• The Journal of Advanced Prosthodontics
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• 제10권6호
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• pp.415-421
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• 2018

PURPOSE. This study investigated the effects of abutment screw lengths on screw loosening and removal torque in external connection implants after oblique cyclic loading. MATERIALS AND METHODS. External connection implants were secured with abutment screws to straight abutments. The abutment-implant assemblies were classified into seven groups based on the abutment screw length, with each group consisting of five assemblies. A cyclic load of 300 N was applied at a $30^{\circ}$ angle to the loading axis until one million cycles were achieved. Removal torque values (RTVs) before and after loading, and RTV differences were evaluated. The measured values were analyzed using repeated measures of analysis of variance with the Student-Newman-Keuls multiple comparisons. RESULTS. All assemblies survived the oblique cyclic loading test without screw loosening. There was a significant decrease in the RTVs throughout the observed abutment screw lengths when the abutment-implant assemblies were loaded repeatedly (P<.001). However, the abutment screw length did not show significant difference on the RTVs before and after the experiment when the abutment screw length ranged from 1.4 to 3.8 mm (P=.647). CONCLUSION. Within the limit of this experiment, our results indicate that the abutment screw length did not significantly affect RTV differences after oblique cyclic loading when a minimum length of 1.4 mm (3.5 threads) was engaged. These findings suggest that short abutment screws may yield stable clinical outcomes comparable to long screws in terms of load resistance.

• The Journal of Advanced Prosthodontics
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• 제8권6호
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• pp.465-471
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• 2016

PURPOSE. The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS. Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of $1.0{\times}10^6$cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS. Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION. Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.

• 대한치과보철학회지
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• 제56권1호
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• pp.1-7
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• 2018

목적: RBM 표면처리한 티타늄 임플란트와 RBM 표면처리 후 saline에 적신 티타늄 임플란트에서 saline에 적신 경우 초기 골유착에 미치는 영향을 제거회전력 및 표면분석을 통해서 알아보고자 한다. 재료 및 방법: 대조군은 RBM 표면처리된 임플란트(이하 RBM)이고, 실험군은 RBM 표면처리 후 saline에 2주간 적신 임플란트(이하 RBM + Sal)이다. 토끼 10마리의 좌우측 경골에 각각 대조군 및 실험군 임플란트를 식립하고, 동시에 식립회전력(ITQ)을 측정한다. 10일 후 임플란트 식립부위를 노출시켜 제거회전력(RTQ)를 측정한다. 실험에 사용된 임플란트 시편의 표면분석을 위해 FE-SEM, EDS, 표면거칠기, Raman 분광분석을 시행하였다. 결과: RBM 표면처리한 티타늄 임플란트와 RBM 표면처리 후 saline에 적신 티타늄 임플란트 사이에 식립회전력 및 제거회전력은 유의미한 차이를 보이지 않았다. 결론: RBM 표면처리 후 saline에 적신 티타늄 임플란트는 RBM 표면처리만 한 티타늄 임플란트보다 초기 골유착에 긍정적인 영향을 미치지 않았다.

• 구강회복응용과학지
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• 제34권1호
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• pp.1-9
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• 2018

목적: Resorbable blasting media (RBM) 표면처리 후 산처리한 티타늄 임플란트와 동일한 표면처리 후 생리식염수에 적신 티타늄 임플란트에서 생리식염수에 적신 경우 초기 골유착에 미치는 영향을 제거회전력 및 표면분석을 통해서 알아보고자 하였다. 연구 재료 및 방법: 대조군은 RBM 표면처리 후 산처리된 임플란트(RBM + HCl)이고, 실험군은 대조군과 동일한 표면처리 후 생리식염수에 2주간 적신 임플란트(RBM + HCl + Sal)이다. 토끼 10마리의 좌우측 경골에 각각 대조군 및 실험군 임플란트를 식립하고, 동시에 식립회전력(ITQ)을 측정하였다. 10일 후 임플란트 식립부위를 노출시켜 제거회전력(RTQ)을 측정하였다. 실험에 사용된 임플란트 시편의 표면분석을 위해 field emission-scanning electron microscopy (FESEM), energy dispersive X-ray Spectroscopy (EDS), 표면거칠기 측정 및 Raman 분광분석을 시행하였다. 결과: RBM 표면처리 및 산처리하여 생리식염수에 적신 티타늄 임플란트에서 대조군에 비해 높은 제거회전력을 나타냈으며, 통계적으로 유의미한 값을 보였다(P = 0.014 < 0.05). 표면거칠기는 실험군에서 더 높은 거칠기를 나타냈다. 결론: 티타늄 임플란트에 RBM 표면처리 및 산처리 후 생리식염수에 적신 것이 생리식염수를 적시지 않은 것 보다 초기 골유착을 향상시키는 것으로 생각된다.

