• Maxillofacial Plastic and Reconstructive Surgery
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• v.40
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• pp.2.1-2.7
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• 2018

With the development of computer-aided design/computer-aided manufacturing (CAD/CAM) technology, it has been possible to reconstruct the cranio-maxillofacial defect with more accurate preoperative planning, precise patient-specific implants (PSIs), and shorter operation times. The manufacturing processes include subtractive manufacturing and additive manufacturing and should be selected in consideration of the material type, available technology, post-processing, accuracy, lead time, properties, and surface quality. Materials such as titanium, polyethylene, polyetheretherketone (PEEK), hydroxyapatite (HA), poly-DL-lactic acid (PDLLA), polylactide-co-glycolide acid (PLGA), and calcium phosphate are used. Design methods for the reconstruction of cranio-maxillofacial defects include the use of a pre-operative model printed with pre-operative data, printing a cutting guide or template after virtual surgery, a model after virtual surgery printed with reconstructed data using a mirror image, and manufacturing PSIs by directly obtaining PSI data after reconstruction using a mirror image. By selecting the appropriate design method, manufacturing process, and implant material according to the case, it is possible to obtain a more accurate surgical procedure, reduced operation time, the prevention of various complications that can occur using the traditional method, and predictive results compared to the traditional method.

• The Journal of the Korean dental association
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• v.53 no.5
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• pp.307-317
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• 2015

Although the long-term success of osseointegrated endosseous implants for the support of fixed dental prostheses has been reported, the increasingly widespread use of implant-supported prostheses has led to problems associated with their structural integrity. The most common biomechanical complications observed in dental implant treatment are fracture and screw loosening. The nature of loosening or fracture of dental implant components is complex, since it involves fatigue, fitness, and varied chewing patterns and loads. To assess the service life of the components of the prosthetic system, a knowledge of the loads transmitted through the system is necessary. Design of the final restoration and occlusion in relation to the geometry of a prosthetic restoration has a great influence on the mechanical loading of the implant. It is proposed that control of force in oral cavity may play a larger role in failures than previously believed. Based on theoretic consideration and clinical experiences with dental implant, this article gives simple guidelines for controlling these loads.

• The Journal of Advanced Prosthodontics
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• v.9 no.3
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• pp.143-151
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• 2017

PURPOSE. The design of the attachment must provide an optimum stress distribution around the implant. In this study, for implant overdentures with a bar/clip attachment or a locator attachment, the stress transmitted to the implant in accordance with the change in the denture base length and the vertical pressure was measured and analyzed. MATERIALS AND METHODS. Test model was created with epoxy resin. The strain gauges made a tight contact with implant surfaces. A universal testing machine was used to exert a vertical pressure on the mandibular implant overdenture and the strain rate of the implants was measured. RESULTS. Means and standard deviations of the maximum micro-deformation rates were determined. 1) Locator attachment: The implants on the working side generally showed higher strain than those on the non-working side. Tensile force was observed on the mesial surface of the implant on the working side, and the compressive force was applied to the buccal surface and on the surfaces of the implant on the non-working side. 2) Bar/clip attachment: The implants on the both non-working and working sides showed high strain; all surfaces except the mesial surface of the implant on the non-working side showed a compressive force. CONCLUSION. To minimize the strain on implants in mandibular implant overdentures, the attachment of the implant should be carefully selected and the denture base should be extended as much as possible.

• The Journal of Advanced Prosthodontics
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• v.9 no.1
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• pp.31-37
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• 2017

PURPOSE. The purpose of this study was to analyze the influence of the platform switching concept on an implant system and peri-implant bone using three-dimensional finite element analysis. MATERIALS AND METHODS. Two three-dimensional finite element models for wide platform and platform switching were created. In the wide platform model, a wide platform abutment was connected to a wide platform implant. In the platform switching model, the wide platform abutment of the wide platform model was replaced by a regular platform abutment. A contact condition was set between the implant components. A vertical load of 300 N was applied to the crown. The maximum von Mises stress values and displacements of the two models were compared to analyze the biomechanical behavior of the models. RESULTS. In the two models, the stress was mainly concentrated at the bottom of the abutment and the top surface of the implant in both models. However, the von Mises stress values were much higher in the platform switching model in most of the components, except for the bone. The highest von Mises values and stress distribution pattern of the bone were similar in the two models. The components of the platform switching model showed greater displacement than those of the wide platform model. CONCLUSION. Due to the stress concentration generated in the implant and the prosthodontic components of the platform switched implant, the mechanical complications might occur when platform switching concept is used.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.4
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• pp.582-610
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• 1992

The long-term success of any dental implant is dependent upon the optimization of stresses which occur during oral function and parafunction. Especially, it has been suggested that there is an unique set of problems associated with joining an osseointegrated implant and a natural tooth with a fixed partial denture. For this particular case, although many literatures suggest different ways to avoid high stress concentrations on the bone surrounding the implant under static and dynamic loading conditions, but few studies on the biomechanical efficacy of each assertion have been reported. The purpose of this investigation was to evaluate the efficacies of clinically suggested methods on stress distribution under static load and shock absorption under dynamic load, using two dimensional finite element method. In FEM models of osseointegrated implant-natural tooth supported fixed partial dentures, calculations were made on the stresses in surrounding bone and on the deflections of abutments and superstructure, first, to compare the difference in stress distribution effects under static load by the flexure of fastening screw or prosthesis, or intramobile connector, and second, to compare the difference in the shock absorption effects under dynamic load by intramobile connector or occlusal veneering with composite resin. The results of this analysis suggest that : 1. Under static load condition, using an implant design with fastenign screw connecting implant abutment and prosthesis or increasing the flexibility of fastening screw, or increasing the flexibility of prosthesis led to the .increase in height of peak stresses in cortical bone surrounding the implant, and has little effect on stress change in bone around the natural tooth. 2. Under static load condition, intramobile connector caused the substantial decrease in stress concentration in cortical bone surrounding the implant and the slight increase in stress in bone around the natural tooth. 3. Under dynamic load condition, both intramobile connector and composite resin veneering showed shock absorption effect on bone surrounding the implant and composite resin veneering had a greater shock absorption effect than intramobile connector.

• 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.62 no.2
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• pp.131-139
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• 2024

In a edentulous patient, various methods can be employed for prosthetic treatment using implants, such as implant-supported fixed prostheses, overdentures, hybrid prostheses, and implant assisted removable partial denture. In this case, in a patient with moderate to severe chronic periodontitis requiring full arch extractions, implants were strategically placed using computer-guided surgery. In the maxilla, due to inadequate bone quality and quantity leading to insufficient initial stability, delayed loading was implemented, and interim prosthesis was used during the osseointegration period. In the mandible, stable initial stability was achieved, allowing for immediate loading to reduce patient discomfort. Primary stability is considered the most crucial factor for obtaining immediate loading, so a thorough clinical and radiological evaluation of the remaining alveolar bone quantity and quality must be conducted before surgery.

• The Journal of the Korean dental association
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• v.56 no.11
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• pp.616-621
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• 2018

This clinical case highlights the failure of long length implants, and the prosthodontic procedures necessary to rehabilitate the maxillary dentition of a patient with microstomia. The integrated digital technology of intra-oral scanning, computer-aided design, and three-dimensional printing can provide an alternative method to make conventional impressions for patients with microstomia who cannot insert the appropriate tray in their mouths.

• 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 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.