• Journal of Periodontal and Implant Science
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• v.22 no.2
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• pp.213.1-213.1
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• 1992

• Journal of Periodontal and Implant Science
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• v.13 no.1
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• pp.67.2-67.2
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• 1983

• Radiation Oncology Journal
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• v.16 no.2
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• pp.167-175
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• 1998

Purpose : It is not a simple task to achieve the ideal isodose curve with a standard vaginal applicator or sing1e plane needle impant in the paravaginal tissue when primary or recurrent gynecological neoplasms(cervical cancers, vaginal cancers and vulvar cancers) are treated as a boost following external beam radiotherapy. The authors introduce the development and construction of a simple, inexpensive, customized applicator for volume implant to maximize the radiation dose to the tumor while minimizing the dose to the rectum and the bladder. Materials and Methods : Nine patients underwent Ir-192 transperineal interstitial implantation for either recurrent(5 cases) or primary(3 cases) cervical cancers or primary vaginal cancer(1 case) between August 1994 and February 1998 at Ajou university hospital. First 3 cases were performed with a sing1e plane implant guided by digital palpation. Because of inadequate isodose coverage in the tumor volume in first 3 cases, we designed and constructed interstitial vaginal applicator for volume implant to improve tumor dose distribution and homogeneity while sparing the surrounding normal tissue. Our applicators consist of vaginal obturator and perineal template that made of the clear acrylamide and dental mold material$(Provil^{(R)})$. The applicators were customized individually according to the tumor size and its location Both HDR and LDR irradiation were given with these applicators accomodating 6 Fr needles(Microselectron Nucletron). The pretreatment planning prior to actual implant was performed whenever possible. Results : Needles can be inserted easily and evenly into the tumor volume through the holes of templates, requiring less efforts and time for the implant procedure. Our applicators made of materials available from commercial vendors. These have an advantage that require easy procedure, and spend relatively short time to construct. Also it was possible to fabricate applicators to individualize according to the tumor size and its location and to achieve the ideal isodose coverage. We found an accurate needle arrangement and ideal dose distribution through the CT scan that was obtained in 3 cases after needle implant. Three patients with primary cervical and vaginal cancers were controlled locally at final follow up. But all recurrent cases failed to do so. Conclusion : The authors introduce inexpensive, simple interstitial vaginal templates which were self-designed and constructed using materials available from commercial vendors such as acrylanide and dental mold material $(Provil^{(R)})$.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.109-123
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• 2009

The aim of the study was to assess the influence of insertion torque of bone quality and to compare axial force, moment and von Mises stress using finite element analysis of plastoelastic property for bone stress and strain by dividing bone quality to its thickness of cortical bone, density of trabecular bone and existence of lower cortical bone when implant inserted to mandibular premolar region. The $Br{\aa}nemark$ MKIII. RP implant and cylindrical bone finite model were designed as cortical bone at upper border and trabecular bone below the cortical bone. 7 models were made according to thickness of cortical bone, density of trabecular bone and bicortical anchorage and von Mises stress, axial force and moment were compared by running time. Dividing the insertion time, it seemed 300msec that inferior border of implant flange impinged the upper border of bone, 550msec that implant flange placed in middle of upper border and 800msec that superior border of implant flange was at the same level as bone surface. The maximum axial force peak was at about 500msec, and maximum moment peak was at about 800msec. The correlation of von Mises stress distribution was seen at both peak level. The following findings were appeared by the study which compared the axial force by its each area. The axial force was measured highest when $Br{\aa}nemark$ MKIII implant flange inserts the cortical bone. And maximal moment was measured highest after axial force suddenly decreased when the flange impinged at upper border and the concentration of von Mises stress distribution was at the same site. When implant was placed, the axial force and moment was measured high as the cortical bone got thicker and the force concentrated at the cortical bone site. The influence of density in trabecular bone to axial force was less when cortical bone was 1.5 mm thick but it might be more affected when the thickness was 0.5 mm. The total axial force with bicortical anchorage, was similar when upper border thickness was the same. But at the lower border the axial force of bicortical model was higher than that of monocortical model. Within the limitation of this FEA study, the insertion torque was most affected by the thickness of cortical bone when it was placed the $Br{\aa}nemark$ MKIII implant in premolar region of mandible.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.3
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• pp.176-182
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• 2020

Purpose: To evaluate the effects of load direction, number of implants, and alignment of implant position on stress distribution in implant, prosthesis, and bone tissue. Materials and Methods: Four 3D models were made to simulate posterior mandible bone block: two implants and 3-unit fixed dental prosthesis (FDP) with a pontic in the center (model M1), two implants and 3-unit FDP with a cantilever pontic at one end (model M2), FDP supported by three implants with straight line placement (model M3) and FDP supported by three implants with staggered implant configuration (model M4). The applied force was 120 N axially or 120 N obliquely. Results: Peak von Mises stresses caused by oblique occlusal force were 3.4 to 5.1 times higher in the implant and 3.5 to 8.3 times higher in the alveolar bone than those stresses caused by axial occlusal force. In model M2, the connector area of the distal cantilever in the prosthesis generated the highest von Mises stresses among all models. With the design of a large number of implants, low stresses were generated. When three implants were placed, there were no significant differences in the magnitude of stress between staggered arrangement and straight arrangement. Conclusion: The effect of staggering alignment on implant stress was negligible. However, the number of implants had a significant effect on stress magnitude.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.67-76
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• 2008