• 대한치과보철학회지
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• 제46권6호
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• pp.561-568
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• 2008

STATEMENT OF PROBLEM: Currently, many implant systems are developed and divided into two types according to their joint connection: external or internal connection. Regardless of the connection type, screw loosening is the biggest problem in implant-supported restoration. PURPOSE: The purpose of this study is to assess the difference in stability of abutment screws between the external and internal hexagonal connection types under cyclic loading. MATERIAL AND METHODS: Each of the 15 samples of external implants and internal abutments were tightened to 30 N/cm with a digital torque gauge, and cemented with a hemispherical metal cap. Each unit was then mounted in a $30^{\circ}$ inclined jig. Then each group was divided into 2 sub-groups based on different periods of cyclic loading with the loading machine (30 N/ cm - 300 N/cm,14 Hz: first group $1{\times}10^6$, $5{\times}10^6$ cyclic loading; second group $3{\times}10^6$, $3{\times}10^6$ for a total cyclic loading of $6{\times}10^6$) The removal torque value of the screw before and after cyclic loading was checked. SPSS statistical software for Windows was used for statistical analysis. Group means were calculated and compared by ANOVA, independent t-test, and paired t-test with ${\alpha}$=0.05. RESULTS: In the external hexagonal connection, the difference between the removal torque value of the abutment screw before loading, the value after $1{\tims}10^6$ cyclic loading, and the value after $1{\times}10^6$, and additional $5{\times}10^6$ cyclic loading was not significant. The difference between the removal torque value after $3{\times}10^6$ cyclic loading and after $3{\times}10^6$, and additional $3{\times}10^6$ cyclic loading was not significant. In the internal hexagonal connection, the difference between the removal torque value before loading and the value after $1{\times}10^6$ cyclic loading was not significant, but the value after $1{\times}10^6$, and additional $5{\times}10^6$ cyclic loading was reduced and the difference was significant (P < .05). In addition, in the internal hexagonal connection, the difference between the removal torque value after $3{\times}10^6$ cyclic loading and the value after $3{\times}10^6$, and additional $3{\times}10^6$ cyclic loading was not significant. CONCLUSION: The external hexagonal connection was more stable than the internal hexagonal connection after $1{\times}10^6$, and additional $5{\times}10^6$ cyclic loading (t = 10.834, P < .001). There was no significant difference between the two systems after $3{\times}10^6$, and additional $3{\times}10^6$ cycles.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제42권1호
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• pp.2-8
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• 2016

Objectives: The purpose of this study was to investigate the effects of low-level laser therapy (LLLT) with a diode gallium-aluminum-arsenide (Ga-Al-As) low-level laser device on the healing and attachment of titanium implants in bone. Materials and Methods: Thirteen New Zealand white male rabbits weighing $3.0{\pm}0.5kg$ were used for this study. Dental titanium implants (3.75 mm in diameter and 8.5 mm in length, US II RBM plus fixture; Osstem, Seoul, Korea) were implanted into both femurs of each rabbit. The rabbits were randomly divided into a LLLT group and a control group. The LLLT was initiated immediately after surgery and then repeated daily for 7 consecutive days in the LLLT group. Six weeks and 12 weeks after implantation, we evaluated and compared the osseointegration of the LLLT group and control group, using histomorphometric analysis, removal torque testing, and resonance frequency analysis (RFA). The results were statistically significant when the level of probability was 0.05 or less based on a non-parametric Mann-Whitney U-test. Results: The implant survival rate was about 96%. Histologically and histomorphometrically, we observed that the titanium implants were more strongly attached in LLLT group than in control group. However, there was no significant difference between the LLLT group and control group in removal torque or RFA. Conclusion: Histologically, LLLT might promote cell-level osseointegration of titanium implants, but there was no statistically significant effects.

