• Journal of Korean Dental Science
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• 제4권2호
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• pp.67-72
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• 2011

Purpose: This study sought to evaluate the effects of bone graft wedging on the initial stability of implants in bone sites of unfavorable quality. Materials and Methods: Three male beagle dogs were used in this study. Osteotomies were performed with parallel drills (${\O}4.1{\times}10mm$), and fixtures (${\O}3.3{\times}8mm$) were placed. The control group was given implants without bone graft. Experiment group A was given implants with minimal initial stability using autobone grafts, whereas experiment group B was given xenografts. Groups were also divided by healing times at 4, 8, and 12 weeks. Results: All implants in the control group failed to osseointegrate. On the other hand, all implants in the experiment groups were clinically well-maintained during the entire experiment period. After 4, 8, and 12 weeks, bone-to-implant contact (BIC) ratio and implant stability quotient (ISQ) increased in the experiment groups. The differences between experiment groups A and B were not statistically significant, however. Conclusion: In unfavorable bone regions for dental implants, bone graft packing into the osteotomy prior to implant placement secured minimal initial stability and showed reasonable BIC ratios and ISQ values throughout the study period.

• Journal of applied mathematics & informatics
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• 제35권1_2호
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• pp.191-204
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• 2017

A new fifth-order weighted Runge-Kutta algorithm based on heronian mean for solving initial value problem in ordinary differential equations is considered in this paper. Comparisons in terms of numerical accuracy and size of the stability region between new proposed Runge-Kutta(5,5) algorithm, Runge-Kutta (5,5) based on Harmonic Mean, Runge-Kutta(5,5) based on Contra Harmonic Mean and Runge-Kutta(5,5) based on Geometric Mean are carried out as well. The problems, methods and comparison criteria are specified very carefully. Numerical experiments show that the new algorithm performs better than other three methods in solving variety of initial value problems. The error analysis is discussed and stability polynomials and regions have also been presented.

• The Journal of Advanced Prosthodontics
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• 제1권1호
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• pp.19-25
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• 2009

STATEMENT OF PROBLEM. Primary stability at the time of implant placement is related to the level of primary bone contact. The level of bone contact with implant is affected by thread design, surgical procedure and bone quality, etc. PURPOSE. The aim of this study was to compare the initial stability of the various taper implants according to the thread designs, half of which were engaged to inferior cortical wall of type IV bone(Group 1) and the rest of which were not engaged to inferior cortical wall(Group 2) by measuring the implant stability quotient(ISQ) and the removal torque value(RTV). MATERIAL AND METHODS. In this study, 6 different implant fixtures with 10 mm length were installed. In order to simulate the sinus inferior wall of type IV bone, one side cortical bone of swine rib was removed. 6 different implants were installed in the same bone block following manufacturer s recommended procedures. Total 10 bone blocks were made for each group. The height of Group 1 bone block was 10 mm for engagement and that of group 2 was 13 mm. The initial stability was measured with ISQ value using Osstell $mentor^{(R)}$ and with removal torque using MGT50 torque gauge. RESULTS. In this study, we found the following results. 1. In Group 1 with fixtures engaged to the inferior cortical wall, there was no significant difference in RTV and ISQ value among the 6 types of implants. 2. In Group 2 with fixtures not engaged to the inferior cortical wall, there was significant difference in RTV and ISQ value among the 6 types of implants(P < .05). 3. There was significant difference in RTV and ISQ value according to whether fixtures were engaged to the inferior cortical wall or not(P < .05). 4. Under-drilling made RTV and ISQ value increase significantly in the NT implants which had lower RTV and ISQ value in Group 2(P < .05). CONCLUSIONS. Without being engaged to the inferior cortical wall fixtures had initial stability affected by implant types. Also in poor quality bone, under-drilling improved initial stability.

• Journal of applied mathematics & informatics
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• 제7권1호
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• pp.215-222
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• 2000

A multigrid algorithm is developed for solving the one- dimensional initial boundary value problem. The numerical solutions of linear and nonlinear Burgers; equation for various initial conditions are studied. The stability conditions are derived by Von -Neumann analysis . Numerical results are presented.

• 대한전기학회논문지
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• 제38권12호
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• pp.1033-1047
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• 1989

A finite element method for the analysis of magnetic fields with hysteresis characteristics is proposed. The method employs Preisach model to describe hysteresis of magnetic material, so that even multi-branch or minor-loop characteristics can be taken into account. The problem can be considered as the analysis of a nonlinear equation where magnetization depends not only on the present value of the magnetic field but also on the past values, and the problem can be solved by the iteration method. Measurements were carried out on soft ferrite EI core for the comparison with computer solution, and good agreements were obtained. is investigated. A theoretical approach to gait study is proposed in which the static stability margins for periodic gaits are expressed in terms of the kinematic gait formula. The effects fo the stride length on static stability are analyzed and the relations between static stability and initial body configurations are examined. It is shown that the moving velocity can be increased to some extent without affecting stability margins for a given initial body configuration. Computer simulations are performed to verify the analysis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.134-140
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• 2007

Nonlinear parabolized stability equations for compressible flow in general curvilinear coordinate system are derived to deal with a broad range of transition prediction problems on complex geometry. A highly accurate finite difference PSE code has been developed using an implicit marching procedure. Blasius flow is tested. The results of the present computation show good agreement with DNS data. Nonlinear interaction can make the T-S fundamental wave more unstable and the onset of its amplitude decay is shifted downstream relative to linear case. For nonlinear calculations, rather small difference in initial amplitude can produce large change during nonlinear region. Compressible secondary instability at Mach number 1.6 is also simulated and showed that 1.1% initial amplitude for primary mode is enough to trigger the secondary growth.

