• The Journal of Korean Academy of Prosthodontics
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• v.45 no.3
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• pp.329-338
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• 2007

Purpose. The aim of this study is to evaluate the effect of TiN coating of abutment screw on the unscrewing torque. Material and methods. Titanium and Gold-Tite abutment screws were classified into two groups, Group A and C respectively, as control groups. Titanium abutment screws with TiN coatings were also classified into two groups, Group B and D, as experimental ones. Group A and B were tightened to 20 Ncm input torque, and Group C and D were tightened to 32 Ncm torque. Detorque values were measured with digital torque gauge during repeated closing and opening experiment. Results. Abutment screws with TiN coating (Group B and D) showed statistically significant higher mean detorque values than those of Group A and C. Discussion. Physical properties of TiN coating, such as low friction coefficient, high hardness and wear resistance, might contribute to higher detorque values. Conclusion. It is suggested that TiN coating of abutment screw help to reduce the risk of screw loosening and improve the stability of screw joint.

• The Journal of Advanced Prosthodontics
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• v.13 no.1
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• pp.65-70
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• 2021

Purpose. Implant mechanical complications, including screw loosening, can influence dental implant success. It has been shown that torque values are affected by contamination occurred in implant-abutment (I/A) interface. This study aimed to examine the effects of blood, saliva, fluoride and chlorhexidine contamination on reverse torque values (RTVs) of abutment screws in oral conditions. Materials and Methods. 50 fixtures were mounted into the stainless-steel holders and divided into five groups (n = 10). Except control group (NC), fixture screw holes in other groups were contaminated with chlorhexidine (CG), saliva (SG), blood (BG), or fluoride (FG). Abutment screws were tightened with a digital torque meter. I/A assemblies were subjected to thermocycling and cyclic loading. The mean RTVs were recorded and data were analyzed with one-way ANOVA and Tukey test. Results. Except for specimens in SG (20.56 ± 1.33), other specimens in BG (21.11 ± 1.54), CG (22.89 ± 1.1) and FG (24.00 ± 1.12) displayed significantly higher RTVs compared to NC (19.00 ± 1.87). The highest RTVs were detected in CG and FG. Conclusion. The obtained data robustly suggest that RTVs were significantly affected by fluid contaminations. Specimens in FG and CG displayed the highest RTVs. Therefore, clinicians should have enough knowledge about probable contaminations in I/A interface in order to manage them during clinical procedure and to inform patients about using oral care products.

• The Journal of Advanced Prosthodontics
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• v.6 no.4
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• pp.302-308
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• 2014

PURPOSE. The purpose of this study was to compare removal torques and surface topography between laser treated and sandblasted, large-grit, acid-etched (SLA) treated implants. MATERIALS AND METHODS. Laser-treated implants (experimental group) and SLA-treated implants (control group) 8 mm in length and 3.4 mm in diameter were inserted into both sides of the tibiae of 12 rabbits. Surface analysis was accomplished using a field emission scanning electron microscope (FE-SEM; Hitachi S-4800; Japan) under ${\times}25$, ${\times}150$ and ${\times}1,000$ magnification. Surface components were analyzed using energy dispersive spectroscopy (EDS). Rabbits were sacrificed after a 6-week healing period. The removal torque was measured using the MGT-12 digital torque meter (Mark-10 Co., Copiague, NY, USA). RESULTS. In the experimental group, the surface analysis showed uniform porous structures under ${\times}25$, ${\times}150$ and ${\times}1,000$ magnification. Pore sizes in the experimental group were 20-40 mm and consisted of numerous small pores, whereas pore sizes in the control group were 0.5-2.0 mm. EDS analysis showed no significant difference between the two groups. The mean removal torque in the laser-treated and the SLA-treated implant groups were 79.4 Ncm (SD = 20.4; range 34.6-104.3 Ncm) and 52.7 Ncm (SD = 17.2; range 18.7-73.8 Ncm), respectively. The removal torque in the laser-treated surface implant group was significantly higher than that in the control group (P=.004). CONCLUSION. In this study, removal torque values were significantly higher for laser-treated surface implants than for SLA-treated surface implants.

