• The Journal of Korean Academy of Prosthodontics
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• v.43 no.6
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• pp.727-735
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• 2005

Statement of problem. Platform switching in implant prosthesis has been used for esthetic and biological purpose. But there are few reports for this concept. Purpose. The purpose of this study is evaluation of platform switching in wide implant by three dimensional finite element analysis. Materials and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for Osstem implant system. Three-dimensional finite element models were developed for (1) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with wide cemented abutment, titanium alloy abutment screw, and prosthesis (2) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with regular cemented abutment, titanium alloy abutment screw and prosthesis(platform switching) was made for finite element analysis. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized to 650N, and round and flat type prostheses were loaded to 200 N. Four loading offset point (0, 2, 4, 6 mm from the center of the implants) were evaluated. Models were processed by the software programs HyperMesh and ANSA. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView were used for post processing. Results. The results from experiment were as follows; 1. von Mises stress value is increased in order of bone, abutment, implant and abutment screw. 2. von Mises stress of abutment screw is lower when platform switching. 3. von Mises stress of implant is lower when platform switching until loading offset 4 mm. 4. von Mises stress of abutment is similar between each other. 5. von Mises stress of bone is slightly higher when platform switching. Conclusion. The von Mises stress pattern of implant components is favor when platform switch ing but slightly higher in bone stress distribution than use of wide abutment. The research about stress distribution is essential for investigation of the cortical bone loss.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.5
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• pp.758-771
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• 1998

Assessment of implant mobility is an important and reliable method to clinically evaluate implant stability. PerioTest is a precise and reproducible device that cam dynamically measure the reaction of damping characteristics of peri-implant tissue. The aim of this study is to evaluate the effects of amount of implant surface area, diameter, type, implantation site, degrees of cortical engagement, and length of time in function on PTVs and to find out the most determining factor on PTVs. The results are as follows 1. 5.0mm diameter implants show significantly lower PTV than that of 3.75mm diameter implants. 2. PTV in the mandible is significantly lower than that of the maxilla 3. In the maxilla, there is no significant difference in PTV during the first year of implant function, but during the second year a significant decrease in PTV is noted. 4. In the mandible, there is a significant decrease in PTV during the first and second year of implant function. 5. Implantation site seems to be the most determining factor on PTV among the influencing factors in this study. In conclusion, the amount of implant surface area, type, degrees of cortical engagement had no significant effect on PTV, but installation site and diameter influenced significantly on PTV

• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.4
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• pp.306-313
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• 2009

Objectives: The aim of the present review was to evaluate survival rate and various factors associated with survival of osseointegrated implants. Patients and methods: The clinical comparisons were performed to evaluate survival rate of 794 endosseous implants that had been inserted between 2004 through 2008 in relation to sex and age of patients, position of implant, implant system and surface characteristics, length and diameter of implant, and bone graft technique. Results: The survival rate of implant was 94.3% in posterior area of maxilla and 98.6% in posterior area of mandible by position of implant, a statistically significant difference. As to diameter of implant, survival rate was 98.4% between the 4.0 and 4.5 mm and 75.0% in larger than 5.0 mm, that was statistically significant difference. There was a statistically significant difference regard to bone graft and surgical technique. The implant survival rate was 89.0% in a placement site which performed sinus lifting, and in case of implant placement with guided bone regeneration technique and without bone grafting was 97.6% and 100% each. Conclusion: According to these findings, this study establishes a relationship between survival rate of implant and position, surface characteristics, diameter of implant and bone graft technique.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.39
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• pp.2.1-2.6
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• 2017

Background: All clinicians are aware of the difficulty of installing a dental implant in posterior maxilla because of proximate position of maxillary sinus, insufficient bone width, and lower bone density. This study is to examine which factors will make the implantation in the posterior maxilla more difficult, and which factors will affect the postoperative implant stability in this region. Methods: Five hundred seventy-three fixtures on the maxilla posterior were included for this study from all the patients who underwent an installation of the dental implant fixture from January 2010 to December 2014 at the Department of Oral and Maxillofacial Surgery in Pusan National University Dental Hospital (Yangsan, Korea). The postoperative implant stability quotient (ISQ) value, fixture diameter and length, presence of either bone graft or sinus lift, and graft material were included in the reviewed factors. The width and height of the bone bed was assessed via preoperative cone beam CT image analysis. The postoperative ISQ value was taken just before loading by using the OsstellTM $mentor^{(R)}$ (Integration Diagnostics AB, Gothenburg, Sweden). The t test and ANOVA methods were used in the statistical analysis of the data. Results: Mean ISQ of all the included data was 79.22. Higher initial bone height, larger fixture diameter, and longer fixture length were factors that influence the implant stability on the posterior edentulous maxilla. On the other hand, the initial bone width, bone graft and sinus elevation procedure, graft material, and approach method for sinus elevation showed no significant impact associated with the implant stability on the posterior edentulous maxilla. Conclusions: It is recommended to install the fixtures accurately in a larger diameter and longer length by performing bone graft and sinus elevation.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.277-288
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• 2002

