• 대한치과보철학회지
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• 제41권4호
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• pp.393-404
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• 2003

Statement of problem. Higher incidence of prosthetic complications such as screw loosening, screw fracture has been reported for posterior single tooth implant. So, there is ongoing research regarding stability of implant-abutment interface. One of those research is increasing the implant diameter and prosthetic table width to improve joint stability. In another part of this research, internal conical type implant-abutment interface was developed and reported joint strength is higher than traditional external hex interface. Purpose. The purpose of this study is to compare stress distribution in single molar implant between external hex butt joint implant and internal conical joint implant when increasing the implant diameter and prosthetic table width : 4mm diameter, 5mm diameter, 5mm diameter/6mm prosthetic table width. Material and method. Non-linear finite element models were created and the 3-dimensional finite element analysis was performed to see the distribution of stress when 300N static loading was applied to model at $0^{\circ},\;15^{\circ},\;30^{\circ}$ off-axis angle. Results. The following results were obtained : 1. Internal conical joint showed lower tensile stress value than that of external hex butt joint. 2. When off-axis loading was applied, internal conical joint showed more effective stress distribution than external hex butt joint. 3. External hex butt joint showed lower tensile stress value when the implant diameter was increased. 4. Internal conical joint showed lower tensile stress value than external hex butt joint when the implant diameter was increased. 5. Both of these joint mechanism showed lower tensile stress value when the prosthetic table width was increased. Conclusion. Internal conical joint showed more effective stress distribution than external hex joint. Increasing implant diameter showed more effective stress distribution than increasing prosthetic table width.

• 대한치과보철학회지
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• 제42권2호
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• pp.226-237
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• 2004

Purpose: Four finite element models were constructed in the mandible having a single implant fixture connected to the first premolar-shaped superstructure, in order to evaluate how the shape of the fixture and the implant-abutment connection would influence the stress level of the supporting tissues fixtures, and prosthethic components. Material and methods : The superstructures were constructed using UCLA type abutment, ADA type III gold alloy was used to fabricate a crown and then connected to the fixture with an abutment screw. The models BRA, END , FRI, ITI were constructed from the mandible implanted with Branemark, Endopore, Frialit-2, I.T.I. systems respectively. In each model, 150 N of vertical load was placed on the central pit of an occlusal plane and 150 N of $40^{\circ}$ oblique load was placed on the buccal cusp. The displacement and stress distribution in the supporting tissues and the other components were analysed using a 2-dimensional finite element analysis . The maximum stress in each reference area was compared. Results : 1. Under $40^{\circ}$ oblique loading, the maximum stress was larger in the implant, superstructure and supporting tissue, compared to the stress pattern under vertical loading. 2. In the implant, prosthesis and supporting tissue, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 3. In the superstructure and implant/abutment interface, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 4. In the implant fixture, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 5 The stress was more evenly distributed in the bone/implant interface through the FRI of trapezoidal step design. Especially Under $40^{\circ}$ oblique loading, The maximum stress was smallest in the bone/implant interface. 6. In the implant and superstructure and supporting tissue, the maximum stress occured at the crown loading point through the ITI. Conclusion: The stress distribution of the supporting tissue was affected by shape of a fixture and implant-abutment connection. The magnitude of maximum stress was reduced with the internal connection type (FRI) and the morse taper type (ITI) in the implant, prosthesis and supporting tissue. Trapezoidal step design of FRI showed evenly distributed the stress at the bone/implant interface.

• 대한치과보철학회지
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• 제32권2호
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• pp.327-353
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• 1994

This study was performed to evaluate the effects of number and alignment of implant fixture and various bar designs on the retention of denture and the stress distribution. Six kinds of photoelastic mandibular models and nine kinds of overdenture specimens were designed. A unilateral vertical load was gradually applied on the right first molar to calculate the maximal dislodgement load of each specimen. A unilateral vertical load of 17 Kgf was applied on the right first molar and a vertical load of 10 Kgf was applied on the interincisal edge region. The stress pattern which developed in each photoelastic model was analyzed by the reflection polariscope. The results obtained were as follows: 1. The maximal dislodgement load reversely increased with the distance from the loading point to the implant fixture, while it linearly increased with that from the most posterior implant fixture to the mesial clip. The maximal dislodgement load also increased with the use of a cantilever bar. 2. Under the posterior vertical load, the stress to the supporting tissue of the denture base increased with the distance from the loading point to the implant future. The stress concentration on the apical area of the implant future reversely increased with the distance from the loading point to the implant future. 3. In the overdentures supported by two implant fixtures under the posterior vertical load. the specimen implanted on lateral incisor areas with a cantilever bar exhibited more favorable stress distribution than that without a cantilever bar. The specimen implanted on the canine areas without a cantilever bar, however, exhibited more favorable stress distribution. 4. In the overdentures supported by three implant fixtures. the specimen implanted ell the midline and canine areas exhibited more favorable stress distribution than that implanted oil the midline and the first premolar areas. 5. In the overdentures supported by four implant fixtures. the specimen implanted with two adjacent implant fixtures exhibited more favorable stress distribution than that implanted at equal distance under the posterior vertical load. 6. Under the anterior vertical load, the overdentures supported by three implant fixtures exhibited stress concentration on the supporting structure of the middle implant future. In overdentures supported by two or four implant futures, no significant difference was noted in stress distribution between the types of bars. These results indicate that the greater the number of implant fixtures, the better the stress distribution is. A favorable stress distribution may be obtained in the overdentures supported by two or three implant fixtures, if the location and the design of the bar are appropriate.