• 대한치과보철학회지
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• 제46권5호
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• pp.490-499
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• 2008

생체 활성 재료는 생체 내에서 자가적으로 인회석 층 (apatite layer)을 형성하여, 골과의 생화학적 결합이 가능해야 한다. 알칼리와 열처리를 통하여 생체 활성 표면을 얻을 수 있는 것으로 보고되고 있다. 본 실험에서는 알칼리 및 열처리를 시행한 임플란트들의 안정성을 평가하고자 하였다. 실험군의 분류로 1군은 대조군인 선반 가공 임플란트군, 2, 3군은 $60^{\circ}C$, 5 M의 NaOH 용액에 24시간 처리한 후, 각각 대기 중 및 진공 상태 $600^{\circ}C$에서 1시간 동안 열처리하였다. 처리된 시편은 FESEM, XPS, TF-XRD 및 AFM을 이용하여 표면 특성을 관찰하고, 임플란트의 안정성을 위해 공진 주파수와 페리오테스트 및 역 토오크를 측정하고, 골유착 안정성에 관한 차이를 비교 분석하여 다음과 같은 결과를 얻었다. 1. 표면 특성: 알칼리 및 열처리를 시행한 2, 3군은 비슷한 양상의 거친 표면을 보여주었다. 알칼리 처리를 시행한 2군과 3군에서 1군과는 달리 높은 함량의 나트륨 이온이 검출되었으며, 결정구조 분석 결과 2군에서 예추석 (antase)과 금홍석 (rutile)이 혼재된 상태로 금홍석이 우세한 양상을 보여주었다. 2. 공진 주파수 분석: 군간 비교에서 12주에 2군이 1, 3군에 비해 통계적으로 유의하게 높은 측정치를 보였다. 주간 비교시, 1, 2군은 4주 이후에 유의한 증가를 보여주었고, 3군은 2주와 4주에서 각각 유의한 증가를 보여주었다 (P < .05). 3. 페리오테스트 분석: 주간 비교에서 1, 2군은 4주 이후에 유의하게 감소를, 3군은 2주와 4주에서 각각 유의한 감소를 보여주었다 (P< .05). 4. 역 토오크 분석: 군간 비교에서는 2, 4, 8주에서는 2군이 1, 3군에 비해 유의하게 높은 측정값을 보여주었다. 주간 비교에서는 1, 3군은 4주, 12주에서 유의한 증가를 보여주었고, 2군은 4주부터 유의한 증가를 보여주었다 (P < .05). 이상의 결과로 볼 때, 알칼리 및 대기 중 열처리를 통해서 적절한 결정 구조의 산화막을 가진 생체 활성화된 무정형의 나트륨 티탄산염 층을 얻을 수 있었고, 알칼리 및 진공 상태 열처리만으로도 나트륨이 함유된 생체 활성화된 표면을 얻을 수 있었다고 사료된다. 또한 이런 처리 과정으로 형성된 표면층들은 임플란트의 초기 골유착에 도움을 줄 수 있는 유용한 방법 중 하나라고 사료된다.

