• 대한치과의사협회지
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• 제58권9호
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• pp.583-589
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• 2020

If the implant is planted in the wrong position or direction, it is disadvantageous for stress distribution, and it is easy to cause complications such as screw loosening, abutment fracture, and implant fracture. If the position or orientation of the implant is not good, efforts should be made to minimize the problem through proper implant prosthetic treatment. In this article, the prosthetic method for facilitating future maintenance in cases with poor implant placement or orientation will be presented.

• 대한치과보철학회지
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• 제34권1호
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• pp.1-14
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• 1996

Abutment screw loosening of dental implant is a major problem in the treatment of dental implant. The purpose of this study was to examine the effect on the prevention of screw loosening according to tightening method and using of washer. In the first experiment, using a implant fixture and precisely fabricated temporary cylinder, the loosening torque was measured by tightening the screw 5 times repeatedly. In the second experiment, the fabricated crown and implant fixture was tightened by the screw that is attatched washer and then the loosening torque was measured after loading it 1800, 12600 times under the force of 150N. The results were as follows. 1. The highest loosening torque appeared after tightening 3 times repeatedly(p<0.01). 2. When the washer was used, the loosening torque was increased significantly under the loading 1800 times(p<0.01), 3. When the washer was used, the loosening torque was increaed under the loading 12600 times, but it is statistically not significant(p<0.01). The first experiment results mean that 3 times repeated tightening screw is most effective clinically. The second results mean that washer is effective in prevention screw loosening, but the effect is decreased with increasing load.

• 대한치과보철학회지
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• 제47권2호
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• pp.125-135
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• 2009

연구목적: 임플란트 치료에서 흔히 발생하는 기계적인 문제점을 하나가 지대주나사의 풀림과 파절이다. 일반적으로 나사 연결의 안정성을 위해서는 지대주나사의 조임회전력에 의한 전하중을 나사의 탄성한계까지 증가시킬 필요가 있다. 그러나 저작운동에 의한 기능부하는 전하중이 가해진 지대주나사에 추가적인 인장력을 가하게 되어 나사의 풀림이나 파절의 가능성을 높인다. 이러한 풀림이나 파절을 방지하면서 동시에 최대의 결합 강도를 가지는 조임회전력을 찾는 연구가 필요하다. 본 연구는 지대주나사의 조임회전력이 임플란트-지대주 연결부 안정성에 미치는 영향을 3차원 유한요소 분석을 통하여 확인하고자했다. 연구 재료 및 방법: External butt joint를 가진 임플란트를 기반으로 3차원 유한요소 해석모형을 설계하였다. 조임회전력에 따른 지대주나사의 전하중을 이론치, 실험치 및 해석치를 비교하여 해석모형을 검증하였다. 검증한 해석모형에서 대해 조임회전력을 10 Ncm, 20 Ncm, 30 Ncm, 그리고 40 Ncm로 각각 적용하고 지대주에 30도 경사지게 250 N의 외부하중을 가하여 유산요소 해석을 실시하였다. 그 결과를 통해 지대주나사의 최대 등가응력을 계산하고 고정체와 지대주 연결부의 응력분포 및 이개거리(gap distance)를 산출하였다. 결과 및 결론: 본 연구조건 하에서 다음과 같은 결과를 얻었다. 1. 전하중은 조임회전력이 클수록 증가하였다. 2. 조임회전력 적용 후 최대 등가응력은 지대주나사 경부에서 발생하였으며, 나사산 체결부에서는 주로 경부쪽 네 개의 나사산에 응력이 집중되었다. 3. 외부하중을 가했을 때에도 조임회전력을 적용했을 때와 동일하게 최대 등가응력은 주로 지대주나사 경부에서 발생하였으나, 10 Ncm의 조임회전력을 적용한 경우에서는 지대주나사 두부밑면에서 발생하였다. 4. 외부하중을 가했을 때 10 Ncm와 20 Ncm의 조임회전력을 적용한 경우에서는 연결부 이개(joint opening) 현상이 관찰 되었다. 5. 조임회전력이 40 Ncm인 경우에는 경사하중에 의해 지대주나사의 경부에 발생하는 최대등가응력이 나사의 소재인 티타늄 합금의 허용응력을 초과하였다. 이상의 결과로 볼 때, 조임회전력은 고정체와 지대주 연결부의 안정성에 영향을 미치는 것이 확인되었다. 임플란트 지대주나사는 임상에서 발생하는 기능 하중을 고려하여 고정체와 지대주 연결의 안정성을 유지할 수 있는 적정 조임회전력의 크기가 제안되어야 한다.

