• 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.

• 대한치과의사협회지
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• 제53권11호
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• pp.804-816
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• 2015

PURPOSE: The aim of this study was to evaluate the influence of the oxide layer removal process in the Co-Cr-Mo (CCM) abutment after casting procedure on the prosthesis settlement and screw stability. MATERIALS AND METHODS: CCM abutments of four different interface conditions (CCM-M; machined, CCM-O; oxide layer formed, CCM-B; blasted, CCM-P; polished after blasted) and gold abutment (Gold-C; Cast with type III Gold alloy) were used. The initial settling values of abutments were evaluated according to the difference of implant-abutment length when the tightening torques were applied at 5 Ncm and 30 Ncm, and the settling values of abutments caused by loading were evaluated according to the difference of implant-abutment length before and after loading with 250 N, 100000 cycle. The loss ratios of removal torque for abutment screws were evaluated according to the difference in value of removal torques under 30 Ncm tightening torque applied before and after cyclic loading. RESULTS: The CCM-P and CCM-B group showed a higher initial settling value compared with the Gold-C group (P<.05), while the Gold-C group showed the highest settling values caused by loading (P<.05) and no significant differences were observed for between CCM groups (P>.05). The loss ratio of removal torque values for the CCM-B, CCM-P groups did not differ significantly from that of the Gold-C group (P>.05). CONCLUSION: Even though the oxide layer was removed by different methods, CCM abutment with internal conical connection structure showed lower abutment settling and similar screw loosening after cyclic loading compared with gold abutment.

• 대한치과기공학회지
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• 제35권4호
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• pp.303-312
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• 2013

Purpose: In this research, non-linear three dimensional finite element models with contact elements were constructed. For the investigations of the distributions of contact stresses, 3 units fixed partial dentures model were studied, especially on the interface of the gold screw and cylinder, abutment screw. Methods: 3 types of models were constructed ; the basic fixed partial denture in molar region with 3 units and 3 implants, the intermediate pontic fixed partial denture model with 3 units and 2 implants, and the extension pontic fixed partial denture model with 3 units and 2 implants. For all types, the external loading due to chewing was simulated by applying $45^{\circ}$ linguo-buccal loading of 300 N to the medial crown. For the simulation of the clamping force which clinically occurs due to the torque, thermal expansion was provided to the cylinder as a preload. Results: Under 300 N concentrated loading to the medial crown, the maximum contact stress between abutment screw and gold screw was 86.85~175.86MPa without preload, while the maximum contact stress on the same area was 25.59~57.84MPa with preload. Conclusion: The preloading affected the outcomes of the finite element stress analysis. Reflecting the clinical conditions, the preloading conditions should be considered for other practical study utilizing FEA. For the study of the contact stresses and related motions, various conditions, such as frictional coefficient changes, gap between contact surfaces, were also varied and analyzed.

• 대한치과보철학회지
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• 제40권4호
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• pp.374-385
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• 2002

A total of 605 implant fixture prosthesis delivered by 3 clinics and 2 laboratories were examined in this study, The object of this study was to determine the proper length of screw head. The depth of access hole were measured and compared to the type of fixture, abutment, gold screw and prosthesis. The results were as follows : 1 The average number of fixtures per patient were 2.97. 2. The number of fixture installed in the upper posterior area are 327(55.56 %), the upper posterior area 171 (28.25%). 3. The depth of access hole is 4.23 mm in shallow area, and 5.46 mm in deep area and the differences were 1.23 mm. 4. The average depth of the aceess hole of the UCLA abutment were 5.02 mm. 5. The number of 4-5 mm access hole depth were 60(22.39%) in abutment screw level and the number of 4-5 mm depth in fixture level were 101 (29.19%). 6. In the shape of screw head, hexed type were 576(95.21%), slotted type were 29(4.79%).

• 대한치과보철학회지
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• 제42권6호
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• pp.628-640
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• 2004

Statement of problem. Wear as a result of repeated closing/opening cycles may decrease the friction coefficient of screw head, threads, and other mating components and, consequently, resistance to opening gradually decreases. It may cause screw loosening, which is one of the most common failures in implant prosthesis. Purpose. The purpose of this study is to evaluate the changes on the head and thread surface of the abutment screws after repeated closing and opening through the examination of tested screws in SEM(scanning electron microscope). Materials and methods. Five species of abutments were selected (3i-three, Avana-two) respectively by two pieces. The implant fixtures were perpendicularly mounted in liquid unsaturated polyesther(Epovia, Cray Valley Inc.) with dental surveyor. Each abutment was secured to the implant fixture by each abutment screw with recommended torque value using a digital torque controller. The abutment screws were repeatedly tightened and removed 20 times with a digital controller. FESEM (field emission scanning electron microscope, Netherland, Phillips co., model:XL 30 SFEG) was used to observe changes of each part caused by repeatedly closing/opening expeiment. First, the Photomicrographs of pre-test screws provided by each manufacturer were taken. The changes of each screw were investigated after every fifth closing and opening experiment with FESEM. Scaning electron microscope photomicrographs of each screw were taken four times. Results. As the number of closing and opening was increased, the wear or distortion of hexed or squared slot that contacted with the driver tip was more severely progressed. Wear or distortion of hexed slot was more severe than that of squared slot and it was more remarkable in the titanium screw than in the gold screw. All the tested screws showed that the width in the crest of their screw thread decreased gradually as the test was proceeded. Conclusions. Conclusively, we recommend the clinical use of gold screw, a periodic exchanges of abutment screws and avoiding repeated closing/opening unnecessarily. We also suggest a more careful manipulation of the abutment screw and screw-driver and using of abutment screw with an acute-angled slot design rather than an obtuse-angled one. Finally, it is suggested that the new slot design and the surface treatment for enduring wear or distortion should be devised.

