• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.105-113
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• 2005

The purpose of this study is to evaluate the effect of loading at three different occlusal surface position of the gold alloy crown on the stress distributions in surrounding bone, utilizing 3-dimensional finite element method. A three dimensional finite element model of an implant with simplified gold alloy crown and supporting bone was developed for this study. A oblique or vertical load of 100 N was applied at the following position at each FE model : 1) center of occlusal surface, 2) a point on the buccal side away from center of occlusal surface (COS) by 2.8mm, 3) a point on the lingual side away from COS by 2.8mm. In the results, Minimum von Mises stresses under vertical load or oblique load of 100N were about 6MPa at the center of occlusal surface and about 40MPa at the point on the buccal side, respectively. From the results we could come to the conclusion that occlusive loading position could be an important factor for establishment of structural safety of supporting bone.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.1
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• pp.1-14
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• 2005

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis of internal connection system(ITI system) according to position and direction of load, under vertical and inclined loading using finite element analysis (FEA). The finite element model of a synOcta implant and a solid abutment with $8^{\circ}$ internal conical joint used by the ITI implant was constructed. The gold crown for mandibular first molar was made on solid abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric cusp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant under both vertical and oblique loading but stresses in the cancellous bone were low under both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. So, the relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 4. In this internal conical joint, vertical and oblique loads were resisted mainly by the implant-abutment joint at the screw level and by the implant collar. Conclusively, It seems to be more important that how long the distance is from center of rotation of the implant itself to the resultant line of force from occlusal contact (leverage). In a morse taper implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. This type of implant-abutment connection can also distribute forces deeper within the implant and shield the retention screw from excessive loading. Lateral forces are transmitted directly to the walls of the implant and the implant abutment mating bevels, providing greater resistance to interface opening.

• Journal of Technologic Dentistry
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• v.38 no.3
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• pp.143-149
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• 2016

Purpose: The purpose of this study is to evaluate the effect of two different oblique mechanical loading to occlusal surfaces of cement retained implant on the stress distributions in surrounding bone, using 3-dimensional finite element method. Methods: A 3-dimensional finite element model of a cement retained implant composed of three unit implants, simplified ceramic crown and supporting bone was developed according to the design of ement retained implant for this study. two kinds of surface distributed oblique loads(100 N) are applied to following occlusal surfaces in the single crowns; 1) oblique load on 2 occlusal points(50N for each buccal cusp, 2 buccal cusps exist), 2) oblique load on 4 occlusal points(25N for each buccal and lingual cusp, 2 buccal and 2 lingual cusps exist) Results: The results of the comparison of the stress distributions on surrounding bone are as follows. In the condition of oblique load on 2 occlusal points, VMS was 741.3 Mpa in the M1(Ø$4.0{\times}13mm$) model and 251.2 Mpa in the M2(Ø$5.0{\times}13mm$) model. It means the stress on the supporting bone is decreased. The results of oblique load on 4 occlusal points are similar to this one. Conclusion: Increasing the diameter of the implant fixture is helpful to distribute the stress on the supporting bone. Also, to obtain the structural stability of the supporting bone, it is effective to distribute the load evenly on the occlusal surface of crown in producing single crown implant.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.257-268
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• 2003

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis according to position and direction of load, under vertical and inclined loading using FEA analysis. The finite element model was designed according to standard fixture (4.1mm restorative component x 11.5mm length). The crown for mandibular first molar was made using UCLA abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric usp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant in both vertical and oblique loading but stresses in the cancellous bone were low in both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. 4. The relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 5. The magnitude of the stress in the supporting bone, fixture and abutment screw was greater with the outward oblique loading than with the inward oblique loading and was the greatest under loading at the centric cusp in a $30^{\circ}$ outward oblique direction. Conclusively, this study provides evidence that bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. But it seems to be more important that how long is the distance from center of rotation of the implant itself to the resultant line of force from occlusal contact(leverage). The goal of improving implants should be to avoid bending of the implant.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.187-197
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• 2013

