• The Journal of Korean Academy of Prosthodontics
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• v.56 no.2
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• pp.114-119
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• 2018

Purpose: Patients who treated implant immediate loading within a week after implant placement at Wonkwang University Dental Hospital Implant Center were evaluated marginal bone resorption. These retrospective analyses are intended to reinforce the clinical evidence for the implant immediate loading. Materials and methods: Medical history and radiographic data were investigated, which were the patients' who treated implant immediate loading and restoration with provisional prostheses between January 2005 and June 2016, at Wonkwang University Dental Hospital Implant Center. Total number of implants was 70, marginal bone resorption was measured according to implant length, diameter and connection type. To measure marginal bone resorption, periapical radiographs were taken when the implants were placed and after 6 month. Statistical analysis was done in Mann-whitney U test and Kruskal-wallis test with SPSS 22.0 software (P<.05). Results: Mean marginal bone resorption around immediately loaded implants according to implant connection type was shown $1.24{\pm}0.72mm$ in internal hexagon connection type and $1.73{\pm}1.27mm$ in external hexagon connection type. There was no statically significant difference in marginal bone resorption with implant length and diameter. Conclusion: Implants with immediated loading in internal hexagon connection type showed less marginal bone resorption significantly than in external hexagon connection type.

• 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.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.1
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• pp.58-66
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• 2020

Implant-Assisted Removable Partial Dentures (IARPDs) treatment is being performed in a fully edentulous patient using implant surveyed prosthesis as an abutment. Implant-supported prosthesis as an abutment of IARPDs is classified into screw-retained and cement-retained type according to the retention type, and each has advantages and disadvantages. The EZ crown system (Samwon DMP, Yangsan, Korea) has a cylinder combined with abutment, and the nickel-titanium spring in this cylinder provides a constant force on the zirconia ball to obtain retention in EZ crown system. In this patient, the natural abutment teeth of the mandibular overdenture was hopeless. We planned implant assisted removable partial denture using anterior implant surveyed prosthesis considering functional and esthetical rehabilitation, cost and patient's needs. When fabricating IARPDs using implant as abutment, we could compensate for the shortcomings of existing implant-supported prosthesis retention type and made the design of removable partial denture easy due to using EZ crown system.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.4
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• pp.365-375
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• 2009

Statement of problems: Stress analysis on implant components of the combined screw- and cement-retained implant prosthesis has not investigated yet. Purpose: The purpose of this study was to assess the load distribution characteristics of implant prostheses with the different prosthodontic retention types, such as cement-type, screw-type and combined type by using 3-dimensional finite element analysis. Material and methods: A 3-dimensional finite element model was created in which two SS II implants (Osstem Co. Ltd.) were placed in the areas of the first premolar and the first molar in the mandible, and three-unit fixed partial dentures with four different retention types were fabricated on the two SS II implants. Model 1 was a cement-retained implant restoration made on two cement-retained type abutments (Comocta abutment; Osstem Co. Ltd.), and Model 2 was a screw-retained implant restoration made on the screw-retained type abutments (Octa abutment; Osstem Co. Ltd.). Model 3 was a combined type implant restoration made on the cement-retained type abutment (Comocta abutment) for the first molar and the screw-retained type abutment (Octa abutment) for the first premolar. Lastly, Model 4 was a combined type implant restoration made on the screw-retained type abutment (Octa abutment) for the first molar and the cement-retained type abutment (Comocta abutment) for the first premolar. Average masticatory force was applied on the central fossa in a vertical direction, and on the buccal cusp in a vertical and oblique direction for each model. Von-Mises stress patterns on alveolar bone, implant body, abutment, abutment screw, and prosthetic screw around implant prostheses were evaluated through 3-dimensional finite element analysis. Results: Model 2 showed the lowest von Mises stress. In all models, the von Mises stress distribution of cortical bone, cancellous bone and implant body showed the similar pattern. Regardless of loading conditions and type of abutment system, the stress of bone was concentrated on the cortical bone. The von-Mises stress on abutment, abutment screw, and prosthetic screw showed the lower values for the screw-retained type abutment than for the cement-retained type abutment regardless of the model type. There was little reciprocal effect of the abutment system between the molar and the premolar position. For all models, buccal cusp oblique loading caused the largest stress, followed by buccal cusp vertical loading and center vertical loading. Conclusion: Within the limitation of the FEA study, the combined type implant prosthesis did not demonstrate more stress around implant components than the cement type implant prosthesis. Under the assumption of ideal passive fit, the screw-type implant prosthesis showed the east stress around implant components.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.2
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• pp.179-190
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• 2012

The installation of an implant in the distal extension area to assist a partial dentrue (IARPD) was used carefully in clinical situations. The purpose of this review on the IARPD is describing the concept, clinical results and guidelines of IARPD. For the review, a literature search was performed using the PubMed. The data from the literature suggest that the placement of the implants could improve function and patient satisfaction. In addition, IARPD reduced the residual ridge resorption. Longer and wider implant should be placed. Less than $15^{\circ}$ angulation may be not harmful. To prevent the loosening of the abutment, modified abutment or resilient attachment should be used. However, the connection method between the clasp retention and IARPD should be considered for long time success. Moreover, longitudinal clinical studies are required for evaluation of IARPD.

