• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.2
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• pp.143-149
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• 2015

In esthetic treatments, it is important to consider the arrangement of teeth and the relation between the teeth and soft tissues. A precise diagnosis and establishing an appropriate treatment plan is essential in an esthetic treatment of anterior maxillary teeth. For a fixed prosthesis to meet esthetic expectations, It is crucial to achieve symmetry and adequate proportions of the gingival contour around the crowns. To achieve an esthetic improvement and creating a favorable environment for gingival healing of a physiologic gingival contour, gingivectomy, crown lengthening and forced eruption can be applied to the appropriate site. All ceramics or porcelain laminate veneer can be selected for esthetic improvement of teeth contour and shade. In this case report, malposition of the remaining teeth made it hard to get an esthetic appearance. Gingivectomy, crown lengthening and provisional restoration insertion were performed before the final prosthesis fabrication to reform the gingival form. This case presents satisfying result esthetically and functionally.

• Journal of Technologic Dentistry
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• v.45 no.3
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• pp.67-73
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• 2023

Purpose: This in vitro study aimed to evaluate the clinical acceptability of precision of fit of the support thickness of Co-Cr alloy copings fabricated using selective laser melting (SLM). Methods: Thirty dental stone models of maxillary left molar abutments were manufactured, images were taken using a scanner, and a computer-aided design program was used to design the form of a conventional metal ceramic crown coping. Overall, 30 single copings were made from Co-Cr alloy using SLM and divided into three support radius groups (0.1, 0.25, and 0.35 mm) of 10 for each. Digitized data were superimposed with three-dimensional inspection software to quantitatively obtain the machinability of a ceramic crown coping, and visual differences were confirmed using a color map. The root mean square values of the ceramic crown coping group were statistically analyzed using one-way analysis of variance (α=0.05). Results: The precision of fit was superior with 0.25 mm compared with 0.1 mm and 0.35 mm, and the results exhibited significant differences (p<0.05). All specimens showed that various support thicknesses did not exceed the clinically permitted value of 120 ㎛, which mean that more than 0.1 mm and 0.35 mm of support radius for SLM was adequate. Conclusion: The support thickness of Co-Cr alloy restoration fabricated using SLM is shown to affect the adaptation.

• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.4
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• pp.309-315
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• 2006

The availability of high-technology systems that use computer-aided design(CAD) and computer-aided machining(CAM) is on the increase. One such system is the Procera system, which fabricates an all-ceramic crown composed of a densely sintered, high-purity aluminum oxide coping combined with a compatible veneering porcelain. Strength, precision of fit, esthetics, cementation, and biocompatibility are among the many factors that concern clinicians when fabricating all-ceramic restorations with this system. This paper reviews the long history and background development of technical, laboratory and clinical applications and presents, in summary form, the data from the many studies on the Procera system.

• Journal of Veterinary Clinics
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• v.18 no.2
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• pp.146-151
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• 2001

This study was carried out to find if the X-irradiation being used for clinical diagnosis during pregnancy would affect fetal development and cause fetal malformation in rats or not. To determine the dose and irradiation frequency of X-irradiation and gestation period by which fetal development would be affected when irradiated during pregnancy, seventy-two Sprague Dawley female rats (8 weeks old) were used for the experiment and grouped into three according to different gestation period of 5-8 days, and 6-12 days of gestation. Experimental rats were irradiated on the daily irradiation conditions of 40, 60, 80 kvp(kilo volt peak), 150 mA(milliampere), 0.25 sec and 4 times/day for both 5-8 days and 10-13 days of gestation, and 100 kvp, 100 mA, 2 min. and 4 times/day for 6-12 days of gestation. Rats were put in a small dark box when irradiated, which animals were sacrificed on the 20th day of gestation and mean litter size, fetal body weight, fetal crown-rump length(CRL) were investigated along with pathological findings. 1. Litter size were significantly decreased in the rats which were irradiated by both 60 and 80 kvp during 5 to 8 days of gestation and by 100 kvp during 6-12 days of gestation compared to those from the control rats(p<0.05) 2. Fetal body weight was significantly decreased in the fetus from the rats which were irradiated by both 60-80 kvp during 5-8 days of gestation and by 100 kvp during 6-12 days of gestation compared to those from the control rats(p<0.05). 3. There was no significant difference of fetal crown-rump length between all the experimental rats and the controls. 4. Fetal absorption, fetal death, and fetal malformation were not observed in the fetus form the rats irradiated by 40-80 kvp during 5-8 and 10-13 days of gestation, however, the pathological findings were found in those from the rats irradiated by 100 kvp during 6-12 days of gestation. 5. The harmful effect of x-irradiation on fetal development was estimated to occur when irradiated during 5-8 days of gestation. These results indicated that even X-irradiation for clinical diagnosis could affect fetal development in the early embryonic stage and when the fetus were exposed to frequent and prolonged x-irradiation with over dose.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.125-132
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• 2004

