• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.207-216
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• 2006

Statement of Problem: To conduct a successful function of implant prosthesis in oral cavity for a long time, it is important that not only structure materials must have the biocompatibility, but also the prosthesis must be designed for the stress, which is occurred in occlusion, to scatter adequately within the limitation of alveolar bone around implant and bio-capacity of load support. Now implant which is used in clinical part has a very various shapes, recently the fixture that has tapered form of internal connection is often selected. However the stress analysis of fixtures still requires more studies. Purpose: The purpose of this study is to stress analysis of the implant prosthesis according to the different implant systems using finite element method. Material and methods: This study we make the finite element models that three type implant fixture ; $Br{\aa}nemark$, Camlog, Frialit-2 were placed in the area of mandibular first premolar and prosthesis fabricated, which we compared with stress distribution using the finite element analysis under two loading condition. Conclusion: The conclusions were as follows: 1. In all implant system, oblique loading of maximum Von mises stress of implant, alveolar bone and crown is higher than vertical loading of those. 2. Regardless of loading conditions and the type of system. cortical bone which contacts with implant fixture top area has high stress, and cancellous bone has a little stress. 3. Under the vertical loading, maximum Von mises stress of $Br{\aa}nemark$ system with external connection type and tapered form is lower than Camlog and Frialit-2 system with internal connection type and tapered form, but under oblique loading Camlog and Frialit-2 system is lower than $Br{\aa}nemark$ system.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.277-288
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• 2002

Seven finite element models were constructed in mandible having single screw-type implant fixture connected to the premolar superstructure, in order to evaluate how the length, diameter and platform shape of a screw-type fixture influence the stress in the supporting tissue around fixtures. Each finite element model was varied in terms of length, diameter, and platform shape of the fixture. In each model, 250N of vertical load was placed on the central pit of an occlusal plane and 250N of oblique load placed on the buccal cusp. The stress distribution in the supporting tissue and the other components was analysed using 2-dimensional finite element analysis and the maximum von Mises stress in each reference area was compared. Under lateral loading, the stress was larger at the abutment/fixture interface, and in the crestal bone, compared to the stress pattern under vertical loading. The amount of stress at the superstructure was similar regardless of the length, diameter and platform shape of a fixture. Around the longer fixture, the stress was decreased at the bone crest and subjacent cancellous bone and increased in the cancellous bone area apical to the fixture. Around the wider fixture, the stress was decreased at the abutment/fixture interface, and the bone crest and increased in the cancellous bone area apical to the fixture. Around the fixture having wider platform, less stress was produced at the abutment/fixture interface and the upper part of the cortical bone, compared to the fixture having standard platform. In conclusion, the stress distribution of the supporting tissue was affected by length, diameter, and platform shape of a fixture, and the fixture which was larger in diameter and length could reduce the stress in the supporting tissues at the bone-fixture interface and bone crest area.

• 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 Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.226-237
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• 2004

Purpose: Four finite element models were constructed in the mandible having a single implant fixture connected to the first premolar-shaped superstructure, in order to evaluate how the shape of the fixture and the implant-abutment connection would influence the stress level of the supporting tissues fixtures, and prosthethic components. Material and methods : The superstructures were constructed using UCLA type abutment, ADA type III gold alloy was used to fabricate a crown and then connected to the fixture with an abutment screw. The models BRA, END , FRI, ITI were constructed from the mandible implanted with Branemark, Endopore, Frialit-2, I.T.I. systems respectively. In each model, 150 N of vertical load was placed on the central pit of an occlusal plane and 150 N of $40^{\circ}$ oblique load was placed on the buccal cusp. The displacement and stress distribution in the supporting tissues and the other components were analysed using a 2-dimensional finite element analysis . The maximum stress in each reference area was compared. Results : 1. Under $40^{\circ}$ oblique loading, the maximum stress was larger in the implant, superstructure and supporting tissue, compared to the stress pattern under vertical loading. 2. In the implant, prosthesis and supporting tissue, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 3. In the superstructure and implant/abutment interface, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 4. In the implant fixture, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 5 The stress was more evenly distributed in the bone/implant interface through the FRI of trapezoidal step design. Especially Under $40^{\circ}$ oblique loading, The maximum stress was smallest in the bone/implant interface. 6. In the implant and superstructure and supporting tissue, the maximum stress occured at the crown loading point through the ITI. Conclusion: The stress distribution of the supporting tissue was affected by shape of a fixture and implant-abutment connection. The magnitude of maximum stress was reduced with the internal connection type (FRI) and the morse taper type (ITI) in the implant, prosthesis and supporting tissue. Trapezoidal step design of FRI showed evenly distributed the stress at the bone/implant interface.

