• The Journal of Korean Academy of Prosthodontics
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• v.37 no.1
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• pp.104-126
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• 1999

The purpose of this study was to compare and evaluate the stress distribution and displacement developed in the abutment teeth and residual ridge area by madibular unilateral distal extension removable partial denture with 2 different retainer designs. The retainers on right and left canine and right 2nd molar were Alters clasp in one model and telescopic crown in the other model. The stress distribution of abutment teeth and residual ridge area on two model were compared and analyzed with 3-dimensional finite element method. 150N and 400N forces were applied vertically, 30 degree and horizontally on the central fossa area of left 1st molar of the removable partial denture, and then stress distribution patterns were analyzed and compared. The results were as follows 1. As the magnitude and angulation of applied force were increased, the magnitude of stress on the right and central residual ridge area and the right canine of the telescopic type increased and comparing to those of the Alters clasp type. 2. As the magnitude and angulation of applied force were increased, the mesial direction of displacement on the right residual ridge area and the right tooth of the telescopic type increased and the distal direction of displacement on left residual ridge area and the left canine increased comparing to those of Akers clasp type. 3. As the vertical force was applied, the distal direction of the displacement of the right tooth were greater and that of the left canine was smaller and the upward displacement of the right canine was greater in telescopic partial denture than those of Akers clasp type. 4. As the 30 degree force was applied, the mesial direction of the displacement of the right tooth were greater and the distal direction of the displacement of the left canine was smaller and the upward displacement of the right canine was greater in telescopic partial denture than those of Akers clasp type. In the horizontal force the results were same in right area tooth but the distal direction of displacement was greater in left canine. 5. In both removable partial dentures, as the magnitude and degree of force were increased, the stress and displacement were increased. The compressive force was dominative than the ten sile force. 6. In both removable partial dentures, the magnitude of stress was greater on mucosal tissue area than that of the alveolar bone area on distal extension residual ridge area but the result was reversed on anterior residual ridge area. The displacement was always greater on mucosal tissue area than that of alveolar bone area.

• The Journal of Korean Academy of Prosthodontics
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• v.26 no.1
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• pp.133-151
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• 1988

The objectives of this study were to compare the position of centric relation guided by means of leaf gauges, bilateral manipulation, chin-point guidance with Lucia jig and self-guided method and the reproducibility, respectively. A Veri-check (Denar Co., Anaheim, California) was employed for examining, and the displacement of position and reproducibility were verified. The following results were obtained. 1. On the sagittal plane, the centric relation guided by means of leaf gauges showed greater posterior displacement than that by means of bilateral manipulation and less than that by means of chin-point guidance with Lucia jig, and self-guided centric relation showed least posterior displacement. The centric relation guided by means of bilateral manipulation showed greater superior displacement than that by means of chin-point guidance with Lucia jig and less than that by means of leaf gauges and self-guided centric relation showed least superior displacement. 2. On the horizontal plane, the centric relation guided by means of chin-point guidance with Lucia jig showed greater posterior displacement than that of bilateral manipulation and less than that leaf gauges, however the self-guided centric relation showed slightly anterior displacement. 3. The anteroposterior displacement measured on sagittal plane and horizontal plane were highly correlated. (p<0.05). 4. The reproducibility of centric relation guided by means of leaf gauges, bilateral manipulation and chin-point guidance with Lucia jig were similar and more reproducible than self-guided centric relation.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.6
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• pp.264-269
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• 2005

The electrostatic comb drive actuator is one of the main building blocks in the field of micro electro-mechanical systems (MEMS). Most of the comb actuators presented previously have fingers that are rectangular in shape which produce a stable, constant force output during actuation. The use of sawtooth fixed fingers in a comb drive, which were presumed to produce an increasing force output with displacement due to the increased number of regions where fringing force, the driving force of comb actuators, appear. The dimensions of the sawtooth were derived from finite element analysis (FEA) of simplified finger models with sawtooth type fingers of various dimension and were compared to the rectangular finger model that showed that the sawtooth type fingers have $7\~9$ times stronger driving force. Finally, comb drive actuators with sawtooth type and rectangular fingers were fabricated and although the gap was bigger, the comb actuator with sawtooth type fingers showed about 1.7 times greater electrostatic force than the one with rectangular fingers at equal driving voltages. In conclusion, using the proposed sawtooth type comb fingers in a comb drive makes it possible to increase its displacement or reduce the driving voltage.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.313-330
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• 1993

