The authors would like to acknowledge all colleagues who made this work possible, especially Drs. Aditya Chhibber and Ravindra Nanda. The authors would like to thank the Biodynamics &#38; Bioengineering Lab at UCONN Health for the facilities provided during the development of this project.

1. Experimental Setup
<ol>
	<li>Mark the precise position for the placement of molar tubes and incisor brackets on the aluminum pegs of the OWT by using a customized &#39;jig&#39;.</li>
	<li>Bond standard self-ligating brackets with composite material. Light cure for 40 seconds.</li>
	<li>Insert a 0.021 x 0.025-inch stainless steel (SS) &#39;ovoid&#39; maxillary archwire into the bracket slots.</li>
	<li>Place the testing apparatus in the glass chamber.</li>
	<li>Check for any unintended archwire activation. Any activation of the archwire will automatically create a force system, which will be displayed on the computer screen.</li>
	<li>Reposition the brackets if any archwire activation is observed. Repeat steps 1.2-1.5.</li>
</ol>
2. Fabrication of a Template Archwire (Figure 4)
<ol>
	<li>Place an archwire (0.021 x 0.025 SS) in the testing apparatus.</li>
	<li>Use a permanent marker to indicate the following: 1) the midline, 2) a point immediately distal to the incisor bracket&#160;(I), and 3) a point immediately mesial to the molar tube (M). Do the same for the contralateral side of the archwire. This is the template arch wire.</li>
	<li>Transfer the archwire with the marked points to a graph paper.</li>
	<li>Make a precise replica of the archwire on the graph paper. 
	NOTE: This graph paper can be used to determine the position of the V-bend for all archwires of the sample.</li>
	<li>Calculate the perimeter of the arch wire segment (L) from I to M.</li>
	<li>Now, mark 11 points from I to M. Each point is a future V-bend position.
	<ol>
		<li>Label each point from a0 to a10.</li>
		<li>Make sure that each bend position is separated from the other by an equal amount.</li>
	</ol>
	</li>
	<li>Obtain a unique number/ratio for each bend position by calculating a/L for each position.</li>
</ol>
3. Placement of V-bends
<ol>
	<li>Take a new archwire from the sample.</li>
	<li>Place it on the template archwire/graph paper and transfer one of the eleven bend positions bilaterally to the archwire.</li>
	<li>Use a rectangular archwire plier or a light wire plier to make symmetrical V-bends at both the positions.</li>
	<li>Place the archwire on a glass slab/flat platform and check the measurement of the angle made by the two ends of the archwire with a protractor.</li>
	<li>Adjust the ends if necessary so that an angle of 150&#176; is created.</li>
	<li>Repeat steps 3.1 to 3.5 for all archwires of the sample.</li>
</ol>
4. Measuring the Force System (Figures 5 and 6)
<ol>
	<li>Open the software program for data recording (see Table of Materials).</li>
	<li>Create a new folder for the data to be saved in.</li>
	<li>Click &#39;run&#39; to start the software. The program will display each of the three forces and three-moment values at each sensor in real-time.</li>
