• Journal of Biomedical Engineering Research
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• v.27 no.6
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• pp.402-408
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• 2006

The choice of suitable hip implant is one of important factors in the total hip arthroplasty (THA). In clinical view point, an improper adaptation of hip implant might induce abnormal stress distribution to the bone, which can shorten the lifespan of replaced hip implant. Currently, interest in the custom-designed hip implants has increased as studies reveal the significance of geometric shape of patient's femur in modeling and designing the implants. In this study, we have developed custom-designed hip implant models with various sizes, and analyzed the stress distribution in the bone and bone cement using the Finite Element Method. It was found that minimizing the gap between implant stem and femoral cavity is crucial to minimize the stress concentration in the bone.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.217-228
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• 2006

Statement of problem: Standard type of ITI solid implant model in the 6.2mm thick jaw bone was axisymmetrically modelled for finite element stress analyses. Purpose: Primary objective was to investigate the influences or the characteristic design configuration of the ITI solid implant model on the bone stress with the course of osseointegration process at the bone/implant interfaces. To simulate the characteristics of the osseointegration process, five different stages of the bone/implant interface model were implemented. As load conditions, vertical load of 50N was taken into consideration. Bone at the cervical region of implant was the areas of concern where the higher level of stress were likely to take place. Results: The results indicated that rather slightly different stress level could be obtained as a function of the osseointegration conditions. Conclusion: Under vertical load, the lower level of stress was observed at the cervical cortical bone in the initial and final stages of osseointegration. Relatively higher stress level, however, was observed during the transitional stages where the osseointegration at the cancellous bone interface were yet to fully develop.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.112-119
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• 2019

PURPOSE. Zirconia materials have been used for implant-retained restorations, but the stress distribution of zirconia is not entirely clear. The aim of this study is to evaluate the stress distribution and risky areas caused by the different design of zirconia restorations on the atrophic bone of the posterior maxilla. MATERIALS AND METHODS. An edentulous D4-type bone model was prepared from radiography of an atrophic posterior maxilla. Monolithic zirconia and zirconia-fused porcelain implant-retained restorations were designed as splinted or non-splinted. 300-N occlusal forces were applied obliquely. Stress analyses were performed using a 3D FEA program. RESULTS. According to stress analysis, the bone between the 1) molar implant and the 2) premolar in the non-splinted monolithic zirconia restoration model was stated as the riskiest area. Similarly, the maximum von Mises stress value was detected on the bone of the non-splinted monolithic zirconia models. CONCLUSION. Splinting of implant-retained restorations can be more critical for monolithic zirconia than zirconia fused to porcelain for the longevity of the bone.

• The korean journal of orthodontics
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• v.31 no.2 s.85
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• pp.173-185
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• 2001

The orthodontic osseointegrated titanium implant, a kind of intraoral skeletal anchorage can be an alternative to tooth-borne anchorage, in case that the conventional tooth-borne anchorage is not available or the anchorage is critical. This study was conducted to elucidate the effect of early loading on the osseointegration of the orthodontic titanium implant and the healing process of the impaired bone at the site of implant after removing it. In two adult beagle dogs24 osseointegrated titanium implants were inserted into the alveolar bone, with 12 implants placed in each dog. In dog1, 6 out of 12 implants were loaded with 200-300gm of force immediately after placing, and the remaining 6 implants were not loaded for 4weeks. In dog2, all 12 implants had healing period of 4weeks, and then were loaded with 200-300gm of force for another 4weeks. Following an observation period of 4 and 8 weeks, the animals were sacrificed. Then the implants and the surrounding bone of dog1 and dog2 were removed, respectively. Undecalcified sections along the long axis of implant were made and the degree of osseointegration was examined under the light microscope. The results were as follows. 1. In the histologic features of tissues around implants anchored in dog1, there was no difference between immediately loaded implants and unloaded implants. Immature woven bone was ingrowing into the thread spaces from the original compacta and in direct contact with the implant surface in part. 2. The premature loading just after 4weeks healing period did not halt the progress of the osseointegration between bone and implant surface. The woven bone around the implants was maturing into the lamellar bone which resembled the structure of the original compacta at the end of 8weeks observation period. 3. Most implants with the inflammed surrounding mucosa were lost or mobile. The mobile implants were encapsulated by fibrous connective tissue which separated the implant surface from the bone. 4. The impaired bone at the site of the implant failed to anchor was showing recovery without inflammatory reaction 2weeks after removing, with the immaure woven bone lined by active osteoblasts and osteoid. Based on the results of this study, the integration of this orthodontic implant seemed to be impaired by the inflammation of the tissue surrounding the Implant rather than by early loading on implant, and increased with time lapsed after placing the implant. The use of implant described in this report can be recommended as an orthodontic anchorage unit immediately after insertion under the careful control of orthodontic force applied and plaque.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.5
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• pp.421-432
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• 2012

This paper is the first paper among two papers which constitute the paper about the structural design of a dental implant. This paper surveyed types and characteristics of dental implants. Merits and shortcomings of clinically used dental implants were analysed through this survey. A new structural model of dental implant was proposed on the basis of survey results. Especially, a comparative structural analysis of the new dental implant and the well known dental implants has been performed using the finite element analysis method. The analysis results confirm that the newly proposed dental implant has a good structural performance. The well known dental implants used for the comparative structural analysis are 3i implant and Sargon implant. These implants are imported dental implants and we could know that most implants clinically used are endosteal implants and these two implants(3i implant and Sargon implant) are also endosteal implants.