• The Journal of Advanced Prosthodontics
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• v.1 no.2
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• pp.97-101
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• 2009

STATEMENT OF PROBLEM. Unlike screw-retention type, fixture-abutment retention in Locking taper connection depends on frictional force so it has possibility of abutment to sink. PURPOSE. In this study, Bicon$^{(R)}$ Implant System, one of the conical internal connection implant system, was used with applying loading force to the abutments connected to the fixture. Then the amount of sinking was measured. MATERIAL AND METHODS. 10 Bicon$^{(R)}$ implant fixtures were used. First, the abutment was connected to the fixture with finger force. Then it was tapped with a mallet for 3 times and loads of 20 kg corresponding to masticatory force using loading application instrument were applied successively. The abutment state, slightly connected to the fixture without pressure was considered as a reference length, and every new abutment length was measured after each load's step was added. The amount of abutment sinking (mm) was gained by subtracting the length of abutment-fixture under each loading condition from reference length. RESULTS. It was evident, that the amount of abutment sinking in Bicon$^{(R)}$ Implant System increased as loads were added. When loads of 20 kg were applied more than 5 - 7 times, sinking stopped at $0.45{\pm}0.09\;mm$. CONCLUSION. Even though locking taper connection type implant shows good adaption to occlusal force, it has potential for abutment sinking as loads are given. When locking taper connection type implant is used, satisfactory loads are recommended for precise abutment location.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.3
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• pp.253-267
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• 2008

The purpose of this study was to evaluate the pattern and the magnitude of stress distribution in the supporting tissues surrounding implant fixture with different diameter of implant fixtures(3i implant, Ø4.0, Ø5.0, Ø6.0mm and UCLA abutments(Ø4.1, Ø5.0, Ø6.0mm using photoelastic stress analysis. Photoelastic model was made with PL-2 resin(Measurements Group, Raleigh, USA) and three implants of each diameter were placed in the mandibular posterior edentulous area distal to the canine. Individual crowns were fabricated using UCLA abutments. Photoelastic stress analysis was carried out to measure the fringe order around the implant supporting structure under simulated loading conditions(15 lb, 30 lb). The results were as follows; 1. The more the diameter of implant fixture was increased, the less the stress concentration on cervical area of fixture was observed under loading. 2. Increasing mesiodistal diameter of implant superstructure had no much influence on stress distribution around implant fixture. 3. The use of smaller abutment had no influence on stress distribution around implant fixture. The use of smaller abutment diameter than that of implant fixture had no favorable effect on implant supporting tissue at biomechanical consideration.

• Journal of Periodontal and Implant Science
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• v.40 no.5
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• pp.244-248
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• 2010

Purpose: The purpose of this study was to radiographically evaluate marginal bony changes in relation to different vertical positions of dental implants. Methods: Two hundred implants placed in 107 patients were examined. The implants were classified by the vertical positions of the fixture-abutment connection (microgap): 'bone level,' 'above bone level,' or 'below bone level.' Marginal bone levels were examined in the radiographs taken immediately after fixture insertion, immediately after second-stage surgery, 6 months after prosthesis insertion, and 1 year after prosthesis insertion. Radiographic evaluation was carried out by measuring the distance between the microgap and the most coronal bone-to-implant contact (BIC). Results: Immediately after fixture insertion, the distance between the microgap and most coronal BIC was $0.06{\pm}0.68\;mm$; at second surgery, $0.43{\pm}0.83\;mm$; 6 months after loading, $1.36{\pm}0.56\;mm$; and 1 year after loading, $1.53{\pm}0.51\;mm$ ($mean{\pm}SD$). All bony changes were statistically significant but the difference between the second surgery and the 6-month loading was greater than between other periods. In the 'below bone level' group, the marginal bony change between fixture insertion and 1 year after loading was about 2.25 mm, and in the 'bone level' group, 1.47 mm, and in 'above bone level' group, 0.89 mm. Therefore, the marginal bony change was smaller than other groups in the 'above bone level' group and larger than other groups in the 'below bone level' group. Conclusions: Our results demonstrated that marginal bony changes occur during the early phase of healing after implant placement. These changes are dependent on the vertical positions of implants.