• Physical Therapy Korea
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• v.8 no.2
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• pp.41-54
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• 2001

Fatigue is the decline in force produced as a result of prolonged muscle activity. Localized muscle fatigue can be identified by a shift toward low in the frequency components of the EMG signal, typically represented by a fall in the median frequency. Previous studies show that a shortened muscle develops a higher fatigue than elongated muscles. The purpose of this study was to investigate the time-related change of median frequency and torque during maximal isometric back extension exercises at different exercise angles ($0^{\circ}$, $12^{\circ}$, $36^{\circ}$, $72^{\circ}$). Twenty healthy subjects (mean age = $24.35{\pm}2.70$) were evaluated in this study. Median frequency was extracted from the EMG signals by fast Fourier transform (FFT). Initial median frequency and the slope of median frequency change over time were computed from linear regression analysis. Pearson's product moment correlation was used to quantify the relationship between slope of median frequency and torque. The results were as follows: 1) Significant differences in y-intercepts of torque regression equation with respect to exercise angle were shown. However, there were no differences in the slopes of the median frequency and torque, and y intercept of the median frequency among exercise angles. 2) There was no significant correlation between slope of median frequency and torque. 3) But there was moderate correlation between median frequency and torque at each exercise angle. In conclusion, the exercise angle during maximal isometric back extension exercise is not a direct effect on slope of median frequency and torque. But results showed that median frequency and torque shift were highly correlated in all subjects.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.506-507
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• 2009

• Journal of Oral Medicine and Pain
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• v.24 no.4
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• pp.455-466
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• 1999

The purpose of this study was to investigate the magnitude of mandibular rotational torque movements in subjects with TMJ sounds, and to analyse correlation between quantitative characteristics of TMJ sounds and mandibular rotational torque movement. Twenty dental college students with TMJ clicking and twenty students without any TMD signs and symptoms were examined by mean of SonoPak and Rotate program of BioPAK system(Bioresearch Inc. MilWaukee, wisconsin, USA) in this study. Mandibular rotational torque movements were recorded and analysed during maximum mouth opening, protrusion, and lateral excursion in frontal and horizontal planes. The obtained results were as follows: 1. On maximum mouth opening, mandibular rotational angle and distance of clicking group were significantly greater than those of control group in frontal plane. (P<0.05). 2. During maximum mouth opening closing, maximum mandibular rotational angle and distance of clicking group were significantly greater than those of control group in frontal plane. (P<0.01). 3. On protrusion, mandibular rotational angle and distance of clickin group were significantly greater than those of control group in horizontal plane. (P<0.05). 4. On lateral excursion, there was no significant difference in mandibular rotational angle and distance between clicking group and control group in frontal and horizontal planes. 5. There were significant correlations between peak amplitude of TMJ sounds and maximum mandibular rotational distance during maximum mouth opening (r=-.481) and mandibular rotational distance on maximum mouth opening (r=-.455) in horizontal plane. 6. There were significant correlations between Above 300/(0-300)Hz ratio of TMJ sounds and mandibular rotational angle (r=-.499) and distance (r=-.457) on maximum mouth opening in frontal plane.

• Journal of Korean Physical Therapy Science
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• v.9 no.3
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• pp.67-75
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• 2002

The purpose of this study was to evaluate the effects of quadriceps femoris flexibility exercise which would improve the degree of knee flexion range of motion, extension torque, and the activities of daily living (ADL) in elderly subjects with degenerative knee arthritis. Fourteen elderly patients (two men and twelve women) with degenerative knee arthritis participated and had a quadriceps femoris flexibility exercise intervention program in this study. The mean age of the patients was 70.00 years for men and 71.16 years for women. This study carried out the experimental study of one group pretest-posttest design, which evaluated the degree of knee flexion range of motion, extension torque, the ADL ability of the patients before and after applying the exercise intervention for five weeks. The results of this study are as follow: 1. The knee flexion ranges of motion of the patients were measured before and after the intervention and the ranges increased significantly both in the left and right knee flexion range of motion (p < 0.05). 2. The peak torque of the knee muscle, the peak torque/body weight, and average power of the patients showed significant increases in both in the left and right knee after applying the intervention (p < 0.05). 3. The intervention produced a significant reduction in pain of the patients (p < 0.05). Their functional activities of ADL improved significantly compared with before the intervention (p < 0.05). It has been shown that the quadriceps femoris flexibility exercise intervention program increased significantly the knee flexion range of motion, and extension torque, as well as an increase in performance of functional activities of ADL of the patients. Thus, the quadriceps femoris flexibility exercise should be considered as one of the therapeutic exercises for the elderly patients with degenerative knee arthritis applied.

