• Title/Summary/Keyword: tension and compression

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THE THREE DIMENSIONAL FINITE ELEMENT ANALYSIS OF STRESS DISTRIBUTION AND DISPLACEMENT IN MANDIBLE ACCORDING TO TREATMENT MODALITIES OF MANDIBULAR ANGLE FRACTURES (하악각 골절의 치료 방법에 따른 하악골의 응력 분포 및 변위에 관한 삼차원 유한요소법적 연구)

  • Ku, Je-Hoon;Kim, Il-Kyu;Chang, Jae-Won;Yang, Jung-Eun;Sasikala, Balaraman;Wang, Boon
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.32 no.3
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    • pp.207-217
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    • 2010
  • The purpose of this study was to evaluate the effects of the stress distribution and displacement in mandible according to treatment modalities of mandibular angle fractures, using a three dimensional finite element analysis. A mechanical model of an edentulous mandible was generated from 3D scan. A 100-N axial load and four masticatory muscular supporting system were applied to this model. According to the number, location and materials of titanium and biodegradable polymer plates, the experimental groups were divided into five types. Type I had a single titanium plate in the superior border of mandibular angle, type II had two titanium plates in the superior tension border and in the inferior compression border of mandibular angle, type III had a single titanium plate in the ventral area of mandibular angle, type IV had a single biodegradable polymer plate in the superior border of mandibular angle, type V had a single biodegradable polymer plate in the ventral area of mandibular angle. The results obtained from this study were follows: 1. Stress was concentrated on the condylar neck of the fractured side except Type III. 2. The values of von-Mises stress of the screws were the highest in the just-posterior screw of the fracture line, and in the just-anterior screw of Type III. 3. The displacement of mandible in Type III was 0.04 mm, and in Type I, II, IV, and V were 0.10 mm. 4. The plates were the most stable in the ventral area of mandibular angle (Type III, V). In conclusion, the ventral area of mandibular angle is the most stable location in the fixation of mandibular angle fractures, and the just- posterior and/or the just-anterior screws of the fracture line must be longer than the other, and surgeons have to fix accurately these screws, and the biodegradable polymer plate also was suitable for the treatment of mandible angle fracture.

Twisting Effect on Supermicroanastomosis of the Superficial Inferior Epigastric Artery in a Rat Model (혈관 비틀림이 백서 천층하복부 동맥의 초미세문합에 미치는 효과)

  • Seo, Mi-Hyun;Kim, Soung-Min;Eo, Mi-Young;Kang, Ji-Young;Myoung, Hoon;Lee, Jong-Ho
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.33 no.5
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    • pp.375-384
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    • 2011
  • Purpose: The advent of microsurgical technique and instruments, particularly in the field of perforator flap and supermicrosurgery, which have expanded the scope of microsurgery. However, supermicroanastomosis without any compression, tension, or distortions must be achieved to reach successful outcomes. Small-caliber vessels, such as those with an internal diameter less than 0.2 mm, are susceptible to inadvertent twisting of the anastomosis. In this study, using the superficial inferior epigastric artery (SIEA)-based flap model in Sprague-Dawley (SD) rats, we evaluated the acceptable limits of twisting effects on supermicroanastomotic sites. Methods: A total of 20 supermicroanastomoses were performed using the SIEA-based flap model in 10 male SD rats, 10-weeks-of-age, weighing 300~350 g. Rats were divided into five groups of two with four flaps as follows: 1) sham, 2) control group with end to end SIEA arterial supermicroanastomosis, 3) experimental I (EA1) with $90^{\circ}$ twisting, 4) experimental II (EA2) with $180^{\circ}$ twisting, and 5) experimental III (EA3) with $270^{\circ}$ twisting of the supermicroanastomosis. Each SIEA was anastomosed using six 11-0 $Ethilon^{(R)}$ (Ethicon Inc. Co., NJ, USA) stitches except in the sham group where the SIEA was only clamped with Supermicro vascular $clamps^{(R)}$ (S&T, Neuhausen, Switzerland) for 20 minutes. Results: The anastomosed arterial patency showed no remarkable changes according to doppler waveforms measured with a Smardop 45 Doppler System (Hadeco Inc., Kawasaki, Japan). The pulsatility index (PI) was increased at postoperative day 10 in the EA2 and EA3 groups, and the resistance index (RI) showed no statistically significant difference between preoperative and postoperative values at 10 days. Histologic specimens from the EA3 group showed increased tunica media necrosis, convolution of the internal elastic lamina, densely packed platelets, fibrin, and erythrocytes. Flap viability and anastomosed vessel patency were not significantly affected by the degree of arterial twisting in this study, other than in the EA3 group where minor effects on arterial patency of the microanastomoses were encountered. Conclusion: It appears that minor twisting on small caliber arteries, used in supermicroanastomoses, can be tolerated. However, twisting should be avoided as much as possible, and more than $180^{\circ}$ twisting must be prevented in clinical practice.