Seven finite element models were constructed in mandible having single screw-type implant fixture connected to the premolar superstructure, in order to evaluate how the length, diameter and platform shape of a screw-type fixture influence the stress in the supporting tissue around fixtures. Each finite element model was varied in terms of length, diameter, and platform shape of the fixture. In each model, 250N of vertical load was placed on the central pit of an occlusal plane and 250N of oblique load placed on the buccal cusp. The stress distribution in the supporting tissue and the other components was analysed using 2-dimensional finite element analysis and the maximum von Mises stress in each reference area was compared. Under lateral loading, the stress was larger at the abutment/fixture interface, and in the crestal bone, compared to the stress pattern under vertical loading. The amount of stress at the superstructure was similar regardless of the length, diameter and platform shape of a fixture. Around the longer fixture, the stress was decreased at the bone crest and subjacent cancellous bone and increased in the cancellous bone area apical to the fixture. Around the wider fixture, the stress was decreased at the abutment/fixture interface, and the bone crest and increased in the cancellous bone area apical to the fixture. Around the fixture having wider platform, less stress was produced at the abutment/fixture interface and the upper part of the cortical bone, compared to the fixture having standard platform. In conclusion, the stress distribution of the supporting tissue was affected by length, diameter, and platform shape of a fixture, and the fixture which was larger in diameter and length could reduce the stress in the supporting tissues at the bone-fixture interface and bone crest area.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.3
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• pp.468-482
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• 1998

Since the concept of osseointegration was introduced by Branemark of Sweden, dental implants have been used for various dental prosthetic treatments. The survival rate of dental implant is likely to be closely related to the total biomechanical role of each component of implant system. The use of interchangeable component is very attractive for dental practitioners because such an approach would save treatment cost, flexibility of prosthetic treatment options as well as conveniences. Therefore, the use of interchangeable implant system has been increasing without scientific assessment of safety and efficacy of various interchangeable implant system. The purpose of this study, therefore, were to compare the geometric characteristic of four interchangeable dental implant screws and the loosening torque of these screws. Four types of dental implant screws tested in this study were Nobelpharma, 3i, Impla-med, Restore. Four screws each of the test specimens were subjected for scanning electron microscopic examinations under the same condition and a 35x magnified standard SEM picture was objected from each test specimen using JSM-5200 scanning microscope. From each of the SEM pictures, eight parameters. i.e., diameter of screw head. screw length, thread pitch, major diameter. neck diameter, neck length, crest width and root width were determined using a caliper. The measurement for each parameters were then corrected for their magnification factor. The loosening torque were also determined by using a torque gauge. All of the measurements were statistically analyzed by ANOVA test and multiple range test. Statistical significance was set in advance at the probability level of less than 0.05. All analyses were done with SPSS software for the personal computer. The conclusion obtained from this studies were summarized as the following; 1. No statistically significances were noted in the thread pitch. and crest width in the four screws, and in the case of major diameter, the Impla-med screw was significantly smaller than the other three screws (p<0.05). Therefore, four implant bolts could be physically inserted in a abutment nuts. 2. The diameter of screw head was decreased in the order of Restore, 3i, Nobelpharma, Impla-med screws and the length of screws were decreased in the order of 3i, Restore, Nobelpharma and Impla-med. The diameter of neck was decreased in the order of Impla-med, Restore. Nobelpharma, 3i screws. The differences of each of these parameters were statistically significant (p<0.05). The width of root of screws were decreased in the order of Nobelpharma, Impla-med, Restore and 3i. The differences among Nobelpharma and Impla-med. Restore and 3i were statistically significant (p<0.05). 3. When the screws were loosening 1, 3, 4 and 5 times, the loosening torque for Impla-med and 3i screws were significantly higher than that of Nobelpharma or Restore screws (p<0.05). However, when statistically smaller than that of 3i, Restore or Nobelpharma screws(p<0.05).

