• The Journal of Advanced Prosthodontics
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• v.5 no.1
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• pp.21-28
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• 2013

PURPOSE. This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS. Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at $30^{\circ}$ to the long axis. The implant fixtures were fixed to the jig, and connected to the abutments with a 30 Ncm tightening torque. A sine curved dynamic load was applied for $10^5$ cycles between 25 and 250 N at 14 Hz. Removal torque before loading and after loading were evaluated. The SPSS was used for statistical analysis of the results. A Kruskal-Wallis test was performed to compare screw loosening between the abutment systems. A Wilcoxon signed-rank test was performed to compare screw loosening between before and after loading in each group (${\alpha}$=0.05). RESULTS. Removal torque value before loading and after loading was the highest in stock abutment, which was then followed by gold cast abutment and CAD/CAM custom abutment, but there were no significant differences. CONCLUSION. The abutment types did not have a significant influence on short term screw loosening. On the other hand, after $10^5$ cycles dynamic loading, CAD/CAM custom abutment affected the initial screw loosening, but stock abutment and gold cast abutment did not.

• The Journal of Advanced Prosthodontics
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• v.13 no.3
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• pp.152-159
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• 2021

Purpose. The aim of this study was to investigate to what extent cyclic load affects the screwless implant-abutment connection for Morse taper dental implants. Materials and Methods. 16 implants (SICvantage max) and 16 abutments (Swiss Cross) were used. The screwless implant-abutment connection was subjected to 10,000 cycles of axial loading with a maximum force of 120 N. For the pull-off testing, before and after the same cyclic loading, the required force for disconnecting the remaining 6 implant-abutment connections was measured. The surface of 10 abutments was examined using a scanning electron microscope 120× before and after loading. Results. The pull-off test showed a significant decrease in the vertical force required to pull the abutment from the implant with mean 229.39 N ± 18.23 before loading, and 204.30 N ± 13.51 after loading (P<.01). Apart from the appearance of polished surface areas and slight signs of wear, no visible damages were found on the abutments. Conclusion. The deformation on the polished abutment surface might represent the result of micro movements within the implant-abutment connection during loading. Although there was a decrease of the pull-off force values after cyclic loading, this might not have a notable effect on the clinical performance.

• Journal of Technologic Dentistry
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• v.44 no.3
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• pp.67-75
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• 2022

Purpose: This study aimed to comparatively evaluate the stress distribution of bones surrounding the implant system to which both titanium and polyetheretherketone (PEEK) abutments are applied using a three-dimensional finite element analysis. Methods: The three-dimensional implant system was designed by the computer-aided design program (CATIA; Dassault Systemes). The discretization process for setting nodes and elements was conducted using the HyperMesh program (Altair), after finishing the design of each structure for the customized abutment implant system. The results of the stress analysis were drawn from the Abaqus program (Dassault Systèmes). This study applied 200 N of vertical load and 100 N of oblique load to the occlusal surface of a mandibular first molar. Results: Under external load application, the PEEK-modeled dental implant showed the highest von Mises stress (VMS). The lowest VMS was observed in the Ti-modeled abutment screws. In all groups, the VMS was observed in the crestal regions or necks of implants. Conclusion: The bones surrounding the implant system to which the PEEK abutment was applied, such as the cortical and trabecular bones, showed stress distribution similar to that of the titanium implant system. This finding suggests that the difference in the abutment materials had no effect on the stress distribution of the bones surrounding implants. However, the PEEK abutments require mechanical and physical properties improved for clinical application, and the clinical application is thought to be limited.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.4
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• pp.359-371
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• 2008

