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Cangul Keskin - One of the best experts on this subject based on the ideXlab platform.
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apical root canal morphology of mesial roots of mandibular first molar teeth with vertucci type ii configuration by means of micro computed tomography
Journal of Endodontics, 2017Co-Authors: Ali Keles, Cangul KeskinAbstract:Abstract Introduction The aim of this study was to assess the features of the apical root canal anatomy and its relation to the level at which 2 separate root canals merge in the mesial roots of the mandibular first molars with Vertucci type II canal configuration by using micro–computed tomography analysis. Methods The anatomic features of the apical 3 mm of root canals in 83 mesial roots of mandibular first molar teeth were investigated by micro–computed tomography and software imaging according to the level at which 2 separate root canals merge. The most apical slice where a visible root canal was detectable was recorded as 0 level. The specimens from where 2 root canals rejoin at within 3 mm from the 0 level were then assigned to group 1 (n = 37), whereas the specimens from where root canals rejoin 3–9 mm from the 0 level were assigned to group 2 (n = 46). Data were presented by using descriptive statistics and Mann-Whitney U tests, with the significance level set at 5%. Results In all specimens the long oval type of cross-sectional shape increased from 50.9% at 1 mm to 80.5% at 3 mm. Group 1 presented significantly higher Major Diameter values compared with group 2 ( P P > .05) between groups. Group 2 displayed significantly higher roundness values than group 1 ( P Conclusions A long oval root cross section of apical root canal anatomy is more prevalent in roots for which 2 root canals merge within apical 3 mm of root canals.
Dan L. Bader - One of the best experts on this subject based on the ideXlab platform.
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The Effect of Transpedicular Screw Design on Its Performance in Vertebral Bone Under Tensile Loads: A Parametric Study.
Journal of Spinal Disorders & Techniques, 2013Co-Authors: Ron N. Alkaly, Dan L. BaderAbstract:STUDY DESIGN A biomechanical study using bovine thoracolumbar spines. OBJECTIVE To study investigated whether thread design parameters aimed at altering the state of stress at the screw-bone interface increase the screw's holding power. SUMMARY AND BACKGROUND DATA Internal spinal fixators utilizing transpedicular screw fixation are used to achieve early stabilization of the injured spine in a range of clinical conditions. Despite advances in the design of internal spinal fixation systems, implant loosening, and catastrophic failures at the screw-bone interface remains a serious complication in adult spine surgery. Although the performance of the screws in the vertebral bone critically depends on ability of screw thread design to provide and maintain adequate bone purchase, the effect of individual thread design parameters on screw performance and the failure process of the screw-bone interface, remains unclear. METHODS On the basis of the AO Schanz thread, this parametric study used 96 lumbar bovine vertebrae instrumented with 19 screw designs to investigate the effects of pitch, ratio of Major to minor Diameter, screw insertion depth, and Major Diameter, on screw performance under pure tensile loading. The effect of vertebral morphometry on screw performance and the extent of damage within the failed screw-bone interface were evaluated. RESULTS The increase in screw insertion depth, screw pitch, and the ratio of Major to minor Diameter, significantly affected screw performance under tensile loads. Complex interactions existed between the Major Diameter and each of the design variables. Vertebral morphometry had little effect on screw performance while the damage within the failed bone-screw interface confined to the immediate region of the screw threads. CONCLUSIONS Design variables, able to reduce shear stresses or modify the complex stress profile at the bone-screw interface, are more effective in preventing early failure of the interface.
Cccc Fourth - One of the best experts on this subject based on the ideXlab platform.
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experimental study on the axial bearing capacity distribution of Major Diameter phc pile in stratified foundation
South China Harbour Engineering, 2009Co-Authors: Li Geng, Cccc FourthAbstract:Based on the pile test of the certain bridge, the static load tests with axial distribution test conducted by burying reinforcement meters in the reinforcement cages of the piles for 2 Major Diameter PHC piles are carried out. The results show that larger the stiffness of soil layer to be, more test load will be transferred to the certain soil layer. The excitation of resistance in the upper soil layer is ahead of that in the lower soil layer. The Major relative displacement of upper pile body caused by Major test load will make the resistance of mud lump soften. The compressions of the Major Diameter PHC piles are the main cause of the pile top settlements under the work load though to the Major stiffness.