• Journal of Technologic Dentistry
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• v.26 no.1
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• pp.69-76
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• 2004

The objective of this finite element method study was to analyze the stress distribution induced on a supporting bone by 3.75mm, 4.0mm, 5.0mm diameter of dental implant fixture(13mm length). 3-dimensional finite element models of simplified gold alloy crown(7mm height) and dental implant structures(gold cylinder screw, gold cylinder, abutment screw, abutment, fixture and supporting bone(cortical bone, cancellous bone) designs were subjected to a simulated biting force of 100 N which was forced over occlusal plane of gold alloy crown vertically. Maximum von Mises stresses(MPa) under vertical loading were 9.693(3.75mm diameter of fixture), 8.885(4.0mm diameter of fixture), 6.301(5.0mm diameter of fixture) and the highest von Mises stresses of all models were concentrated in the surrounding crestal cortical bone. The wide diameter implant was the good choice for minimizing cortical bone-fixture interface stress.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.4
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• pp.424-434
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• 2009

Statement of problem: Problems such as loosening and fractures of retained screws and fracture of implant fixture have been frequently reported in implant prosthesis. Purpose: Implant has weak mechanical properties against lateral loading compared to vertical occlusal loading, and therefore, stress analysis of implant fixture depending on its material and geometric features is needed. Material and methods: Total 28 of external hexed implants were divided into 7 of 4 groups; Group A (3i, FULL $OSSEOTITE^{(R)}$Implant), Group B (Nobelbiocare, $Br{\aa}nemark$ $System^{(R)}$Mk III Groovy RP), Group C (Neobiotec, $SinusQuick^{TM}$ EB), Group D (Osstem, US-II). The type III gold alloy prostheses were fabricated using adequate UCLA gold abutments. Fixture, abutment screw, and abutment were connected and cross-sectioned vertically. Hardness test was conducted using MXT-$\alpha$. For fatigue fracture test, with MTS 810, the specimens were loaded to the extent of 60-600 N until fracture occurred. The fracture pattern of abutment screw and fixture was observed under scanning electron microscope. A comparative study of stress distribution and fracture area of abutment screw and fixture was carried out through finite element analysis Results: 1. In Vicker's hardness test of abutment screw, the highest value was measured in group A and lowest value was measured in group D. 2. In all implant groups, implant fixture fractures occurred mainly at the 3-4th fixture thread valley where tensile stress was concentrated. When the fatigue life was compared, significant difference was found between the group A, B, C and D (P<.05). 3. The fracture patterns of group B and group D showed complex failure type, a fracture behavior including transverse and longitudinal failure patterns in both fixture and abutment screw. In Group A and C, however, the transverse failure of fixture was only observed. 4. The finite element analysis infers that a fatigue crack started at the fixture surface. Conclusion: The maximum tensile stress was found in the implant fixture at the level of cortical bone. The fatigue fracture occurred when the dead space of implant fixture coincides with jig surface where the maximum tensile stress was generated. To increase implant durability, prevention of surrounding bone resorption is important. However, if the bone resorption progresses to the level of dead space, the frequency of implant fracture would increase. Thus, proper management is needed.

• Journal of Technologic Dentistry
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• v.38 no.3
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• pp.151-156
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• 2016

Purpose: The dental implant should be enough to endure chewing load and it's required to have efficient design and use of implant to disperse the stress into bones properly. This study was to evaluate the stress distribution on a supporting bone by lengths and diameters of the implant fixture. Methods: The modeling and analysis of stress distribution was used for the simple molar porcelain crown model by Solidworks as FEM program. It was designed on applying with tightening torque of 20 Ncm of a abutment screw between a cement retained crown abutment and a fixture. The fixtures of experimental model used 10, 13mm by length and 4, 5mm by diameter. A external vertical loading on the two buccal cusps of crown and performed finite element analysis by 100 N. Results: The maximum von Mises stress(VMS) of all supporting bone models by fixture length and diameter were concentrated on the upper side of supporting compact bone. The maximum stress of each model under vertical load were 164.9 MPa of M410 model, and 141.2 MPa of M413 model, 54.3 MPa of M510 model, 53.6 MPa of M513 model. Conclusion: The stress reduction was increase of fixture's diameter than it's length. So it's effective to use the wider fixture as possible to the conditions of supporting bone.