• Maxillofacial Plastic and Reconstructive Surgery
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• v.38
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• pp.31.1-31.7
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• 2016

Background: The objective of this retrospective study was to show results from platform-switched narrow-diameter implants in the posterior edentulous region, which we followed up for more than 1 year after functional loading. Methods: Ninety-eight narrow implants were inserted into 66 patients. After healing, fixed implant-supported prostheses were delivered to the patients, and Periotest and radiographic examinations were performed. After the first year of loading, the implant outcome was again evaluated clinically and radiographically using the Periotest analysis. Crestal bone loss and Periotest values (PTVs) were used to evaluate the effect of surgery, prosthesis, implant, and a host-related factor. A general linear model was used to statistically detect variables statistically associated with crestal bone loss and Periotest value. Results: We followed up on the implants over 1 to 4 years after loading; their survival rate was 100 %, and pronounced differences from PTVs were noted among jaw location, bone quality, and loading period. No difference was detected in bone loss among the variables studied. Bone loss after functional loading was $0.14{\pm}0.39mm$. The stability value from the Periotest was $-3.29{\pm}0.50$. Conclusions: Within the limitations of this study, judicious use of platform-switched narrow implants with a conical connection must be considered an alternative for wide-diameter implants to restore a posterior edentulous region.

• Journal of Periodontal and Implant Science
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• v.49 no.3
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• pp.185-192
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• 2019

Purpose: Implant wall thickness and the height of the implant-abutment interface are known as factors that affect the distribution of stress on the marginal bone around the implant. The goal of this study was to evaluate the long-term effects of supracrestal implant placement and implant wall thickness on maintenance of the marginal bone level. Methods: In this retrospective study, 101 patients with a single implant were divided into the following 4 groups according to the thickness of the implant wall and the initial implant placement level immediately after surgery: 0.75 mm wall thickness, epicrestal position; 0.95 mm wall thickness, epicrestal position; 0.75 mm wall thickness, supracrestal position; 0.95 mm wall thickness, supracrestal position. The marginal bone level change was assessed 1 day after implant placement, immediately after functional loading, and 1 to 5 years after prosthesis delivery. To compare the marginal bone level change, repeated-measures analysis of variance was used to evaluate the statistical significance of differences within groups and between groups over time. Pearson correlation coefficients were also calculated to analyze the correlation between implant placement level and bone loss. Results: Statistically significant differences in bone loss among the 4 groups (P<0.01) and within each group over time (P<0.01) were observed. There was no significant difference between the groups with a wall thickness of 0.75 mm and 0.95 mm. In a multiple comparison, the groups with a supracrestal placement level showed greater bone loss than the epicrestal placement groups. In addition, a significant correlation between implant placement level and marginal bone loss was observed. Conclusions: The degree of bone resorption was significantly higher for implants with a supracrestal placement compared to those with an epicrestal placement.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.2
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• pp.110-119
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• 2016

Purpose: This study is aimed to assess changes of stress distribution dependent on different connection lengths and placement of the fixture top relative to the ridge crest. Materials and methods: The internal-conical connection implant which has a hexagonal anti-rotation index was used for FEM analysis on stress distribution in accordance with connection length of fixture-abutment. Different connection lengths of 2.5 mm, 3.5 mm, and 4.5 mm were designed respectively with the top of the fixture flush with residual ridge crest level, or 2 mm above. Therefore, a total of 6 models were made for the FEM analysis. The load was 170 N and 30-degree tilted. Results: In all cases, the maximum von Mises stress was located adjacent to the top portion of the fixture and ridge crest in the bone. The longer the connection length was, the lower the maximum von Mises stress was in the fixture, abutment, screw and bone. The reduction rate of the maximum von Mises stress depending on increased connection length was greater in the case of the fixture top at 2 mm above the ridge crest versus flush with the ridge crest. Conclusion: It was found that the longer the connection length, the lower the maximum von Mises stress appears. Furthermore, it will help prevent mechanical or biological complications of implants.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.4
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• pp.308-316
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• 2018

Telescopic denture has advantages such as transfer the occlusal force to the long axis of the abutment, easiness of oral hygiene management, increase of retention and stability, splint effect due to secondary fixation between abutments and have been reported a higher success rates than conventional removable partial denture (RPD). However, there are disadvantages such as complex laboratory procedures, long treatment periods and high costs, and high incidence of complications. This clinical report describes two cases, a 4-point supported telescopic denture using telescopic crown and a 2-point supported telescopic denture using conical crown with functionally satisfactory results. Frequent complications of telescopic denture, which are reported in various literature were reviewed. Clinical and laboratory procedures were performed in consideration of complications that reported.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.1
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• pp.39-46
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• 2010

To assess the stress distribution of implant prosthesis induced by intentional misfit using photoelastic model. Stress was measured at the surrounding bone after applying vertical load to the implant. Three implants were placed in each of three photoelastic resin blocks. No misfits were used for the control group, while for the experimental group $100{\mu}m$ misfit after cutting the crown was used. The photoelastic stress analysis was performed. In control group, stress concentration was not shown when the load was not applied, whereas stress concentration was shown only in the loaded part even when load was applied and the stress was distributed in anterior-posterior direction when applying a load in the middle. When intentional misfits were given, stress around the fixture was incurred when tightening the screw even if load was not applied. If the load was applied, stress was concentrated around the implants including areas where the load was applied. In particular, the prosthesis made of UCLA showed more stress concentration as compared with a conical abutment. In the UCLA case, concentration was shown from the apex following through the axis to the cervical area. Prosthesis with misfit makes the stress concentrated though the load was not applied and it induces even more severe stress concentration when the load was applied. This founding demonstrates the importance of the correct prosthesis production.