• 대한치과보철학회지
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• 제43권4호
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• pp.511-518
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• 2005

Purpose: The purpose of this study is to find the effect of rare earth magnet's magnetic field of to the osteoblast around the implant by the means of observation number, and distribution around the implant which is connected to the permanent magnet but not, counted and compared by the number of cells attached to the surface of the implant. Material and method: The permanent magnets, made in the healing cap form, were connected to the implant future, and placed on the culture plate, The osteoblast-like cell: MC3T3-E1 were used for cell culture. As the control group, the implant were connected to normal healing cap, and cultured in the same conditions. 48 hours later, using inverted microscope, the number and distribution of osteoblast around the implant were observed, and 72 hours later, the number of the cells attached to the implant were counted. Results: As a result, the implant connected to the permanent magnet had proved to have a more concentrated cell distribution rate than the control group. The implant connected to the permanent magnet, neck area : which has about 10 gauss magnetic force, had more cells than apex area. The implant connected to the permanent magnet had proven to attach to the osteoblast more productively than control group's implant. Conclusions: This research showed that the magnetic field of the permanent magnet affected the distribution and growth rate of the osteoblast around the implant. In order to support this study, it also had need to monitor the progress of the permanent magnet specifically shown on the neck area, which has10 gauss magnetic force. So after additional research on the distribution and attachment of the cells, and further more, on bone formation, it will be concluded that the clinical applications ,such as immediate loading of implant treatment are possible.

• 대한치과보철학회지
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• 제43권1호
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• pp.61-77
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• 2005

Statement of problem. The implant prosthesis has been utilized in various clinical cases thanks to its increase in scientific effective application. The relevant implant therapy should have the high success rate in osseointegration, and the implant prosthesis should last for a long period of time without failure. Resorption of the peri-implant alveolar bone is the most frequent and serious problem in implant prosthesis. Excessive concentration of stress from the occlusal force and biopressure around the implant has been known to be the main cause of the bone destruction. Therefore, to decide the location and angulation of the implant is one of the major considering factors for the stress around the implant fixture to be dispersed in the limit of bio-capacity of load support for the successful and long-lasting clinical result. Yet, the detailed mechanism of this phenomenon is not well understood. To some extent, this is related to the paucity of basic science research. Purpose. The purpose of this study is to perform the stress analysis of the implant prosthesis in the partially edentulous mandible according to the different nature locations and angulations using three dimensional finite element method. Material and methods, Three 3.75mm standard implants were placed in the area of first and second bicuspids, and first molar in the mandible Thereafter, implant prostheses were fabricated using UCLA abutments. Five experimental groups were designed as follows : 1) straight placement of three implants, 2) 5$^{\circ}$ buccal and lingual angulation of straightly aligned three implants, 3) 10$^{\circ}$ buccal and lingual angulation of straightly aligned three implants. 4) lingual offset placement of three implants, and 5) buccal offset placement of three implants. Average occlusal force with a variation of perpendicular and 30$^{\circ}$ angulation was applied on the buccal cusp of each implant prosthesis, followed by the measurement of alteration and amount of stress on each configurational implant part and peri-implant bio-structures. The results of this study are extracted from the comparison between the distribution of Von mises stress and the maximum Von mises stress using three dimensional finite element stress analysis for each experimental group. Conclusion. The conclusions were as follows : 1. Providing angulations of the fixture did not help in stress dispersion in the restoration of partially edentulous mandible. 2. It is beneficial to place the fixture in a straight vertical direction, since bio-pressure in the peri-implant bone increases when the fixture is implanted in an angle. 3. It is important to select an appropriate prosthodontic material that prevents fractures, since the bio-pressure is concentrated on the prosthodontic structures when the fixture is implanted in an angle. 4. Offset placement of the fixtures is effective in stress dispersion in the restoration of partially edentulous mandible.

