• The Journal of Korean Academy of Prosthodontics
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• v.46 no.4
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• pp.381-395
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• 2008

Purpoose: For decades dental implants have been used widely in the field of prosthetic dentistry. However there is confusion when establishing treatment plans in cases where some teeth are remained but an insufficient number of implants can be used due to limited anatomical status and ecomomical problems. Many clinicians have tried to connect natural teeth and implants, and it still has controversy. But, there have been few studies on mechanical analysis of connecting natural teeth and implants with konus telescopic removable partial dentures. The purpose of this study was to analyze the stress distribution of prosthesis, abutment and alveolar bone when teeth and implants were connected with the konus telescopic denture, by means of 3-dimensional finite element analysis. Material and methods: The assumption of this study was that there were 2 mandibular canine (11 mm in length, 4 mm in diameter) and 2 implants(10 mm in length, 4 mm in diameter) which are located in the second premolar region. The mandible, teeth, implants, abutments, and connectors are modeled, and analyzed with the commercial software, ANSYS Version 8.1(Swanson, Inc., USA). The control group used implants instead of natural teeth. 21038 elements, 23544 nodes were used in experimental group and 107595 elements, 21963 nodes were used in control group, Stress distribution was evaluated under 150 N vertical load on 3 experimental conditions - between teeth and implants (Load case 1), posterior to implants (Load case 2), between natural teeth (Load case 3). Results: 1. In all load cases, higher von mises stress value was observed in the experimental group. 2. Maximum von miss stress observed in all load cases and all locations were as follows ; a. 929.44 Mpa in the experimental group, 640.044 Mpa in the control group in outer crown and connector - The experimental group showed 1.45 times high value compared with the control group. b. 145,051 Mpa in the experimental group, 142.338 Mpa in the control group in abutment - The experimental group showed 1.02times high value compared with the control group. c. 32.489 Mpa in the experimental group, 25.765 Mpa in the control group in alveolar bone - The experimental group showed 1.26times higher value compared with the control group. 3. All maximum von mises stress was observed in load case 2, and maxim von mises stress in alveolar bone was 32.489 Mpa at which implant failure cannot occur. 4. If maximum von mises stress is compared between two groups, the value of the experimental group is 1.02 times higher than the control group in abutment, 1.26 times higher than the control group in alveolar bone. Conclusion: If natural teeth and implants are connected with the konus telescopic denture, maximum stress will be similar in abutment, 1.26 times higher in alveolar bone than the control group. With this result, there may be possible to make to avoid konus telescopic dentures where natural teeth and implants exist together.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.2
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• pp.125-145
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• 2001

To compare the stress distribution patterns between cement-retained and screw-retained implant supported fixed prostheses according to four different abutment types, a three dimensional finite element analysis was performed. The hypothetical three unit fixed partial denture case was modelled on the three implants(10mm length and 3.75 diameter) in mandibular bone. Four angles of implantation(vertical, 10, 15 and 20 degree inclined mesially) were created and three different directions of force (vertical, oblique, horizontal) were applied at the center of the second premolar and distal end of the first molar for each cases. Within the limits of this study, the results were as follows, 1. In vertically installed cases, the more stress was concentrated at upper components, but mesially inclined cases, the more stress was concentrated at cortical bone. 2, The more inclined mesially the more stress was observed, especially at cortical bone. 3. The cement-retained models showed lower principal stress and more even stress distribution than the screw-retained models. 4. The similar stress distribution pattern was showed in model 1 and model 2, model 3 and model 4. 5. The more stress was observed when the loads were applied at the distal end of 1st molar than the center of 2nd premolar. 6 The fixture and the model as a whole, lesser stress values were observed when vertical loads were applied as compared to horizontal and oblique loads.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.69-75
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• 2004

The degree of the indentation damage and strength degradation for 3Y-TZP ceramics and (Y,Nb)-TZP/$Al_2O_3$ dental implant composites was investigated under the Hertzian cyclic fatigue. Fatigue tests were conducted at contact loads of 500 to 3000 N and up to $10^6$ cycles in exact in vitro environments. At 500 N, no strength degradation and crack generation was observed up to $5{\times}10^5$ contact cycles. Fatigue properties of 3Y-TZP ceramics was superior to (Y,Nb)-TZP/ㅍ composites due to stress relief caused by the phase transformation from tettagonal to monoclinic phase. As contact load increased, the drastic reduction in strength was found when the damage transition from ring to radial crack occurred. The extent of strength degradation was more pronounced in vitro environments probably due to chemical corrosion of artificial saliva through cracks introduced during large numbers of contacts.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.2
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• pp.158-168
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• 2015

This article describes how to use digital system in a fully edentulous case that diagnosis to definitive prosthesis fabrication. While proceeding oral scan and CBCT taking, digital markers were attached on maxillary palate and lower existing denture. Using CBCT image and oral scan image, the bone contour and anatomical structures were analyzed and flapless surgical guide, customized abutment and prosthesis were made. After the osseointegration, the definitive prosthesis was fabricated using the oral scan image with scan body. It provides clinicians with a fast workflow and improves clinical efficiency.