Implant requires long lasting, strong osseointegration using bio-mechanical interlocking by bone ingrowth. In regarding the size level for bone ingrowth, the micro-patterning would enhance bone response. Micro-patterning can increase the area contacting the bone tissues. Therefore, it may distribute the load to the surrounding bone tissue, more effectively. This study compared and analyzed the load distributing effect with the shape and number of micro-patterning. For the optimal comparison of threads, the assumptions different from general finite element analysis model were made. It was assumed that the implant was axisymmetric and infinitely long. The implant was assumed to be completely embedded in the infinitely long cortical bone and to have 100% bone apposition. The implant-bone interface had completely fixed boundary conditions and received an infinitely big axial load. The condition of threads were as follows. The reference model 1 had conventional thread. Model 2 had 2 micro-patterns on the upper flank of the thread. Model 3 had 2 micro-patterns on the lower flank of the thread. Model 4 had 2 micro-patterns on the upper and lower flanks of the thread. Model 5 had 3 micro patterns on the upper and lower flanks of the thread. The results were as follows: 1. The thread with micro-patterns distributed stress better than the conventional thread. 2. The thread with micro-patterns on the lower flank distributed stress better than that with micro-patterns on the upper flank. 3. The thread with 3 micro-patterns distributed stress better than that with 2 micro-patterns, However, an area with stress concentration occurred.

• 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.385-393
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• 2009

Statement of problem: High stress concentration on the crestal cortical bone has been regraded as a major etiologic factor jeopardizing long term stability of endosseous implants. Purpose: To investigate if the design characteristics of crestal module, i.e. internal type, external type, and submerged type, affect stress distribution on the crestal cortical bone. Material and methods: A cylindrical shaped implant, 4.3 mm in diameter and 10 mm in length, with 3 different crestal modules, i.e. internal type, external type, and submerged type, were analysed. An axisymmetric scheme was used for finite elment formulation. A vertical load of 50 N and an oblique load of 50N acting at $45^{\circ}$ with the implant's long axis was applied. The peak crestal bone stress acting at the intersection of implant and crestal bone was compared. Results: Under vertical load, the crestal bone stress was high in the order of internal, external, and submerged types. Under the oblique loading condition, it was in the order of internal, submerged, and external types. Conclusion: Crestal module design was found to affect the level of the crestal bone stresses although the actual amount was not significant.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.4
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• pp.615-643
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• 1998

The purpose of this study was to evaluate the effect of cantilever length, load, and implant number on the stress distribution of implant supported fixed prosthesis. In the replica of an edentulous human mandible, four or five implants were placed and spaced evenly between the mental foramina and symmetrical gold alloy cast superstructures with cantilever were fabricated. Strain gauges were placed in buccal and lingual side of implants. 9, 15, 21kg of loads at varying cantilever lengths were applied to the occlusal surface of fixed prostheses. The strains were recorded from each gauge and principal stresses were calculated The results were as follows : 1. Increasing the length of the cantilever increased the stresses on the bone supporting implants. and the ratio of increase became high as increasing the load. 2. In the model with four implants, the highest compressive stress was measured on lingual side of the first implants nearest loading point and the highest tensile stress was measured on buccal side of the second implants. 3. In the model with five implants, the highest compressive stress was measured on lingual side of the first implants nearest loading point. And the highest tensile stress was measured on buccal side of the second implants, and lingual side of the third implants. 4. There was no significant change of the magnitude of stress on the most distal imp]ant of non cantilevered side as increasing the cantilever length or load. 5. In general, the superstructure supported by five implants reduced the stress and was less affected by cantilever length compared to the support provided by four implants.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.484-488
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• 1997

Three-dimensional finite element analyses were used to compare the stress distribution and the stability of the fixation among seven different tibial components and to investigate the effect due to implant materials in total knee arthroplasty. The components included an intact tibia(Type I), Cemented Cobalt-Chromium tibial tray implanted with a PMMA cemented Co-Cr stem(Type II), Cemented Co-Cr tibial tray with a uncemented Co-Cr stem(Type III), Cemented Ultra High Molecular Weight Polyethylene (UHMWPE) tibial tray with a cemented UHMWPE stem (Type IV), Cemented UHMWPE tray with a uncemented UHMWPE stem(Type V), Cemented Co-Cr tray without a stem(Type VI), and Cemented UHMWPE tray without a stem(Type VII). Uncemented components were assumed to have complete bony in growth and a rigid state of fixation between component and bone. The interface between bone/cement/component of cemented components was also assumed to be fully bonded. Bi-condylar forces were applied. The results indicated that Uncemented stem components provided lower bone stress shielding and stress concentration. The UHMWPE tray and stem component showed better agreement with the intact tibia than the Co-Cr Alloy tray and stem components. If the implant tray can be fixed firmed without a stem, Cemented PE tray without a stem(Type VII) may be recommended to give the best characteristics in the sense of stress distribution and stability.