Statements of problem: All ceramic fixed partial denture cores can be made by the slip casting method and the advanced alumina tape method. The fracture resistance of these core connector areas is relatively low. Purpose: The purpose of this study is to standardize the appropriate volumetric figure and location of the connectors in the alumina core fabricated in alumina tape to be used in fixed partial dentures by way of topology optimization. Material and method: A maxillary anterior three-unit bridge alumina core with teeth form and surrounding periodontal apparatus model was used to ultimately design the most structurally rigid form of the connector. Loadings from a $0^{\circ}$, $45^{\circ}$ and $60^{\circ}$ to the axis of each tooth were applied and analyzed with the 3-D finite element analysis method. Using the results from these experiments, the topology optimization was applied and the optimal reinforcement layout of connector was obtained and the detail shape in the fixed partial denture core was designed. Results: The modified prosthesis with the form of a bulk in the lower lingual surface of the connector in the event, reduced the stress concentration up to 20% in the 3-D FEA. Conclusion: The formation of a bulk in the lower lingual connector area of an alumina core for a fixed partial denture decreases the stress to a clinically favorable measure but does not harm the esthetic point of view. This result illustrates the possibility of clinical application of the modified form designed by the topology optimization method.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.41 no.4
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• pp.190-193
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• 2015

Objectives: A mesiodens appears most commonly as a supernumerary tooth impacted in the anterior maxilla. The purpose of this study is analyze mesiodens clinically. Materials and Methods: Gender, crown form, direction of impaction, relation to permanent incisors, and chief complaints of patients with extracted mesiodens were analyzed. Results: Patients were analyzed for motivation to visit the hospital; 85.4% of the patients were referred from other hospitals. Mesiodens was more common in males than in females (3.7:1), and 70.1% of patients had only one mesiodens, while 29.6% had two mesiodenses. Of the mesiodenses, 61.4% were of the aconical form, and the most common direction was upward (62.4%), followed by the normal position (26.0%) and the horizontal position (11.6%). The mesiodenses caused orthodontic problems with the permanent incisors in 46.3% of cases. Mesiodens associated with dentigerous cyst was rarely observed in our patient group. Conclusion: Mesiodens is more common in males than in females and often affects the permanent incisors. Thus, careful clinical and radiological evaluations of mesiodenses are important.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.3
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• pp.253-258
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• 2016

The development of translucent zirconia enabled clinicians to choose a monolithic zirconia crown as one treatment modality in the posterior dentition. Careful occlusal adjustments are recommended for monolithic zirconia crowns because grinding zirconia inevitably causes phase transformation, which may deteriorate mechanical properties. intraoral scanners enable the clinician to scan and superimpose a complete tooth structure before preparation onto the prepared abutment. This technique helps to reproduce the original tooth form and occlusion of the patient. In this case report, prostheses were fabricated for patients with cracked or fractured tooth by applying intraoral scanner, Computer aided design-computer aided manufacturing (CAD-CAM) and monolithic zirconia crown to reproduce the occlusion of original tooth and to minimize occlusal adjustment. The clinical results were satisfactory in both esthetic and functional aspects.