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experimental study on the axial bearing capacity distribution of Major Diameter phc pile
Port & Waterway Engineering, 2009Co-Authors: Li Geng, Cccc FourthAbstract:Based on the pile test of a sea-crossing bridge,the static load tests with axial distribution test conducted by burying reinforcement meters in the reinforcement cages of the piles for 4 large-Diameter PHC piles are carried out.The results show that the pile toes of large-Diameter PHC piles should reach favorable compressible soil layer because the stiffness affects the ultimate capacity significantly.The large-Diameter PHC piles behave as end-bearing friction piles.When the large-Diameter PHC piles with favorable compressible supporting course are covered by thick weak ground layer,the decrease of upper soil friction should be considered in design.The compressions of large-Diameter PHC piles are the main cause of the pile top settlements under the work load although the stiffness of pile body is large.
Dennis J. Callahan - One of the best experts on this subject based on the ideXlab platform.
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Mechanical performance of standard and cannulated 4.0-mm cancellous bone screws.
Journal of Orthopaedic Research, 2000Co-Authors: Greg A. Brown, Tracey Mccarthy, Craig A. Bourgeault, Dennis J. CallahanAbstract:The mechanical performance of bone screws is determined by their pull-out strength (holding power), compressive force, stripping torque, yield bending moment, ultimate bending moment, and fatigue strength. These parameters are related to the parameters of the screw design, including Major thread Diameter, minor thread Diameter, thread length, pitch, shaft Diameter, cannulation Diameter, and material properties. The goal of the study was to theoretically predict the static performance of five 4.0-mm, 45-46-mm-long, cancellous, partially threaded standard and cannulated bone screws and compare the predictions with experimental measurements. A secondary goal was to determine if cannulation of the bone screw diminished its mechanical performance. The predicted values for pull-out force, compressive force, and stripping torque were determined by the thread length, Major thread Diameter, and thread shape factor. The screws with the largest Major thread Diameter and longest thread length had the greatest pull-out force, compressive strength, and stripping torque. However, when correcting for the thread length, a higher thread shape factor compensated for a smaller Major Diameter. The coefficient of determination (r2) for the correlation between the predicted and measured pull-out force improved from 0.75 to 0.90 when the theoretical model included the thread shape factor. The yield and ultimate bending moments are a function of the section modulus and material properties of the screw. The Ace solid screw had the greatest section modulus and yield and ultimate bending moments. The experimental data support the theoretical models for predicting the mechanical performance of bone screws. The design of the bone screws can be optimized on the basis of theoretical modeling. The strong correlation between the predicted and measured parameters allows comparison between bone screws without repeated experimental tests. Theoretical and experimental results show that cannulation of the bone screw did not inherently diminish its mechanical performance.
Marco Antonio Hungaroduarte - One of the best experts on this subject based on the ideXlab platform.
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micro computed tomography analysis of the root canal anatomy and prevalence of oval canals in mandibular incisors
Journal of Endodontics, 2013Co-Authors: Marcela Milanezi De Almeida, Norberti Bernardineli, Ronald Ordinolazapata, M H Villasboas, Pablo Andres Amorososilva, Christian Giampietro Brandao, Bruno Martini Guimaraes, Ivaldo Gomes De Moraes, Marco Antonio HungaroduarteAbstract:Abstract Introduction This study aimed to describe the anatomy of the mandibular incisors by using micro–computed tomography. Methods Mandibular incisors (n = 340) were scanned at 19-μm voxel size resolution, and the numbers of canals were classified according to Vertucci classification, as well as the Major and minor Diameters of the root and root canals, presence of oval canals, and three-dimensional analysis of the apical third were also measured. Data were presented in terms of median and range for each anatomic classification. Results Overall, the specimens had 1 root canal (N = 257). The second most prevalent anatomy was Vertucci type III (N = 56). These anatomies represent 92% of the sample. The medians of the Major Diameter at the 1-, 2-, and 3-mm level of the most prevalent anatomies were 0.36, 0.39, and 0.47 mm for type I and 0.41, 0.51, and 0.66 mm for type III, respectively. The apical volume appears to be constant among these anatomies (0.63 and 0.59 mm3). Oval canals were found at the 1-mm apical level, with a prevalence of 16.7% for Vertucci type I and 37.5% for Vertucci type III. The presence of oval canals increased at the 3-mm apical level to 32.4% and 76.2% for Vertucci type I and III classifications, respectively. Conclusions Type I and III configurations represent 92% of the mandibular incisors studied. Within these anatomic configurations, oval-shaped canals in the apical third were not uncommon and more prevalent in the type III anatomy.