	<li>Wait for approximately 10-15 seconds for the fluctuations in data recording software to stop. Ensure that the graph lines on the software for all the components of the force system show a &#39;flat&#39; line. 
	NOTE: all six measurements at each sensor will show negligible values (forces &#60; 1 g and moments &#60; 10 g mm).</li>
	<li>Gently remove the &#39;testing apparatus&#39; from the platform. Use a Weingart plier to insert an archwire into the molar tubes.</li>
	<li>Open the door of the incisor bracket with a periodontal scaler.</li>
	<li>Lift the anterior portion of the archwire and insert it into the bracket slot. Make sure that the midline of the archwire coincides with the midline of the testing apparatus.</li>
	<li>Return the testing apparatus to the platform and close the door of the glass chamber.</li>
	<li>Set the temperature at 37 &#176;C. Wait for one minute for the temperature of the glass chamber to adjust.</li>
	<li>Click the &#39;start saving&#39; button on the software and allow the software to save/transfer data for at least 10 seconds. Click the &#39;start saving&#39; button again to end data transfer, then click &#39;stop&#39;. 
	NOTE: Each measurement cycle generates 100 readings over the 10 second period for each component (Fx, Fy, Fz, Mx, My, and Mz).</li>
	<li>Go to the document containing the saved data, and copy/export the data set to a custom designed data analysis spreadsheet (see Supplementary Table). Choose the correct V-bend position number and the specific wire sample to insert the data.</li>
	<li>Repeat steps 4.3 to 4.11 for the 10 archwires of that specific bend position.</li>
	<li>Now, copy the calculated means and standard deviations for the archwires to a separate spreadsheet to create a graphical representation of the data.</li>
	<li>Repeat steps 4.2 to 4.13 for all bend positions and types of archwires. 
	NOTE: The archwires include, Stainless-Steel (SS) and Beta-Titanium (&#223;-Ti), with the following sizes: 0.016 x 0.022 inch, 0.017 x 0.025 inch, and 0.019 x 0.025 inch.</li>
</ol>
5. Error Evaluation
<ol>
	<li>Run the computer/software as described in steps 4.1-4.4</li>
	<li>Remove the &#39;testing apparatus&#39; from the platform.</li>
	<li>Obtain a straight length 0.021 x 0.025-inch SS wire. Using a light wire plier, bend one end of the wire into a small hook. Insert the free end of the archwire into the molar tube from the distal side.</li>
	<li>Place the testing apparatus back on the platform.</li>
	<li>Attach a known weight (50 g) to the hook. Let it hang freely in the vertical plane by removing any type of interference. Close the door of the glass chamber.</li>
	<li>Follow steps 4.10-4.11.</li>
	<li>Repeat steps 5.1-5.6 for the incisor bracket.</li>
	<li>Enter the Fz values for both the brackets and Mx for the molar tube as &#39;measured value.&#39;</li>
	<li>Now apply the equations of equilibrium (see Supplementary Text) to calculate the &#39;expected value.&#39;</li>
</ol>