• International Journal of Fluid Machinery and Systems
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• v.8 no.2
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• pp.102-112
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• 2015

In the Nordic grid, a trend observed the recent years is the increase in grid frequency variations, which means the frequency is outside the normal range (49.9-50.1 Hz) more often. Variations in the grid frequency leads to changes in the speed of rotation of all the turbines connected to the grid, since the speed of rotation is closely related to the grid frequency for synchronous generators. When the speed of rotation changes, this implies that the net torque acting on the rotating masses are changed, and the material of the turbine runners must withstand these changes in torque. Frequency variations thus leads to torque oscillations in the turbine, which become dynamical loads that the runner must be able to withstand. Several new Francis runners have recently experienced cracks in the runner blades due to fatigue, obviously due to the runner design not taking into account the actual loads on the runner. In this paper, the torque oscillations and dynamic loads due to the variations in grid frequency are simulated in a 1D MATLAB program, and measured grid frequency is used as input to the simulation program. The maximum increase and decrease in the grid frequency over a 440 seconds interval have been investigated, in addition to an extreme event where the frequency decreased far below the normal range within a few seconds. The dynamic loading originating from grid frequency variations is qualitatively found by a constructed variable $T_{stress}$, and for the simulations presented here the variations in $T_{stress}$ are found to be around 3 % of the mean value, which is a relatively small dynamic load. The important thing to remember is that these dynamic loads come in addition to all other dynamic loads, like rotor-stator interaction and draft tube surges, and should be included in the design process, if not found to be negligible.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.2
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• pp.169-181
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• 2003

Statement of problem : The survival rate of wide diameter implants was lower than of 3.75-mm implants in some clinical researches. Purpose : The purpose of this study was to investigate the influence of implant diameter on the osseointegration of implants in the rabbit femoral condyle and tibial metaphyses by means of removal torque measurements and histomorphometric analysis. Material and Method : Ten adult New Zealand White rabbits were used in this study Two 3.75-mm diameter implants were inserted through one cortical layer in the tibial metaphyses and one 3.75-mm diameter implant was inserted in the femoral condyle. 5.0-mm diameter implants were inserted in the other leg in the same manner. A total of 60 implants (3.75-mm diameter implants:30 : 5.0-mm diameter implants:30) were installed. After a healing time of 4 and 12 weeks, the peak removal torque values required to shear off the implants were recorded. From the removal torque values (Ncm) obtained, the mean shear stress ($N/mm^2$) was calculated. And the percentage of direct bone-to-implant contact and the percentage of bone area inside the thread were measured by Kappa Image Base-metreo. The Student's t-test was undertaken for statistical analysis (p<0.05). Results : The removal torque value of 5.0-mm diameter implants was higher than of 3.75-mm diameter implants (p<0.05). The difference of shear stress value between 3.75-mm and 5.0-mm diameter implants was not statistically significant (p>0.05). The percentage direct bone-to-implant contact had no statistical difference between two groups (p>0.05). The percentage of bone area inside the thread had no statistical difference between two groups (p>0.05). Conclusion It is concluded that the quality f osseointegration is not influenced by increasing implant diameter.

• Korean Journal of Agricultural Science
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• v.50 no.4
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• pp.773-784
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• 2023

In this study, we developed a dynamic model and steering controller model for an autonomous tractor and evaluated their performance. The traction force was measured using a 6-component load cell, and the rotational speed of the wheels was monitored using proximity sensors installed on the axles. Torque sensors were employed to measure the axle torque. The PI (proportional integral) controller's coefficients were determined using the trial-error method. The coefficient of the P varied in the range of 0.1 - 0.5 and the I coefficient was determined in 3 increments of 0.01, 0.05, and 0.1. To validate the simulation model, we conducted RMS (root mean square) comparisons between the measured data of axle torque and the simulation results. The performance of the steering controller model was evaluated by analyzing the damping ratio calculated with the first and second overshoots. The average front and rear axle torque ranged from 3.29 - 3.44 and 6.98 - 7.41 kNm, respectively. The average rotational speed of the wheel ranged from 29.21 - 30.55 rpm at the front, and from 21.46 - 21.63 rpm at the rear. The steering controller model exhibited the most stable control performance when the coefficients of P and I were set at 0.5 and 0.01, respectively. The RMS analysis of the axle torque results indicated that the left and right wheel errors were approximately 1.52% and 2.61% (at front) and 7.45% and 7.28% (at rear), respectively.