• Journal of Periodontal and Implant Science
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• v.52 no.6
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• pp.496-508
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• 2022

Purpose: This study aimed to compare the long-term survival rate and peri-implant marginal bone loss between different types of dental implant-abutment connections. Methods: Implants with external or internal abutment connections, which were fitted at Gangneung-Wonju National University Dental Hospital from November 2011 to December 2015 and followed up for >5 years, were retrospectively investigated. Cumulative survival rates were evaluated for >5 years, and peri-implant marginal bone loss was evaluated at 1- and 5-year follow-up examinations after functional loading. Results: The 8-year cumulative survival rates were 93.3% and 90.7% in the external and internal connection types, respectively (P=0.353). The mean values of marginal bone loss were 1.23 mm (external) and 0.72 mm (internal) (P<0.001) after 1 year of loading, and 1.20 mm and 1.00 mm for external and internal abutment connections, respectively (P=0.137) after 5 years. Implant length (longer, P=0.018), smoking status (heavy, P=0.001), and prosthetic type (bridge, P=0.004) were associated with significantly greater marginal bone loss, and the use of screw-cement-retained prosthesis was significantly associated (P=0.027) with less marginal bone loss. Conclusions: There was no significant difference in the cumulative survival rate between implants with external and internal abutment connections. After 1 year of loading, marginal bone loss was greater around the implants with an external abutment connection. However, no significant difference between the external and internal connection groups was found after 5 years. Both types of abutment connections are viable treatment options for the reconstruction of partially edentulous ridges.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.197-206
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• 2006

Statement of problem: One of common problems associated with single teeth dental implant prosthetic is the loosening of screws that retain the implants. Purpose: The maintenance of screw joint stability is considered a function of the preload achieved in the screw when the suggested initial tightening torque is applied. The purpose of this study was to investigate acquired preload after initial clamping torque for estimating screw joint stability. Material and methods: A comparative study on the effect of initial clamping of two types of implant systems with different connections was conducted Three dimensional non-linear finite element analysis is adopted to compare the characteristics of screw preloads and stress distributions between two different types of implant systems composed with abutment, screw, and fixture under the same loading and boundary conditions. Results: 1. When the initial clamping torque of 32Ncm was applied to the implant systems, all types of implants generated the maximum effective stress at the first helix region of screw. 2. Morse taper connection types of implants generate lower stress distributions compared to those by butt joint connection types or implants due to large contact surface between abutment and fixture. 3. The internal types of implant systems with friction grip type implant systems have higher resistance to screw loosening than that of the external types of implant systems since the internal types of implant systems generated larger preload than that generated by the external types for the same tightening moments.

• Tribology and Lubricants
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• v.37 no.4
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• pp.136-143
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• 2021

This paper presents the loosening behavior that occurs after the application of an external load to internal and external connection types of dental implants using the finite element method. We use fastening force between an abutment and a fixture to clamp the dental implant system; however, loosening and breakage may occur owing to cyclic external loads. In this study, we considered the initial fastening condition in the pre-load analysis and then investigated the change in stress and contact surface status when applying external loads. After the application of the initial fastening load, we verified that the internal connection-type model exhibited a relatively lower stress distribution than that of the external connection-type one. Moreover, we found that the former model showed a lower stress concentration after the application of the external load. In addition, after the application of this load, we found that the higher the shear load acting on the implant system, the higher the possibility of loosening. The study results showed the change in stress distribution and contact surface according to the connection type of the dental implants and the phenomenon of loosening by cyclic loads. We expect that the results of this study will be useful for the study of reliability and design of dental implant systems.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.5
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• pp.617-625
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• 2003

Statement of problem : There are many studies focused on the effect of shape of futures on stress distribution in the mandibular bone. However, there are no studies focused on the effect of the abutment types on stress distribution in mandibular bone. Purpose : The purpose of this study is to investigate the effect of three different abutment types on the stress distributions in the mandibular bone due to various loads by performing finite element analysis. Material and method : Three different implant systems produced by Warantec (Seoul, Korea), were modeled to study the effect of abutment types on the stress distribution in the mandibular bone. The three implant systems are classified into oneplant (Oneplant, OP-TH-S11.5). internal implant (Inplant, IO-S11.5) and external implant (Hexplant, EH-S11.5). All abutments were made of titanium grade ELI. and all fixtures were made of titanium grade IV. The mandibular bone used in this study is constituted of compact and spongeous bone assumed to be homogeneous, isotropic and linearly elastic. A comparative study of stress distributions in the mandibular bone with three different types of abutment was conducted. Results : It was found that the types of abutments have significant influence on the stress distribution in the mandibular bone. It was due to difference in the load transfer mechanism and the size of contact area between abutment and fixture. Also the maximum effective stress in the mandibular bone was increased with the increase of inclination angle of load. Conclusion : It was concluded that the maximum effective stress in the bone by the internal implant was the lowest among the maximum effective stresses by other two types.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.1
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• pp.60-70
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• 2007