• The Journal of Advanced Prosthodontics
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• v.3 no.4
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• pp.204-215
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• 2011

PURPOSE. The aim of this retrospective study is to analyze the relationship between local factors and survival rate of dental implant which had been installed and restored in Seoul Veterans Hospital dental center for past 10 years. And when the relationship is found out, it could be helpful to predict the prognosis of dental implants. MATERIALS AND METHODS. A retrospective study of patients receiving root-shaped screw-type dental implants placed from January 2000 to December 2009 was conducted. 6385 implants were placed in 3755 patients. The following data were collected from the dental records and radiographs: patient's age, gender, implant type and surface, length, diameter, location of implant placement, bone quality, prosthesis type. The correlations between these data and survival rate were analyzed. Statistical analysis was performed with the use of Kaplan-Meier analysis, Chi-square test and odds ratio. RESULTS. In all, 6385 implants were placed in 3755 patients (3120 male, 635 female; mean age $65{\pm}10.58$ years). 108 implants failed and the cumulative survival rate was 96.33%. There were significant differences in age, implant type and surface, length, location and prosthesis type (P<.05). No significant differences were found in relation to the following factors: gender, diameter and bone quality (P>.05). CONCLUSION. Related factors such as age, implant type, length, location and prosthesis type had a significant effect on the implant survival.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.269-275
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• 2013

Purpose: The aim of this retrospective study was to evaluate the influence of implant diameter, length and placement to implant stability. Materials and methods: Total 90 implants (US II plus$^{TM}$, Osstem co, Busan, Korea) of 72 patients were determined as experimental samples. The factors of diameters(${\phi}$ 4 mm, ${\phi}$ 5 mm), lengths (10 mm, 11.5 mm, 13 mm), and implant placement (maxilla, mandible) were analyzed. The stability of the implants was measured by resonance frequency analysis (RFA) at the time of implant placement and impression taking. The difference of ISQ values according to patient's gender was evaluated by Independent t-test. ISQ values were compared between implant diameter, length and placement using one-way ANOVA and Tukey HSD test (${\alpha}=.05$). To compare ISQ values between at the time of surgery and impression taking, paired t-tests were used (${\alpha}=.05$). Results: The change of implant length did not show significant different on the ISQ value (P>.05). However, 5 mm diameter implants had higher ISQ values than 4 mm diameter implants (P<.05). Implants placed on the mandible showed significantly higher ISQ values than on the maxilla (P<.05). Conclusion: In order to increase implant stability, it is better to select the wider implant, and implants placed on mandible are possible to get higher stability than maxilla. ISQ values at impression taking showed higher implant stability than ISQ values at implant placement, it means that RFA is clinically effective method to evaluate the change of implant stability through the osseointegration. The consideration of the factors which may affect to the implant stability will help to determine the time of load applying and increase the implant success rate.

• Journal of Technologic Dentistry
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• v.26 no.1
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• pp.69-76
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• 2004

The objective of this finite element method study was to analyze the stress distribution induced on a supporting bone by 3.75mm, 4.0mm, 5.0mm diameter of dental implant fixture(13mm length). 3-dimensional finite element models of simplified gold alloy crown(7mm height) and dental implant structures(gold cylinder screw, gold cylinder, abutment screw, abutment, fixture and supporting bone(cortical bone, cancellous bone) designs were subjected to a simulated biting force of 100 N which was forced over occlusal plane of gold alloy crown vertically. Maximum von Mises stresses(MPa) under vertical loading were 9.693(3.75mm diameter of fixture), 8.885(4.0mm diameter of fixture), 6.301(5.0mm diameter of fixture) and the highest von Mises stresses of all models were concentrated in the surrounding crestal cortical bone. The wide diameter implant was the good choice for minimizing cortical bone-fixture interface stress.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.6
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• pp.440-448
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• 2012

Purpose: The purpose of this study was to evaluate marginal bone loss of the alveolar crest on implants with or without guided bone regeneration and variables that have influenced. Methods: The clinical evaluation were performed for survival rate and marginal bone loss of 161 endosseous implants installed with guided bone regeneration (GBR) in 83 patients from September 2009 to October 2010 in relation to sex and age of patients, position of implant, implant system, length and diameter of implant. Study group (n=42) implant with GBR procedure, control group (n=41) implant without GBR technique. Simultaneous GBR approach using resorbable membranes combined with autogenous bone graft or freeze-dried bone allograft or combination. Radiographic examinations were conducted at healing abutment connection and latest visit. Marginal bone level was measured. Results: Mean marginal bone loss was 0.73 mm in study group, 0.63 mm in control group. Implants in maxillary anterior area (1.21 mm) were statistically significant in study group (P<0.05), maxillary posterior area (0.81 mm) in control group (P<0.05). Mean marginal bone loss 1.47 mm for implants with diameter 3.4 mm, 0.83 mm for implants of control group with diameter 4.0 mm (P<0.05). Some graft materials showed an increased marginal bone loss but no statistically significant influence of sex, implant type or length. Conclusion: According to these findings, this study demonstrated the amount of marginal bone loss around implant has maintained a relative stable during follow-up periods. We conclude that implants with GBR had similar survival rate and crestal bone level compared with implants in native bone.