• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.3
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• pp.189-198
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• 2017

Purpose: This study aims to analyze the stress distribution of mandibular molar restoration supported by the implants with external hex and internal taper abutment connection design. Materials and Methods: Models of external connection (EXHEX) and internal connection (INCON) implants, corresponding abutment/crowns, and screws were developed. Supporting edentulous mandibular bony structures were designed. All the components were assembled and a finite element analysis was performed to predict the magnitude and pattern of stresses generated by occlusal loading. A total of 120 N static force was applied both by axial (L1) and oblique (L2) direction. Results: Peak von Mises stresses produced in the implants by L2 load produced 6 - 15 times greater than those by L1 load. The INCON model showed 2.2 times greater total amount of crown cusp deflection than the EXHEX model. Fastening screw in EXHEX model and upside margin of implant fixture in INCON model generated the peak von Mises stresses by oblique occlusal force. EXHEX model and INCON model showed the similar opening gap between abutment and fixture, but intimate sealing inside the contact interface was maintained in INCON model. Conclusion: Oblique force produced grater magnitudes of deflection and stress than those by axial force. The maximum stress area at the implant was different between the INCON and EXHEX models.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.2
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• pp.157-168
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• 2008

Statement of problem: Over the past two decades, implant supported fixed prosthesis have been widely used. However, there are few studies conducted systematically and intensively on the splinting effect of implant systems in mandible. Purpose: The purpose of this study was to investigate the changes in stress distributions in the mandibular implants with splinting or non-splinting crowns by performing finite element analysis. Materials and methods: Cortical and cancellous bone were modeled as homogeneous, transversely isotropic, linearly elastic. Perfect bonding was assumed at all interfaces. Implant models were classified as follows. Group 1: $Br{{\aa}}nemark$ length 8.5mm 13mm splinting type Group 2: $Br{{\aa}}nemark$ length 8.5mm 13mm Non-splinting type Group 3: ITI length 8.5mm 13mm splinting type Group 4: ITI length 8.5mm 13mm Non-splinting type An load of 100N was applied vertically and horizontally. Stress levels were calculated using von Mises stresses values. Results: 1. The stress distribution and maximum von Mises stress of two-length implants (8.5mm, 13mm) was similar. 2. The stress of vertical load concentrated on mesial side of implant while the stress of horizontal load was distributed on both side of implant. 3. Stress of internal connection type was spreading through abutment screw but the stress of external connection type was concentrated on cortical bone level. 4. Degree of stress reduction was higher in the external connection type than in the internal connection type.

• Journal of the Korean Institute of Gas
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• v.20 no.3
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• pp.73-77
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• 2016

This paper presents the displacement behavior safety of hollow shafts with an equivalent volume for various cross sectional area using a finite element method. The FEM results indicate that the hollow shafts with X-type or Y-type columns between outer tube, middle tube and inner tube may reduce a maximum displacement at the middle length of hollow shafts. Especially, the load-bearing column of X-type or Y-type hollow shaft is directly connected between outer tube and inner tube without a shift for reducing the vertical displacement. And increased thickness of a load-bearing column is recommended for reducing the vertical displacement and increasing the displacement behavior safety for an equivalent volume of a hollow shaft.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.2
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• pp.151-155
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• 2017

Purpose: The aim of this study was to evaluate screw removal torque of the two-piece zirconia abutment with the novel titanium component compared to the conventional one-piece titanium abutment in the internal connection implant before and after dynamic cyclic loading. Materials and methods: Two types of the abutment assemblies with internal connection were prepared and divided into the groups; titanium abutment-titanium abutment screw assemblies as control, and zirconia abutment-titanium socket-titanium abutment screw assemblies as experimental group. A total of 12 abutments and implants were used of six assemblies each group. Each assembly was tightened to 30 Ncm. A cyclic load of 300 N at an angle of 30 degrees in reference to the loading axis was applied until one million cycles or failure. The removal torque values (RTVs) of the abutment screws were measured with a digital torque gauge before and after cyclic loading. The RTVs of the pre load and post load were analyzed with t-test, and P-values < .05 were considered statistically significant. Results: The assemblies of both groups survived all after the dynamic cyclic loading test without screw loosening. The statistically significant differences were found between the mean RTVs before and after the cyclic loading in both groups (P < .05). The RTV differences for the control and the experimental group were $-7.25{\pm}1.50Ncm$ and $-7.33{\pm}0.93Ncm$, respectively. Statistical analysis revealed that the RTV differences in both groups were not significantly different from each other (P > .05). Conclusion: Within the limitation of this study, the two-piece zirconia abutment with the titanium component did not show a significant RTV difference of the abutment screw compared to the titanium abutment after dynamic cyclic loading.

• Korean Journal of Ichthyology
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• v.18 no.1
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• pp.27-35
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• 2006

During spawning season of female in a Korean oily bitterling, Acheilognathus koreensis, the ventral region near the base of the pectoral fin becomes to be protruded outward of body and enlarged. This ventral process consists of both organs as rectum (vent) and inner ovipositor. The rectum consists of mucosa, lamina propria-submucosa, muscularis, and squamous epithelial layer (peritoneum=serosa) surrounding them. The mucosa contains numerous mucous cells meaning acid mucopolysaccharides in nature. The inner ovipositor is similar to that of the rectum, but the mucosa have no mucous cell, unlike that of the rectum. Whereas, the outer ovipositor has a straight and long tube which are not connected with the ventral process any more. The outer ovipositor was similar to the structure of the inner ovipositor in the ventral process. However, the outer ovipositor has no muscularis, and consists of three layers: mucosa, lamina propria-submucoa, and squamous epithelia. The outer ovipositor without the muscularis seems serves as a tube that eggs discharged from the outer ovipositor allow to send inside mussel, unlike that of the inner ovipositor performing rhythmic contractions of the layers of the muscularies for propelling to the matured oocytes to the outer ovipositor.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.306-309
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• 2010