PURPOSE. The purpose of this study was to evaluate various core designs on stress distribution within zirconia crowns. MATERIALS AND METHODS. Three-dimensional finite element models, representing mandibular molars, comprising a prepared tooth, cement layer, zirconia core, and veneer porcelain were designed by computer software. The shoulder (1 mm in width) variations in core were incremental increases of 1 mm, 2 mm and 3 mm in proximal and lingual height, and buccal height respectively. To simulate masticatory force, loads of 280 N were applied from three directions (vertical, at a $45^{\circ}$ angle, and horizontal). To simulate maximum bite force, a load of 700 N was applied vertically to the crowns. Maximum principal stress (MPS) was determined for each model, loading condition, and position. RESULTS. In the maximum bite force simulation test, the MPSs on all crowns observed around the shoulder region and loading points. The compressive stresses were located in the shoulder region of the veneer-zirconia interface and at the occlusal region. In the test simulating masticatory force, the MPS was concentrated around the loading points, and the compressive stresses were located at the 3 mm height lingual shoulder region, when the load was applied horizontally. MPS increased in the shoulder region as the shoulder height increased. CONCLUSION. This study suggested that reinforced shoulder play an essential role in the success of the zirconia restoration, and veneer fracture due to occlusal loading can be prevented by proper core design, such as shoulder.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.321-329
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• 2002

Bending moments results from offset overloading of dental implant, which may cause stress concentrations to exceed the physiological capacity of cortical bone and lead to various kinds of mechanical failures. The purpose of this study was to compare the distributing pattern of stress on the finite element models with the different angulated placement of dental implant in mandibular posterior missing areas. The three kinds of finite element model, were designed according to 3 main configurations: Model 1(parallel typed placement of 2 fixtures), Model 2(15. distal angulated placement of one fixture on second molar area), Model 3(15. mesial angulated placement of one fixture on second molar area). The cemented crowns for mandibular first and second molars were made on the two fixtures (4mm 11.5). Three-dimensional finite element models by two fixtures were constructed with the components of the implant and surrounding bone. A 200N vertical static load were applied to the center of central fossa and the point 2mm apart from the center of central fossa on each model. The preprocessing, solving and postprocessing procedures were done by using FEM analysis software NISA/DISPLAY IV Version 10.0((Engineering Mechanics Research Corporation, USA). Von Mises stresses were evaluated and compared in the supporting bone, fixtures, and abutment. The results were as following : (1) Under the point loading at the central fossa, the direction of angulated fixture affected the stress pattern of implants. (2) Under the offset loading, the position of loading affected more on the stress concentration of implants compare to the angulated direction of implants. The results had a tendency to increase the stress on the supporting bone, fixture and screw under the offset loads when the placement angulation of implant fixture is placed toward mesial or distal direction. In designing of the occlusal scheme for angulated placement, placing the occlusal contacts axially during chewing appears to have advantages in a biomechanical viewpoint.

• The Journal of Advanced Prosthodontics
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• v.9 no.5
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• pp.371-380
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• 2017

PURPOSE. The aim of this study is to evaluate and compare the stress distribution in Locator attachments in mandibular two-implant overdentures according to implant locations and different loading conditions. MATERIALS AND METHODS. Four three-dimensional finite element models were created, simulating two osseointegrated implants in the mandible to support two Locator attachments and an overdenture. The models simulated an overdenture with implants located in the position of the level of lateral incisors, canines, second premolars, and crossed implant. A 150 N vertical unilateral and bilateral load was applied at different locations and 40 N was also applied when combined with anterior load at the midline. Data for von Mises stresses in the abutment (matrix) of the attachment and the plastic insert (patrix) of the attachment were produced numerically, color-coded, and compared between the models for attachments and loading conditions. RESULTS. Regardless of the load, the greatest stress values were recorded in the overdenture attachments with implants at lateral incisor locations. In all models and load conditions, the attachment abutment (matrix) withstood a much greater stress than the insert plastic (patrix). Regardless of the model, when a unilateral load was applied, the load side Locator attachments recorded a much higher stress compared to the contralateral side. However, with load bilateral posterior alone or combined at midline load, the stress distribution was more symmetrical. The stress is distributed primarily in the occlusal and lateral surface of the insert plastic patrix and threadless area of the abutment (matrix). CONCLUSION. The overdenture model with lateral incisor level implants is the worst design in terms of biomechanical environment for the attachment components. The bilateral load in general favors a more uniform stress distribution in both attachments compared to a much greater stress registered with unilateral load in the load side attachments. Regardless of the implant positions and the occlusal load application site, the stress transferred to the insert plastic is much lower than that registered in the abutment.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.17-40
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• 1987

