fidelity(absolute marginal discrepancy and internal gap) of various zirconia-based all-ceramic crowns fabricated with different CAD/CAM(computer-assisted design/computer-assisted manufacturing) systems and conventional cast metal-ceramic crowns. Material and methods: A resin tooth of lower right second premolar was prepared. After an impression was taken, one metal master die was made. Then 40 impressions of metal master dies were taken for working dies. 10 crowns per each system were fabricated using 40 working dies. Metal-ceramic crowns were cast by using the conventional method, and Procera, Lava, and Cerec inLab crowns were fabricated with their own CAD/CAM manufactruing procedures. The vertical marginal discrepancies and internal gaps of each crown groups were measured on a metal master die without a luting agent. The results were statistically analyzed using the one-way ANOVA and Tukey's HSD test. Results: 1. Vertical marginal discrepancies were $50.6{\pm}13.9{\mu}m$ for metal-ceramic crowns, $62.3{\pm}15.7{\mu}m$ for Procera crowns, $45.3{\pm}7.9{\mu}m$ for Lava crowns, and $71.2{\pm}2.0{\mu}m$ for Cerec inLab crowns. 2. The Internal gaps were $52.6{\pm}10.1{\mu}m$ for metal-ceramic crowns, $161.7{\pm}18.5{\mu}m$ for Procera crowns, $63.0{\pm}10.2{\mu}m$ for Lava crowns, and $73.7{\pm}10.7{\mu}m$ for Cerec inLab crowns. Conclusion: 1. The vertical marginal discrepancies of, 4 crown groups were all within the clinically acceptable range($120{\mu}m$). 2. The internal gaps of LAVA, Cerec inlab, and metal-ceramic crowns were within clinically acceptable range except Procera crown($140{\mu}m$).