• 대한치과보철학회지
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• 제38권5호
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• pp.695-703
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• 2000

The purpose of this study was to evaluate the effects of fabrication and tightening methods of gold cyliner on the preload of the standard abutment. Three linear strain gauges (KFR-02N-120-C1-23, Kyowa, Japan) were mounted longitudinally on the 5.5mm Standard abutment (Nobel Biocare, Sweden) and three kinds of gold cylinders such as, as-received gold cylinder, gold cylinder after casting, and plastic cylinder after casting with type IV gold alloy were connected over the top of the standard abutment. Two kinds of tightening methods, such as manual torque with handhold screwdriver and electronic torque using Electronic torque controller were used to generate preload on the abutment. The result were as follows; 1. The preload generated by tightening cast plastic cylinder with handhold screw driver, was the lowest among the six groups. 2. The preload generated by cast plastic cylinder was lower than those by gold cylinders regardless of the tightening methods. 3. The electronic torque controller produced higher torque values than the handheld screwdriver.

• 대한치과보철학회지
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• 제45권3호
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• pp.345-353
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• 2007

Statement of problem. Implant abutment screw joints tend to loosen under clinical conditions. Abutment screw loosening results in loss of preload in function. Purpose. Anti-rotational inner post screw (ARIPS) systems were compared with conventional abutment screws to reduce screw loosening. Reverse torque values were evaluated. Material and methods. 32 implant assemblies (Warentec, Co, Ltd, Seoul, Korea) were organized as the 30-Ncm-torque conventional groups and 30-Ncm-torque ARIPS groups in external and internal system. The specimens were tested to 106 cycles at a load of 200N. Preload reverse torque, postload reverse torque, and the ratio of postload reverse torque to preload reverse torque were evaluated. The data were analyzed with unpaired t-test in external and internal systems. Results. In the ratio of postload reverse torque to preload reverse torque, the ARIPS groups showed significant differences than the conventional screw group in both external and internal system. Conclusion. Within the limitations of this study, abutment screw loosening was effectively reduced using ARIPS system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.333-338
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• 2000

This paper presents an experimental study and numerical thermal deformation analysis in the home appliance, Video Cassette Recorder. Analyzing the change axial force of a set screw according to the change of temperature in the drum assembly, we can determine the initial torque in tightening set screw. The torque will have the preload boss not be separated from the bearing. Also we conduct the fundamental experiment to constitute a boundary condition of the numerical analysis. With the result of this study, we can change the material of preload boss, copper, for aluminum.

• 대한치과보철학회지
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• 제36권5호
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• pp.721-737
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• 1998

Abutment screw loosening of implant restorations is a common problem in the treatment of dental implant. The purpose of this study was to calculate stress and preload from the elongation measurements and to determine maximum tightening torque without plastic deformation of the screw. The length of each gold alloy UCLA screw was measured after tightening to the manufacturer's recommended torque of 32 N-cm. Similarity, titanium UCLA screws were measured after tightening to the manufacturer's recommended torque of 20 N-cm. Loosening torque was also measured after tightening to 32 N-cm torque for gold alloy abutment screws and 20 N-cm for titanium abutment screws. The results were as follows ; 1. There was a regressive relationship between screw elongation and tightening torque (gold alloy : $r^2=0.987$, titanium : $r^2=0.978$), and the mean preload calculated from elongation measurements was $501.11{\pm}26.85\;N$ (gold alloy) and $399.43{\pm}7.61\;N$ (titanium). 2. Stress calculated for the gold alloy and titanium screws at maximum recommended tightening torque was less than 60% of their respective yield strengths and with-in the elastic range. Maximum tightening torque without plastic deformation was 61 N-cm (gold alloy) and 39 N-cm (titanium). 3. For titanium screws, there was a significant difference between loosening after trial 1 and loosening after trials 2 to 5 (p<0.05). No statistically significant difference was seen in mean loosening torques between the first and subsequent trials for gold alloy screws.

