• Journal of Dental Rehabilitation and Applied Science
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• v.22 no.1
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• pp.75-87
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• 2006

The purpose of this study was to investigate the effects of prostheses misfit, cantilever on the stress distribution in the implant components and surrounding bone using three dimensional finite element analysis. Two standard 3-dimensional finite element models were constructed: (1) 3 ITI implant supported, 3-unit fixed partial denture and (2) 3 ITI implant supported, 3-unit fixed partial denture with a distal cantilever. variations of the standard finite element models were made by placing a $100{\mu}m$ or $200{\mu}m$ gap between the fixture, the abutment and the crown on the second premolar and first molar. Total 14 models were constructed. In each model, 244 N of vertical load and 244 N of $30^{\circ}$ oblique load were placed on the distal marginal ridge of the distal molar. von Mises stresses were recorded and compared in the crowns, abutments, crestal compact bones, and trabecular bones. The results were obtained as follows: 1. In the ITI implant system, cement-retained prostheses showed comparatively low stress distributions on all the implant components and fixtures regardless of the misfit sizes under vertical loading. The stresses were increased twice under oblique loading especially in the prostheses with cantilever, but neither showed the effects of misfit size. 2. Under the oblique loading and posterior cantilever, the stresses were highly increased in the crestal bones around ITI implants, but effects of misfit were not shown. Although higher stresses were shown on the apical portion of trabecular bones, the effects by misfit were little and the stresses were increased by the posterior cantilever. 3. When the cement loss happened in the ITI implant supported FPD with misfit, the stresses were increased in the implant componets and supporting structures.

• Advances in biomechanics and applications
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• v.1 no.2
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• pp.95-109
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• 2014

Peri-acetabular bone ingrowth plays a crucial role in long-term stability of press-fit acetabular cups. A poor bone ingrowth often results in increased cup migration, leading to aseptic loosening of the implant. The rate of peri-prosthetic bone formation is also affected by the polar gap that may be introduced during implantation. Applying a mechano-regulatory tissue differentiation algorithm on a two-dimensional plane strain microscale model, representing implant-bone interface, the objectives of the study are to gain an insight into the process of peri-prosthetic tissue differentiation and to investigate its relationship with implant-bone relative displacement and size of the polar gap. Implant-bone relative displacement was found to have a considerable influence on bone healing and peri-acetabular bone ingrowth. An increase in implant-bone relative displacement from $20{\mu}m$ to $100{\mu}m$ resulted in an increase in fibrous tissue formation from 22% to 60% and reduction in bone formation from 70% to 38% within the polar gap. The increase in fibrous tissue formation and subsequent decrease in bone formation leads to weakening of the implant-bone interface strength. In comparison, the effect of polar gap on bone healing and peri-acetabular bone ingrowth was less pronounced. Polar gap up to 5 mm was found to be progressively filled with bone under favourable implant-bone relative displacements of $20{\mu}m$ along tangential and $20{\mu}m$ along normal directions. However, the average Young's modulus of the newly formed tissue layer reduced from 2200 MPa to 1200 MPa with an increase in polar gap from 0.5 mm to 5 mm, suggesting the formation of a low strength tissue for increased polar gap. Based on this study, it may be concluded that a polar gap less than 0.5 mm seems favourable for an increase in strength of the implant-bone interface.

• Journal of Periodontal and Implant Science
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• v.39 no.sup2
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• pp.253-259
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• 2009

Purpose: This study was aimed to evaluate the effect of implant drilling speed on the composition of particle size of collected bone debris. Methods: $Br{\aa}nemark$ $System^{(R)}$ drills were used to collect bone debris from 10 drilling holes (1 unit) at 1,500 rpm (Group A) and 800 rpm (Group B) in bovine mandible. After separating particles by size into > 500 ${\mu}m$, between 250 ${\mu}m$ and 500 ${\mu}m$, and < 250 ${\mu}m$ fractions, particle wet volume, dry volume, and weight were measured and the proportion of 3 fractions of bone debris to total wet volume, dry volume and weight was calculated as wet volume % , dry volume % and weight %. Results: No significant differences were found between Group A and B in wet volume, dry volume, and weight. However, of >500 ${\mu}m$ fractions, Group B had significantly higher wet volume %(P = 0.0059) and dry volume %(P = 0.0272) than in Group A. Conclusions: The drilling speed influenced the composition of particle size in collected drilling bone debris. The drilling in 800 rpm produced the more percentage of large particles than in 1,500 rpm. However, the drilling speed didn't effect on total volume of and weight of bone debris.

• Journal of International Society for Simulation Surgery
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• v.1 no.1
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• pp.13-15
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• 2014

Nowadays, with advanced 3D printing techniques, the custom-made implant can be manufactured for the patient. Especially in skull reconstruction, it is difficult to design the implant due to complicated geometry. In large defect, an autograft is inappropriate to cover the defect due to donor morbidity. We present the process of manufacturing the 3D custom-made implant for skull reconstruction. There was one patient with skull defect repaired using custom-made 3D titanium implant in the plastic and reconstructive surgery department. The patient had defect of the left parieto-temporal area after craniectomy due to traumatic subdural hematoma. Custom-made 3D titanium implants were manufactured by Medyssey Co., Ltd. using 3D CT data, Mimics software and an EBM (Electron Beam Melting) machine. The engineer and surgeon reviewed several different designs and simulated a mock surgery on 3D skull model. During the operation, the custom-made implant was fit to the defect properly without dead space. The operative site healed without any specific complications. In skull reconstruction, autograft has been the treatment of choice. However, it is not always available and depends on the size of defect and donor morbidity. As 3D printing technique has been advanced, it is useful to manufacture custom-made implant for skull reconstruction.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.5
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• pp.617-625
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• 2003

