• The Journal of Korean Academy of Prosthodontics
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• v.56 no.2
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• pp.105-113
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• 2018

Purpose: The purpose of this study was to investigate the effects of the insertion depth of an immediately loaded implant on the stress distribution of the surrounding bone and the micromovement of the implant using the three-dimensional finite element analysis. Materials and methods: A total of five bone models were constructed such that the implant platform was positioned at the levels of 0.00 mm, 0.25 mm, 0.50 mm, 0.75 mm, and 1.00 mm depth from the crest of the cortical bone. A frictional coefficient of 0.3 and the insertion torque of 35 Ncm were simulated on the interface between the implant and surrounding bone. A static load of 178 N was applied to the provisional prosthesis with a vertical load in the axial direction and an oblique load at $30^{\circ}$ with respect to the central axis of the implant, then a finite element analysis was performed. Results: The implant insertion depth significantly affected the stress distribution on the surrounding bone. The largest micromovement value of the implant was $39.34{\mu}m$. The oblique load contributed significantly to the stress distribution and micromovement in comparison to the vertical load. Conclusion: Increasing the implant insertion depth was advantageous in dispersing the concentrated stress in the cortical bone and did not significantly affect the micromovement associated with early osseointegration failure.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.271-279
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• 2019

There are several unfavorable conditions regarding alveolar bone condition that may compromise the denture patient's satisfaction. Chewing efficiency may not be satisfactory when alveolar bone is deficient, and the denture stability could hardly be achieved when alveolar bone shape is irregular. Implant overdenture can be useful to provide satisfactory denture experience compared to conventional denture. The attachment for implant overdenture can be classified into bar attachment and solitary attachment. When the positions of the implants are in the mandibular anterior region, bar attachment may be favorable to obtain a rigid support of the entire denture. When implants are distributed both on anterior and posterior region, a solitary attachment could be considered for ease of removal and maintenance. This report presents implant overdenture cases with the patients that had unilateral mandibular alveolar bone atrophy conditions. Different abutments were chosen based on the individual patient's mandibular alveolar bone condition and the treatments were successful in terms of patient satisfaction.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.224-235
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• 2013

A passively fitting prosthesis is an essential prerequisite to attain long-lasting success and maintenance of osseointegration. However, true "passive fit" can not be achieved with the present implant-supported prosthesis fabrication protocol. Many clinical situations are suitably treated with cantilevered implant-supported fixed restorations. The purpose of this study was to compare the stress distribution pattern and magnitude in supporting tissues around ITI implants with cantilevered, implant-supported, screw-retained fixed prosthesis according to the fitness of superstructures. Photoelastic model was made with PL-2 resin (Measurements, Raleigh, USA) and three ITI implants (${\phi}4.1{\times}10mm$) were placed in the mandibular posterior edentulous area distal to the canine. Anterior and posterior extended 4-unit cantilevered FPDs were made with different misfit in the superstructures. 4 types of prosthesis were made by placing a $100{\mu}m$ gap between the abutment and the crown on the second premolar and/or the first molar. Photoelastic stress analysis were carried out to measure the fringe order around the implant supporting structure under simulated loading conditions (30 lb).

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.4
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• pp.365-375
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• 2009

Statement of problems: Stress analysis on implant components of the combined screw- and cement-retained implant prosthesis has not investigated yet. Purpose: The purpose of this study was to assess the load distribution characteristics of implant prostheses with the different prosthodontic retention types, such as cement-type, screw-type and combined type by using 3-dimensional finite element analysis. Material and methods: A 3-dimensional finite element model was created in which two SS II implants (Osstem Co. Ltd.) were placed in the areas of the first premolar and the first molar in the mandible, and three-unit fixed partial dentures with four different retention types were fabricated on the two SS II implants. Model 1 was a cement-retained implant restoration made on two cement-retained type abutments (Comocta abutment; Osstem Co. Ltd.), and Model 2 was a screw-retained implant restoration made on the screw-retained type abutments (Octa abutment; Osstem Co. Ltd.). Model 3 was a combined type implant restoration made on the cement-retained type abutment (Comocta abutment) for the first molar and the screw-retained type abutment (Octa abutment) for the first premolar. Lastly, Model 4 was a combined type implant restoration made on the screw-retained type abutment (Octa abutment) for the first molar and the cement-retained type abutment (Comocta abutment) for the first premolar. Average masticatory force was applied on the central fossa in a vertical direction, and on the buccal cusp in a vertical and oblique direction for each model. Von-Mises stress patterns on alveolar bone, implant body, abutment, abutment screw, and prosthetic screw around implant prostheses were evaluated through 3-dimensional finite element analysis. Results: Model 2 showed the lowest von Mises stress. In all models, the von Mises stress distribution of cortical bone, cancellous bone and implant body showed the similar pattern. Regardless of loading conditions and type of abutment system, the stress of bone was concentrated on the cortical bone. The von-Mises stress on abutment, abutment screw, and prosthetic screw showed the lower values for the screw-retained type abutment than for the cement-retained type abutment regardless of the model type. There was little reciprocal effect of the abutment system between the molar and the premolar position. For all models, buccal cusp oblique loading caused the largest stress, followed by buccal cusp vertical loading and center vertical loading. Conclusion: Within the limitation of the FEA study, the combined type implant prosthesis did not demonstrate more stress around implant components than the cement type implant prosthesis. Under the assumption of ideal passive fit, the screw-type implant prosthesis showed the east stress around implant components.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.4
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• pp.412-419
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• 2022