The propagating crack problems under dynamic plane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems in orthortropic material, it is important to know the dynamic stress components and dynamic displacement components around the crack tip. Therefore the dynamic stress components of dynamic stress field and dynamic displacement components of dynamic displacement field in the crack tip of orthotropic material under the dynamic load and the steady state in crack propagation were derived. When the crack propagation speed approachs to zero, the dynamic stress component and dynamic displacement components derived in this study are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determinded by using the concept of crack closure closure energy with the dynamic stresses and represented according to physical properties of the orthotrophic material and crack speeds. The faster the crack velocity, the greater the stress value of stress components in crack tip. The stress value of the stress component of crack tip is greater when fiber direction coincides with the crack propagation than when fider direction is normal to the crack propagation.

• The korean journal of orthodontics
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• v.15 no.1
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• pp.7-22
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• 1985

The purpose of this study was to analyze the stress distribution and the displacement in the maxillary complex after the application of the reverse headgear. The direction of force was parallel to the occlusal plane. Orthopedic force,300gm, was applied to the maxilla of the dry human skull in a forward direction. The stress distribution and the displacement within the maxillary Complex was analyzed by a 3-dimensional finite element method. The results were as follows: 1. The stress distribution at the molar region was greater than that at the anterior. 2. The stress distribution at the lateral side of the premaxilla was greater than that at the middle aide, especially high stress was noted at the canine eminence. 9. Compressive stress was noted only at the frontozygomatic suture of the zygomatic arch. 4. A forward, upward, and sideward displacement was noted at the entire nodal points of the zygomaticomaxillary suture portion. A displacement with a slight rotation was observed on the transverse palatine suture. 5. The maximum stress was observed at the lateral side of the maxillary tuberosity area, and generally the forward and downward displacement was noted at all this area.

• Journal of the Korean Society of Physical Medicine
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• v.9 no.1
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• pp.93-99
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• 2014

PURPOSE: The purpose of this study was to compare three dimensional displacement and peak velocity of the center of mass (COM) during obstacle crossing in young and older adults. METHODS: 10 young adults (6 males/4 females, $24.6{\pm}1.9$ years, age range: 22.0-26.9) and 10 older adults (1 male/9 females, $76.9{\pm}5.1$ years, age range: 65.2-81.2) participated in the study. Both groups crossed an obstacle, which is 10% of leg length, and COM was measured using motion analysis system. Independent t-test was used to find significant differences between two groups. RESULTS: The older adults showed significantly greater and faster COM displacement and peak velocity in mediolateral (M-L) direction as compared with young adults (p<.01 and p<.001 respectively). However, the young adults showed significantly greater and faster COM displacement and peak velocity in anteroposterior (A-P) direction as compared with older adults (p<.05 and p<.001 respectively). Furthermore, the young adults showed faster peak velocity of COM in vertical direction as compared with older adults (p<.001). However, no significant difference was found in the COM displacement in vertical direction between two groups. CONCLUSION: Greater and faster COM displacement and peak velocity in M-L direction in older adults were due to compensatory adjustment for appropriate contact on base of support of swing limb. Thus, the motion of the COM in M-L direction may be a crucial factor to identify risk of falls in older adults.

• Physical Therapy Korea
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• v.23 no.3
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• pp.68-75
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• 2016

Background: Shoulder horizontal adduction (HA) is performed in many activities of daily living. The limited range of motion (LROM) of HA is affected by the tightness of the posterior deltoid, infraspinatus, teres major, and posterior capsule of glenohumeral joint. The LROM of shoulder HA contributes to excessive scapular abduction. Objects: The aim of this study is to compare the scapular abduction distance and three-dimensional displacement of the scapula during shoulder horizontal adduction between subjects with and without the LROM of shoulder HA. Methods: 24 subjects (12 people in LROM group and 12 people in normal ROM group) participated. Subjects with less than $115^{\circ}$ of HA ROM were included in LROM group. Shoulder HA was performed 3 times for measuring scapular abduction distance and three-dimensional displacement of the scapula. Tape measure was used for measuring scapular abduction distance. Scapular abduction distance was normalized by dividing the scapular size. Polhemus Liberty was used for measuring the three-dimensional displacement of the scapula. Results: Normalized scapular abduction distance was significantly greater in LROM group than normal ROM group (p<.001). Three-dimensional displacement of the scapula during shoulder HA was greater in LROM group than normal ROM group (p<.05). Conclusion: LROM group had a greater scapular abduction and three-dimensional displacement of the scapula during shoulder HA compared to normal ROM group.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.331-341
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• 1993