Multiscale modeling of reinforced/prestressed concrete thin-walled structures

  • Laskar, Arghadeep;Zhong, Jianxia;Mo, Y.L.;Hsu, Thomas T.C.
    • Interaction and multiscale mechanics
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    • v.2 no.1
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    • pp.69-89
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    • 2009
  • Reinforced and prestressed concrete (RC and PC) thin walls are crucial to the safety and serviceability of structures subjected to shear. The shear strengths of elements in walls depend strongly on the softening of concrete struts in the principal compression direction due to the principal tension in the perpendicular direction. The past three decades have seen a rapid development of knowledge in shear of reinforced concrete structures. Various rational models have been proposed that are based on the smeared-crack concept and can satisfy Navier's three principles of mechanics of materials (i.e., stress equilibrium, strain compatibility and constitutive laws). The Cyclic Softened Membrane Model (CSMM) is one such rational model developed at the University of Houston, which is being efficiently used to predict the behavior of RC/PC structures critical in shear. CSMM for RC has already been implemented into finite element framework of OpenSees (Fenves 2005) to come up with a finite element program called Simulation of Reinforced Concrete Structures (SRCS) (Zhong 2005, Mo et al. 2008). CSMM for PC is being currently implemented into SRCS to make the program applicable to reinforced as well as prestressed concrete. The generalized program is called Simulation of Concrete Structures (SCS). In this paper, the CSMM for RC/PC in material scale is first introduced. Basically, the constitutive relationships of the materials, including uniaxial constitutive relationship of concrete, uniaxial constitutive relationships of reinforcements embedded in concrete and constitutive relationship of concrete in shear, are determined by testing RC/PC full-scale panels in a Universal Panel Tester available at the University of Houston. The formulation in element scale is then derived, including equilibrium and compatibility equations, relationship between biaxial strains and uniaxial strains, material stiffness matrix and RC plane stress element. Finally the formulated results with RC/PC plane stress elements are implemented in structure scale into a finite element program based on the framework of OpenSees to predict the structural behavior of RC/PC thin-walled structures subjected to earthquake-type loading. The accuracy of the multiscale modeling technique is validated by comparing the simulated responses of RC shear walls subjected to reversed cyclic loading and shake table excitations with test data. The response of a post tensioned precast column under reversed cyclic loads has also been simulated to check the accuracy of SCS which is currently under development. This multiscale modeling technique greatly improves the simulation capability of RC thin-walled structures available to researchers and engineers.

THE EFFECT OF EXOGENOUS ELECTRIC CURRENTS ON CYCLIC NUCLEOTIDES IN FELINE ALVEOLAR BONE (외인성전류가 고양이 치조골의 cyclic nucleotides에 미치는 영향에 관한 연구)

  • Kim, Young-Bok;Lee, Jong-Heun;Yang, Won-Sik
    • The korean journal of orthodontics
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    • v.14 no.2
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    • pp.187-202
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    • 1984
  • There are evidences that exogenous electric currents are capable of enhancing bone formation and resolution, and that the conversion of the bioelectric response to biochemical activity provides the directional component of orthodontic tooth movement. In addition, evidence has implicated cyclic nucleotides in alveolar bone cellular activation mechanism during orthodontic tooth movement. In view of these evidences, this study was performed to investigate the effects of exogenous electric currents on cyclic nuclotide levels in feline alveolar bone and the possible clinical application of electric currents as an additional orthodontic tool. In the first study, three groups of three adult cats were subjected to application of a constant direct current of $10{\pm}2$ microamperes to gingival tissue near maxillary canine noninvasively for 1, 3, and 7 days respectively. In the second study, three groups of three adult cats each were treated by an electric-orthodontic procedure for 1, 3, and 7 days respectively. The left maxillary (control) canine received an orthodontic force of 80gm alone at time of initiation, while the right maxillary (experimental) canine received combined force-electric stimulation (80gm of force and $10{\pm}2$ microamperes of a constant D.C. currents). Alveola, bone samples were obtain from the mesial (tension and/or cathode) and the distal (compression and/or anode) sites surrounding maxillary canines as well as from contralateral control sites. The samples were extracted, boiled, homogenized, and the supernatants were assayed for cyclic nucleotides (cAMP, cGMP) by a radioimmunoassay method. And also the amount of tooth movement was measured in the second study. On the basis of this study, the following conclusions can be drawn: 1. The fluctuation pattern of cyclic nucleotide levels in alveolar bone treated by exogenous electric currents was similar to that treated by orthodontic force. 2. The cAMP levels in alveolar bone of electrically treated teeth significantly elevated above the control values. And of electrically treated teeth, the values of the anode sites were higher than those of the cathode sites. 9. The cGMP levels in alveolar bone of electrically treated teeth elevated above the control values at the initiation phase of treatment, but dropped below the control values at time of termination. And of electrically treated teeth, the values of the cathode sites were higher than those of the anode sites. 4. The rate of tooth movement in teeth . treated by force-electric combination increased with the length of treatment as compared to that treated by mechanical force alone.