• Journal of Dental Rehabilitation and Applied Science
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• v.39 no.4
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• pp.250-259
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• 2023

The use of digital technology in fixed prosthetic treatment using implants enables predictive treatment through diagnosis and virtual surgery by integrating clinical and radiological information of patients. Existing digital scanning methods require several components to be removed, such as removing the healing abutment and connecting the scan body. In the scannable healing abutment developed in consideration of this point, scanning is performed directly on the healing abutment, maintaining soft tissue sealing and simplifying scanning. Digital technology can also be used when obtaining the intermaxillary relationship. Recently, various digital technologies have been reported to acquire the intermaxillary relationship of edentulous patients using surgical guides, patient-specific scanning devices, or scans of the inside of temporary dentures. In this case, the implant-supported fixed prosthesis treatment was performed through scanning the scannable healing abutment and the inner side of the temporary denture to obtain the intermaxillary relationship, thereby simplifying the treatment process and obtaining aesthetically and functionally excellent clinical results.

• The Journal of Korean Academy of Prosthodontics
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• v.62 no.3
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• pp.243-252
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• 2024

When fabricating definitive implant-supported fixed prostheses in upper and lower completely edentulous patients, it is crucial to get information about the vertical dimension, jaw relationship, implants, abutments and gingival contour. In this case, temporary prostheses were used to take the information. The temporary prosthesis was scanned outside of the mouth so that it increased the efficiency of scanning it. During the scan of the prosthesis, a scan zig which connected both posterior parts of the prosthesis was used to minimize the scan errors. We report this case because we obtained satisfactory functional and esthetic results by using the digital technology.

• Journal of Dental Rehabilitation and Applied Science
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• v.38 no.2
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• pp.97-109
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• 2022

Purpose: This study aims to investigate the risk indicators contributing to implant failure, and analyze the relationship between risk indicators and marginal bone loss (MBL) through long-term follow-up over 3 years. Materials and Methods: From 2003 to 2017, patients' medical charts with a history of dental implant surgery at Chonnam National University Dental Hospital were reviewed retrospectively. The patient's demographic variables, and clinical variables were recorded. Periapical radiographs were used to evaluated the changes in MBL around implants. And we analyzed implant survival rates. Multiple regression analysis with backward elimination was conducted to correlate the patient's clinical variables and implant failure and Pearson correlation analysis was performed to the correlated between implant long-term survival rates and MBL and initial stability. Results: In multiple regression analysis, there was a statistically significant negative correlation between abutment connection type (β = -.189, P < .05), with or without SPT (β = -.163, P < .05), diabetes (β = -.164, P < .05), osteoporosis (β = -.211, P < .05) and MBL. Anticoagulant medication influenced the long-term success rate of implants. PTV values at the second implant surgery showed a statistically significant negative correlation with long-term implant survival (P < .05). Conclusion: For the long-term success of the implant, the appropriate abutment connection type must be selected and the periodic SPT is recommended. Systemic diseases such as diabetes and osteoporosis and anticoagulant medication should be considered. Furthermore, since high PTV at the second implant surgery correlated with the long-term survival rates of the implant, initial stability should be carefully considered before undergoing the prosthetic procedure.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.4
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• pp.345-351
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• 2015

Purpose: The purpose of this study was to evaluate the proper axial thickness of zirconia abutment applied to implant in the anterior region. Materials and methods: Zirconia abutments were prepared at different axial wall thickness by processing pre-sintered zirconia blocks via CAD/CAM to obtain equal specimens. The abutments were each produced with a thickness of 0.5 mm (Group 1), 0.8 mm (Group 2), 1.2 mm (Group 3), or 1.5 mm (Group 4). The implant used in this study was a external connection type one (US, Osstem, Pussan, Korea) product and the zirconia abutment was prepared via replication of a cemented abutment. The crowns were prepared via CAM/CAM with a thickness of 1.5 mm and were cemented to the abutments using $RelyX^{TM}$ UniCem cement. A universal testing machine was used to apply load at 30 degrees and measure fracture strength of the zirconia abutment. Results: Fracture strength of the abutments for Group 1, Group 2, Group 3, and Group 4 were $236.00{\pm}67.55N$, $599.00{\pm}15.80N$, $588.20{\pm}33.18N$, and $97.83{\pm}98.13N$, respectively. Group 1 showed a significantly lower value, as compared to the other groups (independent Mann-Whitney U-test. P<.05). No significant differences were detected among Group 2, Group 3, and Group 4 (independent Mann-Whitney U-test. P>.05). Conclusion: Zirconia abutment requires optimal thickness for fracture resistance. Within the limitation of this study, > 0.8 mm thickness is recommended for zirconia abutment in anterior implants.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.2
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• pp.201-212
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• 2012

There are some similar aspects at histological and morphological characteristics between the peri-implant tissue and periodontal tissue and the direct attachment between the titanium and soft tissue around the implant called as "Functional ankylosis" can prevent the apical infiltration of inflammatory and bone resorption around implant. But, the repeated connection and disconnection of the abutment can destroy the mucosal barrier of soft tissue around the implant and can cause the marginal bone resorption. The amount of marginal bone resorption may reduced if the prosthetic abutment is placed at that time of surgery. Connection of the prosthetic abutment at surgery was limited because the low accuracy of conventional method, but by using of Cone Beam Computed Tomography(CBCT) and guide surgery, the 3-dimensional accuracy of implant placement became much higher than before and it became possible. This is a clinical case of immediate connection of prosthetic abutment and provisional restoration by using of precise CBCT diagnosis and pre-fabricated zirconia customized abutment at surgery and the alternative method is described in this article because of the clinically contentable results.