<ol>
	<li>Burstone, C. J., Koenig, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Force+systems+from+an+ideal+arch.">Force systems from an ideal arch.</a> Am J Orthod. 65 (3), 270-289 (1974).</li><li>Koenig, H. A., Burstone, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Force+systems+from+an+ideal+arch:+Large+deflection+considerations.">Force systems from an ideal arch: Large deflection considerations.</a> Angle Orthod. 59 (1), 11-16 (1989).</li><li>Burstone, C. J., Koenig, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Creative+wire+bending:+The+force+system+from+step+and+V+bends.">Creative wire bending: The force system from step and V bends.</a> Am J Orthod and Dentofac Orthop. 93 (1), 59-67 (1988).</li><li>Ronay, F., Kleinert, W., Melsen, B., Burstone, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Force+system+developed+by+V+bends+in+an+elastic+orthodontic+wire.">Force system developed by V bends in an elastic orthodontic wire.</a> Am J Orthod and Dentofac Orthop. 96 (4), 295-301 (1989).</li><li>Demange, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Equilibrium+situations+in+bend+force+systems.">Equilibrium situations in bend force systems.</a> Am J Orthod and Dentofac Orthop. 98 (4), 333-339 (1990).</li><li>Isaacson, R. J., Lindauer, S. J., Conley, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Responses+of+3-dimensional+arch+wires+to+vertical+V+bends:+Comparisons+with+existing+2-dimensional+data+in+the+lateral+view.">Responses of 3-dimensional arch wires to vertical V bends: Comparisons with existing 2-dimensional data in the lateral view.</a> Semin Orthod. 1 (1), 57-63 (1995).</li><li>Upadhyay, M., Shah, R., Peterson, D., Takafumi, A., Yadav, S., Agarwal, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Force+system+generated+by+elastic+archwires+with+vertical+V+bends:+A+three-dimensional+analysis.">Force system generated by elastic archwires with vertical V bends: A three-dimensional analysis.</a> Eur J Orthod. 39 (2), 202-208 (2017).</li><li>Gurgel, J. A., Kerr, S., Powers, J. M., LeCrone, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Force-deflection+properties+of+superelastic+nickel-titanium+archwires.">Force-deflection properties of superelastic nickel-titanium archwires.</a> Am J Orthod Dentofacial Orthop. 120 (4), 378-382 (2001).</li><li>Gurgel, J. A., Kerr, S., Powers, J. M., Pinzan, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Torsional+properties+of+commercial+nickel-titanium+wires+during+activation+and+deactivation.">Torsional properties of commercial nickel-titanium wires during activation and deactivation.</a> Am J Orthod Dentofacial Orthop. 120 (1), 76-79 (2001).</li><li>Hazel, R. J., Rohan, G. J., West, V. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Force+relaxation+in+orthodontic+arch+wires.">Force relaxation in orthodontic arch wires.</a> Am J Orthod. 86 (5), 396-402 (1984).</li><li>Lundgren, D., Owman-Moll, P., Kurol, J., Martensson, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+orthodontic+force+and+tooth+movement+measurements.">Accuracy of orthodontic force and tooth movement measurements.</a> Br J Orthod. 23 (3), 241-248 (1996).</li><li>Goldberg, A. J., Burstone, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+evaluation+of+beta+titanium+alloys+for+use+in+orthodontic+appliances.">An evaluation of beta titanium alloys for use in orthodontic appliances.</a> J Dent Res. 58 (2), 593-600 (1979).</li><li>Kusy, R. P., Whitley, J. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+and+mechanical+characteristics+of+stainless+steel,+titanium-molybdenum,+and+nickel+titanium+archwires.">Thermal and mechanical characteristics of stainless steel, titanium-molybdenum, and nickel titanium archwires.</a> Am J Orthod Dentofacial Orthop. 131 (2), 229-237 (2007).</li><li>Kapila, S., Sachdeva, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+and+clinical+applications+of+orthodontic+wires.">Mechanical properties and clinical applications of orthodontic wires.</a> Am J Orthod Dentofacial Orthop. 96 (2), 100-109 (1989).</li><li>Verstrynge, A., Humbeeck, J. V., Willems, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-vitro+evaluation+of+the+material+characteristics+of+stainless+steel+and+beta-titanium+orthodontic+wires.">In-vitro evaluation of the material characteristics of stainless steel and beta-titanium orthodontic wires.</a> Am J Orthod Dentofacial Orthop. 130 (4), 460-470 (2006).</li><li>Tominaga, J. Y., Tanaka, M., Koga, Y., Gonzales, C., Kobayashi, M., Yoshida, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimal+loading+conditions+for+controlled+movement+of+anterior+teeth+in+sliding+mechanics.">Optimal loading conditions for controlled movement of anterior teeth in sliding mechanics.</a> Angle. 79 (6), 1102-1107 (2009).</li><li>Cattaneo, P. M., Dalstra, M., Melsen, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+finite+element+method:+A+tool+to+study+orthodontic+tooth+movement.">The finite element method: A tool to study orthodontic tooth movement.</a> J Dent Res. 84 (5), 428-433 (2005).</li><li>Fotos, P. G., Spyrakos, C. C., Bernard, D. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Orthodontic+forces+generated+by+a+simulated+archwire+appliance+evaluated+by+the+finite+element+method.">Orthodontic forces generated by a simulated archwire appliance evaluated by the finite element method.</a> Angle Orthod. 60 (4), 277-282 (1990).</li><li>Geramy, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alveolar+bone+resorption+and+the+center+of+resistance+modification+(3-D+analysis+by+means+of+the+finite+element+method.">Alveolar bone resorption and the center of resistance modification (3-D analysis by means of the finite element method.</a> Am J Orthod Dentofacial Orthop. 117 (4), 399-405 (2000).</li></ol>