• 대한치과보철학회지
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• 제44권2호
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• pp.197-206
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• 2006

Statement of problem: One of common problems associated with single teeth dental implant prosthetic is the loosening of screws that retain the implants. Purpose: The maintenance of screw joint stability is considered a function of the preload achieved in the screw when the suggested initial tightening torque is applied. The purpose of this study was to investigate acquired preload after initial clamping torque for estimating screw joint stability. Material and methods: A comparative study on the effect of initial clamping of two types of implant systems with different connections was conducted Three dimensional non-linear finite element analysis is adopted to compare the characteristics of screw preloads and stress distributions between two different types of implant systems composed with abutment, screw, and fixture under the same loading and boundary conditions. Results: 1. When the initial clamping torque of 32Ncm was applied to the implant systems, all types of implants generated the maximum effective stress at the first helix region of screw. 2. Morse taper connection types of implants generate lower stress distributions compared to those by butt joint connection types or implants due to large contact surface between abutment and fixture. 3. The internal types of implant systems with friction grip type implant systems have higher resistance to screw loosening than that of the external types of implant systems since the internal types of implant systems generated larger preload than that generated by the external types for the same tightening moments.

• The Journal of Advanced Prosthodontics
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• 제14권1호
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• pp.22-31
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• 2022

PURPOSE. The purpose of this study was to investigate the misfit and screw preload at the implant abutment connection of implant supported fixed dental prosthesis with cantilever (ICFDP) manufactured using different digital manufacturing techniques and to compare the screw preload before and after cyclic loading. MATERIALS AND METHODS. Mandibular jaw model with four intra-foraminal implants was scanned using digital scanner. Stereolithography file was used to design a framework with nonengaging (NE) abutments and 10 mm cantilever distal to one terminal implant. Five frameworks were constructed using combined digital-conventional techniques (CAD-cast), and five frameworks were constructed using three-dimensional printing (3DP). Additional CAD-cast framework was constructed in a way that ensures passive fit (PF) to use as control. Scanning electron microscope (SEM) measured the implant abutment connection misfit. Sixty screws were used on the corresponding frameworks. Screws were torqued and pre-cyclic loading reverse torque value (RTV) was recorded. Frameworks were subjected to 200,000 loading cycles with a loading point 9 mm from the center of terminal implants adjacent to the cantilever and post-cyclic loading RTVs were recorded. RESULTS. Microscopic readings showed significant differences between frameworks. PF demonstrated the lowest measurements of 16.04 (2.6) ㎛ while CAD-cast demonstrated the highest measurements of 29.2 (3.1) ㎛. In all groups, RTVs were significantly lower than the applied torque. Post-cyclic loading RTV was significantly lower than pre-cyclic loading RTV in PF and 3DP frameworks. Differences in RTVs between the three manufacturing techniques were insignificant. CONCLUSION. Although CAD-cast and three-dimensionally printed (3DP) both produce frameworks with clinically acceptable misfit, 3DP might not be the technique of choice for maintaining screw's preload stability under an aggressive loading situation.

• 대한치과보철학회지
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• 제46권4호
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• pp.396-408
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• 2008

