• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.177-194
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• 1991

The purpose of this study was to analyze the magnitude and distribution of stress using a photoelastic model from a distal extension removable partial dentures with three kinds of mandibular major connectors, that is, lingual bar, linguoplate, and swing-lock attachment. A photoelastic model was made of the epoxy resin(PC-1) and hardener(PCH-1) and coated with plastic cement-1 (PC-1) at the lingual surface of the epoxy model and set with three kinds of chrome-cobalt removable partial dentures. A bilateral vertical load of 15kg to the middle portion of the metal bar crossing both the first molars of the right and the left, and a unilateral vertical load of 12.5kg to the right first molar were applied with the use of specially designed loading device and the reflective circular polariscope was used to analyze the photoelastic model under each condition. The following results were obtained : 1. When the bilateral vertical load was applied, the magnitude and distribution of the stress concentration of the edentulous area and the terminal abutment or adjacent teeth was in the order of lingual bar, linguoplate, swing-lock attachment. 2. When the unilateral vertical load was applied, the magnitude and distribution of the stress concentration of the edentulous area and the terminal abutment or adjacent teeth was in the order of lingual bar, linguoplate, swing-lock attachment. 3. When the unilateral vertical load was applied, the magnitude and distribution of the stress concentration of the termial abutment or adjacent teeth on the non-loaded side showed the least stress distribution in case of swing-lock attachment. 4. When the bilateral vertical load and the unilateral vertical load were applied the swing-lock attachment showed the mildest uniform stress distribution on the edentulous area and the alveolar bone around the abutment teeth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6846-6851
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• 2015

In this study, equation of calculating vertical stress increment developing in underneath of the embankment due to the extension of embankment width was derived through the use of theory of elasticity. Concept of the origin of plane was adopted to simplify derivation procedure for obtaining the equation. Comparing the results of the equation for calculating vertical stress increment with those of the numerical analyses, differences in the magnitudes of vertical stress increments decrease as the depths below embankment increase. Comparing the vertical stress increments with horizontal distances which correspond to certain depth, vertical stress increments obtained from the derived equation were slightly greater than those of numerical analyses.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.4
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• pp.643-659
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• 1993

This study was performed for the purpose of evaluating the stress distributions around five different types of implants according to their structures. The stress distribution around the surrounding bone was analysed by two-dimensional photoelastic method. Five epoxy resin models were made, and vertical and lateral forces were applied to the models. A circular polariscope was used to record the isochromatic fringes. The results of this study were summerized as follows : 1. Threaded type implants showed more even stress distribution patterns than cylinderical type implants when vertical and lateral forces were applied. 2. The stress concentrated patterns were observed at the neck portion and middle portion of the cylindrical type implants comparing with threaded type implants when vertical force was applied. 3. Model 1 and model 4 which are tthreaded type implants showed similar stress distribution patterns at the middle and apical portions and more stress was concentrated at the neck porion of model 1 comparing with model 4 when vertical force was applied. The stresses around model 1 were more evenly distributed when lateral force was applied. 4. More stress was concentrated at the neck and middle portion of cylindrical type implants than threaded type implants when lateral force was applied. 5. Model 1 showed the most even stress distribution patterns when lateral force was applied and stress distribution did no occured at the apical portion of modedl 2 when lateral force was applied. 6. There were almost no differences in stress concentrated patterns with or without having hollow design. And the stress concentrated patterns were observed at the corner of apex in model 5 which has hollow design when vertical force was applied.

• Geomechanics and Engineering
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• v.22 no.5
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• pp.375-384
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• 2020

In this study, the application of conventional cubic law to a deep depth condition was experimentally evaluated. Moreover, a modified equation for estimating the rock permeability at a deep depth was suggested using precise hydraulic tests and an effect analysis according to the vertical stress, pore water pressure and fracture roughness. The experimental apparatus which enabled the generation of high pore water pressure (< 10 MPa) and vertical stress (< 20 MPa) was manufactured, and the surface roughness of a cylindrical rock sample was quantitatively analyzed by means of 3D (three-dimensional) laser scanning. Experimental data of the injected pore water pressure and outflow rate obtained through the hydraulic test were applied to the cubic law equation, which was used to estimate the permeability of rock fracture. The rock permeability was estimated under various pressure (vertical stress and pore water pressure) and geometry (roughness) conditions. Finally, an empirical formula was proposed by considering nonlinear flow behavior; the formula can be applied to evaluations of changes of rock permeability levels in deep underground facility such as nuclear waste disposal repository with high vertical stress and pore water pressure levels.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.301-311
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• 2002

The purpose of this study was to compare the distributing pattern of stress on the finite element models with the different vertical bone level of implant fixture. The two kinds of finite element models were designed according to vertical bone level around fixture ($4.0mm{\times}11.5mm$). The cemented crowns for mandibular first and second molars were made. Three- dimensional finite element model was created with the components of the implant and surrounding bone. Vertical loads were applied with force of 200N distributed within 0.5mm radius circle from the center of central fossa and distance 2mm and 4 mm apart from the center of central fossa. Von-Mises stresses were recorded and compared in the supporting bone, fixtures, abutment screws, and crown. The results were as following : (1) In vertical loading at the center circle of central fossa on model 1 and 2, the difference from vertical bone in implant placement did not affect the stress pattern on all components of implant except for crown. (2) With offset distance incerasing and the bone level of implant decreasing, the concentration of stress occured in the buccal side of long crown, around the buccal crestal bone, and on the fixture- abutment interface. As a conclusion, the research showed a tendency to increase the stress on the supporting bone, fixture and screw under the offset loads when the vertical level of bone around fixture was different. Since the same vertical bone bed has more benefits than the different bone bed around fixtures, it is important to prepare a same vertical level of bone bed for the success of implants under occlusal loads.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1C
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• pp.33-39
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• 2009