Statement of problem: The cement-type abutment would be needed for the reduction of its body in order to correct the axis and to assure occlusal clearance. In the case of intraoral preparation, there is a potential risk that generated heat could be transmitted into the bone-implant interface, where it can cause deterioration of tissues around the implant and failed osseointegration. Purpose: The purpose of this study was to assess the difference of the heat transmitting effect on external and internal connection implant types under various conditions. Material and method: For evaluating the effects of alternating temperature, the thermocoupling wires were attached on 3 areas of the implant fixture surface corresponding to the cervical, middle, and apex. The abutments were removed 1mm in depth horizontally with diamond burs and were polished for 30 seconds at low speed with silicone points using pressure as applied in routine clinical practice. Obtained data were analyzed using Mann-Whitney rank-sum test and Wilcoxon / Kruskal-Wallis Tests. Result: Increased temperature on bone-implant interface was evident without air-water spray coolant both at high speed reduction and low speed polishing (p<.05). But, the difference between connection types was not shown. Conclusion: The reduction procedure of abutment without using proper coolant leads to serious damage of oral tissues around the implant irrespective of external and internal connection type.

• The Journal of Advanced Prosthodontics
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• v.10 no.5
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• pp.388-394
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• 2018

PURPOSE. To measure axial displacement of different implant-abutment connection types and materials during screw tightening at the recommended torque by using a contact scanner for two-dimensional (2D) and three-dimensional (3D) analyses. MATERIALS AND METHODS. Twenty models of missing mandibular left second premolars were 3D-printed and implant fixtures were placed at the same position by using a surgical guide. External and internal fixtures were used. Three implant-abutment internal connection (INT) types and one implant-abutment external connection (EXT) type were prepared. Two of the INT types used titanium abutment and zirconia abutment; the other INT type was a customized abutment, fabricated by using a computer-controlled milling machine. The EXT type used titanium abutment. Screws were tightened at $10N{\cdot}cm$, simulating hand tightening, and then at the manufacturers' recommended torque ($30N{\cdot}cm$) 10 min later. Abutments and adjacent teeth were subsequently scanned with a contact scanner for 2D and 3D analyses using a 3D inspection software. RESULTS. Significant differences were observed in axial displacement according to the type of implant-abutment connection (P<.001). Vertical displacement of abutments was greater than overall displacement, and significant differences in vertical and overall displacement were observed among the four connection types (P<.05). CONCLUSION. Displacement according to connection type and material should be considered in choosing an implant abutment. When adjusting a prosthesis, tightening the screw at the manufacturers' recommended torque is advisable, rather than the level of hand tightening.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.3 s.168
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• pp.179-186
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• 2005

A comparative study of stress distributions in the maxillary bone with three different types of abutment was conducted. Finite element analysis was adopted to determine stress generated in the bone with the different implant systems with micro threads (Onebody type implant, Internal type implant, and External type implant). It was found that the types of abutments and the number of micro threads have significant influence on the stress distribution in the maxillary bone. They were due to the difference in the load transfer mechanism and the size of contact area between abutment and fixture. Also the maximum effective stress in the maxillary bone was increased with increasing inclination angle of load. It was concluded that the maximum effective stress in the bone was the lowest by the internal implant among the maximum effective stresses by other two types of implants and by appropriate number of micro threads, and that the specific number of micro thread was existed to decrease the maximum effective stress in the maxillary bone due to different implant systems and loading conditions.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.2
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• pp.385-402
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• 1996

