• Restorative Dentistry and Endodontics
• /
• v.33 no.3
• /
• pp.184-197
• /
• 2008

This study was to investigate the influence of combining composite resins with different elastic modulus, and occlusal loading condition on the stress distribution of restored notch-shaped non-carious cervical lesion using 3D finite element (FE) analysis. The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. A notch-shaped cavity was modeled and filled with hybrid, flowable resin or a combination of both. After restoration, a static load of 500N was applied in a point-load condition at buccal cusp and palatal cusp. The stress data were analyzed using analysis of principal stress. Results showed that combining method such that apex was restored by material with high elastic modulus and the occlusal and cervical cavosurface margin by small amount of material with low elastic modulus was the most profitable method in the view of tensile stress that was considered as the dominant factor jeopardizing the restoration durability and promoting the lesion progression.

• The Journal of Korean Academy of Prosthodontics
• /
• v.33 no.1
• /
• pp.32-47
• /
• 1995

The purpose of this study was to determine the displacement of prosthesis & abutment and the stress distribution patterns induced in the periodontium by applying force to the fixed prosthesis. Two levels of periodontal support were compared using two-dimensional finite element stress analysis after placement of 3unit or 4 unit fixed partial denture(FPD) in case of missing of the lower first molar. Concentrated vertical load was delivered at the cusp tip of the second bicuspid or the central fossa of the pontic. The following results were obtained : 1. The greater the loss of alveolar bone in abutment teeth area, the greater the displacement of FPD and the stress concentration in alveolar bone around abutment. 2. The amount and direction of displacement and distribution of stress in the 4-unit FPD was better than those in the 3-unit FPD. 3. Multiple abutments reduced the amount of mesial and downward displacement of the weaked abutments and more uniformly distributed the stresses.

• International Journal of Safety
• /
• v.7 no.1
• /
• pp.21-25
• /
• 2008

The occurrence of a corona is that electrical discharge due to the heterogeneity that occurs when an electrical field is concentrated in an electrode due to a cusp formed on said electrode. Wire treatment at the end of a 154kV dead end clamp for end users accelerates the occurrence of corona, which in turn leads to power loss and noise. In this study, the characteristics of the corona which occurs between porcelain insulators and support clamps of overhead lines used in l54kV power receiving facilities for end users were investigated. The corona, which cannot be identified by one common method, was measured utilizing a UV image camera. A risk assessment for fire damage and its status was suggested. The stress distribution of the electrical field by length of bare wire was suggested by means of the finite element method (FEMLAB). As a result, it was found to affect a porcelain insulators. These results can be utilized for the enhancement of clamp installation and safety in power facilities.

• The Journal of Korean Academy of Prosthodontics
• /
• v.31 no.4
• /
• pp.580-610
• /
• 1993

The purpose of this study was to analyse the deflection and stress distribution at the supporting bone and it's superstructure by the alteration of angulation between implant and it's implant abutment. For this study, the free-end saddle case of mandibular first and second molar missing would be planned to restore with fixed prosthesis. So the mandibular second premolar was prepared for abutment, and the cylinder type osseointegrated implant was placed at the site of mandibular second molar for abutment. The finite element stress analysis was applied for this study. 13 two-dimensional FEM models were created, a standard model at $0^{\circ}$ and 12 models created by changing the angulation between implant and implant abutment as increasing the angulation mesially and distally with $5^{\circ}$ unittill $30^{\circ}$. The preprocessing decording, solving and postprocessing procedures were done by using FEM analysis software PATRAN and SUN-SPARC2GX. The deflections and von Mises stresses were calculated under concentrated load (load 1) and distributed load(load 2) at the reference points. The results were as follows : 1. Observing at standard model, the amount of total deflection at the distobuccal cusp-tip of pontic under concentrated load was largest of all, and that at the apex of implant was least of all, and the amount of total deflection at the buccal cusp-tip of second premolar under distributed load was largest of all, and that at the apex of implant was least of all. 2. Increasing the angulation mesially or distally, the amounts of total deflection were increased or decreased according to the reference points. But the order according to the amount of total deflection was not changed except apex of second premolar and central fossa of implant abutment under concentrated load during distal inclination. 3. Observing at standard model, the von Mises stress at the distal joint of pontic under concentrated load was largest of all, and that at the apex of implant was least of all. The von Mises stress at the distal margin of second premolar under distributed load was largest of all, and that at the apex of Implant was least of ail. 4. Increasing the angulation of implant mesially, the von Mises stresses at the mesial crest of implant were increased under concentrated load and distributed load, but those were increased remarkably under distributed load and so that at $30^{\circ}$ mesial inclination was largest of all. 5. Increasing the angulation of implant distally, the von Mises stresses at the distal crest of implant were increased remarkably under concentrated load and distributed load, and so those at $30^{\circ}$ distal inclination were largest of all.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.31 no.3
• /
• pp.248-254
• /
• 2005