• Journal of Periodontal and Implant Science
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• v.49 no.5
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• pp.310-318
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• 2019

Purpose: Surface alterations of titanium discs following instrumentation with either a nylon brush or a metal brush were evaluated. Methods: A total of 27 titanium discs with 3 surface types (9 discs for each type), including machined (M) surfaces, sandblasted and acid-etched (SA) surfaces, and surfaces treated by resorbable blast media (RBM), were used. Three discs were instrumented with a nylon brush, another 3 discs were instrumented with a metal brush, and the remaining 3 discs were used as controls for each surface type. Surface properties including the arithmetic mean value of a linear profile (Ra), maximum height of a linear profile (Rz), skewness of the assessed linear profile (Rsk), arithmetic mean height of a surface (Sa), maximum height of a surface (Sz), developed interfacial area ratio (Sdr), skewness of a surface profile (Ssk), and kurtosis of a surface profile (Sku) were measured using confocal microscopy. Results: Instrumentation with the nylon brush increased the Ra, Sa, and Sdr of the M surfaces. On the SA surfaces, Ra, Sa and Sdr decreased after nylon brush use. Meanwhile, the roughness of the RBM surface was not affected by the nylon brush. The use of the metal brush also increased the Ra, Sa, and Sdr of the M surface; however, the increase in Sdr was not statistically significant (P=0.119). The decreases in the Rz, Sz, Ra, Sa, and Sdr of the SA surfaces were remarkable. On the RBM surfaces, the use of the metal brush did not cause changes in Ra and Sa, whereas Rz, Sz, and Sdr were reduced. Conclusions: Titanium surfaces were altered when instrumented either with a nylon brush or a metal brush. Hence, it is recommended that nylon or metal brushes be used with caution in order to avoid damaging the implant fixture/abutment surface.

• The Journal of Advanced Prosthodontics
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• v.14 no.2
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• pp.70-77
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• 2022

PURPOSE. This study evaluated screw loosening and 3D crown displacement after cyclic loading of implant-supported incisor crowns cemented with original titanium bases or with three compatible, nonoriginal components. MATERIALS AND METHODS. A total of 32 dental implants were divided into four groups (n = 8 each): Group 1 used original titanium bases, while Groups 2-4 used compatible components. The reverse torque value (RTV) was evaluated prior to and after cyclic loading (1,200,000 cycles). Samples (prior to and after cyclic loading) were scanned with a microcomputed tomography (micro-CT). Preload and postload files were superimposed by 3D inspection software, and 3D crown displacement analysis was performed using root-mean-square (RMS) values. All datasets were analyzed using one-way ANOVA and Tukey's post hoc analysis. RESULTS. Significant variations were observed in the postload RTV, depending on the titanium base brand (P < .001). The mean postload RTVs were significantly higher in Groups 1 and 2 than in the other study groups. While evaluating 3D crown displacement, the lowest mean RMS value was shown in the original Group 1, with the highest RMS value occurring in Group 4. CONCLUSION. Within the limitations of this in vitro study and under the implemented conditions, it was concluded that the manufacturer brand of the titanium base significantly influenced screw loosening following the fatigue test and influenced 3D crown displacement after cyclic loading.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.4
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• pp.347-353
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• 2022

Traditional denture treatment is often performed in patients with the completely edentulous maxilla and the bilateral edentulous posterior mandible. However, with a long-term prognosis, a complication called 'combination syndrome' may occur in this oral environment. In this case, by applying an implant-assisted removable partial denture (IARPD), it is possible to preserve the alveolar bone and prevent combination syndrome. In this case, when additional implants are placed in the edentulous area, the stress applied to the abutment due to the movement of the removable denture can be reduced, so it is possible to design an esthetic clasp using resin rather than metal, and flexible denture base resin is used. As a treatment for maxillary complete denture and mandibular flexible IARPD, it showed an esthetic and functional long-term prognosis with minimal cost and surgery.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.2
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• pp.169-181
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• 2008