For treatment of partially edentulous patients, a treatment using implant is widely used. Treatment method using implant are implant fixed prostheses and removable partial dentures, and for patients with severe bone resorption, removable implant overdenture with the effects of aesthetic and reducing cost can be used as treatment options. Specially, prosthesis with milled-bar and attachment has the effect of being splinted between implant fixtures, higher retention and stability than conventional removable partial denture. And it has the effect of improvement of aesthetic through lip support by denture base. In this case, the patient with severe alveolar bone resorption and partial edentulous maxilla and mandible was treated by implant-assisted removable partial denture using Milled-bar and ADD-TOC attachment. The esthetic was improved by removing the clasp because of effects of additional retention by using the attachment, and reducing palatal coverage of implant-assisted removable partial denture. The clinical results were satisfactory on the aspect of aesthetic and masticatory function.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.10a
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• pp.15-15
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• 2003

치과재료에 사용되는 금속재료는 주로 스테인리스강, 타이타늄, Ni-Ti, Co-Cr등과 같은 특수합금이 주로 사용되고 있다. 이들 재료는 치과 보철물과 교정재료 및 충전재료로 주로 사용되고 있으며 그 외 치과에서 사용되는 기기나 기구에도 많이 활용되고 있다. 특히 치과 보철물을 사용하여 치료를 원하는 환자가 최근에 급격히 증가하면서 임플란트 고정체와 나사 등을 이용한 치료법의 연구와 개발이 필요하게 되어 세계적으로 연구와 투자가 활발히 진행되고 있다. 그러나 재료의 설계나 합금의 설계 및 제품의 설계상의 문제로 인하여 생체조직과 결합하는데 많은 문제점이 임상적으로 발생되고 있다. 즉 임플란트 표면의 생체적합성부여, 고정체와의 결합시 파절이나 풀림현상, 골에 고정체로 사용하는 나사의 강도와 내마모성문제 등이 개선되어야 할 문제점으로 남아있다. 또한 총의치에 사용되는 자석 어태치먼트의erosion-corrosion문제, 교정선의 탄성 과 마모저항문제 등은 앞으로 계속적인 연구를 행하여야할 과제로 남아있다. 또한 국소의치에서 사용되는 frame은 정밀주조법을 통하여 제조하며 주조상의 결함 등으로 인한 클라스프의 파절 문제점이 발생되고 있다. 따라서 본 연구에서는 치과재료로 사용되는 임플란트 고정체, 나사, 교정용 선등의 문제점을 고찰하고, 지금까지 이루어진 연구를 중심으로 최적의 개선 조건을 찾고자하였다. 최근첨단소재 및 금속재료를 사용하여 치과재료 합금을 설계할 수 있는 연구가 활발히 진행된다면 수입에 의존하고 있는 고가의 치과재료를 값이 싼 고성능의 제품으로 대체할 수 있는 효과가 클 것으로 생각된다.>$\rho$$\sub$0/=1.8 %. As t$\sub$Co/ increases, a transition from the regime of co-existence of superparamagnetic and ferromagnetic behaviors to ferromagnetic behavior was observed. Tunneling barrier called "decay length for tunneling" for the films having the thickness of Co layer from 1.4 to 1.6 nm was measured to be ranged from 0.004 to 0.021 ${\AA}$$\^$-1/.문에 기업간 관계를 연구하는 측면에서는 탐험적 연구성격이 강하다. 더 나아가 본 산업의 주된 연구가 질적이고 기업내부만을 연구했던 것에 비교하면 시초적이라고 할 수 있다. 또한 관계마케팅, CRM 등의 이론적 배경이 되고 있는 신뢰와 결속의 중요성이 재확인하는 결과도 의의라고 할 수 있다. 그리고 신뢰는 양사 간의 상호관계에서 조성될 수 있는 특성을 가진 반면, 결속은 계약관계 초기단계에서 성문화하고 규정화 할 수 있는 변수의 성격이 강하다고 할 수가 있다. 본 연구는 복잡한 기업간 관계를 지나치게 협력적 측면에서만 규명했기 때문에 많은 측면을 간과할 가능성이 있다. 또한 방법론적으로 일방향의 시각만을 고려했고, 횡단적 조사를 통하고 국내의 한 서비스제공업체와 관련이 있는 컨텐츠 공급파트너

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.1
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• pp.127-134
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• 2022