• 구강회복응용과학지
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• 제31권1호
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• pp.60-66
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• 2015

임플란트 수복물의 기계적 실패 요인들 중 가장 잦은 빈도를 보이는 것은 지대주 나사의 풀림이나 파절로 알려져 있다. 이렇게 지대주나, 나사가 파절된 경우 그 잔사들을 임플란트 고정체의 손상 없이 완전히 제거해야만 한다. 때로는 잔사들을 제거할 수 없는 경우나 제거 과정에서 고정체와 나사를 연결하는 부위가 손상되어 임플란트를 지속하여 사용할 수 없는 경우가 발생하여 임상가를 곤란하게 만드는 경우가 있다. 본 증례보고에서는 각기 다른 세가지 임상상황에서 임플란트 고정체의 손상 없이 성공적으로 파절편을 제거한 사례들을 보고하고 나사가 파절된 임상상황에서 대처할 수 있는 방법들에 대해 고찰해 보고자 한다.

• 대한치과보철학회지
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• 제46권5호
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• pp.500-510
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• 2008

연구목적: 최근 지대주 나사에 WC/C 또는 TiN 코팅이 연구되고 있으며, 이들을 금속표면에 코팅 시 마찰계수의 감소와 부식에 대한 저항, 물리적 취약함의 해소 등의 효과를 얻을 수 있으며. 코팅된 지대주 나사에서 마모와 적합도, 풀림력이 향상되었다는 결과들이 보고되고 있다. 본 연구에서는 지대주 나사에 적용된 코팅이 나사 풀림에 미치는 영향을 알아보아 임상적으로 문제가 되고 있는 지대주 나사의 풀림현상을 해소하는데 그 목적이 있다. 연구재료 및 방법: 코팅되지 않은 타이타늄 지대주 나사와 (그룹 A) WC/C (그룹 B)와 TiN (그룹 C)으로 코팅된 지대주 나사의 10회 반복 착탈시 풀림력 및 표면의 변화를 비교해본 결과 다음과 같은 결론을 얻었다. 결과: 1. 반복 착탈 전, 그룹 A는 일정한 방향성을 가진 다소 거친 표면이 관찰되었으 나 그룹 B와 그룹 C는 코팅된 입자들이 관찰되었으며 코팅층이 전체적으로 균일하고 매끈한 모양을 나타내었다. 2. 반복 착탈 전, 그룹 B에 비해 그룹 C의 표면에서 코팅 입자의 크기가 더 크고 두껍게 코팅 된 모양을 나타내었다. 3. 반복 착탈 후, 그룹 A와 그룹 B에서는 지대주 나사 표면의 마모와 변형이 관찰 되었으며 그룹 B에서는 코팅 입자의 탈락 현상을 볼 수 있었다. 4. 반복 착탈 전과 후의 지대주 나사 무게의 변화를 측정한 결과 그룹 A가 가장 큰 감소를 보였으며, 그룹 C가 그룹 B 보다 무게의 변화가 적었으나 두 그룹간 통계적으로 유의한 차이는 없었다. 5. 그룹 B와 그룹 C는 그룹 A에 비해 높은 평균 풀림력을 나타내었고 통계학적으로 유의할 만한 차이가 있었다. 6. 그룹 A에서 그룹B 와 그룹 C보다 평균 풀림력의 감소 경향이 더욱 현저 하게 나타났다. 결론: 결론적으로, WC/C 또는 TiN 코팅된 지대주 나사는 반복적인 사용 후에도 코팅되지 않은 타이타늄 지대주 나사에 비해 뚜렷한 표면 변화를 보이지 않았으며 마모에 대한 저항성이 우수하였고 높은 풀림력을 나타내었다. 따라서 지대주 나사에 WC/C 또는 TiN 코팅을 적용 시 나사 풀림의 문제점을 개선할 수 있을 것으로 사료된다.