• The Journal of Advanced Prosthodontics
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• 제5권1호
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• pp.21-28
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• 2013

PURPOSE. This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS. Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at $30^{\circ}$ to the long axis. The implant fixtures were fixed to the jig, and connected to the abutments with a 30 Ncm tightening torque. A sine curved dynamic load was applied for $10^5$ cycles between 25 and 250 N at 14 Hz. Removal torque before loading and after loading were evaluated. The SPSS was used for statistical analysis of the results. A Kruskal-Wallis test was performed to compare screw loosening between the abutment systems. A Wilcoxon signed-rank test was performed to compare screw loosening between before and after loading in each group (${\alpha}$=0.05). RESULTS. Removal torque value before loading and after loading was the highest in stock abutment, which was then followed by gold cast abutment and CAD/CAM custom abutment, but there were no significant differences. CONCLUSION. The abutment types did not have a significant influence on short term screw loosening. On the other hand, after $10^5$ cycles dynamic loading, CAD/CAM custom abutment affected the initial screw loosening, but stock abutment and gold cast abutment did not.

• 구강회복응용과학지
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• 제26권3호
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• pp.273-283
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• 2010

이 연구는 다수의 임플란트에 의해 지지되는 보철물과 단일 임플란트 보철물에서 호환 가능한 세 가지 종류의 나사의 풀림토크값을 측정하여 나사 결합부 안정성에 차이가 있는지를 알아보고자 하였다. 이를 위해, 네 개의 외부 육각 임플란트에 직접 연결되는 임플란트 상부구조물을, 아크릴릭 레진을 이용한 연결인상법으로 얻은 총 6개의 실험모형에 20 Ncm의 힘으로 조인 후, 각 나사의 풀림토크값을 총 2회 측정하였다. 사용한 지대주 나사는 토크타이트(TorqTite), 골드타이트(Gold-Tite), 그리고, 티타늄(Titanium) 나사였다. 또한, 단일 임플란트 수복의 경우 를 가정하여 총 5개의 실험모형 상의 2개의 임플란트에, 한 개의 지대주(GoldAdapt Engaging)를 다시 세 종류의 나사로 연결한 후, 각 나사의 풀림토크값을 총 2회 측정하였다. 나사의 풀림토크값의 비교를 위한 통계적 분석을 혼합모형(mixed model)을 이용하여 유의수준 .05에서 실시한 결과, 다수 임플란트 지지 상부구조물의 경우, 나사의 종류에 따른 풀림토크값은 통계적으로 유의성 있는 차이를 보이지 않았다(p>0.05). 그러나 단일 임플란트 지대주의 경우에는 통계적으로 유의성 있는 차이를 보였으며(p=0.0175), 토크타이트 나사(p=0.0462)와 티타늄 나사(p=0.0348)는 각각, 골드타이트 나사보다 유의성 있게 큰 풀림토크값을 보였으나, 두 나사 간에는 유의성 있는 차이가 없었다(p>0.05). 이상의 연구 결과로 보아, 서로 다른 종류의 나사가 나사 결합부의 초기 안정성에 미치는 영향은, 단일 임플란트 보철물의 경우에서와는 달리, 다수의 임플란트에 의해 지지되는 보철물의 경우에는 미미하다고 할 수 있다.

• 대한치과보철학회지
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• 제40권2호
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• pp.193-200
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• 2002

For the purpose of decreasing the chair time in implant cases, the time needed to loosening and fastening the screw must be shortened. Nowadays, the two typical designs of screw head are slot and hexa form. This study aimed at the shortening of loosening and fastening time by modifying the slot and hexa form. Total of twelve dentists participate in these experiments, four of them were experienced and eight of them were novice dentists. 1. There were many differences in the speeds of screw loosening and fastening between personal experiences. Experienced dentists are faster than novice dentists. 2. There were many differences in the speeds by angulation of the implant, by the conditions of the muscle tonicity. 3. Revised slot and hexa Heads show the slightly shortened time for acrew looseing and fastening.

• 대한치과기공학회지
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• 제26권1호
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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.

• 대한치과보철학회지
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• 제41권4호
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• pp.519-531
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• 2003

Statement of problem : Chronic implant screw loosening remains a problem in restorative practices. Some implant manufactureres have introduced abutment screws with treated material, surfaces and macrostructures in an effort to reduce potential loosening. Purpose : This study evaluated the materials and loading cycles on detorque value after dynamic continous fatigue test in the sinulated conditions of posterior single restoration. Material and method : Fourteen of each of the following abutment screws - titanium alloy, gold alloy, gold-tite, and titanium alloy modified - were used in test. SEM is used to verify macrostructures of each screws. $ZrO_2/Al_2O_3$ composite abutment was tightened on $4{\times}10.0mm$ titanium external implant at 30 Ncm. Cyclic loading machine delivered dynamic loading forces between 20 and 320N for 100,000, 200,000, 300,000, 500,000, and 1,000,000 cycles at frequencies 14Hz. Torque and detorque value after loading was measured. Results : All measued screws had different screw length and thread form. Titanium modified screw had greater detorque value than others before and after cyclic loadings(p<0.05). All abutment screws had no significant change in mean percentage of detorque value after loading to initial value after less than 500.000 cyclic loadings, but significant lower value after 1,000,000 cycles(p<0.05). Conclusion : Within limintations of this study all abutment screws may be loosend after about 1 year use. Annual check-up is nessasary to prevent screw loosening.