The aim of this study was to compare the retention and stability of implant overdenture according to the shape and the number of magnetic attachment. The experimental groups were designed for the number of implants(1, 2, 4) and shape of magnetic attachments(flat, cushion, dome type) resulting in 9 subgroups. 45 attachments were tested attached to $Br{\aa}nemark$ system implants which were planted on a mandibular model. Each attachment was composed of the magnet assembly embedded in a overdenture sample and the abutment keeper screwed into the implants. Dislodging tensile forces were applied to the overdenture samples using an Instron(cross-head speed 50.80mm/min) in 3 directions simulating function: vertical, oblique, and anterior-posterior. The loading was repeated 10 times in each direction for 45 samples. The values of maximum dislodging force of each subgroup were processed statistically using SPSS V. 12.0 at the 0.05 level of significance. The results of this study were as follows: 1. Flat type magnetic overdenture was the most retentive when subjected to vertically directed forces and dome type was the lest retentive when subjected to obliquely directed forces(p<0.05). 2. In case of planting one implant, flat type had a higher vertically retentive force than anterior-posteriorly retentive force. In case of planting two implants, flat type and dome type had a higher vertically retentive force and in case of planting four implants, flat type and cushion type had a higher vertically retentive force than anterior-posteriorly retentive force(p<0.05). 3. The incremental number of dental implant, without regards to the three types of magnetic attachment shapes, showed higher retention of overdenture(p<0.05). From the results, if a patient need much more retention of implant overdenture, flat type magnetic overdenture would be a good treatment. In case of the bruxism where excessive lateral forces are already present, dome type could be expected to produce better results. In case of planting one implant, flat type is more stable than the other shape of magnet and in case of two implant, flat type and dome type are more stable and in case of four implants, flat type and cushion type are more stable. Planting more than two implants and using flat type magnetic attachment would provide better retention and stability of implant overdenture

• Journal of Multimedia Information System
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• v.6 no.2
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• pp.67-74
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• 2019

Bone density is one of the factors in the early failure of dental implants and doctors should make a preoperative assessment of jaw bone density using patient's CT data before dental implant surgery in order to find out whether the patient has osteoporosis and osteopenia. The main goal of this study was to propose a method that based on image processing techniques in order to provide accurate information about where to drill and place an abutment screw of implants in the jaw bone for doctors and reduce human activity for the estimation of the local cancellous bone density of mandible using CT data. The experiment was performed on a computed tomography data of the jaw bone of two different individuals. We assumed that the result of the estimation of jaw bone density depends on the angle of drilling and average HU (Hounsfield Unit) values were used to evaluate the quality of local cancellous bone density of mandible. As a result of this study, we have been developed a toolbox that can be used to estimate jaw bone density automatically and found a positive correlation between the angle of the drill and time complexity but a negative correlation between the diameter of the drill and time complexity.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.3
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• pp.352-362
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• 2005

Statement of problem. Accurate impression is essential to success of implant prostheses. But there have been few studies about the accuracy of fixture-level impression techniques in internal connection implant systems. Purpose. The purpose of this study was to compare the accuracy of two fixture-level impression techniques in two conditions (parallel and divergent) and to assess the effect of tightening sequences and forces on stresses generated on superstructures in internal connection implant system (Astra Tech). Material and methods. Two metal master frameworks made from two abutments (Cast-to Abutment ST) each and a corresponding, passively fitting, dental stone master cast with four fixture replicas (Fixture Replica ST) were fabricated. Ten dental stone casts for each impression techniques (direct unsplinted & splinted technique) were made with vinyl polysiloxane impressions from the master cast. Strain gauges for each framework were fixed midway between abutments to measure the degree of framework deformation on each stone cast. Pairs of strain gauges placed opposite each other constituted one channel (half Wheatstone bridge) to read deformation in four directions (superior, inferior, anterior, and posterior). Deformation data were analyzed using one-way ANOVA and the Tukey test at the .01 level of significance. And the effect of tightening sequences (right-to-left and left-to-right) and forces (10 Ncm and 20 Ncm) were assessed with ten stone casts made from parallel condition by the splinted technique. Deformation data were analyzed using paired t-test at the .01 level of significance. Conclusions. Within the limitations of this study, the following conclusions could be drawn. 1. Frameworks bent toward the inferior side on all casts made by both direct unsplinted and splinted impression techniques in both parallel and divergent conditions. 2. There was no statistically significant difference of accuracy between the direct unsplinted and splinted impression techniques in both parallel and divergent conditions (P>.01). 3. There was no statistically significant difference of stress according to screw tightening sequences in casts made by the splinted impression technique in parallel condition (P>.01). 4. Greater tightening force resulted in greater stress in casts made by the splinted impression technique in parallel condition (P<.01).