The authors have nothing to disclose.

Orthodontic archwires have been studied in various ways8,9,10,11. They have also been evaluated for various mechanical properties, but they have seldom been analyzed for determining the force system they are going to create12,13,14,15. Three-point bending tests are po...

An important aspect of clinical orthodontic treatment is the knowledge of the force system produced by multibracket appliances. A clear understanding of the underlying biomechanical principles can help deliver predictable results and minimize potential side effects1. Recent years have seen a trend away from placing bends in archwires by building more activation with bracket position and design; however, comprehensive orthodontic treatment still requires placement of bends in archwires. Bends, when placed in different types and sizes of archwires, can create a wide variety of force systems suitable for different types of tooth movement. Although the force systems can become quite complex when multiple teeth are considered, a helpful starting point can involve a simple two-bracket system.
To date, V-bend mechanics have primarily been analyzed in the second order only, utilizing mathematical models1,2,3,4,5 and/or computer-based analysis/simulations6. This has yielded a basic understanding of the force system involved in the second order interaction of the arch wires with adjacent brackets (Figure 1). However, these methods impose certain boundary conditions in order to run&#160;simulations that might not hold true in actual clinical situations and deviations might occur. Recently, a new in vitro model involving force transducers was proposed for measuring three dimensional (3D) forces and moments created by evaluating not only second order archwire-bracket interactions but also in the third order7. However, the effect of different types of archwires on the force system at various bend positions along the incisor molar archwire span was not evaluated. Also, the study only involved evaluation of elastic orthodontic archwires, which are not the primary archwires on which tooth movement occurs. Therefore, the aim of this study was to evaluate the force system created by the placement of a V-bend at different locations in rectangular stainless steel and beta-titanium archwires in a 3D set up involving the molar and incisor brackets. Clinicians need to know the force system applied on the dentition when a specific combination of archwire bracket combination is used to fix a malocclusion.
The described technique has been developed to study the orthodontic force system in all the three planes of space, mimicking clinical reality. It is to be understood that it is extremely difficult to measure the force system clinically; therefore, such measurements have to be carried out&#160;in vitro. It is assumed that the force system created by a V-bend in the laboratory would be similar if replicated in the patient&#39;s mouth. A workflow was created to evaluate how the experimental set up has to be configured (Figure 2).
The orthodontic wire tester (OWT) is an innovative product developed by Division of Orthodontics in collaboration with the Bioengineering &#38; Biodynamics Laboratory, UConn Health, Farmington, CT, USA (Figure 3). It is designed to accurately mimic the arrangement of the maxillary teeth within the mouth and some intra-oral conditions while providing measurements of the force system created in all the three planes of space. The major mechanical components of the OWT are a Data acquisition device (DAQ), nano Force/Torque Sensors, humidity sensors, temperature sensors, and a personal computer. The testing apparatus is placed in a glass enclosure having temperature/humidity controls. This allows for partial simulation of the intraoral environment. The DAQ serves as the interface for the three sensors:&#160;humidity sensor, force/moment sensor,&#160;thermistor&#160;and the testing apparatus with the sensors situated on a platform&#160;(Figure 3). These are linked to a software program. The software is a platform and a development environment for visual programming and is used to control different types of hardware. It was chosen to automate the orthodontic wire tester.
A series of aluminum pegs are arranged on the testing apparatus to represent the teeth of the maxillary dental arch. Two of the pegs representing the right central incisor and right first molar are connected to sensors/load cells (S1 and S2). A load cell is a mechanical device that can measure the forces and moments applied to it in all the three planes (x-y-z): Fx, Fy, and Fz; and Mx, My, and Mz. The pegs are systematically positioned to create a dental arch form. Each peg is separated from the other by a precisely recorded measurement that is calculated using average tooth widths as observed in patients undergoing orthodontic treatment. The shape chosen for the experiment is an &#39;ovoid&#39; arch form created from a standardized template.