• 대한치과보철학회지
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• 제44권3호
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• pp.325-332
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• 2006

Statement of problem. Primary implant stability has long been identified as a prerequisite to achieve osseointegration. So the application of a simple, clinically applicable noninvasive test to assess implant stability and osseiointegratation are considered highly desirable. Purpose. The purpose of this study was to evaluate the ISQ value and the insertion torque of the 3 different implant system, then to evaluate whether there was a correlation between ISQ value and insertion torque; and to determine whether implant design has an influence on either insertion torque or ISQ value. Material and method. The experiment was composed of 3 groups: depending on the implant fixture design. Group1 was Branemark type parallel implant in $3.75{\times}7mm$. Group2 was Oneplant type straight implant in $4.3{\times}8.5mm$. Group3 was Oneplant type tapered implant in $4.3{\times}8.5mm$. Depending on the density of the bone, 2 types of bone were used in this experiment. Type I bone represented for cortical bone, type II bone represented for cancellous bone. With the insertion of the implant in type I and type II bone, the insertion torque was measured, then the ISQ value was evaluated, and then the correlation between insertion torque and ISQ value was analyzed Result and conclusion. Within the limitations of this study, the following conclusions were drawn. 1. Within the 3 different implants, the insertion torque value and ISQ value were higher in type I bone, when compared with type II bone.(p<0.05) 2. In type I and type II bone, Oneplant type tapered implant has the highest value in insertion torque.(p<0.05) 3. In type I and type II bone, there was no difference in ISQ values among the 3 types of implant. (p>0.05) 4. Significant linear correlation was found in $Br{\aa}nemark$ type parallel implant: $3.75{\times}7mm$ in type II bone.

• 대한치과보철학회지
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• 제45권2호
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• pp.274-282
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• 2007

Statement of problem: Main consideration was given to the stresses at the site of implant entry into the cortical bone at the alveolar crest. As a suspectible factor affecting the occurrence of stress concentrations, the contact angle between the implant and the alveolar crest bone was addressed. Purpose: The purpose of this study is to evaluate angles between the alveolar crest bone and the implant effect on the implant crestal area induced stresses using a finite element method. Material and methods: Cylindrically shaped, standard size ITI implants entering into alveolar crest with four different contact angles of 0, 15, 30, and 45 deg. with the long axis of the implant were axisymmetrically modelled. Alterations of stresses around the implants were computed and compared at the cervical cortical bone. Results and conclusion: The results demonstrated that regardless of the difference of the implant/alveolar crest bone contact angles, stress concentration occurred at the cervical bone and the angle differences led to insignificant variations in stress level.

• 구강회복응용과학지
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• 제20권1호
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• pp.57-70
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• 2004

The significance of occlusion has regained its popularity in dentistry with the introduction of implant therapy. Literature has reported that the clinical success and longevity of dental implants can be achieved by biomechanically controlled occlusion. Occlusal overload is known to be one of the main causes for implant failure. Evidences have suggested that occlusal overload contribute to early implant bone loss as well as deosseointegration of successfully integrated implants. Unlike natural teeth, osseointegrated implants are ankylosed to surrounding bone without the periodontal ligament (PDL) which provides mechanoreceptors as well as shock-absorbing function. Moreover, the crestal bone around dental implants may act as a fulcrum point for lever action when a force (bending moment) is applied, indicating that implants/implant prosthesis could be more susceptible to crestal bone loss by applying force. Hence, it is essential for clinicians to understand inherent differences between teeth and implants and how force, either normal or excessive force, may influence on implants under occlusal loading. The purposes of this paper are to review the importance of implant occlusion, to establish the optimum implant occlusion with biomechanical rationale, to provide clinical guidelines of implant occlusion and to discuss how to manage complications related to implant occlusion.

• 품질경영학회지
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• 제36권2호
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• pp.59-66
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• 2008

Dental implant has recently become one of the most viable treatment options for regaining the oral function and dental aesthetics compared with conventional fixed or removable dentures. Dental implants vary in material, dimensions, geometries, surface properties, and interface geometries. It has been reported that there has been a proliferation of manufacturers who produce implants using various materials and surface treatments, and the dentist needs to select from over 2,000 different dental implants and abutments in a specific treatment situation. Unfortunately, however, no metrics have been specifically identified for the purpose of quality assessment and selection of an appropriate dental implant. This study aims to provide practical guidelines for quality assessment of dental implant based on clinical data. Like other medical devices and materials, the superiority related to specific characteristics of the dental implant needs to be verified through extensive clinical studies. The procedures of clinical monitoring for dental implants have been proposed along with a case study to exemplify the usefulness of clinical monitoring for the purpose of continuous quality improvement in medical industry.

• Design & Manufacturing
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• 제11권1호
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• pp.30-33
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• 2017

In this study, the mold technology for manufacturing of porous implant was investigated. Firstly, we considered the concept of insert molding technology with 3D printing of porous inert part. The part on implant was designed in the end region of the implant. And then main implant bodies were manufactured using conventional machining method. The other porous parts were designed and optimized with molding simulation. As the feature size of porous implant was so small that perfect feature of it using 3D printing technology could not be obtained. So, we proposed another scheme for manufacturing of the porous implant in the replace of the former approach. Polymer mold cores with 3D printing technology were considered. The effects of addictive manufacturing process parameters on the properties of mechanical and dimensional accuracy were investigated. Direct 3D printed polymer mold cores were designed and manufactured under the simulation of thermal and molding analysis. It was shown that 3D printed mold core with polymer could be adapted to the injection molding for porous implant.