The purpose of this study was to clarify the effect of clasp design on abutment tooth adjacent to a distal extension base under the influence by the location of functional loading. The RPI clasp, the Akers clasp and the combination clasp were selected for evaluation. Tests were performed at 10Kg, 20Kg, 30Kg loads on the buccal, central, lingual, mesial and distal positions of loading platform of each mandibular distal extension partial denture. The laser reflexion method was used for three dimensional measurement of abutment movement, which is possible to measure precisely without contact. The movement in the mesiodistal(X), buccolingual(Y), and occlusoapical(Z) directions and the rotational movement(R) were measured, and in addition, the total movement (SV) as expressed by the three dimensional summation vector independent of direction was calculated. The data were analyzed using Student t-test, p<.05. The following results were obtained from this study; 1. Clasp design did not generally affect the direction of abutment tooth movement except the movement in an undesirable occlusal direction in case of the Akers clasp and the combination clasp. 2. The greater the load on the prosthesis, the greater was the abutment tooth movement, and the direction of abutment tooth movement was affected by positional loading. 3. Each prosthesis was dislodged from the test base under the small amount of load in the distal load position, and the buccal loading showed the greatest abutment tooth movement under the maximum load. 4. RPI clasp was evaluated as the most favorable design.

• The Journal of Advanced Prosthodontics
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• v.8 no.4
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• pp.304-312
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• 2016

PURPOSE. The aim of this study was to investigate the stress distribution of 2-short implants (2SIs) installed in a severely atrophic maxillary molar site. MATERIALS AND METHODS. Three different diameters of internal connection implants were modeled: narrow platform (NP), regular platform (RP), and wide platform (WP). The maxillary first molars were restored with one implant or two short implants. Three 2SI models (NP-oblique, NP-vertical, and NP-horizontal) and four single implant models (RP and WP in a centered or cantilevered position) were used. Axial and oblique loadings were applied on the occlusal surface of the crown. The von Mises stress values were measured at the bone-implant, peri-implant bone, and implant/abutment complex. RESULTS. The highest stress distribution at the bone-implant interface and the peri-implant bone was noticed in the RP group, and the lowest stress distribution was observed in the 2SI groups. Cantilevered position showed unfavorable stress distribution with axial loading. 2SI types did not affect the stress distribution in oblique loading. The number and installation positions of the implant, rather than the bone level, influenced the stress distribution of 2SIs. The implant/abutment complex of WP presented the highest stress concentration while that of 2SIs showed the lowest stress concentration. CONCLUSION. 2SIs may be useful for achieving stable stress distribution on the surrounding bone and implant-abutment complex in the atrophic posterior maxilla.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.4
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• pp.506-521
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• 2007

Statement of problem: The cumulative success rate of wide implant is still controversial. Some previous reports have shown high success rate, and some other reports shown high failure rate. Purpose: The aim of this study was to analyze, and compare the biomechanics in wide implant system embeded in different width of crestal bone under different occlusal forces by finite element approach. Material and methods: Three-dimensional finite element models were created based on tracing of CT image of second premolar section of mandible with one implant embedded. One standard model (6mm-crestal bone width, 4.0mm implant diameter central position) was created. Varied crestal dimension(4, 6, 8 mm), different diameter of implants(3.3, 4.0, 5.5, 6.0mm), and buccal position implant models were generated. A 100-N vertical(L1) and 30 degree oblique load from lingual(L2) and buccal(L3) direction were applied to the occlusal surface of the crown. The analysis was performed for each load by means of the ANSYS V.9.0 program. Conclusion: 1. In all cases, maximum equivalent stress that applied $30^{\circ}$ oblique load around the alveolar bone crest was larger than that of the vertical load. Especially the equivalent stress that loaded obliquely in buccal side was larger. 2. In study of implant fixture diameter, stress around alveolar bone was decreased with the increase of implant diameter. In the vertical load, as the diameter of implant increased the equivalent stress decreased, but equivalent stress increased in case of the wide implant that have a little cortical bone in the buccal side. In the lateral oblique loading condition, the diameter of implant increased the equivalent stress decreased, but in the buccal oblique load, there was not significant difference between the 5.5mm and 6.0mm as the wide diameter implant. 3. In study of alveolar bone width, equivalent stress was decreased with the increase of alveolar bone width. In the vertical and oblique loading condition, the width of alveolar bone increased 6.0mm the equivalent stress decreased. But in the oblique loading condition, there was not a difference equivalent stress at more than 6.0mm of alveolar bone width. 4. In study of insertion position of implant fixture, even though the insertion position of implant fixture move there was not a difference equivalent stress, but in the case of little cortical bone in the buccal side, value of the equivalent stress was most unfavorable. 5. In all cases, it showed high stress around the top of fixture that contact cortical bone, but there was not a portion on the bottom of fixture that concentrate highly stress and play the role of stress dispersion. These results demonstrated that obtaining the more contact from the bucco-lingual cortical bone by installing wide diameter implant plays an important role in biomechanics.