<table><tbody><tr><td>Force/Torque&amp;nbsp; Sensors/Transducers</td><td>Nano17 F/T Sensors,&amp;nbsp; ATI Industrial Automation, Apex, NC, USA</td><td></td><td>Part of the OWT</td></tr><tr><td>CHS Series Humidity&amp;nbsp; Sensor Units</td><td>&amp;nbsp; TDK Corporation</td><td></td><td>Part of the OWT</td></tr><tr><td>Temperature sensors</td><td>(Murata NTSDXH103FPB30 thermistor) Murata Manufacturing Co., Ltd</td><td></td><td>Part of the OWT</td></tr><tr><td>LabVIEW 7.1.&amp;nbsp;</td><td>Laboratory Virtual Instrumentation Engineering Workbench, Version 7.1</td><td></td><td>Software Program</td></tr><tr><td>Self-Ligating brackets&amp;nbsp;</td><td>Empower Series, American Orthodontics.</td><td></td><td>Orthodontic Brackets</td></tr><tr><td>Stainless steel archwires</td><td>Ultimate Wireforms, Inc. in Bristol, CT</td><td></td><td>Archwires</td></tr><tr><td>Beta-Titanium Archwires</td><td>Ultimate Wireforms, Inc. in Bristol, CT</td><td></td><td>Archwires</td></tr><tr><td>Data acquisition device (DAQ)</td><td>National Instruments (NI) USB 6210</td><td></td><td>Part of the OWT</td></tr><tr><td>Ortho Form III (Archform template)</td><td>3M Oral Care, St. Paul, MN, USA</td><td></td><td>Ovoid arch form</td></tr><tr><td>Weingart Plier</td><td>Hu-Friedy Mfg. Co., LLC Chicago, IL</td><td></td><td>Orthodontic Plier</td></tr><tr><td>Light wire Plier</td><td>Hu-Friedy Mfg. Co., LLC Chicago, IL</td><td></td><td>Orthodontic Plier</td></tr></tbody></table>

force system with vertical v-bends: a 3d in vitro assessment of elastic and rigid rectangular archwires

A proper understanding of the force system created by various orthodontic appliances can make treatment of patients efficient and predictable. Reducing the complicated multi-bracket appliances to a simple two-bracket system for the purpose of force system evaluation will be the first step in this direction. However, much of the orthodontic biomechanics in this regard is confined to 2D experimental studies, computer modeling/analysis or theoretical extrapolation of existing models. The objective of this protocol is to design, construct and validate an in vitro 3D model capable of measuring the forces and moments generated by an archwire with a V-bend placed between two brackets. Additional objectives are to compare the force system generated by different types of archwires among themselves and to previous models. For this purpose, a 2 x 4 appliance representing a molar and an incisor has been simulated. An orthodontic wire tester (OWT) is constructed consisting of two multi-axis force transducers or load cells (nanosensors) to which the orthodontic brackets are attached. The load cells are capable of measuring the force system in all the three planes of space. Two types of archwires, stainless-steel and beta-titanium of three different sizes (0.016 x 0.022 inch, 0.017 x 0.025 inch and 0.019 x 0.025 inch), are tested. Each wire receives a single vertical V-bend systematically placed at a specific position with a predefined angle. Similar V-bends are replicated on different archwires at 11 different locations between the molar and incisor attachments. This is the first time an attempt has been made in vitro to simulate an orthodontic appliance utilizing V-bends on different archwires.

The total force and total moment experienced by each sensor at the center of the sensor plate are represented by their three orthogonal components: Fx, Fy, and Fz representing the forces along the x-axis, y-axis, and z-axis, respectively; and Mx, My, and Mz representing the moments around the same axes. The initial measurements at the sensors are converted mathematically to the force and moment values experienced by the bra...

Watch this Scientific Journal Video about Force System with Vertical V-Bends: A 3D In Vitro Assessment of Elastic and Rigid Rectangular Archwires at JoVE.com

Force System with Vertical V-Bends: A 3D In Vitro Assessment of Elastic and Rigid Rectangular Archwires

The method presented here is designed to construct and validate an in vitro 3D model capable of measuring the force system generated by different archwires with V-bends placed between two brackets. Additional objectives are to compare this force system with different types of archwires and to previous models.

