Earticle

연구 목적: 임플란트의 하부구조를 상부 구조와 연결하는 레진시멘트의 접착강도를 높이기 위한 기계적 화학적인 표면 처리 방법들이 연구 되고 있다. 이 연구에서 다양한 크기의 Al2O3 sandblasting과 Silano Pen으로 표면처리한 티타늄 과 레진 시멘트의 접착강도를 알아보고자 한다. 연구 방법: 12개의 티타늄(Ti-6A1-4V)시편을 디스크 형태로 제작하여 자가중합 수지에 매립하였다. 이들을 각각 6개 의 군으로 나누어 50㎛, 90㎛, 110㎛ 등 3가지 크기의 Al2O3로 sandblasting 하는 조건과 Al2O3로 sandblasting한 후 Silano Pen(Bredent, bredent GmbH &Co.KG, Senden, Germany)을 사용한 군으로 나누었다. 표면처리 한 티타늄 표면에 레진시멘트(Duolink dual syringe, Bisco, USA)으로 접착하였다. 그 후 증류수(37℃)에 24시간 보관 후 접착강 도 실험을 시행하였고, SEM을 사용하여 표면처리 한 표면과 접착강도 실험 후 파절양상을 관찰하였다. 결과: 통계학적 분석에 따르면 Silano Pen을 사용하여 표면처리한 군들의 접착강도가 높았다(P<0.05). 결론: Silano Pen을 사용하는 것이 티타늄과 레진시멘트의 접착강도를 증가 시킨다.

Purpose: All ceramic crown, made from zirconia instead of metal for core material, is recognized the best esthetical prosthesis. Recently, high-priced zirconia blocks and expensive CAD/CAM machines come into use for making zirconia core. In this study, slip casting process is adapted to evaluate the possibility of the recycling the remained parts of zirconia block after machining. Methods: Remained zirconia blocks were reduced to powders with zirconia mortar, and screened with 180 mesh sieve. Passed powders were ball milled under various conditions to obtain the optimum zirconia slip for casting. Solid casting method was used for casting the specimens with plaster mold. Formed specimens were dried and biscuit fired at 1,000 for 1 hour. Biscuit fired specimens were finished with exact shape of square pillar. Finished specimens were fired from 1,200 to 1,550 at 50 intervals for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM. Results: Above examinations indicated that the optimum firing temperture was 1,500 , and when fired at this temperature for 1 hour, apparent porosity was 0% and flexural strength was 680 . SEM photomicrographs showed uniform 200~300 grain size, which is equal with microcture of sintered commercial zirconia block. when compare 24% linear shrinkage of cast specimen with 20% linear shrinkage of CAD/CAM machined block, it was estimated that the size controlling of cast core was not so difficult. Conclusion: According to the all of this experimental results, the cast zirconia core produced from the remained parts of zirconia block was possible to use for all ceramic denture.

Purpose: The objective of this study is to find out physical properties and the flexural strength changed by the low temperature degradation of the block which is needed to make bio-prosthetic dentistry which is better than feldspar affiliated ceramic made by building up ceramic powder and also to apply this to the clinical use of zirconia monolithic all-ceramic crown. Methods: Flexural strength of each sample was evaluated before and after the Low Temperature Degradation ,and physical properties of the Tetra Zirconia Block containing 3mol % was evaluated as well. The average and standard deviation of each experimental group were came out of the evaluation. Statistical package for social science 18.0 was used for statistics. Results: The average density of the monolithic all-ceramic crown was 6.0280 0.0147g/cm, the relative density was 99.01 %. When the sample was sintered at 1480 the diameter of average particle was 396.62 33.71nm. All the samples had no monolithic peak after XRD evaluation but only had tetragonal peak. There were statistically significant differences in the result of flexural strength of the samples evaluated after and before the low temperature degradation, the flexural strength before the low temperature degradation was 1747.40 ßÁ, at the temperature of 130 the flexural strength after the low temperature degradation was 1063.99 (p<0.001). There was statistically significant difference in the result of strength of 1020.07 after the low temperature degradation at the temperature of 200 (p<0.001). Conclusion: The block which was made for this evaluation possesses such an excellent strength among dental restorative materials that it is thought to have no problems to use for tetragonal zirconia polycrystal.

