• The Journal of Korean Academy of Prosthodontics
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• v.41 no.5
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• pp.674-688
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• 2003

Statement of Problem : With increasing demand of the implant-supported prosthesis, it is advantageous to use the different platform width of the fixture according to bone quantity and quality of the patients. Purpose : The purpose of this study was to assess the loading distributing characteristics of two implant designs according to each platform width of fixture, under vertical and inclined loading using finite element analysis. Material and method : The two kinds of finite element models were designed according to each platform width of future (4.1mm restorative component x 11.5mm length, 5.0mm wide-diameter 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, 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction and 200N at the buccal cusp in a 300 transverse direction individually Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment screw. Results : The stresses were concentrated mainly at the cortex in both vertical and oblique load ing but the stresses in the cancellous bone were low in both vertical and oblique loading. 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. Increasing the platform width of the implant fixture decreased the stress in the supporting bone, future and abutment screw. Increased the platform width of fixture decreased the stress in the crown and platform. Conclusion : Conclusively, this investigation provides evidence that the platform width of the implant fixture directly affects periimplant stress. By increasing the platform width of the implant fixture, it showed tendency to decreased the supporting bone, future and screw. But, further clinical studies are necessary to determine the ideal protocol for the successful placement of wide platform implants.

• Journal of Dental Rehabilitation and Applied Science
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• v.17 no.4
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• pp.245-256
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• 2001

The purpose of this study is to analyze the mechanical stress and displacement on the jaws during the simulated bilateral clenching task on the three-dimensional finite element model of the dentated skull with unilateral molar loss. For this study, the computed tomography(G.E.8800 Quick, USA) was used to scan the total length of human skull in the frontal plane at 2.0mm intervals. The fully assembled finite element model consists of the articular disc, maxilla, mandible, teeth, periodontal ligament and cranium. The FE model was used to simulate the bilateral clenching in intercuspal position. The loading condition was the force of the masseter muscle exerted on the mandible as reported by Korioth et al. degrees of freedom of the zygomatic region where the masseter muscle is attached were fixed as restraints. In order to reflect the actual action of the muscles force, the displacement of the region was attached where the muscle is connected to the temporal bone and restraint conditions were given values identical to values at the attachment region of the masticatory muscle but with the opposite direction of the reaction from when the muscle force is acted on the mandible. Although the mandible generally has higher displacement and von Mises stress than the maxilla, its mandibular corpus on the molar-loss side has a higher stress and displacement than the molar-presence side. Because the displacement and von Mises Stress was the highest on the lateral surface of mandibular corpus with molar loss, the stress level of the condyle on the molar-loss side is greater than that of the molar-presence side, which in turn caused the symphysis of the mandible to bend. In conclusion, the unilateral posterior bite collapse with molar loss under para-functional activities such as bruxism and clenching can affect the stress concentration on the condyle and mandibular corpus. It is therefore necessary to consider the biomechanical function of dento-skeleton under masticatory force while designing the occlusal scheme of restoration on alveolar bone with the posterior collapse.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.3
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• pp.202-210
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• 2014

Purpose: The aim of this study was to evaluate the stress concentration and distribution whether restoring the cavity or not while restoring with metal ceramic crown on tooth with abfraction lesion using finite element analysis. Materials and methods: Maxillary first premolar was selected and made a total of 10 finite element model. Model 1 was natural tooth; Model 2 was tooth with metal ceramic crown restoration which margin was positioned above 2 mm from CEJ; Model 3 was tooth with metal ceramic crown restoration which margin was positioned on CEJ; Model 4 was natural tooth which has abfraction lesion; Model 5 and 6 had abfraction lesion and the other condition was same as model 2 and 3, respectively; Model 7 was natural tooth which had abfraction lesion restored with composite resin; Model 8 and 9 was tooth with metal ceramic crown after restoring on abfraction lesion with composite resin; Model 10 was restored tooth on abfraction lesion with composite resin and metal ceramic crown restoration which margin is positioned on lower border of abfraction lesion. Load A and Load B was also designed. Von Mises value was evaluated on each point. Results: Under load A or load B, on tooth with abfraction lesion, stress was concentrated on the apex of lesion. Under load A or load B, on tooth that abfraction lesion was restored with composite resin, the stress value was reduced on the apex. Conclusion: In case of abfraction lesion was restored with composite resin, the stress was concentrated on the apical border of restored cavity regardless of marginal position. It was favorable to place crown margin on the enamel for restoring with metal ceramic crown.