The purpose of this study was to investigate the distribution of stress within the regenerated bone surrounding the implant using three dimensional finite element stress analysis method. Using ANSYS software revision 6.0 (IronCAD LLC, USA), a program was written to generate a model simulating a cylindrical block section of the mandible 20 mm in height and 10 mm in diameter. The $5.0{\times}11.5-mm$ screw implant (3i, USA) was used for this study, and was assumed to be 100% osseointegrated. And it was restored with gold crown with resin filling at the central fossa area. The implant was surrounded by the regenerated type IV bone, with 4 mm in width and 7 mm apical to the platform of implant in length. And the regenerated bone was surrounded by type I, type II, and type III bone, respectively. The present study used a fine grid model incorporating elements between 250,820 and 352,494 and nodal points between 47,978 and 67,471. A load of 200N was applied at the 3 points on occlusal surfaces of the restoration, the central fossa, outside point of the central fossa with resin filling into screw hole, and the functional cusp, at a 0 degree angle to the vertical axis of the implant, respectively. The results were as follows: 1. The stress distribution in the regenerated bone-implant interface was highly dependent on both the density of the native bone surrounding the regenerated bone and the loading point. 2. A load of 200N at the buccal cusp produced 5-fold increase in the stress concentration at the neck of the implant and apex of regenerated bone irrespective of surrounding bone density compared to a load of 200N at the central fossa. 3. It was found that stress was more homogeneously distributed along the side of implant when the implant was surrounded by both regenerated bone and native type III bone. In summary, these data indicate that concentration of stress on the implant-regenerated bone interface depends on both the native bone quality surrounding the regenerated bone adjacent to implant and the load direction applied on the prosthesis.

• The Journal of Korean Academy of Prosthodontics
• /
• v.40 no.1
• /
• pp.53-67
• /
• 2002

This study was aimed to analyze the stress distribution of implant and supporting tissue in single tooth implant restoration using Branemark $system^{(R)}$(Nobel Biocare, Gothenberg, Sweden) and Bicon system(Bicon Dental Implants, Boston, MA). Two dimensional finite element analysis model was made at mandibular first premolar area As a crown materials porcelain, ceromer, ADA type III gold alloy were used. Tests have been performed at 25Kgf vertical load on central fossa of crown portion and at 10Kgf load with $45^{\circ}$ lateral direction on cusp inclination. The displacement and stresses of implant and supporting structures were analyzed to investigate the influence of the crown material and the type of implant systems by finite element analysis. The results were obtained as follows : 1. The type of crown material influenced the stress distribution of superstructure, but did not influence that of the supporting alveolar bone. 2. The stress distribution of ceromer and type III gold alloy and porcelain is similar. 3. Stress under lateral load was about twice higher than that of vertical load in all occlusal restorative materials. 4. In Bicon system, stress concentration is similar in supporting bone area but CerOne system generated about 1.5times eater stress more in superstructure material. 5. In Branemark models, if severe occlusal overload is loaded in superstvucture. gold screw or abutment will be fractured or loosened to buffer the occlusal overload but in Bicon models such buffering effect is not expected, so in Bicon model, load can be concentrated in alveolar bone area.