Purpose: Fracture strength of all-ceramic 3-unit fixed partial dentures manufactured by CAD/CAM and copymilling systems were evaluated. Methods: Zirconia cores were made by milling the pre-sintered zirconia block by CAD/CAM or copy milling method followed by subsequent sintering. By building-up the corresponding porcelains on the core, all-ceramic bridges were fabricated, and those were evaluated in comparison with PFM fixed partial denture. Results: During the flexural test of the 3-unit PFM bridge, the porcelain started to chip or break at 507.28( 62.82)kgf and the metal framework did not break until the maximum load level of 800kgf which was set in the testing instrument of this study. However, among all-ceramic restoration test groups, Everest(EV) group showed a peeling off or breakage of the porcelain from 365.64( 64.96)kgf and the core was broken at 491.77( 55.62)kgf. Those values of Zirkonzahn(ZR) were 431.03( 58.47)kgf and 602.74( 48.44)kgf, respectively. The break strength of the porcelain of PFM(PM) group was significantly higher than that of EV (p<0.05) group and there was no significant difference when comparing to that of ZR (p>0.05). ZR group showed higher break strength than that of EV group however there was no significant difference (p>0.05). The break strength of cores were in the increasing order of EV < ZR < PM (p<0.05). Conclusion: We could find that even though the PM group fractured at much higher value than all-ceramic cores, the breakage values of the porcelain of PM group with crack formation or delamination, which will be regarded as clinical failure, was significantly higher than that of EV group and not significantly higher than that of ZR group at p-values of 0.05. The break strength of ZR group was higher than that of EV group at an insignificant level(p>0.05).

Purpose: The purpose this study was to evaluate the marginal fitness of metal copings fabricated using rapid prototyping method and to compare the fitness with copings by conventional method. Then clinical availability of fixed dental prostheses (FDPs) fabricated using rapid prototyping method shall be confirmed based on marginal fitness. Methods: Ten same cases of3 unit FDPs epoxy models (abutment teeth 14 and 16) were manufactured. Each of ten epoxy models were scanned by 3shape D-700 scanner to be designed by experienced technician, and photopolymer 3 unit FDPs were fabricated using rapid prototyping methodand fabricated using Lost wax technique (LW) with same models. Marginal fitness of 3 unit FDPs were measured by silicone replica technique. T-test of independent sample for statistical analysis was executed with SPSS 12.0K for Windows. ( =.05) Results: Significantly higher mean (SD) marginal fitness (P<.000) were observed in the RP group (95.9 (18.0) compared to the conventionally LW group (80.1 (13.8) . Conclusion: Marginal fitness of LW group showed excellent rather than RP group. However marginal fitness of 3 unit FDPs fabricated by RP method did not get out of clinical allowance value range significantly to allow clinical application.

Purpose: Zirconia blocks for all ceramic dentures are divided into two groups. One is pre-heated block and the other is binder added block. In this study, the possibility of recycling the remained parts of binder added block after CAD/CAM machining with slip casting process was investigated. Methods: Owing to the binder added block contain large amount of organic matter, Binder burn-out was must be carried out before ball milling for preparing the casting slip. Binder burn-out was accomplished at 600 for 10 hours. Ball milling was performed with 5 zirconia ball and 60 polyethylene bottle. From 0% to 5% at 1% intervals of alumina was added to zirconia powder for preparing slip. Solid casting was achieved with plaster mold. Cast bodies were dried and sintered at 1,500 for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM, EDS and XRD analysis were executed. Results: Optimum slips for casting was prepared with 300g ball, 100g powder, and 180g distilled water. Cast body without alumina showed 26% of linear shrinkage, 6.07 of apparent density, and 470 of three point bend strength. On the other hand, as received zirconia block, which was sintered at the same conditions, showed 23% of linear shrinkage, 6.10 of apparent density, and 680 of three point bend strength. When 3% of alumina was added to zirconia, sintered body showed 23% of linear shrinkage, 6.10 of apparent density, and 780 of three point bend strength. SEM photomicrographs and EDS analysis showed alumina particles uniformly dispersed in zirconia matrix, and XRD analysis showed no phase transformation of tetragonal zirconia particles was occurred when alumina was added. Conclusion: According to the all of this experimental results, 3% of alumina added cast zirconia body showed excellent mechanical properties more than as received binder containing zirconia block