• Restorative Dentistry and Endodontics
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• v.34 no.1
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• pp.69-79
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• 2009

The purpose of this study was to evaluate the influence of elastic modulus of restorative materials and the number of interfaces of post and core systems on the stress distribution of three differently restored endodontically treated maxillary second premolars using 3D FE analysis. Model 1, 2 was restored with a stainless steel or glass fiber post and direct composite resin. A PFG or a sintered alumina crown was considered. Model 3 was restored by EndoCrown. An oblique 500 N was applied on the buccal (Load A) and palatal (Load B) cusp. The von Mises stresses in the coronal and root structure of each model were analyzed using ANSYS. The elastic modulus of the definitive restorations rather than the type of post and core system was the primary factor that influenced the stress distribution of endodontically treated maxillary premolars. The stress concentration at the coronal structure could be lowered through the use of definitive restoration of high elastic modulus. The stress concentration at the root structure could be lowered through the use of definitive restoration of low elastic modulus.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.259-271
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• 2013

The purpose of this study was to make the stress distribution produced by simulated different load under two types of internal connection implant system (stepped and tapered type) by means of 3D finite element analysis, The finite element model was designed with the parallel placement of the one fixtures ($4.0mm{\times}11.5mm$) with reverse buttress thread on the mandibular 1st molar. Two models were loaded with 200 N magnitude in the vertical direction on the central position of the crown, the 1.5 mm and 3 mm buccal offset point from the central position of the fixture. The oblique load was applied at the angle of $30^{\circ}$ on the crown surface. Von Mises stress value was recorded and compared in the fixture-bone interface in the bucco-lingual dimension. The results were as follows; 1. The loading conditions of two internal connection implant systems (stepped and tapered type) were the main factor affecting the equivalent bone strain, followed by the type of internal connections. 2. The stepped model had more mechanical stability with the reduced max. stress compared to $11^{\circ}$ tapered models under the distributed oblique loading. 3. The more the contact of implant-abutment interface to the inner wall of implant fixture, the less stress concentration was reduced.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.3
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• pp.186-194
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• 2015

Purpose: To evaluate the effects of implant location and length on stress distribution and displacement in osseointegrated-implants that were associated with mandibular distal extension removable partial dentures (DERPD). Materials and Methods: A sagittally cut model with the #33, #34 teeth and a removable partial denture of the left mandible was used. Seven models were designed with NX 9.0. Models A, B, C had implants with lengths of 11, 6, 4 mm, respectively, under the denture base of the #37 artificial tooth. Models D, E, F had implants with lengths of 11, 6, 4 mm, respectively, under the denture base of the #36 artificial tooth. Model G did not have any implants. Axial force (250 N) was loaded on #36 central fossa. The finite element analysis was performed with MSC Nastran. Von Mises stress maps were plotted to visualize the results. Results: The models of #37 implant placement showed much lower stress concentration on the surrounding bone of the implant compared with #36. The #36 implant position tended to reduce displacement more than #37. Conclusion: When an IARPD is designed, the distal positioning of implant placement has more advantages in the edentulous bone of DERPD on the prognosis of short implants and the stress distribution of edentulous alveolar bone. Using implants with longer lengths are important for stress distribution. However, Additional studies are necessary of the effects of length on implant survival.

• Journal of Mechanical Science and Technology
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• v.15 no.4
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• pp.413-421
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• 2001

A simple procedure to add and remove material simultaneously along the boundary is developed to optimize the shape of a two dimensional elastic problems and to minimize the maximum von Mises stress. The results for the two dimensional infinite plate with a hole, are close to the theoretical results of an elliptical boundary and the stress concentration is reduced by half for the fillet problem. The proposed shape optimization method, when compared with existing derivative based shape optimization methods has many features such as simplicity, applicability, flexibility, computational efficiency and a much better control on stresses on the design boundary.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.2
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• pp.27-34
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• 1999

The growth-strain method was used for shape optimization, which carries out the optimization by distributing uniformly the distributed parameter such as von Mises stress and shear strain energy density. Shape optimization is carried out by iteration of stress analysis and growth strain analysis. In this study, the effect of growth ratio in the method was investigated and then the range of the adequate value of the growth ratio was determined. Also the growth-strain method was improved by applying the linear PID control theory in order to control volume required by a designer. Finally, an automatic shape optimization system was built up by the improved growth-strain method with a commercial software using finite element method. The effectiveness and practicability of the developed shape optimization system was verified by some examples.

• Journal of Korean Society for Quality Management
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• v.31 no.4
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• pp.194-202
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• 2003

In this paper, we propose goodness of fit test statistics for exponentiality in accelerated life tests data based on Kullback­Leibler information functions. This acceleration model is assumed to be a tampered random variable model. The procedure is applicable when the exponential parameter using the data from accelerated life tests is or is not specified under null hypothesis. And we compare the power of the proposed test statistics with Kolmogorov­Smirnov, Cramer von Mises and Anderson­Darling statistics in the small sample.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.4
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• pp.38-43
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• 2015

This study performed a finite element stress analysis of pipe system connected by bellows based on APDL(ANSYS Parametric Design Language) customizing. The effects of different shapes of developed pipes for various parameters are studied using the finite element commercial package for this study. The structural behavior of complex pipe structures with bellows was also investigated to study the interactions between bellows and other parts. Based on the ANSYS APDL, the effect of initial axial and lateral displacements, and internal temperature and pressure on the Von Mises stress distribution is also analyzed.