• Kyungpook Mathematical Journal
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• 제51권4호
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• pp.435-456
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• 2011

The Chebyshev collocation method in [21] to solve stiff initial-value problems is generalized by using arbitrary degrees of interpolation polynomials and arbitrary collocation points. The convergence of this generalized Chebyshev collocation method is shown to be independent of the chosen collocation points. It is observed how the stability region does depend on collocation points. In particular, A-stability is shown by taking the mid points of nodes as collocation points.

• 대한치과보철학회지
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• 제47권3호
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• pp.335-341
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• 2009

연구목적: 충분한 골질과 골량은 임플란트의 조기 실패 방지와 초기 안정성을 위해서 중요한 사항으로 알려져 있다. 임플란트 길이나 직경이 초기 안정성에 미치는 영향을 연구한 다수의 실험들이 골과의 접촉면적을 달리하였기 때문에 직경과 길이만이 초기 안정성에 미치는 실제 영향을 파악하는데 한계가 있다. 이에 유사한 표면적을 가지는 임플란트를 통하여 길이와 직경 상대적 변화가 초기 안정성에 미치는 영향을 알아보고자 하였다. 연구 재료 및 방법: 골질에 따라 피질골과 해면골의 두께가 다른 4종류의 폴리우레탄 모형골을 임플란트 식립에 사용하였다. 유사한 표면적과 형태를 가지나 직경과 길이가 서로 다른 임플란트 ($3.5{\times}13.0\;mm$, $4.0{\times}11.5\;mm$, $4.5{\times}10.0\;mm$, $5.0{\times}8.5\;mm$) 10개를 식립하고 식립 회전력과 공진 주파수를 측정하였다. 결과 및 결론: 초기 안정성에 영향을 미치는 주 요소는 골질이었으며 (P < .05), 식립 회전력과 공진 주파수 모두 골질이 우수할수록 높은 측정치를 보였다. 2. D1, D2, D3 모형골에서 임플란트의 직경이 커지고 길이가 짧아짐에 따라 공진 주파수는 유의한 차이를 보이지 않았으나 (P >.05), 식립 회전력은 증가하였다 (P <.05). 3. D4 모형골에서는 임플란트의 직경이 커지고 길이가 짧아짐에 따라 공진주파수와 식립 회전력 모두 감소하였다 (P <.05). 이상의 결과로부터 골질이 양호한 조건에서는 길이가 짧더라도 직경이 큰 임플란트의 사용이 초기 안정성 측면에서 부가적 수술의 대안이 될 수 있을 것으로 생각된다.

• 대한조선학회논문집
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• 제45권4호
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• pp.455-461
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• 2008

This article describes a part of collaborative research between industry and academy to develop an initial hull form of 46 feet motor yacht. Hydrodynamic performances such as stability, resistance and seaworthiness were estimated after completing the procedure of hull form design in the initial design stage.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권6호
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• pp.518-528
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• 2008

Purpose: The long-term experience of using osseointegrated implants for prosthetic rehabilitation of the edentulous patients shows that high success rates can be predictably achieved. Primary implant stability has been identified to be a prerequisite to achieve osseointegration. In this study, we set up the amount of removed bone so that it differed on implant installation site for each group. The influence of each initial stability on secondary stability and osseointegration was compared with time lapse using resonance frequency analysis and histomorphometric analysis. Materials and methods: A total 27 US $II^{(R)}$ (Osstem, Korea) implants were placed in the mandibular edentulous area of 3 beagle dogs. The implant site was prepared by the conventional technique with drills, and three experimental groups were divided into under-drilling group, normal-drilling group and over-drilling group. The Implant Stability Quotient (ISQ) was measured at intervals of immediately, 4, 8, 12 weeks after placement using $Osstell^{(R)}$ mentor RFA. After the animals were sacrificed, histomorphometric evaluation was executed for measuring BIC and BD. Results: 1) The under-drilled group showed most high ISQ value for whole experiment period. 2) Bone-to-implant-contact(BIC) showed the tendency to be increased gradually as the experiment period passed except the 8 weeks of the normal group. 3) The under-drilled group showed most high bone density(BD) level for whole experiment period, and it was expressed the aspect to be increased gradually according to an experiment period passage in the average of all group. 4) Resonance frequency analysis and histomorphometric analysis are presumed by generally proportional. Conclusions: As this research result, it seems that there are some correlation between resonance frequency analysis and histomorphometric analysis. As are accomplished osseointegration stably so that more superior at the region which the overpressure comes to add, it will be applicable method in clinical field.