Purpose: The aim of this study was to determine the reliability and accuracy of measurements in digital models(CEREC AC) compared to stone models. Methods: A master model(500B-1, Nissin Dental Product, Japan) with the prepared upper full arch tooth was used. Conventional impression and then stone model(n=10) were produced from this master model, and on the other hands, digital impressions were made with the CEREC AC intra-oral scanner(n=10). One examiner measured two times the intercanine, intermolar distance, dental arch length. The stone model were measured using a digital caliper. The t-student test for paired samples and intraclass correlation coefficient(ICC) were used for statistical analysis. Results: The measurement of two methods showed very good reliability. At the intra-examiner reliability of measurement, ICC at the stone and CEREC AC model were 0.81 and 0.94. The mean difference between measurements made directly on the stone models and those made on the CEREC AC model was 0.20~0.28 , and was statistically significant(P=0.001). Conclusion: These in vitro studies show that accuracy of the digital impression is similar to that of the conventional impression. These results will have to be confirmed in further clinical studies.

Purpose: This study was conducted to investigate the colors of zirconia and veneered ceramics according to the build-up method of veneer porcelain. Methods: The samples were divided into three groups: a group for which a liner was applied to the zirconia surface and dentine coating was built up and burned (Cz1), a group for which the dentine coating was directly built up and burned (Cz2), and a group for which the samples were wash-burned with dentine coating and a dentine coating was built up and burned again (Cz3). The the colors were measured with a Spectrophoto-meter. Results: The average L* value of the Cz3 group was the highest among the groups at 59.1 0.5 (P<0.05), followed by Cz2 at 57.5 0.8 and Cz1 at 56.6 1.3. The a* value of Cz3 was negative at -0.0 0.0 and the a* values of Cz2 and Cz1 were positive at 0.2 0.1 and 0.4 0.0, respectively (P<0.05). The b* of Cz1 was the highest at 11.2 0.6, followed by Cz3 at 10.8 0.5 and Cz2 at 10.5 0.8 (P<0.05). Conclusion: Compared to other experimental groups, the Cz3 groups showed the brightest colors with high brightness and relatively low green and yellow levels.

Purpose: The purpose of this in vitro study was to compare the marginal fit of POM restorations with 3 different thickness of metal coping. Methods: 2.0 Occlusal reduction, 1.0mm preparation of axial wall with 6degree taper, and chamfer margin was prepared a maxillary first premolar on dentiform. Duplicate prepared die and, make 30 individual dies with Ni-Cr metal. Make 3 groups of 30 press ceramic on Metal crown with different thickness of metal coping; 10 of 0.1 , 10 of 0.3 , 10 of 0.5 thickness metal coping. The marginal fit of the crowns was evaluated 50 points per 1 crown, around the crown margin circumference under a optical microscope at original magnification 100. A 1-way analysis of variance (ANOVA) was used to compare data. Results: The mean marginal discrepancy for POM with 0.1 metal copings was 72.56 , 67.83 for 0.3 metal coping POMs, and 72.56 for 0.5mm metal coping POM. The 1-way ANOVA showed significant difference among 3 groups. Conclusion: The marginal fit of pressed-on-metal (POMs) was best with 0.3 thickness of metal coping, fallowing by 0.1 , and 0.5 in the order.

Purpose: The purpose of this study was to investigate to effect of the electro-polishing condition according to electrolyte temperature and current and polishing time on surface morphology and composition by scanning electron microscopy(SEM) and energy dispersive X-ray spectrometer(EDS) in dental casting Co-Cr-Mo alloys. Methods: 16 specimens were divided into 4 groups which have each 4 specimens. The size of specimens were 10 wide and 5 height. the electro-polishing of specimens are by polishing solution temperature and times in Co-Cr- Mo alloy by SEM and EDS analysis. Results: The results shows that most smooth surface is obtained when electro-polishing is performed at 49 for 30-40sec with electro gap of 10mm and 8 voltage. Conclusion: The morphologies of specimens after electro-polishing were scratch absent and significant between at 40 for 45sec and at 49 for 45sec.