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Mechanical Properties and Stress-Strain Model of Re-Bars Coldly Bent and Straightened (굽힌 후 편 철근의 기계적 성질과 응력-변형률 모델)

  • Chun, Sung-Chul;Tak, So-Young;Ha, Tae-Hun
    • Journal of the Korea Concrete Institute
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    • v.24 no.2
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    • pp.195-204
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    • 2012
  • In the construction of high-rise buildings, bent re-bars are manually straightened to connect slabs to core-walls, which are usually cast before floor structures. During cold bending and straightening of re-bars, plastic deformation causing work hardening, Bauschinger effect and aging hardening is unavoidable. Tensile tests of coldly bent and straightened re-bars were conducted with test parameters of grade, diameter, and bend radius of re-bars as well as age between bending and straightening. Test results showed that proportional limits were lower and strain hardening occurred without yield plateaus. Inside and outside of re-bars with compression and tension deformations, respectively, during bending showed lower yield points due to Bauschinger effect and no yield plateaus due to work hardening, respectively. When re-bar grade was higher, yield point became significantly lower where Grade 400 re-bars had yield strengths lower than specified yield strength of 400 MPa. Because the surface of re-bar has higher strength than the core of re-bar, Bauschinger effect was more obvious for higher-grade re-bars. When age between bending and straightening was greater, yield strength increased and elongation decreased (i.e. embrittlement occurs). Using measured data, stress-strain relationship for straightened re-bars was developed based on Ramberg-Osgood model, which can be used to evaluate stiffness of joints when straightened re-bars are applied.

A STUDY ON THE MANDIBULAR MOMENTS ACCORDING TO ANTERO-POSTERIOR PLACEMENT OF PIVOT ON LOWER NATURAL DENTITION (자연치열에 설치한 pivot의 전후방 일치변화에 따른 하악의 moment에 관한 연구)

  • Lee Hyun-Shick;Park Nam-Soo;Choi Dae-Gyun
    • The Journal of Korean Academy of Prosthodontics
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    • v.31 no.3
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    • pp.394-410
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    • 1993
  • This study was accomplished for appreciation of the mandibular moments according to antero- posterior movement of pivot placed on the lower natural dentition. For this study, 20 subjects(male, $21\sim30$ yrs., average age 24) in the category of normal occlusion were selected, and the intraoral Vitallium clutches were cast and fabricated for each subjects. A 2-dimension PSD(Position Sensitive Detector, Hamamatsu Photonics Co., Japan) was attached to maxillary clutch in a mode of three dimensional control and LED (Light Emit Diode, Hamamatsu Photonics Co., Japan) was set up on mandibular clutch. Both clutches were set into oral cavity of each subjects and adjusted. Then the subjects were allowed to intercuspated with maximal bite force while the pivoting ball in the mid-line moving from anterior toward posterior position. The displacement scales were recorded by CCD camera(Sony, CCD-TR-705) and VCR, The conclusions were as follows : 1. When the subject was allowed to bite the metal pivoting ball in the midline of lower dentition with maximal bite force voluntarily while moving from lower central incisor to canine, 1st premolar, End premolar, 1st molar and 2nd molar. The lever actions on the pivot were revealed in all subjects. The equilibrium of moment were revealed on the pivots of 1st premolar(14 subjects), End premolar(4 subjects), and canine(2 subjects) areas. 2. The changes of loading on the TMJ according to antero-posterior positional changes of metal pivoting ball were able to recognize as follow. Compression on the TMJ was increased when the pivot moves anteriorly from the equilibrium point, and tension on the TMJ was increased when posteriorly. 3. 13 subjects were recognized their habitual chewing sides(Rights, Left8), and 7 subjects were not. During maximal biting, mandible was displaced toward their habitual chewing sides on the metal pivoting ball in the frontal plane. 4. In cephalometric analysis, the average genial angle of 20 subjects was $116.75^{\circ}$ and the average mandibular body length was 79.77mm. The equilibrium points of mandibular moment were positioned more posteriorly in the subjects having larger Genial angle than in the smaller(p<0.05). Relationships among the angle between FH plane and occlusal plane, the angle between occlusal plane and mandibular plane , and mandibular body length were not significant(p>0.05).