연구목적: 임플랜트 치료에서 가장 흔히 발생하는 기계적 문제점 중 하나는 나사의 풀림이다. 지대주 나사에 조임회전력을 가하는 목적은 나사를 신장시켜, 신장된 나사의 인장력에 의한 지대주와 고정체간의 압축력을 통해 연결부의 안정성을 부여하는 데 있다. 조임 회전력의 결과로 나타나는 전하중의 크기는 다양한 요소에 의해 영향을 받기 때문에, 동일한 조임회전력을 적용하였다 할지라도 임플랜트 시스템의 종류에 따라 전하중의 크기가 달라질 수 있다. 따라서 지대주 나사 연결부의 안정성을 위한 다양한 임플랜트 시스템의 적정 조임회전력 크기에 관한 연구가 필요하다. 본 연구에서는 external butt joint와 두 가지 internal cone 연결형태를 갖는 임플랜트 시스템들에서 지대주 나사의 조임회전력이 임플랜트-지대주 나사 연결부의 안정성에 미치는 영향을 하중 전후의 풀림회전력 측정을 통해 알아보고자 하였다. 연구재료 및 방법: External butt joint 형태를 가지는 US II 시스템과 $8^{\circ}$ internal cone 연결형태의 SS II 및 $11^{\circ}$ internal cone 연결형태의 GS II 시스템에서 20 Ncm, 30 Ncm, 그리고 40 Ncm의 각기 다른 조임회전력을 적용한 후 초기 풀림회전력 및 상실률과 $10^5$회의 반복하중 후의 풀림회전력 및 상실률을 비교 분석하였다. 연구결과 및 결론: 1. 초기 풀림회전력과 하중 후 풀림회전력은 조임회전력의 크기가 증가할수록 크게 나타났다 (P < .05). 2. 초기 풀림회전력 상실률은 SS II 시스템에서는 조임회전력 크기에 따른 차이가 없었으나 (P > .05), GS II와 US II에서는 20 Ncm 보다 40Ncm의 조임회전력에서 더 낮게 나타났다 (P < .05). 3. 하중 후 풀림회전력 상실률은 세 시스템 모두 30 Ncm의 조임회전력을 가했을 때 가장 낮게 나타났다 (P < .05). 4. 하중 후 풀림회전력 상실률은 SS II, GS II, 그리고 US II 순으로 높아지는 경향을 보였다. 5. 초기 풀림회전력과 하중 후 풀림회전력 상실률 간에는 상관관계가 없었다 (P > .05). 이상의 결과로부터 임플랜트 시스템의 종류뿐만 아니라 조임회전력의 크기 또한 지대주 나사의 풀림회전력 상실에 영향을 준다는 것을 알 수 있다. 따라서 임플랜트-지대주 나사 연결부 안정성 유지를 위해서는 임플랜트 시스템마다 적정 조임회전력이 제시되어야 하고, 또한 임상에서 이를 준수하는 것이 매우 중요하다고 생각된다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.183-186
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• 2003

Long shafts for power transmission should transmit torsional load with vibrational stability. Hybrid shafts made of unidirectional fiber-reinforced composite and metal have high fundamental bending natural frequency as well as high torque transmission capability. However, thermal residual stresses due to the coefficient difference of thermal expansion of the composite and metal are developed so that the high residual stresses decrease fatigue resistance of the hybrid shafts, especially at low operating temperatures. In this work, axial compressive preload was given to the shaft in order to change the residual stresses. Static and fatigue torsional tests were performed and correlated with stress analyses with respect to the preload and service temperature.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.897-898
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• 2013

• 대한치과보철학회지
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• 제48권1호
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• pp.61-68
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• 2010

연구 목적: 임플란트 보철물의 유지 나사에 적용되는 전하중은 나사를 조임으로써 임플란트와 지대주 사이에 인장력이 발생하면서 나사가 신장되는 힘을 말한다. 이 연구는 전하중에 영향을 미치는 생역학적 요인들과 나사 풀림에 기여하는 다양한 요인에 대하여 문헌을 고찰하고자 하였다. 연구 재료 및 방법: 1981년부터 2009년까지 발표된 나사 풀림을 다룬 임상연구 중 설정한 기준에 합당한 문헌을 요약하여 나사 풀림의 빈도를 밝혔고 나사의 안정성과 전하중에 관한 생역학을 다룬 문헌을 조사하고 요약하였다. 또한, 본 교실에서 연구한 실험실적 결과도 포함시켰다. 결과 및 결론: 나사 풀림의 정도는 나사에 토크를 가하는 기술이 발달함에 따라 현저히 감소하고 있다. 그 외에도 나사의 재질, 마찰계수를 감소시키기 위한 피복 기술의 발달 및 나사산의 모양 등 전하중에 영향을 줄 수 있는 요인을 고찰하였다. 전하중이 일정 수준 이하로 떨어지게 되면 나사의 움직임이 발생하게 되는데 이는 장기적으로 축적되어 피로파절 및 응착 마모, 소성 변형 등을 유발하게 되므로 주의해야 한다. 최적의 전하중을 주기 위해서는 토크 렌치를 이용하고 환자의 재내원시 다시 토크를 가하는 방법 등이 추천된다.