• The Journal of Advanced Prosthodontics
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• v.8 no.6
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• pp.465-471
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• 2016

PURPOSE. The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS. Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of $1.0{\times}10^6$cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS. Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION. Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.3
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• pp.329-338
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• 2007

Purpose. The aim of this study is to evaluate the effect of TiN coating of abutment screw on the unscrewing torque. Material and methods. Titanium and Gold-Tite abutment screws were classified into two groups, Group A and C respectively, as control groups. Titanium abutment screws with TiN coatings were also classified into two groups, Group B and D, as experimental ones. Group A and B were tightened to 20 Ncm input torque, and Group C and D were tightened to 32 Ncm torque. Detorque values were measured with digital torque gauge during repeated closing and opening experiment. Results. Abutment screws with TiN coating (Group B and D) showed statistically significant higher mean detorque values than those of Group A and C. Discussion. Physical properties of TiN coating, such as low friction coefficient, high hardness and wear resistance, might contribute to higher detorque values. Conclusion. It is suggested that TiN coating of abutment screw help to reduce the risk of screw loosening and improve the stability of screw joint.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.1
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• pp.31-42
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• 2007

The purpose of this study was to compare the stress distribution according to the splinting condition and non-splinting conditions on the finite element models of the two units implant prostheses. The finite element model was designed with the parallel placement of two fixtures ($4.0mm{\times}11.5mm$) on the mandibular 1st and 2nd molars. A cemented abutment and gold screw were used for superstructures. A FEA models assumed a state of optimal osseointegration, as the bone quality, inner cancellous bone and outer 2 mm compact bone was designed. This concluded that the cortical and trabecular bone were assumed to be perfectly bonded to the implant. Splinting condition had 2 mm contact surface and non-splinting condition had $8{\mu}m$ gap between two implant prosthesis. Two group (Splinting and non-splinting) were loaded with 200 N magnitude in vertical axis direction and were divided with subdivision group. Subdivision group was composed of three loading point; Center of central fossa, the 2 mm and 4 mm buccal offset point from the central fossa. Von Mises stress value were recorded and compared in the fixture-bone interface and bucco-lingual sections. The results were as follows; 1. In the vertical loading condition of central fossa, splinting condition had shown a different von Mises stress pattern compared to the non-splinting condition, while the maximum von Mises stress was similar. 2. Stresses around abutment screw were more concentrated in the splinting condition than the non-splinting condition. As the distance from central fossa increased, the stress concentration increased around abutment screw. 3. The magnitude of the stress in the cortical bone, fixture, abutment and gold screw were greater with the 4 mm buccal offset loading of the vertical axis than with the central loading.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.1
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• pp.119-130
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• 2007

Statement of problem: A few dry lubricants were applied to abutment screws for the improvement of joint stability. Purpose: The purpose of this study was to evaluate the surface change and fit of TiN-Coated abutment screw through the examination of tested screws in the field emission scanning electron microscope(FE-SEM;Netherland, Phillips co., model:XL 30 SFEG) after repeated closing and opening. Materials and method: Titanium(3i/implant Innovations Inc, USA) and Gold-Tite abutment screws(3i/implant Innovations Inc, USA) were selected for Group A and C respectively. TiN coated titanium abutment screws were also divided into two groups, Group B and D. Abutment screws of each group and the fit of abutment screw/implant fixture/abutment were observed on FE-SEM after repeated closing and opening test respectively. Results: 1. The abutment screws of TiN coated groups(Group B and D) showed more remarkable wear resistance in the threads of the screw than those of the other group(Group A and C). 2. There were more severe wear and defect of TiN coating in Group D tightened to 32 Ncm than Group B to 20 Ncm. 3. There was no difference in the fit of abutment screw/fixture/abutment among four groups, Group A, Group B, Group C and Group D. Conclusion: Under the conditions of this study, it is suggested that TiN coating of abutment screw be clinically acceptable and be expected to reduce the risk of abutment screw loosening. TiN coating of abutment screw showed good resistance against wear and the adequate fit of abutment screw/implant fixture/abutment.

• 대한치과보철학회:학술대회논문집
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• 2001.11a
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• pp.51-51
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• 2001

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.3
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• pp.246-254
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• 2008

STATEMENT OF PROBLEM: The cast abutment has advantages of overcoming angulation problem and esthetic problem. However, when a gold-machined UCLA abutment undergoes casting, the abutment surfaces in contact with the implant may change. PURPOSE: The purpose of this study was to compare the detorque values of prefabricated machined abutments with gold-premachined cast-on UCLA abutments before and after casting in two types of internal implant-abutment connection systems: (1) internal hexagonal joint, (2) internal octagonal joint. Furthermore, the detorque values of two implant-abutment connection systems were compared. MATERIALS AND METHODS: Twenty internal hexagonal implants with an 11-degree taper and twenty internal octagonal implants with an 8-degree taper were acquired. Ten prefabricated titanium abutments and ten gold-premachined UCLA abutments were used for each systems. Each abutment was torqued to 30 N㎝ according to the manufacturer's instructions and detorque value was recorded. The detorque values were measured once more, after casting with gold alloy for UCLA abutment, and preparation for titanium abutments. Group means were calculated and compared using independent t-test and paired t-test (${\alpha}$=0.05). RESULTS: The results were as follows: 1. The detorque values between titanium abutments and UCLA-type abutments showed significant differences in internal octagonal implants (P<0.05), not in internal hexagonal implants (P>0.05). 2. In comparison of internal hexagonal and octagonal implants, the detorque values of titanium abutments had significant differences between two connection systems on the initial analysis (P<0.05), not on the second analysis (P>0.05) and the detorque values of UCLA-type abutments were not significantly different between two connection systems (P>0.05). 3. The detorque values of titanium abutments and UCLA-type abutments decreased significantly on the second analysis than the initial analysis in internal hexagonal implants (P<0.05), not in internal octagonal implants (P>0.05). CONCLUSION: Casting procedures of UCLA-type abutments had no significant effect on screw loosening in internal implant-abutment connection systems, and UCLA-type abutments showed higher detorque values than titanium abutments in internal octagonal implants.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.2
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• pp.156-171
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• 2002