• 대한치과보철학회지
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• 제46권3호
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• pp.246-254
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• 2008

STATEMENT OF PROBLEM: The cast abutment has advantages of overcoming angulation problem and esthetic problem. However, when a gold-machined UCLA abutment undergoes casting, the abutment surfaces in contact with the implant may change. PURPOSE: The purpose of this study was to compare the detorque values of prefabricated machined abutments with gold-premachined cast-on UCLA abutments before and after casting in two types of internal implant-abutment connection systems: (1) internal hexagonal joint, (2) internal octagonal joint. Furthermore, the detorque values of two implant-abutment connection systems were compared. MATERIALS AND METHODS: Twenty internal hexagonal implants with an 11-degree taper and twenty internal octagonal implants with an 8-degree taper were acquired. Ten prefabricated titanium abutments and ten gold-premachined UCLA abutments were used for each systems. Each abutment was torqued to 30 N㎝ according to the manufacturer's instructions and detorque value was recorded. The detorque values were measured once more, after casting with gold alloy for UCLA abutment, and preparation for titanium abutments. Group means were calculated and compared using independent t-test and paired t-test (${\alpha}$=0.05). RESULTS: The results were as follows: 1. The detorque values between titanium abutments and UCLA-type abutments showed significant differences in internal octagonal implants (P<0.05), not in internal hexagonal implants (P>0.05). 2. In comparison of internal hexagonal and octagonal implants, the detorque values of titanium abutments had significant differences between two connection systems on the initial analysis (P<0.05), not on the second analysis (P>0.05) and the detorque values of UCLA-type abutments were not significantly different between two connection systems (P>0.05). 3. The detorque values of titanium abutments and UCLA-type abutments decreased significantly on the second analysis than the initial analysis in internal hexagonal implants (P<0.05), not in internal octagonal implants (P>0.05). CONCLUSION: Casting procedures of UCLA-type abutments had no significant effect on screw loosening in internal implant-abutment connection systems, and UCLA-type abutments showed higher detorque values than titanium abutments in internal octagonal implants.

• 대한치과보철학회지
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• 제42권6호
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• pp.664-670
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• 2004

Statement of problem. One of the common problems of dental implant prosthesis is the loosening of the screw that connects each component, and this problem is more common in single implant-supported prostheses with external connection. Purpose. The purpose of this study was to examine the changes of detorque values of abutment screws with external connection in different abutment heights. Materials and methods. After cyclic loading on three different abutment heights, detorque values were measured. Abutments were retained with titanium abutment screws tightened to 30 Ncm (30.5 kgmm) with digital torque gauge as recommended by the manufacturer. Replacing abutments, implants and titanium abutment screws with new ones at every measurement, initial detorque values were measured six times. In measuring de torque values after cyclic loading, Avana Cemented Abutments of 4.0 mm collar, 7.0 mm height (Osstem Co., Ltd., Seoul, Korea) were used with three different lengths of 5.0, 8.0, 11.0 mm. Shorter abutments were made by milling of 11.0 mm abutment to have the same force-exercised area of 4.5 mm diameter. Sine curve force (20N-320N, 14Hz) was applied, and detorque values were measured after cyclic loading of 2 million times by loading machine. Detorque values of initial and after-loading were measured by digital torque gauge. One-way ANOVA was employed to see if there was any influence from different abutment heights. Results. The results were as follows: 1. The initial detorque value was 27.8$\pm$0.93 kgmm, and the ratio of the initial detorque value to the tightening torque was 0.91(27.8/30.5). 2. Measured detorque values after cyclic loading were declined as the height of the abutment increased, that was, 5.0 mm; 22.3$\pm$0.82 kgmm, 8.0 mm; 21.8$\pm$0.93 kgmm, and 11.0 mm; 21.3$\pm$0.94 kgmm. 3. One-way ANOVA showed no statistically significant differences among these (p>0.05). 4. Noticeable mobility at the implant-abutment interface was not observed in any case after cyclic loading at all.