• 대한치과보철학회지
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• 제45권4호
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• pp.492-505
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• 2007

Statement of problem: An orthodontic miniscrew implant has been used as a skeletal anchorage for orthodontic treatment. However, any relation among the influence of the cortical bone, morphologic differences of orthodontic miniscrew implants and new bone formation hasn't been made clear yet. Purpose: The purpose of this study was to evaluate whether the orthodontic miniscrew implant could work as an intraoral skeletal anchorage immediately and stably for orthodontic treatment after insertion of it. Material and methods: Two types of orthodontic miniscrew implants were used in this experiment; tapered type and straight type. One hundred and sixty eight orthodontic miniscrew implants were inserted into the tibiae of 21 rabbits and sacrificed on 3, 7, 11, 14, 21 and 28days later after insertion of them to study removal torque values and histologic and histomorphometric analyses. Results: The results were as follows. 1. The removal torque values of the tapered type were higher than those of the straight type in all groups(p<0.05). 2. There wasn't any distinguishing differences between the tapered type and the straight type about the new bone formation percentage. 3. The removal torque values for both the tapered type and the straight type were gradually decreased at early stages of the test but started to increase at the 7 days group of the straight type and the 11 days group of the tapered type. 4. New bone formation percentage was increased gradually for both the tapered and the straight types as time passed(p<0.05). 5. It was found that the tapered type showed lower values in the cortical bone about both the maximum equilibratory stress distribution and the maximum principal stress distribution than the straight type in linear finite elements analysis. Conclusion: According to the research, the removal torque values were decreased at 7 days group of the tapered type and 11 days group of the straight type after the insertion of the orthodontic miniscrew implants in tibiae of rabbits. Considering the human bone activity, it is better to apply the orthodontic force $3{\sim}4$ weeks later than to apply it immediately after the insertion of orthodontic miniscrew implants. Considering that general orthodontic force is about $250{\sim}500$ grams, the tapered type can be worked as a stable skeletal anchor age in an orthodontic treatment even if the orthodontic force is applied on it immediately after the insertion of it.

• 대한기계학회논문집B
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• 제27권7호
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• pp.938-947
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• 2003

In this paper, we derived the formula for estimating the power of the electric motors needed to operate the Decanter-type centrifuge. In the derivation of the formula the sludge-removal torque is to be supplied from the formula derived in the first paper. The intricate nature of the transmission mechanism in the planetary gear trains of the sludge-removal power and torque has been clarified in this second paper. In particular we considered two-motor system, where the main motor drives the machine while the differential-speed control motor plays the role of braking in adjusting the differential speed. Sample calculation for the specific design treated in the first paper showed that the selection criterion for the main motor depends on the lower limit of the differential speed; when the lower limit is set low, it should be selected based on the steadily operating power, while it should be selected based on the starting power when the lower limit is set high. The total power required by both the main motor and the differential-speed control motor increases as the differential speed is decreased. It is suggested that the power loss in the differential-speed control motor could be minimized by attaching an electric generator to it.

• 한국산업융합학회 논문집
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• 제26권4_2호
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• pp.623-628
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• 2023

The purpose of this study was to evaluate the fracture strength and removal torque value (RTV) of a conventional angled abutment and a newly developed angled abutment (Beauty up abutment) with an angulated screw access hole. Each abutment was divided into a control group and an experimental group (n = 20, respectively). To measure the fracture strength, the abutment was connected to the internal hex implant with 30 Ncm torque, and a load was applied at 30 degree angle with cross-head speed of 1 mm/min using a universal testing machine according to the ISO 14801:2016 standard. To measure RTV, each abutment was fastened to the implant with 30 Ncm torque. Retightening was performed after 10 minutes, and initial RTV was measured with a digital torque gauge. After retightening, a load of 250 N was applied to the abutment at a 30 degree angle using a chewing simulator. After a total of 100,000 repeated loads, RTV was measured. Statistical analysis was performed using Wilcoxon signed rank test and Mann-Whitney U test (α = .05). The fracture strength of the experimental group was statistically significantly lower than that of the control group (P = .009). There was no significant difference between initial RTV and post-loading RTV between the experimental group and the control group (P = .753, P = .527, respectively), and cyclic loading did not significantly affect RTV in both groups (P = .078).