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Comparison of the Immediate Effects of Two Types of Muscle Energy Techniques Applied to the Hamstring of Adults in Their Twenties With or Without Low Back Pain on the Pelvic Inclination and the Length of the Hamstring (요통 유무에 따른 20대 성인의 넙다리뒤근에 적용한 두 가지 근에너지 기법 종류에 따른 골반 경사각 및 넙다리뒤근 길이에 미치는 즉각적 효과 비교)

  • Hwang, Lee-kyeong;Kim, Suhn-yeop
    • Physical Therapy Korea
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    • v.29 no.1
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    • pp.37-47
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    • 2022
  • Background: Lower back pain (LBP) is a major cause of disability and a common musculoskeletal disorder encountered at some point in life. Dysfunction of the lumbar vertebrae has been associated with decreased flexibility of the hamstrings, which exhibited a strong positive correlation with LBP. Hamstring tension affects lumbar pelvic rhythm. We aimed to activate pelvic stability with compression by Active Therapeutic Movement (ATM), muscle energy technique (MET) was applied to increase the flexibility of the hamstring. Objects: In this study, we aimed to investigate the effects of MET with ATM and general MET were applied to the hamstring of adults, who were in their twenties with nor without LBP, on their pelvic inclination and the length of their hamstring. Methods: A total of 32 subjects were briefed about the purpose of this study and agreed to participate voluntarily. Before the experiment, all subjects were pre-examined, and they were divided into an LBP group and a no lower back pain group accordingly. Thereafter, all subjects participated in both in a crossover manner. After at least one week, they switched to another group and participated in the same experiment. Results: The study results revealed that both groups demonstrated significant results in the modified active knee extension test (p < 0.01) and the sit and reach test (p < 0.01) performed to assess the hamstring flexibility; an interaction (p < 0.05) was noted. Moreover, a more significant difference was observed between the MET with ATM and the general MET. Although significant results were obtained for the pelvic inclination (p < 0.01), interaction was not noted. Conclusion: Conclusively, in this study, when the MET with ATM was applied to the two groups, there was a significant difference compared to the general MET for hamstring flexibility, but it was confirmed that there was no significant difference for the pelvic inclination.

Nonlinear Analysis of Steel-concrete Composite Girder Using Interface Element (경계면 요소를 사용한 강·콘크리트 혼합 거더의 비선형 거동 해석)

  • Kwon, Hee-Jung;Kim, Moon Kyum;Cho, Kyung Hwan;Won, Jong Hwa
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.4A
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    • pp.281-290
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    • 2009
  • In this study, an analysis technique of hybrid girder considering nonlinearity of steel-concrete contact surface is presented. Steel-concrete hybrid girder shows partial-interaction behavior due to the deformation of shear connectors, slip and detachment at the interface, and cracks under the applied loads. Therefore, the partial-interaction approach becomes more reasonable. Contact surface is modeled by interface element and analyzed nonlinearly because of cost of time and effort to detailed model and analysis. Steel and Concrete are modeled considering non-linearity of materials. Material property of contact surface is obtained from push-out test and input to interface element. For the constitutive models, Drucker-Prager and smeared cracking model are used for concrete in compression and tension, respectively, and a von-Mises model is used for steel. This analysis technique is verified by comparing it with test results. Using verified analysis technique, various analyses are performed with different parameters such as nonlinear material property of interface element and prestress. The results are compared with linear analysis result and analysis result with the assumption of full-interaction.