• Restorative Dentistry and Endodontics
• /
• v.20 no.2
• /
• pp.655-669
• /
• 1995

Restorative procedures can lead to weakening tooth due to reduction and alteration of tooth structure. It is essential to prevent fractures to conserve tooth. Among the several parameters in cavity designs, cavity isthmus is very important. In this study, amalgam 0 cavity was prepared on maxillary first premolar. Two dimensional finite element models were made by serial photographic method and isthmus(1/4, 1/3, 1/2, 2/3 of intercuspal distance) were varied. Three or four-nodal mesh were used for the two dimensional finite element models. The periodontal ligament and alveolar bone surrounding the tooth were excluded in these models. 1S model was sound tooth with no amalgam cavity. B model was assumed perfect bonding between the restoration and cavity wall. Both compressive and tensile forces were distributed directly to the adjacent regions. A load of 500N was applied vertically at the first node from the lingual slope of the buccal cusp tip. This study analysed von Mises stress, 1 and 2 directional normal stress and Y and Z axis translation with FEM software Super SAPII Version 5.2 (Algor Interactive System Co.) and hardware 486 DX2 PC. The results were as :follows : 1. 1S model was slightly different with 1B model in stress distibution. 1S, 2B, 3B, 4B models showed similiar stress distribution. 2. 1S model and four B models showed similiar pattern in Y axis and Z axis translation. 3. 1S model and four B models showed the bending phenomenon in the translation. 4. As increasing of the width of the cavity, experimental group was similiar with the control group in stress distribution. 5. As increasing of the width of the cavity, experimental group was similiar with the control group in Y and Z axis tranlation.

• Restorative Dentistry and Endodontics
• /
• v.23 no.1
• /
• pp.163-174
• /
• 1998

The purpose of this study is to evaluate the distribution of stress in the root end resected teeth. The finite element method was used to compare stresses along the root and retrograde filling material in seven two-dimensional models of mandibular 2nd premolar. Each model was endodontic treatment and gold crown' restoration. Each model divided with amagam core restoration or gold casting post restoration. Thus each model divided with shape of root end resection, depth of retropreparation and exposure length of root in the bony cavity. The seven models were classified as in the table 1 below. A load of 500N was applied $45^{\circ}$ diagonally on the lingual slope of the buccal cusp. These mode were analyzed with two dimensional finite element methods. The results of this study were as follows : 1. The maximum tensile stress along the inner canal wall was shown on the model 7. 2. When the model 1 was compared with the model 5, the maximum tensile stress along the inner canal wall showed the model 1. 3. Less equivalent stress was shown on the model 6 and more equivalent stress was shown on the model 4. 4. More shear stress was shown on the retrograde filling material of the model 7. 5. The models with increased length of exposed root in the bony cavity demonstrated a gradual increase to the tensile stress in X direction which occurred approximately a boundary between the bone and exposed root in' the bony cavity. 6. The model which had a case of matching the apex of post and a boundary between the bone and exposed root in the bony cavity demonstrated more increase tensile stress in X direction than other models.

• The Journal of Korean Academy of Prosthodontics
• /
• v.47 no.4
• /
• pp.365-375
• /
• 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
• /
• v.48 no.3
• /
• pp.181-188
• /
• 2010

Purpose: The purpose of this study was to compare the stress distribution characteristics of four different abutment connections on SS-$III^{(R)}$ fixture under occlusal loading, using 3-dimensional finite element method. Materials and methods: The fixture of SS-$III^{(R)}$ (Osstem, Korea) with 4 mm diameter and 11.5 mm length and 4 types of abutments were analyzed; Solid, Com-Octa, ComOcta Gold, and Octa abutment. The models were placed in the area of first molar in the mandible. The 4 loading conditions were; (1) the vertical loading of 100 N on the central fossa, (2) the vertical loading of 100 N on the buccal cusp, (3) the $30^{\circ}$ inclined loading of 100 N to lingual side on the central fossa, and (4) the $30^{\circ}$ inclined loading of 100 N to the lingual side on the buccal cusp. The 3G.Author program was used, the von-Mises stress was calculated and the stress contours were plotted on each part of the implant systems and the surrounding bone structures. Results: Regardless of abutment types and loading conditions, higher stress concentration was observed at the cortical bone. In cancellous bone, the highest stress was observed at apical portion and the maximum stress occurred at the implant neck. The higher internal stress was observed in the fixtures than in the bone. The lowest stress was observed at loading condition 1 and the stress concentration was also lower than any other loading conditions. Conclusion: Within the limitation of the result of this study, it seems that the abutment connection type does not affect much on the stress distribution of bone structure.