• Journal of Periodontal and Implant Science
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• v.54 no.2
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• pp.122-135
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• 2024

Purpose: This retrospective study aimed to assess the long-term cumulative survival rate of titanium, sandblasted, large-grit, acid-etched implants over a 10-year follow-up period and investigate the factors affecting the survival rate and change in marginal bone loss (MBL). Methods: The study included 400 patients who underwent dental implant placement at the Department of Periodontology of Seoul National University Dental Hospital (SNUDH) between 2005 and 2015. Panoramic radiographic images and dental records of patients were collected and examined using Kaplan-Meier analysis, Cox proportional hazards regression analysis, and multiple regression analysis to determine the survival rates and identify any factors related to implant failure and MBL. Results: A total of 782 implants were placed with a follow-up period ranging from 0 to 16 years (mean: 8.21±3.75 years). Overall, 25 implants were lost, resulting in a cumulative survival rate of 96.8%. Comparisons of the research variables regarding cumulative survival rate mostly yielded insignificant results. The mean mesial and distal MBLs were 1.85±2.31 mm and 1.59±2.03 mm, respectively. Factors influencing these values included age, diabetes mellitus (DM), jaw location, implant diameter, bone augmentation surgery, and prosthetic unit. Conclusions: This study found that the implant survival rates at SNUDH fell within the acceptable published criteria. The patients' sex, age, DM status, implant location, implant design, implant size, surgical type, bone augmentation, and prosthetic unit had no discernible influence on long-term implant survival. Sandblasted, large-grit, acid-etched implants might offer advantages in terms of implant longevity and consistent clinical outcomes.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.4
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• pp.482-491
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• 2007

Statement of problem: The screws of dental implant, having various thread types, can be categorized into different classes by their geometrical form, and each type transmits dissimilar amount and form of stress to alveolar bone. Purpose: The purpose of this study was to find an inclination angle of the screw thread that is favorable in distributing the stresses to alveolar bone. Material and methods: In this study, We used three dimensional finite element analysis with modeling having three types of thread inclination angles and fixed pitch-0.8 mm (single thread type with $3.8^{\circ}$ inclination, double thread type with $7.7^{\circ}$ inclination, triple thread type with $11.5^{\circ}$ inclination). Results: The results obtained from this study were as follows; 1. When the number of thread increased, the amount of Von-Mises stress was reduced since the generated stress was effectively distributed. 2. Since the maximum principal stress affects on the alveolar bone can influence deeply on the longevity of the implants when comparing the magnitude of the maximum principal stress double thread had least amount of stress. This shows that the double thread screw gave best result. Conclusion: In conclusion, double, and triple thread screws were found to be more effective on distribution of the stress than the single thread screws. But, increasing in the thread inclination angle such as triple thread screw relate on the magnitude of the maximum principal stress affecting on the alveolar bone can become problematic. Thus, effective combination of thread number and thread inclination angle can help prolonging the longevity of implant.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.4
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• pp.573-592
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• 1994

A two-stage procedure is ideal for getting a successful osseointegration. But if a one-stage procedure can achieve a similar osseointegration, the one-stage procedure has several advantages. The purpose of this study was to observe the initial bone formation and bone remodeling of open type (nonsubmerged) and closed type (submerged) titanium implants. Eight ITI hollow-screws and eight Branemark fixtures were divided into two groups (submerged and nonsubmerged) and were installed on the lower jaws of four mongrel dogs. The animals were sacrificed three months later and bone sections with implants were processed for light microscopic and fluorescent microscopic observation. The results were as follows : 1 There was no significant difference in bone-to-implant contact between submerged and nonsubmerged implants. 2. Smooth surface titanium implants showed more bone-to-implant contact than that of titanium plasma coated implants histologically. 3. Under fluorescent microscopy, the active bone remodeling and new bone formation were observed in the interface zone. 4. Under fluorescent microscopy, submerged and nonsubmerged implants had no difference in bone remodeling pattern, and intramembranous bone formation was more prominent. 5. The connective tissue fibers orienting perpendicularly toward implant surface were oberved in the neck of implants.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.8 no.1
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• pp.96-103
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• 1999

Restoration of missing oral tissues by using implant therapy is one of viable options in prosthodontic treatment. The purpose of oral rehabilitation are function, esthetics and phonetics. Recently, with the increasing esthetic demand of the patient, dentists and laboratory technicians are more concern ed about natural appearance of implant prostheses. There are so many factors which affect final esthetic results of treatment such a shape, color, proportion, gingival contour etc. To provide natural and vivid looking artificial prostheses to a patient, the careful diagnosis, treatment plan and laboratory Support is crucial. Several cases will be reviewed and discussed in terms of material, gingival shape, contour, speech and connection mode etc. to fabricate natural looking implant prostheses.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.631-639
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• 2000

Root-form endosseous implants which are in use today have a variety of materials, designs and surface characteristics. Among them, pure titanium surface implants and titanium matrix coated with HA are popular as well as are available in many studies. Rate of clinical success is obviously lower in jaw with cancellous bone than dense bone. In order to increase the rate of success in poor bone quality. More advanced techniques of implant surgery and surface treatment of implant fixture body have been developed. As a successful result, the installation of HA coated implant in bone quality type III or IV became highly successful. Since most clinical studies were performed without knowing the characteristics of HA coated implants, it has been impossible to come up with proper clinical data. Therefore the characterization of HA coated implants is essential to understand long term clinical performance and the predictability of HA coated implant system Our results showed that HA coated implants had the success rate at 93.7% in bone quality type III, IV for 3.8 years, and the fixture of Steri-Oss showed more stability with time.