The purpose of this study was to analyze how the stability of the implant prostheses and the loosening of the fastening screw was affected when the various types of Hex structure provided for the effect of anti-rotation of the single prostheses were given. Three dimensional finite element model was designed with which the implants with the external hex type of 0.75mm, 1.5mm and the implant with the internal hex type of 0.75mm, 1.5mm and the implant with the external hex type of $15^{\circ}$ tapered shape of 0.75mm were supposed to completely osseointegrate to the mandible. After fininshing the finite element model, the preload of 10N at the fastening screw was applied and then the vertical and $30^{\circ}$ lateral load of 200N was applied respectively at the cusp tips of the prostheses. The following results were obtained : 1. In case of displacement, the amount of displacement was increased at the internal hex type(model C, D) than at the external hex type(model A, B, E) when the vertical and lateral load was applied. 2. Less equivalent stress was represented at the model B with increased external hex height than at the model A when the vertical and lateral load was applied. 3. Much stress was represented at the model E with increased hex angle than at the model A in case of the stress happened to the implant body and the fastening screw when the vertical and lateral load was applied. 4. Much equivalent stress was represented at the model D with deepened internal hex height than at the model C when vertical and lateral load was applied. 5. The least stress was taken at the model B and the most stress was taken at the model D in case of the stress happened to the implant when the vertical and lateral load was applied. 6. The least stress was taken at the model C at the vertical load. And the least stress was taken at the model B at lateral load in case of the stress happened to the fastening screw. As a results of this study, the good lateral stability of prostheses and less stress of the component of implant was taken when the external hex height was increased, and the risk of neck fracture of implant and fastening screw was increased when the internal hex height was deepned because of long screw neck portion and thin implant neck portion.

• Journal of Technologic Dentistry
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• v.35 no.3
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• pp.201-207
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• 2013

Purpose: In this study, the loosening torque test was conducted with three implant products that are produced, approved and sold in Korea, which are manufactured in different fixture and abutment tightening methods (internal submerged type, internal morse taper type, and external type) to examine the loosening torque of the screw according to the method of tightening the implant fixture and abutment. Methods: In the loosening torque test, the three types of fixtures and abutments with different tightening methods were tightened by rotating them clockwise with a $30N{\cdot}cm$ force using a driver equipped with an electric torque meter. The results of the test are as follows. Results: The loosening torque values of the internal submerged type, internal morse taper type and external type implants were $24.10{\pm}0.742N{\cdot}cm$, $29.10{\pm}1.710N{\cdot}cm$, and $26.60{\times}1.636N{\cdot}cm$, respectively. Conclusion: The screw loosening torque values of the three fixture and abutment tightening methods were analyzed via Kruskal Wallis test layout, and they were significantly different (p<0.05).

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.544-561
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• 2005

Purpose : This study was to assess the loading distributing characteristics of implant systems with internal connection or external connection under vertical and inclined loading using finite element analysis. Materials and methods : Two finite element models were designed according to type of internal connection or external connection The crown for mandibular first molar was made using cemented 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 centric cusp tip in a 15$^{\circ}$ inward inclined direction (loading condition B), or 200N at the centric cusp tip in a 30$^{\circ}$ outward inclined direction (loading condition C) respectively. Von Mises stresses were recorded and compared in the supporting bone, fixture, abutment and abutment screw. Results : 1. In comparison with the whole stress or the model 1 and model 2, the stress pattern was shown through th contact of the abutment and the implant fixture in the model 1, while the stress pattern was shown through the abutment screw mainly in the model 2. 2. Without regard to the loading condition, greater stress was taken at the cortical bone, and lower stress was taken at the cancellous bone. The stress taken at the cortical bone was greater at the model 1 than at the model 2, but the stress taken at the cortical bone was much less than the stress taken at the abutment, the implant fixture, and the abutment screw in case of both model 1 and model 2. 3. Without regard to the loading condition, the stress pattern of the abutment was greater at the model 1 than at the model 2. 4. In comparison with the stress distribution of model 1 and model 2, the maximum stress was taken at the abutment in the model 1. while the maximum stress was taken at the abutment screw in the model 2. 5. The magnitude of the maximum stress taken at the supporting bone, the implant fixture, the abutment, and the abutment screw was greater in the order of loading condition A, B and C. Conclusion : The stress distribution pattern of the internal connection system was mostly distributed widely to the lower part along the inner surface of the implant fixture contacting the abutment core through its contact portion because of the intimate contact of the abutment and the implant fixture and so the less stress was taken at the abutment screw, while the abutment screw can be the weakest portion clinically because the greater stress was taken at the abutment screw in case of the external connection system, and therefore the further clinical study about this problem is needed.