Among many contributing factors of implant failure, excessive loading and inflammation contribute mainly to increasing implant failure rate. Especially, poor oral hygiene around implants is one of the most common reasons for implant failure. When implant prosthesis fails to function, the clinician should re-diagnose and plan treatment using the remaining implants. Additional implantation may be needed to make a new type of prosthesis or either implant-assisted RPD and implant overdenture treatment may be performed using the remaining implants. In this article, a patient whose fixed implant prosthesis in the maxilla had failed of poor oral hygiene maintenance was reported to be recovered with removable implant overdenture by using remaining implant abutments and a milled bar with additional retentive elements. Through this treatment, the clinical results were satisfactory in terms of esthetics, masticatory function recovery and oral hygiene management.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.1
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• pp.36-43
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• 2012

Purpose: To analyze the stress distribution of the implant and its supporting structures through 3D finite elements analysis for implants with different hexagon heights and to make the assessment of the mechanical stability and the effect of the elements. Materials and methods: Infinite elements modeling with CAD data was designed. The modeling was done as follows; an external connection type ${\phi}4.0mm{\times}11.5mm$ Osstem$^{(R)}$ USII (Osstem Co., Pusan, Korea) implant system was used, the implant was planted in the mandibular first molar region with appropriate prosthetic restoration, the hexagon (implant fixture's external connection) height of 0.0, 0.7, 1.2, and 1.5 mm were applied. ABAQUS 6.4 (ABAQUS, Inc., Providence, USA) was used to calculate the stress value. The force distribution via color distribution on each experimental group's implant fixture and titanium screw was studied based on the equivalent stress (von Mises stress). The maximum stress level of each element (crown, implant screw, implant fixture, cortical bone and cancellous bone) was compared. Results: The hexagonal height of the implant with external connection had an influence on the stress distribution of the fixture, screw and upper prosthesis and the surrounding supporting bone. As the hexagon height increased, the stress was well distributed and there was a decrease in the maximum stress value. If the height of the hexagon reached over 1.2mm, there was no significant influence on the stress distribution. Conclusion: For implants with external connections, a hexagon is vital for stress distribution. As the height of the hexagon increased, the more effective stress distribution was observed.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.3
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• pp.209-214
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• 2010

Purpose: The purpose of this study was to investigate whether the re-osseointegration of the implants that had mechanical unscrewing possibly occurred or not. Furthermore, if it happened, the degree of re-osseointegration was evaluated by comparing with previous osseointegration. Materials and methods: The smooth implant (commercial pure titanium 99%) specimens, whose diameter and length was 3.75 mm, 4 mm, respectively were produced. Two implants were inserted into each tibia of 7 New Zealand female white rabbits weighing at least 3.0 kg. The torque removal force for each implant after 6 weeks of implants placement was measured and included in group I. The torque removal forces were assessed after the fixtures were re-screwed to original position and the subjects were allowed to have 4 more weeks for healing and included in group II. One rabbit was sacrificed after first measurement and produced 4 slide specimens in group I, and two rabbits were sacrificed after 2nd measurement, 7 slide specimens, in group II for histomorphologic investigations. All slide specimens were assessed based on the proportion of BIC (bone-implant contact) as well as CBa (Bone area in the cortical passage) value produced by counting the screw threads embedded in the compact bones under the optical microscopic analysis (${\times}20$). Statistical analysis was conducted to evaluate the torque removal force, BIC and CBa between group I and II. Results: As for the torque removal force, the result was $10.8{\pm}3.6$ Ncm for group I and $20.2{\pm}9.7$ Ncm for group II. Furthermore, the torque removal force of group II increased by 98.1% in average compared to group I (P<.05). On the other hand, histomorphologic analysis displayed that there was no statistical significance in BIC and CBa values between group I and the group II (P>.05), and RT/BIC and RT/CBa between group I and group II were statistically significant (P<.05). Conclusion: It is possible to obtain more substantial re-osseointegration within shorter periods than the period needed for the initial osseointegration in case of iatrogenically unscrewed implants.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.214-220
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• 2013

Implant prosthodontics is beneficial for edentulous patients in enhancing the support, retention, stability, phonation and so on. Various types of prosthesis supported by implant, including implant retained- or supported- overdenture for the removable type and ceramo-metal and fixed prostheses with processed acrylic teeth for the fixed type, are frequently used. Treatment planning for the prosthesis with implant must be made after considering individual characteristics such as form of residual ridge, soft tissue, interocclusal relationship, economic status. Fixed prosthesis with processed acrylic teeth (also known as 'implant hybrid prosthesis' or 'bone anchored bridge') has the advantages of both removable and fixed prosthesis such as proper soft tissue profile, esthetic outcome, increased masticatory efficiency and psychological stability. The 73-years-old female patient came to the department of prosthodontics, Dental hospital of Yonsei University. She was diagnosed with Kennedy class I partial edentulism in the maxilla and complete edentulism in the mandible. This article reports a satisfactory clinical and esthetic outcome of full mouth rehabilitation using removable partial denture in the maxilla and implant hybrid prosthesis in the mandible.