Purpose: The purpose of this study was to survey periodontal status using oral health index in the elderly population and determine methods for improving oral health status. Methods: The date collected from ‘The fifth korean national health and nutrition examination survey 2010’ was analyzed in this study. Statistical analysis was done using the Statistical Package for Social Sciences version 19.0 for windows. We determined frequencies and percentage, calculating means, and standard deviations, and determining statistical significance using logistic regression analysis, multiple regression analysis. Results: General characteristics showed differences in oral health behaviors associated with gender, age, residence, education. General characteristics showed differences in periodontal status associated with gender, family type, gender, residence, education. Oral health behaviors showed differences in periodontal status associated with using oral health care products, dental treatment. Conclusion: In conclusion, in order to improve oral health of the elderly, the importance and needs of periodontal status should be emphasized. periodontal status related education for the elderly should be operated

Purpose: The purpose of this study is to lay the groundwork for the development of appropriate training courses for a rapidly changing digital technology in the field of Dental technology. Methods: The subjects of this study were dental technicians, dental technology students, a professor of dental technology in Daegu and Gyeongbuk area and a self-administered structured questionnaire survey was conducted for 350 randomly selected people. Collected data were analyzed using SPSS Win 17.0 statistics program and analysis techniques include the frequency, percentage and cross-analysis. Results: The results of the survey are as follows. The usefulness of Major subjects was Full Denture laboratory (4.72 points), Dental Morphology (4.71 points), Crown and Bridge laboratory (4.69 points) in the instructor’s group. The usefulness of Major subjects was Dental Morphology (4.56 points), Full Denture (4.36 points), Crown and Bridge laboratory (4.69 points) in the student’s group. The usefulness of Major subjects was Dental Morphology (4.58 points), Dental Morphology laboratory (4.34 points), Partial Denture laboratory (4.30 points) in the dental technician’s group. Subject with the highest usefulness of required course to open was CAD/CAM lecture and laboratory, the highest proportion of 91.2% and Implant laboratory was very useful (91.2%) in the instructor’s group. Subject with the highest usefulness of required course to open was CAD/CAM lacture and laboratory, the highest proportion of 90.0% and Implant laboratory was very useful (91.2%) in the student’s group. Subject with the highest usefulness of required course to open was CAD/CAM lacture and laboratory, the highest proportion of 91.2% and Implant laboratory was very useful (90.2%) in the dental technician’s group. Conclusion: Semester of the subjects was required establishment of CAD/CAM lecture and laboratory in the third year first semester (85.1%) and Implant laboratory in the third year second semester the third year was the highest proportion of 94.1% in the instructor’s group. 87.0% of students need to open CAD/CAM lacture and laboratory in the third year first semester, Implant laboratory in the third year second semester the third year was the highest proportion of 85.0% in the student’s group. Semester of the subjects was required establishment of CAD/CAM lecture and laboratory in the third year first semester (81.0%) and Implant laboratory in the third year second semester the third year was the highest proportion of 80.0% in the dental technician’s group.

Purpose: This study was conducted to prepare the fundamental data on oral hygiene of the elderly and to assess the behavior of oral hygiene, subjective oral health, oral health problem among the elderly, and to contribute to successful enhancement of life in their declining years. Methods: The author surveyed the behavior of oral hygiene, subjective oral health, oral health problem to 192 elderly at a health center of Busan using structured self- administered questionnaire from Nov. 2nd 2009 to Feb. 10th 2010. Collected data were analysed by SPSS WIN 18.0 statistical program for frequency, percentage production, 2 (Chi-square) verification, t-test, One-way ANOVA, Logistic Regression. Results: The distribution of total subjects by oral health behaviors were 56.8% for “have ever trained how to tooth brushing”, 76.6% for “correctly performed tooth brushing by himself ”, 71.8% for “tooth brushing a day is two times and less”, 87.5% for “it doesn’t tooth brushing in meals and after” and 53.6% for “it doesn’t use the facility for oral health”, respectively. The distribution of total subjects by the state of perceived oral health were 51.0% for “feel the oral discomfort”, 51.6% for “feel the comfortable chewing on starchy food”, respectively. The mean point of perceived oral health by general characteristics of total subjects were statistically significant difference in sex, type of medical insurance, smoke, exercise, and chronic disease. The mean point of perceived oral health by oral health behaviors of total subjects were statistically significant difference in educational experience on tooth brushing, recognition for tooth brushing by himself, tooth brushing a day, and tongue cleaning. The risk factors of perceived oral health were type of medical insurance and chronic disease in general characteristics, tooth brushing in meals and after and tooth brushing a day, and tongue cleaning in oral health behaviors. Conclusion: The author recommend to the prevention of chronic disease, carry out the tooth brushing in meals and after, three times and over tooth brushing a day and tongue cleaning for oral health. and the author consider that it need to prepare the active countermeasure to oral health such as reeducation for oral health and supply to the tongue cleaner