The purpose of this study was to measure and compare the strains produced by screw-tightening implant frameworks fabricated by aye different fabrication methods; (1) one-piece cast using plastic sleeve, (2) one-piece cast using gold cylinder, (3) laser welding, (4) soldering, and (5) electrical discharge machining, and also to measure and compare the strains produced when the order of screw tightening was changed A research model incorporating eighteen strain gages was made to measure the fit of implant frameworks in three dimensions. Three implants aligned in an arc were fixed on the top ends of the L-shape aluminum bars of the research model, and standard abutments were joined to the implants with abutment screws. Five types of implant framework were placed on the abutments and screwed by a torque wrench using 10 Ncm. Under the conditions of this study, the following conclusions were drawn: 1. The electrical discharge machining group showed the smallest magnitude of strain, followed by the soldering group, the laser welding group, the one-piece cast group using gold cylinder, and the one-piece cast group using plastic sleeve. However, among the magnitude of strain for the remaining groups except the electrical discharge machining group, there were not significant differences. 2. When the order of screw tightening was changed, there were not significant differences in the magnitude of strain. 3. In comparison with the electrical discharge machining group, the laser welding group and the one-piece cast groups showed greater horizontal distortion and the soldering group showed greater horizontal and vertical distortion.

• Journal of Dental Rehabilitation and Applied Science
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• v.17 no.4
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• pp.307-314
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• 2001

To evaluate the effect of misfit in two implant-supported fixed partial dentures in the posterior of the mandible, variations of the standard finite element models were made by changing the location of the gap as follows: 1) no gap present; 2) located between the gold cylinder and the abutment on the distal implant; 3) gap located between the gold cylinder and the abutment on the mesial implant. The results of this study were as follows: 1. When the location of the gap was close to the load applied on the prosthesis, the stress in the prosthesis, implant components and surrounding bone increased. 2. The presence of cantilever increased the stress in the prosthesis, implant and surrounding bone significantly, regardless of the presence of the gap. 3. When there was a gap between the prosthesis and abutment, the stress in the bone around the implant increased. 4. When passive fit was achieved, the stress was distributed widely in each component with less peak stress in each component. 5. The inner structures of the implant components, the gold screw and the abutment screw bear more stress when the prosthesis did not exhibit passive fit with the abutments than when passive fit was present.

• The Journal of Korean Academy of Prosthodontics
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• v.28 no.2
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• pp.199-215
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• 1990

This study was to analyze the stress distribution of implant and supporting tissue in $Br{\aa}nemark$ osseointegration implant. The analysis has been conducted by using the axisymmetric finite element method and type of model according to crown material. Tests have been performed at 1 kg load on central fossa of crown portion. Each type of model was designed differently according to crown material. 1) Porcelain fused to metal crown(Model A) 2) Composite resin veneered crown(Model B) 3) Acrylic resin veneered crown(Model C) 4) Type III gold crown(Model D) The displacements and stresses of implant and supporting structures were analyzed to investigate the influence of the type of crown material. The results were obtained as follows : 1. Displacement of implant was shown uniformly downward displacement in all models and abutments were observed distally downward displacement. 2. In supporting tissues, stress was concentrated on the crest of compact bone and the spongy bone below implant. 3. The PFM and the type III gold crown showed the largest concentration of stress at the crest of compact bone and the spongy bone below implant, respectively. Acrylic resin artificial teeth and composite resin veneered crown indicated almost the same distribution of stress. 4. The gold screw, the abutment screw and the top of abutment showed the concentration of stress in implants of every model.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.2
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• pp.97-103
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• 2016

When chewing forces are repetitively applied to a dental implant, gaps are often generated at the interface surfaces between the abutment and the fixture, which results in some deterioration, such as loosening of the fastening screw, dental retraction, and fixture fractures. To cope with such problems, a sealing-type abutment having a number of grooves along the conical-surface circumference was previously developed, and it showed better sealing performance than conventional ones. To enhance the sealing performance, a new model in which a gold ring is inserted into the top groove of the sealing-type abutment is developed in this study. In addition, a manufacturing process is developed, and performance evaluations, such as fatigue and sealing tests, are carried out. The evaluation results show that the gold-ring-inserted sealing abutment yields better performance than conventional ones.