Purpose: The purpose of this study was to investigate the stress distribution in mandibular implant overdentures with telescopic crowns compared to bar attachment. Material and methods: Three-dimensional finite element models consisting of the mandibular bone, 4 implants, and primary bar-splinted superstructure or secondary splinted superstructure with telescopic crowns were created. Vertical and oblique loads were directed onto the occlusal areas of the superstructures to simulate the maximal intercuspal contacts and working contacts such as group function occlusion. Maximum stress and stress distribution were analysed in mandibular bone, implant abutments, and superstructures. Results: 1. In comparison of von Mises stress on mandibular bone, telescopic overdenture had a little lower stress values in vertical load and working side load except oblique load. In the mandible, the telescopic overdenture distributed more uniform stress than the bar overdenture. 2. In comparison of von Mises stress on implant abutments, telescopic overdenture had much lower stress values in all load conditions. In implant abutments, the telescopic overdenture distributed stress similar to the bar overdenture. Stress was concentrated on the distal surfaces of the posterior implant abutments in both mandibular overdentures. 3. In comparison of von Mises stress on superstructures, the telescopic overdenture had much more stress values in all load conditions. However, the telescopic overdenture distributed more uniform stress on superstructure than the bar overdenture. In the bar overdenture, stress was concentrated on each cental area of bar structures and connected area between implant abutments and bar structures. Conclusion: In the results of this study, the telescopic overdenture had lower stress values than the bar overdenture in mandibular bone and implant abutments, but more stress values in superstructures. However, if optimal material was selected in making superstructures, the telescopic overdenture was compared to the bar overdenture in stress distribution.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.3
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• pp.328-334
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• 2009

Statement of problem: Pier abutments act as a Class I fulcrum lever system when the teeth are incorporated in a fixed partial denture with rigid connectors. Therefore non-rigid connector incorporated into the fixed partial denture might reduce the stresses created by the leverage. Purpose: The purpose of this study was to evaluate, by means of finite element method, the effects of non-rigid connectors and supporting alveolar bone level on stress distribution for fixed partial dentures with pier abutments. Material and methods: A 2-dimensional finite element model simulating a 5-unit metal ceramic fixed partial denture with a pier abutment with rigid or non-rigid designs, the connector was located at the distal region of the second premolar, was developed. In the model, the lower canine, second premolar, and second molar served as abutments. Four types of alveolar bone condition were employed. One was normal bone condition and others were supporting bone reduced 20% height at one abutment. Two different loading conditions, each 150 N on 1st premolar and 1st molar and 300N on 1st molar, were used. Results: Two types of FPD were displaced apically. The amount of displacement decreased in an almost linear slope away from the loaded point. Non-rigid design tended to cause the higher stresses in supporting bone of premolar and molar abutments and the lower stresses in that of canine than rigid design. Alveolar bone loss increased the stresses in supporting bone of corresponding abutment. Conclusion: Careful evaluation of the retentive capacity of retainers and the periodontal condition of abutments may be required for the prosthetic design of fixed partial denture with a pier abutment.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.203-210
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• 2019

Purpose: The purpose of this study was to verify the effect of the abutment superimposition process on the final virtual model in the scanning process of single and 3-units bridge model using a dental model scanner. Materials and methods: A gypsum model for single and 3-unit bridges was manufactured for evaluating. And working casts with removable dies were made using Pindex system. A dental model scanner (3Shape E1 scanner) was used to obtain CAD reference model (CRM) and CAD test model (CTM). The CRM was scanned without removing after dividing the abutments in the working cast. Then, CTM was scanned with separated from the divided abutments and superimposed on the CRM (n=20). Finally, three-dimensional analysis software (Geomagic control X) was used to analyze the root mean square (RMS) and Mann-Whitney U test was used for statistical analysis (${\alpha}=.05$). Results: The RMS mean abutment for single full crown preparation was $10.93{\mu}m$ and the RMS average abutment for 3 unit bridge preparation was $6.9{\mu}m$. The RMS mean of the two groups showed statistically significant differences (P<.001). In addition, errors of positive and negative of two groups averaged $9.83{\mu}m$, $-6.79{\mu}m$ and 3-units bridge abutment $6.22{\mu}m$, $-3.3{\mu}m$, respectively. The mean values of the errors of positive and negative of two groups were all statistically significantly lower in 3-unit bridge abutments (P<.001). Conclusion: Although the number of abutments increased during the scan process of the working cast with removable dies, the error due to the superimposition of abutments did not increase. There was also a significantly higher error in single abutments, but within the range of clinically acceptable scan accuracy.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.4
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• pp.364-370
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• 2015