The propagating crack problems under dynamic antiplane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems by theoretical method or experimental method in orthotropic material, it is important to know the dynamic stress intensity factor in the vicinity of crack tip. Therefore the dynamic stress field and dynamic displacement field with dynamic stress intensity factor of orthotropic material in mode III were derived. When the crack propagation speed approachs to zero, the dynamic stress components and dynamic displacement components derived in this paper are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determined by using the concept of crack closure energy with the dynamic stresses and dynamic displacements derived in this paper. Finally, the characteristics of crack propagation are studied with the properties of orthotropic material and crack speed. The variation of angle .alpha. between fiber direction and crack propagating direction and crack propagation speed fairly effect on stress component and displacement component in crack tip. The influence of crack propagation speed on the speed on the stress and displacement is greater in the case of .alpha.=90.deg. than in the case of .alpha.=0.deg. and the faster the crack propagation speed, the greater the stress value and displacement value.

• The Journal of Advanced Prosthodontics
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• v.11 no.6
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• pp.305-312
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• 2019

PURPOSE. The purpose of this study was to compare computer-aided design/computer-aided manufacturing (CAD/CAM) abutment and prefabricated abutment in Morse taper internal connection type implants after cyclic loading. MATERIALS AND METHODS. The study was conducted with internal type implants of two different manufacturers (Group Os, De). Fourteen assemblies were prepared for each manufacturer group and divided into 2 groups (n=7): prefabricated abutments (Os-P, De-P) and CAD/CAM abutments (Os-C, De-C). The amount of axial displacement and the removal torque values (RTVs) were measured before and after cyclic loading (10⁶ cycles, 3 Hz with 150 N), and the tensile removal force to dislodge the abutments was measured after cyclic loading. A repeated measures ANOVA and a pattern analysis based on the logarithmic regression model were conducted to evaluate the effect of cyclic loading on the axial displacement. The Wilcoxon signed-rank test and the Mann-Whitney test was conducted for comparison of RTV reduction% and tensile removal forces. RESULTS. There was no significant difference between CAD/CAM abutments and prefabricated abutments in axial displacement and tensile removal force; however, significantly greater RTV reduction% after cyclic loading was observed in CAD/CAM abutments. The correlation among the axial displacement, the RTV, and the tensile removal force was not significant. CONCLUSION. The use of CAD/CAM abutment did not significantly affect the amount of axial displacement and tensile removal force, but presented a significantly greater removal torque reduction% than prefabricated abutments. The connection stability due to the friction at the abutment-implant interface of CAD/CAM abutments may not be different from prefabricated abutment.

• Physical Therapy Korea
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• v.31 no.1
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• pp.72-78
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• 2024

Background: Limitations of shoulder range of motion (ROM), particularly shoulder internal rotation (SIR), are commonly associated with musculoskeletal disorders in both the general population and athletes. The limitation can result in connective tissue lesions such as superior labrum tears and symptoms such as rotator cuff tears and shoulder impingement syndrome. Maintaining the center of rotation of the glenohumeral joint during SIR can be challenging due to the compensatory scapulothoracic movement and anterior displacement of the humeral head. Therefore, observing the path of the instantaneous center of rotation (PICR) using the olecranon as a marker during SIR may provide valuable insights into understanding the dynamics of the shoulder joint. Objects: The aim of the study was to compare the displacement of the olecranon to measure the rotation control of the humeral head during SIR in individuals with and without restricted SIR ROM. Methods: Twenty-four participants with and without restricted SIR ROM participated in this study. The displacement of olecranon was measured during the shoulder internal rotation control test (SIRCT) using a Kinovea (ver. 0.8.15, Kinovea), the 2-dimensional marker tracking analysis system. An independent t-test was used to compare the horizontal and vertical displacement of the olecranon marker between individuals with and without restricted SIR ROM. The statistical significance was set at p < 0.05. Results: Vertical displacement of the olecranon was significantly greater in the restricted SIR group than in the control group (p < 0.05). However, no significant difference was observed in the horizontal displacement of the olecranon (p > 0.05). Conclusion: The findings of this study indicated that individuals with restricted SIR ROM had significantly greater vertical displacement of the olecranon. The results suggest that the limitation of SIR ROM may lead to difficulty in rotation control of the humeral head.