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Browsing by Subject "Biomechanical Phenomena"
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Item Biomechanical properties of rat pulmonary artery in hypoxia-induced pulmonary hypertension(1991) Griffith, Steven L.Item Comparison of movement rate with different initial moment-to-force ratios(Elsevier, 2019-08-01) Li, Shuning; Chen, Jie; Kula, Katherine S.; Mechanical Engineering and Energy, School of Engineering and TechnologyIntroduction: The objective of this clinical prospective study was to evaluate the effect of the two treatment strategies, translation or controlled tipping followed by root correction, on canine retraction efficiency, specifically canine movement rate. Methods: Twenty-one patients who needed bilateral maxillary canine retraction to close extraction space as part of their treatment plan were selected for this study. Segmental T-loops designed for controlled tipping or for translation were applied randomly to each side. Two digital maxillary dental casts (taken pre- and post-treatment) were used to measure the tooth displacements of each patient. The coordinate system located at the center of canine crown on the pre-treatment model with the three axes defined in the mesial-distal (M-D), buccal-lingual (B-L), and occlusal-gingival (O-G) directions was used to express the six tooth displacement components. The movement rates on the occlusal plane and in the M-D direction were computed. Movement rates were calculated by dividing the M-D displacements or the resultant displacement on the occlusal plane with the corresponding treatment time. Results: T-loops for controlled tipping moved canines faster (33.3% on occlusal plane and 38.5% in the M-D direction) than T-loops for translation. The differences are statistically significant (p = 0.041 on the occlusal plane and 0.020 in the M-D direction). Conclusion: 1. Moment-to-force ratio (M/F) impacts on the canine movement rate in a maxillary canine retraction treatment with segmented T-loop mechanism. 2. Within the neighborhood of the ratio for translation, lower M/F moves canine faster than higher M/F both on occlusal plane and in the M-D direction.Item A Comparison of the Force-Moment Systems Generated by Orthodontic Stainless Steel T-loop and Triangular Springs(1999) Albright, David A.; Chen, Jie; Baldwin, James J.; Hohlt, William F.; Katona, Thomas R.; Shanks, James C.The force-moment systems of orthodontic T-loops have been widely described and investigated. A simpler triangular loop spring design has been employed in the graduate orthodontic clinic at Indiana University School of Dentistry. To date, no investigators have specifically examined and compared the force systems generated by these two loop configurations. The objective of this study was to compare the force systems generated by a T-loop and two different geometric shapes of triangular loops. A sample of 20 T-loops and 40 triangular loop springs were studied. The triangular loops were constructed in two different geometric configurations (n = 20 in each group) utilizing the same linear amount of wire as used in the T-loop fabrication. One set of triangular loops was the same height as the T-loop (isosceles shape); the other set was the same width as the T-loop (equilateral shape). Force and moment components along three mutually perpendicular axes (x, y, and z) were analyzed, with particular emphasis on the force system generated in the sagittal plane. The force-moment systems generated upon mesio-distal (x axis) activation were measured by a transducer connected to a computer for data collection and analysis. Statistical analysis utilized repeated measures of variance models (ANOVA). Multiple comparisons were made using Fisher's Protected Least Significant Differences at a 95-percent overall confidence level. On initial ligation, there were no significant differences between the loops in the M/F ratios in the sagittal plane (p = 0.75). For all other activation distances, the equilateral triangular loops produced greater M/F ratios than both the isosceles and T-loops (p = 0.0001), and the isosceles triangular loops generated greater M/F ratios than the T-loops (p < 0.0035).Item High resolution ultrasound imaging for repeated measure of wound tissue morphometry, biomechanics and hemodynamics under fetal, adult and diabetic conditions(PLOS, 2020-11-23) Gnyawali, Surya C.; Sinha, Mithun; El Masry, Mohamed S.; Wulff, Brian; Ghatak, Subhadip; Soto-Gonzalez, Fidel; Wilgus, Traci A.; Roy, Sashwati; Sen, Chandan K.; Surgery, School of MedicineNon-invasive, repeated