Statement of problem : There are many studies focused on the effect of shape of futures on stress distribution in the mandibular bone. However, there are no studies focused on the effect of the abutment types on stress distribution in mandibular bone. Purpose : The purpose of this study is to investigate the effect of three different abutment types on the stress distributions in the mandibular bone due to various loads by performing finite element analysis. Material and method : Three different implant systems produced by Warantec (Seoul, Korea), were modeled to study the effect of abutment types on the stress distribution in the mandibular bone. The three implant systems are classified into oneplant (Oneplant, OP-TH-S11.5). internal implant (Inplant, IO-S11.5) and external implant (Hexplant, EH-S11.5). All abutments were made of titanium grade ELI. and all fixtures were made of titanium grade IV. The mandibular bone used in this study is constituted of compact and spongeous bone assumed to be homogeneous, isotropic and linearly elastic. A comparative study of stress distributions in the mandibular bone with three different types of abutment was conducted. Results : It was found that the types of abutments have significant influence on the stress distribution in the mandibular bone. It was due to difference in the load transfer mechanism and the size of contact area between abutment and fixture. Also the maximum effective stress in the mandibular bone was increased with the increase of inclination angle of load. Conclusion : It was concluded that the maximum effective stress in the bone by the internal implant was the lowest among the maximum effective stresses by other two types.

• Journal of the Korean institute of surface engineering
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• v.43 no.1
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• pp.17-24
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• 2010

In this study, surface characteristics of dental implant fixture with various manufacturing process have been researched using electrochemical methods. The dental implant fixture was selected with 5 steps by cleaning, surface treatment and sterilization with same size and screw structure; the 1st step-machined surface, 2nd step-cleaned by thinner and prosol solution, 3th step-surface treated by RBM (resorbable blasting media) method, 4th step-cleaned and dried, 5th step-sterilized by gamma-ray. The electrochemical behavior of dental implant fixture has been evaluated by using potentiostat (EG&G Co, 2273A) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion surface was observed using field-emission scanning electron microscopy (FE-SEM) and energy dispersive x-ray spectroscopy (EDS). The step 5 sample showed the cleaner and rougher surface than step 3 sample. The step 5 sample of implant fixture treated by RBM and gamma sterilization showed the low corrosion current density compared to others. Especially, the step 3 sample of implant fixture treated by RBM was presented the lowest value of corrosion resistance and the highest value of corrosion current density. The step 3 sample showed the low value of polarization resistance compared to other samples. In conclusion, the implant fixture treated with RBM and gamma sterilization has the higher corrosion resistance, and corrosion resistance depends on the step of manufacturing process.

• Journal of Technologic Dentistry
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• v.36 no.3
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• pp.179-184
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• 2014

Purpose: This study was performed to investigate the release behavior of bioactive materials as a BMP-2 embedding on the porous titanium implant. Methods: Porous Ti implant samples were fabricated by sintering of spherical Ti powders in a high vacuum furnace. Specimens diameter and height were 4mm and 10mm. Embedding materials were used to stamp ink. Sectional images, porosity and release behavior of porous Ti implants were evaluated by scanning electron microscope(SEM), mercury porosimeter and UV-Vis-NIR spectrophotometer. Results: Internal pore structure was formed fully open pore. Average pore size and porosity were $8.993{\mu}m$ and 8.918%. Embedding materials were released continually and slowly. Conclusion: Porous Ti implant was fabricated successfully by sintering method. Particles are necking strongly each other and others portions were vacancy. Therefore bioactive materials will be able to embedding to porous Ti implants. If the development of the fusion implant of the bioactive material will be able to have the chance to several patients.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.6
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• pp.611-624
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• 2001

A precise fit of the implant prosthesis is one of the most important factors in preventing mechanical complications. To analyze the degree of the misfit of implant prosthesis, a modal testing experiment was accomplished. And. to interpret the modal testing analysis mathematically, three-dimensional finite element models were established. In the experimental modal testing analysis, with a laser displacement meter, FFT analyzer, impact hammer, etc., natural frequencies of the models with various degree of prosthesis fit were determined after the frequency response function were calculated. In the finite element analysis, the natural frequencies and mode shapes of the models which simulated those of experimental modal testing were computed. The results were as follows: 1. Natural frequencies of the prosthesis-abutment were related to the contact state between components. 2. In the modal testing experiment, the natural frequencies increased from $50{\mu}m$ to $200{\mu}m$ gap and reached a plateau. 3. In the finite element analysis, the natural frequencies decreased gradually according to the in crease of the gap size. 4. In the finite element analysis, the mode shapes of model 1 with misfitting prosthesis showed different patterns from those without misfitting prosthesis. 5. The devices including a laser displacement meter used in this study were useful for measuring the natural frequencies of an implant prosthesis which had various degrees of fit.

• 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 the Korea institute of electronic communication sciences
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• v.9 no.11
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• pp.1227-1232
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• 2014

This paper relates 10% shrink from $0.13{\mu}m$ design for core devices as well as input and output (I/O) devices different from previous poly length shrink size only. We analyzed body effect with different channel length and doping profile simulation. After fixing the gate oxide module process, LDD implant conditions were optimized such as decoupled plasma nitridation of gate oxide, TEOS oxide $100{\AA}$ before LDD implant and 22o tilt-angle(45o twist-angle) LDD implant respectively to match the spice DC parameters of pre-shrink and finally matched them within 5%.