Experimental and numerical investigation on flexural response of reinforced rubberized concrete beams using waste tire rubber

  • Memduh Karalar;Hakan Ozturk;Yasin Onuralp Ozkilic
    • Steel and Composite Structures
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    • v.48 no.1
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    • pp.43-57
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    • 2023
  • The impacts of waste tire rubber (WTR) on the bending conduct of reinforced concrete beams (RCBs) are investigated in visualization of experimental tests and 3D finite element model (FEM) using both ANSYS and SAP2000. Several WTR rates are used in total 4 various full scale RCBs to observe the impact of WTR rate on the rupture and bending conduct of RCBs. For this purpose, the volumetric ratios (Vf) of WTR were chosen to change to 0%, 2.5%, 5% and 7.5% in the whole concrete. In relation to experimental test consequences, bending and rupture behaviors of the RCBs are observed. The best performance among the beams was observed in the beams with 2.5% WTR. Furthermore, as stated by test consequences, it is noticed that while WTR rate in the RCBs is improved, max. bending in the RCBs rises. For test consequences, it is clearly recognized as WTR rate in the RCB mixture is improved from 0% to 2.5%, deformation value in the RCB remarkably rises from 3.89 cm to 7.69 cm. This consequence is markedly recognized that WTR rates have a favorable result on deformation values in the RCBs. Furthermore, experimental tests are compared to 3D FEM consequences via using ANSYS software. In the ANSYS, special element types are formed and nonlinear multilinear misses plasticity material model and bilinear misses plasticity material model are chosen for concrete and compression and tension elements. As a consequence, it is noticed that each WTR rates in the RCBs mixture have dissimilar bending and rupture impacts on the RCBs. Then, to observe the impacts of WTR rate on the constructions under near-fault ground motions, a reinforced-concrete building was modelled via using SAP2000 software using 3-D model of the construction to complete nonlinear static analysis. Beam, column, steel haunch elements are modeled as nonlinear frame elements. Consequently, the seismic impacts of WTR rate on the lateral motions of each floor are obviously investigated particularly. Considering reduction in weight of structure and capacity of the members with using waste tire rubber, 2.5% of WTR resulted in the best performance while the construction is subjected to near fault earthquakes. Moreover, it is noticeably recognized that WTR rate has opposing influences on the seismic displacement behavior of the RC constructions.

Photoelastic Stress Analysis of Fixed Partial Dentures (가공의치(架工義齒)에 작용(作用)하는 Stress에 관(關)한 광탄성학적(光彈性學的) 분석(分析))

  • Cho, Won-Haeng
    • The Journal of Korean Academy of Prosthodontics
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    • v.18 no.1
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    • pp.15-35
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    • 1980
  • The purpose of this study was to investigate stresses in the various components of fixed partial dentures restoring the posterior teeth of the lower jaw, and to measure quantitatively the effects of certain modifications in structural design on the stresses in the restorations using two-dimensional photoelasticity. Two-dimensional photoelastic methods were used in this study. Several models of fixed partial dentures were constructed. Shoulder less margins and anatomic occlusal reduction were incorporated in Model 1. Rounded shoulders and flat occlusal reduction were incorporated in Model 2, while Model 3 was a cantilever fixed partial denture. Other similar fixed partial dentures were constructed with V and U notches deliverately included in the region of the fixed joints for comparative reasons. The birefringent materials used in this study were PSM-1 and PSM-5 in standard sheets. PSM-1 was used for constructing the substructure, and PSM-5 was used in making the components of the fixed partial dentures. The two materials were used in the construction of composite photoelastic models. Improved artificial stone was used to represent dental cement in luting the composite photoelastic models. Static loading procedures were used at preplanned sites to represent occlusal loads in the mouth. 35 mm color and B/W film were used to record isochromatics in accordance with photoelastic procedures. Data reduction was performed using the grid method, which helped in, the mathematical integration procedure (Shear difference method) to separate the principal stresses. The results were as follows. 1. Fixed partial dentures do not function in bending as a symmetrical beam. Alternate areas of tension and compression were demonstrated when multiple contact loading was used. 2. The weakest part in posterior fixed partial dentures is the fixed joint. 3. (1) Models I and modified Model I were loaded on the pontic using a 50 pound vertical static load. The shear stress near the posterior fixed joint in Model 1 (U notches) was+129.4 p.s.i., and at the same fixed joint in modified Model 1 (V notches) was+239.4 p.s.i. The concentration of stress in fixed joint was reduced by 50% when U notches replaced the V notches. (2) Modified Model 2 was loaded using a multiple contact loader at a total load of 125 pounds. The difference between the principal stresses (${\sigma}_1-{\sigma}_2$), shear stress, at the V notches was+600 p.s.i., and at the U notches was+3l7 p.s.i. The shear stress was reduced by 50% when U notches replaced the V notches. V-grooves at the fixed joints should be avoided, and should be replaced by regular shaped U-grooves. 4. Cantilever fixed partial dentures had much higher stresses at the fixed joint than fixed partial dentures that were attached at both ends.

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