interrogation of the same wound is necessary to understand the tissue repair continuum. In this work, we sought to test the significance of non-invasive high-frequency high-resolution ultrasound technology for such interrogation. High-frequency high-resolution ultrasound imaging was employed to investigate wound healing under fetal and adult conditions. Quantitative tissue cellularity and elastic strain was obtained for visualization of unresolved inflammation using Vevo strain software. Hemodynamic properties of the blood flow in the artery supplying the wound-site were studied using color Doppler flow imaging. Non-invasive monitoring of fetal and adult wound healing provided unprecedented biomechanical and functional insight. Fetal wounds showed highly accelerated closure with transient perturbation of wound tissue cellularity. Fetal hemodynamics was unique in that sharp fall in arterial pulse pressure (APP) which was rapidly restored within 48h post-wounding. In adults, APP transiently increased post-wounding before returning to the pre-wounding levels by d10 post-wounding. The pattern of change in the elasticity of wound-edge tissue of diabetics was strikingly different. Severe strain acquired during the early inflammatory phase persisted with a slower recovery of elasticity compared to that of the non-diabetic group. Wound bed of adult diabetic mice (db/db) showed persistent hypercellularity compared to littermate controls (db/+) indicative of prolonged inflammation. Normal skin strain of db/+ and db/db were asynchronous. In db/db, severe strain acquired during the early inflammatory phase persisted with a slower recovery of elasticity compared to that of non-diabetics. This study showcases a versatile clinically relevant imaging platform suitable for real-time analyses of functional wound healing.Item The Effects of Altering Interbracket Position on Closing Loops of Similar Dimensions(2002) Wilson, Don; Katona, Thomas R.; Baldwin, James J.; Chen, Jie; Hohlt, William F.; Shanks, JamesOrthodontic closing loops offer an efficient approach to consolidate extraction spaces. They allow for efficient tooth movement by lowering the load deflection rate, increasing potential activation, and by forming posterior anchorage units that can effectively resist displacement. The closing loop under investigation is a cross-leg delta loop. No studies have been done on this unique spring and the force systems created by altering its interbracket position. It is simple to fabricate chairside and produces fairly predictable moment to force ratios (M:F). The legs are crossed so the spring is activated in the same direction as its original bends, thus giving a more uniform distribution of stress within the spring, potential permanent deformation of the spring is decreased, reduced load deflection, and a greater overall range of activation. The cross-leg delta is simpler to fabricate than the more common T-loop since it needs two fewer bends. The material chosen for loop fabrication was 0.016 x 0.022 inch stainless steel wire due to its common use in clinic and research. Allowing for patient comfort and the fact that taller loops produce greater moment to force ratios, 7mm was chosen as the height of the cross-leg delta loop. The purpose of this study was to measure the spring generated forces and moments when altering the interbracket position of the closing loop. The null hypotheses are that there will not be any differences in the forces generated in the x (Fx) and y (Fy) directions, moments about the bucco-lingual axis (Mz), and M:F ratios in the sagittal plane (Mz:Fx) will not be altered by changing the interbracket position of cross-leg delta loops of same dimensions. A total of 120 loops, grouped as four sets of loops with 30 loops in each set: L1010, Ll 109, L1208, Ll307, were fabricated. The first two digits represent the length of the mesial leg and the last two digits represent the length of the distal leg for a total of 20mm in overall length. Each sequential set had the mesial leg increased by 1mm and the distal leg decreased by 1mm such that the most asymmetric set (L1307) had a 13mm mesial and a 7mm distal leg. The testing apparatus measured forces and moments along 3 mutually perpendicular axes (x, y, and z). Horizontal activation of the loop was performed by placing measured 1mm and 2mm stops over the wire. Data were collected from each set of loops. The cross-leg delta loops with symmetric 15° gable bends were compared for differences in moments and forces using repeated measures analysis of variance (ANOVA) models. Separate analyses were