Fixed restoration using implants for patients with posterior partial edentulism is generalized technique. As patient demands increase, the functional and esthetic implant restoration to achieve similar results to lost natural teeth is becoming an important issue. It is inevitable to use customized CAD/CAM abutments rather than ready-made abutments for the creation of implant prosthesis which closely resembles natural teeth. Using CAD/CAM abutment made it possible to obtain natural emergency profiles for posterior implant prostheses, ensuring more comfortable, efficient management of oral hygiene. However, keratinized gingiva with sufficient width and height for a natural emergence profile is required to use a large diameter CAD/CAM abutment which ensures stability and esthetics of hard/soft tissue around the implants. In this case, for esthetical and functional implant zirconia prosthesis, soft tissue graft was performed and customized CAD/CAM abutments were used following ridge augmentation, sinus graft and implantation. Satisfactory results were obtained functionally and esthetically through periodic clinical evaluation, and I hereby report this case.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.114-118
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• 2017

Purpose: The aim of this study was to investigate the effects of a titanium component for the zirconia abutment in the internal connection implant system on screw loosening under thermocycling conditions. Materials and Methods: Internal connection titanium abutments and external connection zirconia abutments with titanium sockets were connected respectively to screw-shaped internal connection type titanium implants with 30 Ncm tightening. These implant-screw-abutment assemblies were divided into two groups of five specimens each; titanium abutments as control and zirconia abutments with titanium sockets as experimental group. The specimens were subjected to 2,000 thermocycles in water baths at $5^{\circ}C$ and $55^{\circ}C$, with 60 seconds of immersion at each temperature. The removal torque values (RTVs) of the abutment screws of the specimen were measured before and after thermocycling. RTVs pre- and post-thermocycling were investigated in statistics. Results: There was not screw loosening identified by tactile and visual inspection in any of the specimens during or after thermocycling. The mean RTV difference for the control group and the experimental group were $-1.34{\pm}2.53Ncm$ and $-1.26{\pm}2.06Ncm$, respectively. Statistical analysis using an independent t-test revealed that no significant differences were found in the mean RTV difference of the groups (P > 0.05). Conclusion: Within the limitations of this in vitro study, the titanium socket for the zirconia abutment did not show a significant effect on screw loosening under thermal stress compared to the titanium abutment in the internal connection implant.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.5-19
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• 2003

A series of centrifuge model tests were conducted to investigate the behavior of piled bridge abutments subjected to lateral soil movements induced by approach embankments. The effect of clay layer depth and the rate of embankment construction on piled bridge abutments are the main focus of this study. Tests were performed for two loading types: (1) incremental loading applied in six lifts to the final embankment height; (2) instant loading corresponding to the final embankment height applied in one lift quickly. A variety of instrumentations such as LVDTs, strain gauges, earth pressure transducers, and pore pressure transducers are installed in designed positions in order to clarify the soil-pile interaction and the short- and long-term behavior for piled bridge abutments adjacent to surcharge loads. Based on the results of a series of centrifuge model tests, the distribution of lateral flow induced by staged embankment construction has trapezoidal distribution. The maximum lateral soil pressure is about 0.75$\gamma$H at surcharge loading stage, and about 0.35 $\gamma$H at over 80% consolidated stage.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.273-283
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• 2010

This study evaluated the effect of 3 different compatible screws on the detorque values in a multiple implant-supported superstructure and single implant abutments. An implant superstructure directly connected to 4 implants was screwed to 6 experimental dental stone casts made by acrylic resin splinted impressions, using 20 Ncm. The detorque values of screws were measured twice. Three compatible abutment screws used in this study were TorqTite screw, Gold-Tite screw, and, Titanium screw. And, using single implant abutments (GoldAdapt Engaging abutments), the detorque values of 3 different screws were measured twice on 2 implants of 5 experimental casts. According to statistical analysis of detorque values using mixed model at a .05 level of significance, no statistically significant differences among 3 different compatible screws were found in a multiple implant-supported superstructure (p>0.05). But, in single implant abutments, statistically significant differences among 3 different compatible screws were found (p=0.0175). The detorque values of TorqTite(p=0.0462) and Titanium(p=0.0348) screws were significantly higher than those of Gold-Tite screw, but no statisticantly significantlydifferences were found between TorqTite and Titanium screws(p>0.05). Therefore, various compatible screws showed significant effects on the detorque values for single implant abutment, but, showed no significant effects for a multiple implant-supported superstructure.