• Journal of Technologic Dentistry
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• v.42 no.3
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• pp.220-227
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• 2020

Purpose: This study aims to investigate the cusp variation pattern of the Korean mandibular second premolar and to determine the difference in tooth diameter and surface area using a virtual three-dimensional model. Methods: Dental casts from 69 students were scanned as a virtual dental models with a three-dimensional dental model scanner. Tooth diameter, absolute and relative individual areas, total crown area, the number of lingual cusps and central groove pattern were analyzed using RapidForm 2004. The Mann-Whitney U-test and the Kruskal-Wallis test were performed to verify sexual dimorphism, the difference in tooth diameter and surface according to the cusp variation pattern (α=0.05). Results: There was no significant difference except in buccolingual diameter (p<0.05) and buccolingual diameter at the cervix (p<0.05). The relative surface area of the total clinical crown was 65.76% for the buccal half and 34.24% for the lingual half, with a ratio of 2:1. In the case of the presence of two lingual cusps, the ratio was 21.47% for the mesiolingual half and 14.12% for the distaolingual half, with a ratio of 3:2. The dominant central groove patterns of the second premolar were the H-pattern (42.0%), followed by the Y-pattern (37.7%), then the U-pattern (20.3%). The relative buccal half was largest in the U-pattern central groove and the relative lingual half was largest in the Y-pattern central groove (p<0.05). Conclusion: This study is significant in that it measured quantitative surface areas and the findings could be a meaningful reference to comprehend dental anatomy in Koreans.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.5
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• pp.584-593
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• 2006

Statement of problem : Dental implant which has been developed gradually through many experiments and clinical applications is presently used to various dental prosthetic treatments. To conduct a successful function of implant prosthesis in oral cavity for a long time, it is important that not only structure materials must have the biocompatibility, but also the prosthesis must be designed for the stress, which is occurred in occlusion, to scatter adequately of load support. Therefore, it is essential to give the consideration about the stress analysis of supporting tissues for higher successful rates. Purpose : Recently, many implant manufacturing company produce various taper design of root form implant, the fixture is often selected. However, the stress analysis of taper form fixture still requires more studies. Material and method : This study we make the element models that five implant fixture; Branemark system(Nobel Biocare, Gothenberg, Sweden), Camlog system(Altatec, Germany), Astra system(Astra Tech, Sweden), 3i system(Implant Innovations Inc, USA), Avana system(Osstem, Korea) were placed in the area of mandibular first premolar and prosthesis fabricated, which we compared with stress distribution using the three-dimension finite element analysis under two loading condition. Results : This study compares the aspect of stress distribution of each system with the standard of Von mises stress, among many resulted from finite element analysis so that this research gets the following results. 1. In all implant system, oblique loading of maximum Von mises stress of implant, alveolar bone and crown is higher than vertical loading of those. 2. Regardless of loading conditions and type of system, cortical bone which contacts with implant fixture top area has high stress, and cancellous bone has a little stress. under the vertical loading, maximum Von mises stress is more higher in order of Branemark, Camlog, Astra, 3i, Avana. under the horizontal loading, maximum Von mises is more higher in order of Camlog, Branemark, Astra, 3i, Avana.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.207-216
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• 2006

Statement of Problem: To conduct a successful function of implant prosthesis in oral cavity for a long time, it is important that not only structure materials must have the biocompatibility, but also the prosthesis must be designed for the stress, which is occurred in occlusion, to scatter adequately within the limitation of alveolar bone around implant and bio-capacity of load support. Now implant which is used in clinical part has a very various shapes, recently the fixture that has tapered form of internal connection is often selected. However the stress analysis of fixtures still requires more studies. Purpose: The purpose of this study is to stress analysis of the implant prosthesis according to the different implant systems using finite element method. Material and methods: This study we make the finite element models that three type implant fixture ; $Br{\aa}nemark$, Camlog, Frialit-2 were placed in the area of mandibular first premolar and prosthesis fabricated, which we compared with stress distribution using the finite element analysis under two loading condition. Conclusion: The conclusions were as follows: 1. In all implant system, oblique loading of maximum Von mises stress of implant, alveolar bone and crown is higher than vertical loading of those. 2. Regardless of loading conditions and the type of system. cortical bone which contacts with implant fixture top area has high stress, and cancellous bone has a little stress. 3. Under the vertical loading, maximum Von mises stress of $Br{\aa}nemark$ system with external connection type and tapered form is lower than Camlog and Frialit-2 system with internal connection type and tapered form, but under oblique loading Camlog and Frialit-2 system is lower than $Br{\aa}nemark$ system.