performed for Fx, Fy, Mz and Mz:Fx. Since the data was not normally distributed, a rank transformation was used. Pairwise comparisons were made using the Sidak method to control the overall significance level at 5%. Altering the interbracket position of a cross-leg delta loop did not cause major changes on the anterior and posterior forces in the x direction. Statistically significant differences in vertical forces (Fy), were much more pronounced when loops were positioned asymmetrically. Posteriorly positioned loops caused a statistically significant intrusive force on the anterior and extrusive force on the posterior segment was observed. As the loop was positioned more posteriorly, moments (Mz) acting in a clockwise direction on the anterior bracket decreased. More posteriorly positioned loops caused increased moments (Mz) in a counter-clockwise direction on the posterior bracket. As the loop was positioned more posteriorly, the M:F ratios in the sagittal plane acting on the anterior bracket decreased (Mz:Fx). More posteriorly positioned loops generated increased M:F ratios on the posterior bracket in the sagittal plane (Mz:Fx). Ideally, a posteriorly positioned closing loop would be used in a deep bite case needing maximum posterior anchorage. The intrusive force and decreased M:F ratio (Mz:Fx) on the anterior segment would cause more tipping and intrusion as space closure was carried out. The posteriorly positioned loop would generate increased moments (Mz) on the posterior bracket leading to increased M:F ratios in the sagittal plane (Mz:Fx). The extusive forces on the posterior segment would open the bite while the increased M:F ratios (Mz:Fx) would cause less tipping and increased anchorage. The study showed that altering the interbracket position of a closing loop can significantly alter the M:F ratio as well as the vertical and horizontal forces on the anterior and posterior segments. These results are important because the clinician can incorporate asymmetrically positioned loops to facilitate more efficient anchorage preparation. A posteriorly positioned loop can also generate an intrusive force on the anterior segment to help control overbite while retracting individual teeth or a segment en mass.Item The Effects of First-and Second-Order Gable Bend Angles on Forces and Moments Generated by Triangular Loops(2002) Le, Yen P.; Chen, Jie; Katona, Thomas R.; Baldwin, James J.; Hohlt, William F.; Shanks, James C.Many orthodontic spring designs have been used to close extraction spaces. The triangular loop is an often-used spring in the Graduate Orthodontic Clinic at the Indiana University School of Dentistry. Previous studies of the triangular loop have focused on its geometry and dimensions with various in-plan (second-order) gable bend angles. To date, no investigator has studied the effect of out-of-plane (first-order) gable angle on the in-plane forces and moments generated by the triangular loop. Thus, the purposes of this study are: (1) to determine the effect of first-order gable bend angles on the forces and moments produced by triangular loops and (2) to show that the effects of first- and second-order gable bends are independent of each other. Three hundred sixty triangular loops were divided equally into 36 groups with combinations of 0°, 15°, and 30° first- and second-order gable bend angles. Force and moment components along three mutually perpendicular axes (x, y, and z) were measured. The x, y, and z axes are the mesiodistal, occlusogingival, and buccolingual axes respectively. Separate statistical analyses were performed for Fx, Fy, Fz, Mx, My, Mz, Mz/Fx and My/Fx. Comparisons were made between the 36 groups and between activation distances. The Sidak multiple comparison adjustment method was used to control the overall confidence level at 95%. The hypotheses are (1) the first-order gable bends do not affect the forces and moments generated by triangular loops, and (2) the first and second-order behaviors are independent of each other. The results support the first hypothesis partially. It was shown that the magnitude of Fx and Mz/Fx increased significantly with second-order gable bends but did not change with first-order bends. The magnitude of My/Fx increased significantly with increasing first-order gable bend angles but did not change significantly with second-order gable bends. The second hypothesis is also accepted. The effects of first- and second-order gable angles are independent of each other. Both first- and second-order gable angles are needed to have an appropriate force/moment system for tooth translation.