Vertical soil stress near a pile subjected to negative skin friction (NSF) may be reduced due to shear transfer at the pile-soil interface. A three-dimensional finite difference analysis has been performed to clarify the influence of vertical and horizontal stress reductions on the pile behavour. In addition, a simple equation has been proposed to estimate vertical stress reduction of the soil near the pile. The vertical and horizontal stresses are reduced by substantial amount compared to corresponding stress components at the Greenfield condition. The horizontal extent of vertical stress reduction of the soil near the pile is rather limited to about up to 4-8 D, where D is the pile diameter. The findings from the current research indicate that widely used $\beta$-method may result in over-estimation of dragload (compressive force on piles due to NSF) and hence stress reduction needs to be incorporated in the original equation.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.4
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• pp.21-27
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• 2011

Soil stress distribution under loading is one of the important problems in civil engineering. Many models have been proposed to interpret the stress distribution in soil and most models assume that the soil is homogeneous and isotropic. Therefore, the actual stress distribution may be different. In addition, With the increase of the top load, soil stress does not increase linearly. In this study, vertical stress changes in sandy soil according to top load increase were measured through experiments. Experimental results, vertical soil stress due to top load increase showed an initial nonlinear behavior and when the load increases to some extent, vertical soil stress showed a linear behavior. ${\alpha}$ value obtained by existing theories always 1.00. But, ${\alpha}$ value by experiment was observed from 0.91 to 1.22 and ${\alpha}$ value was increased with increasing distance from the loading plate.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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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.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.2
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• pp.169-182
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• 2005

The purpose of this study was to compare the stress distribution around the surrounding bone according to the splinted and non-splinted conditions on the finite element models of the two implant crowns with the different vertical bone level. The finite element model was designed with the parallel placement of the two fixtures ($4.0mm{\times}11.5mm$) with reverse buttress thread on the mandibular 1st and 2nd molars. As the bone quality, the inner cancellous bone and the outer 2 mm cortical bone were designed, and the cortical and cancellous bone were assumed to be perfectly bonded to the implant fixture. The splinted model(Model 1) had 2 mm contact surface and the non-splinted model(Model 2) had $8{\mu}m$ gap between two implant crowns. Two group (Splinted and non-splinted) was loaded with 200 N magnitude in the vertical and oblique directions on the loading point position on the central position of the crown, the 2 mm and 4 mm buccal offset point from the central position. Von Mises stress value was recorded and compared in the fixture-bone interface in the bucco-lingual and mesio-distal sections. The results were as follows; 1. In the vertical loading condition of central position, the stress was distributed on the cortical bone and the cancellous bone around the thread of the fixture in the splinted and non-splinted models. In the oblique loading condition, the stress was concentrated toward the cortical bone of the fixture neck, and the neck portion of 2nd molar in the non-splinted model was concentrated higher than that of 1st molar compared to the splinted model. 2. In the 2 mm buccal offset position of the vertical loading compared to the central vertical loading, stress pattern was shifted from apical third portion of the fixture to upper third portion of that. In the oblique loading condition, the stress was distributed over the fixture-bone interface. 3. In the 4 mm buccal offset position of the vertical loading, stress pattern was concentrated on the cortical bone around the buccal side of the fixture thread and shifted from apical third portion of the fixture to upper third portion of that in the splinted and non-splinted models. In the oblique loading, stresses pattern was distributed to the outer position of the neck portion of the fixture thread on the mesio-distal section in the splinted and non-splinted models. Above the results, it was concluded that the direction of loading condition was a key factor to effect the pattern and magnitude of stress over the surrounding bone of the fixture under the vertical and oblique loading conditions, although the type with or without proximal contact did not effect to the stress distribution.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.2
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• pp.385-402
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• 1996

The purpose of this study was to analyze how the stability of the implant prostheses and the loosening of the fastening screw was affected when the various types of Hex structure provided for the effect of anti-rotation of the single prostheses were given. Three dimensional finite element model was designed with which the implants with the external hex type of 0.75mm, 1.5mm and the implant with the internal hex type of 0.75mm, 1.5mm and the implant with the external hex type of $15^{\circ}$ tapered shape of 0.75mm were supposed to completely osseointegrate to the mandible. After fininshing the finite element model, the preload of 10N at the fastening screw was applied and then the vertical and $30^{\circ}$ lateral load of 200N was applied respectively at the cusp tips of the prostheses. The following results were obtained : 1. In case of displacement, the amount of displacement was increased at the internal hex type(model C, D) than at the external hex type(model A, B, E) when the vertical and lateral load was applied. 2. Less equivalent stress was represented at the model B with increased external hex height than at the model A when the vertical and lateral load was applied. 3. Much stress was represented at the model E with increased hex angle than at the model A in case of the stress happened to the implant body and the fastening screw when the vertical and lateral load was applied. 4. Much equivalent stress was represented at the model D with deepened internal hex height than at the model C when vertical and lateral load was applied. 5. The least stress was taken at the model B and the most stress was taken at the model D in case of the stress happened to the implant when the vertical and lateral load was applied. 6. The least stress was taken at the model C at the vertical load. And the least stress was taken at the model B at lateral load in case of the stress happened to the fastening screw. As a results of this study, the good lateral stability of prostheses and less stress of the component of implant was taken when the external hex height was increased, and the risk of neck fracture of implant and fastening screw was increased when the internal hex height was deepned because of long screw neck portion and thin implant neck portion.