강철도 플레이트거더교의 경우 일반적으로 레일의 폭보다 거더 사이의 폭이 넓기 때문에 거더에 편심이 작용하게 된다. 이러한 편심 영향으로 거더 내측 상부플랜지에 휨변형이 일어나게 되어, 상부플랜지와 수직보강재 용접이음부에 반복하중에 의한 피로균열이 발생되고 있는 것으로 보고되고 있다. 본 연구에서는 공용중인 강철도 플레이트거더교를 대상교량으로 하여 공용하중에 대한 구조해석을 실시하였다. 대상교량에 대한 현장계측을 기초로 구조모델링을 검증하였고, 검증된 구조모델링을 사용하여 열차하중 하에서의 상부플랜지와 수직보강재 용접연결부에서의 피로균열 보강방안에 대한 구조해석을 실시하였다. 또한 상부플랜지와 수직보강재 용접이음부 상세해석을 통하여 피로균열 발생위치를 확인하고 연결이음부의 적절한 보강방안을 제시하고자 한다.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.2
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• pp.113-132
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• 2005

The purpose of this study was to assess the stress-induced pattern at the supporting bone, the implant fixture, the abutment and the abutment screw according to a friction-fit joint (Astra; Model 1) or slip- fit joint (Frialit-2; Model 2) in the internal connection system under vertical and inclined loading using finite element analysis. In conclusion, in the internal connection system of the implant and the abutment connection methods, the stress-induced pattern at the supporting bone, the implant fixture, the abutment and the abutment screw according to the abutment connection form had difference among them, and the stress distribution pattern usually had a widely distributed tendency along the inner surface of the implant fixture contacting the abutment post. The magnitude of the stress distributed in the supporting bone, the implant fixture, the abutment and the abutment screw was higher in the friction-fit joint than in the slip-fit joint. But it is considered that the further study is necessary about how this difference in the magnitude of the stress have an effect on the practical clinic.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.1 no.1
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• pp.18-22
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• 2008

A ganglion cyst contains clear high viscous fluid within dense fibrous connective tissue wall communicating with joint or tendon sheath, but is not frequent around the knee joint. A hard mass at the medial side of the knee joint of the 73 years old woman, mimic to hard tumor mass was diagnosed as the ganglion using ultrasonography. Ultrasonography was a useful diagnostic tool of the cystic lesion although the consistency of the mass was hard enough to be suspected as a tumor mass.

• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.1
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• pp.55-74
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• 2006

The external contour of an implant can have significant effects on the load transfer characteristics and may result in different bone failure rates for different implant system. The purpose of this study was to investigate the effects of crest module shape and occlusal load direction on bone failure modes of five commercially available dental implant systems. Five different implant systems with internal connection; ITI (Model 1), Astra (Model 2), Bicon (Model 3), Friadent (Model 4), and Paragon (Model 5), comparable in size, but different in thread profile and cest module shapes, were compared using the finite element method. Conclusively, in the internal connection system of the implant-abutment connection methods, the stress-induced pattern at the supporting bone according to the abutment connection form had differenence among them, and implants with narrowing crestal module cross-sections at the top of the cortical bone created more favorable load transfer characteristics in this region. But it is considered that the future study is necessary about how this difference in the magnitude of the stress have an effect on the practical clinic.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.136-147
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• 2009

Statement of problem: Since the introduction of the concept of osseointegration in dental implants, high long-term success rates have been achieved. Though the use of dental implants have increased dramatically, there are few studies on domestic implants with clinical and objective long-term data. Purpose: The aim of this retrospective study was to provide long-term data on the $Implantium^{(R)}$ implant, which features a sandblasted and acid-etched surface and internal connection with microthreads. Material and methods: 106 $Implantium^{(R)}$ implants placed in 38 patients at Yonsei University Hospital were examined to determine the effect of various factors on implant success and marginal bone loss, through clinical and radiographic results during a 6 to 30 month period. Results: 1. Out of a total of 106 implants placed in 38 patients, one fixture was lost, resulting in a 99.1% cumulative survival rate. 2. Among the 96 implants which were observed throughout the study period, the survival rates were 97.0% in the maxilla and 100% in the mandible. The survival rate in the posterior regions was 98.9% and 100% in the anterior regions. 3. The mean bone loss during the first year after prosthesis placement was 0.17 mm, while the mean annual bone loss after the first year was 0.04 mm, which was statistically less than during the first year(P<.05). 4. There was no significant difference in marginal bone loss according to age during the first year(P>.05), but after the first year, the mean annual bone loss in patients above 50 years was significantly greater(P<.05) compared with patients under 50 years. 5. No significant difference in marginal bone loss was found according to the following factors: gender, jaw, location in the arch, type of implant(submerged or non-submerged), presence of bone grafts, type of prostheses, and type of opposing dentition(P<.05). Conclusion: Based on these results, the sole factor influencing marginal bone loss was age, while factors such as gender, jaw, location in the arch, type of implant, presence of bone grafts, type of prostheses and type of opposing dentition had no significant effect on bone loss. In the present study, the success rate of the $Implantium^{(R)}$ implant with a SLA surface and internal connection with microthreads was satisfactory up to a maximum 30 month period, and the marginal bone loss was in accord with the success criteria of dental implants.