• 구강회복응용과학지
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• 제23권1호
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• pp.31-42
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• 2007

The purpose of this study was to compare the stress distribution according to the splinting condition and non-splinting conditions on the finite element models of the two units implant prostheses. The finite element model was designed with the parallel placement of two fixtures ($4.0mm{\times}11.5mm$) on the mandibular 1st and 2nd molars. A cemented abutment and gold screw were used for superstructures. A FEA models assumed a state of optimal osseointegration, as the bone quality, inner cancellous bone and outer 2 mm compact bone was designed. This concluded that the cortical and trabecular bone were assumed to be perfectly bonded to the implant. Splinting condition had 2 mm contact surface and non-splinting condition had $8{\mu}m$ gap between two implant prosthesis. Two group (Splinting and non-splinting) were loaded with 200 N magnitude in vertical axis direction and were divided with subdivision group. Subdivision group was composed of three loading point; Center of central fossa, the 2 mm and 4 mm buccal offset point from the central fossa. Von Mises stress value were recorded and compared in the fixture-bone interface and bucco-lingual sections. The results were as follows; 1. In the vertical loading condition of central fossa, splinting condition had shown a different von Mises stress pattern compared to the non-splinting condition, while the maximum von Mises stress was similar. 2. Stresses around abutment screw were more concentrated in the splinting condition than the non-splinting condition. As the distance from central fossa increased, the stress concentration increased around abutment screw. 3. The magnitude of the stress in the cortical bone, fixture, abutment and gold screw were greater with the 4 mm buccal offset loading of the vertical axis than with the central loading.

• 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.

• The Journal of Advanced Prosthodontics
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• 제8권2호
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• pp.131-136
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• 2016

PURPOSE. The aim of this study was to observe stress concentration in the implant, the surrounding bone, and other components under the pull-out force during the crown removal. MATERIALS AND METHODS. Two 3-dimensional models of implant-supported conventional metal ceramic crowns were digitally constructed. One model was designed as a vertically placed implant ($3.7mm{\times}10mm$) with a straight abutment, and the other model was designed as a 30-degree inclined implant ($3.7mm{\times}10mm$) with an angled abutment. A pull-out force of 40 N was applied to the crown. The stress values were calculated within the dental implant, the abutment, the abutment screw, and the surrounding bone. RESULTS. The highest stress concentration was observed at the coronal portion of the straight implant (9.29 MPa). The stress concentrations at the cortical bone were lower than at the implants, and maximum stress concentration in bone structure was 1.73 MPa. At the abutment screws, the stress concentration levels were similiar (3.09 MPa and 3.44 MPa), but the localizations were different. The stress at the angled abutment was higher than the stress at the straight abutment. CONCLUSION. The pull-out force, applied during a crown removal, did not show an evident effect in bone structure. The higher stress concentrations were mostly observed at the implant and the abutment collar. In addition, the abutment screw, which is the weakest part of an implant system, also showed stress concentrations. Implant angulation affected the stress concentration levels and localizations. CLINICAL IMPLICATIONS. These results will help clinicians understand the mechanical behavior of cement-retained implant-supported crowns during crown retrieval.