Force System with Vertical V-Bends: A 3D In Vitro Assessment of Elastic and Rigid Rectangular Archwires

A proper understanding of the force system created by various orthodontic appliances can make treatment of patients efficient and predictable. Reducing ...

force-system-with-vertical-v-bends-3d-vitro-assessment-elastic-rigid

Research

Education

JoVE Journal

JoVE Core

Civil Engineering

Mechanical Engineering

Bioengineering

Unit 1

Horizontal and Vertical Curves

Force System Resultants

SCIENTISTS IN ACTION

10.6K Views.  University of Connecticut Health. De methode die hier gepresenteerd is ontworpen te construeren en valideren van een in vitro 3D-model staat voor het meten van de kracht-systeem gegenereerd door verschillende archwires met V-bochten tussen twee haakjes geplaatst. Bijkomende doelstellingen zijn te vergelijken deze kracht systeem met verschillende types van archwires en aan de voorgaande modellen.

Video: Force System with Vertical V-Bends: A 3D In Vitro Assessment of Elastic and Rigid Rectangular Archwires

An Improved Mechanical Testing Method to Assess Bone-implant Anchorage

Recent advances in material science have led to a substantial increase in the topographical complexity of implant surfaces, both on a micro- and a nano-scale. As such, traditional methods of describing implant surfaces -&#160;namely numerical determinants of surface roughness -&#160;are inadequate for predicting in vivo performance. Biomechanical testing provides an accurate and comparative platform to analyze the performance of biomaterial surfaces. An improved mechanical testing method to test the anchorage of bone to candidate implant surfaces is presented. The method is applicable to both early and later stages of healing and can be employed for any range of chemically or mechanically modified surfaces -&#160;but not smooth surfaces. Custom rectangular implants are placed bilaterally in the distal femora of male Wistar rats and collected with the surrounding bone. Test specimens are prepared and potted using a novel breakaway mold and the disruption test is conducted using a mechanical testing machine. This method allows for alignment of the disruption force exactly perpendicular, or parallel, to the plane of the implant surface, and provides an accurate and reproducible means for isolating an exact peri-implant region for testing.

An improved method to mechanically test bone anchorage to candidate implant surfaces is presented. This method allows for alignment of the disruption force exactly perpendicular, or parallel, to the plane of the implant surface, and provides an accurate means to direct the disruption forces to an exact peri-implant region.

Recent advances in material science have led to a substantial increase in the topographical complexity of implant surfaces, both on a micro- and a ...

A Coupled Experiment-finite Element Modeling Methodology for Assessing High Strain Rate Mechanical Response of Soft Biomaterials

This study offers a combined experimental and finite element (FE) simulation approach for examining the mechanical behavior of soft biomaterials (e.g. brain, liver, tendon, fat, etc.) when exposed to high strain rates. This study utilized a Split-Hopkinson Pressure Bar (SHPB) to generate strain rates of 100-1,500 sec-1. The SHPB employed a striker bar consisting of a viscoelastic material (polycarbonate). A sample of the biomaterial was obtained shortly postmortem and prepared for SHPB testing. The specimen was interposed between the incident and transmitted bars, and the pneumatic components of the SHPB were activated to drive the striker bar toward the incident bar. The resulting impact generated a compressive stress wave (i.e. incident wave) that traveled through the incident bar. When the compressive stress wave reached the end of the incident bar, a portion continued forward through the sample and transmitted bar (i.e. transmitted wave) while another portion reversed through the incident bar as a tensile wave (i.e. reflected wave). These waves were measured using strain gages mounted on the incident and transmitted bars. The true stress-strain behavior of the sample was determined from equations based on wave propagation and dynamic force equilibrium. The experimental stress-strain response was three dimensional in nature because the specimen bulged. As such, the hydrostatic stress (first invariant) was used to generate the stress-strain response. In order to extract the uniaxial (one-dimensional) mechanical response of the tissue, an iterative coupled optimization was performed using experimental results and Finite Element Analysis (FEA), which contained an Internal State Variable (ISV) material model used for the tissue. The ISV material model used in the FE simulations of the experimental setup was iteratively calibrated (i.e. optimized) to the experimental data such that the experiment and FEA strain gage values and first invariant of stresses were in good agreement.

The current study prescribes a coupled experiment-finite element simulation methodology to obtain the uniaxial dynamic mechanical response of soft biomaterials (brain, liver, tendon, fat, etc.). The multiaxial experimental results that arose because of specimen bulging obtained from Split-Hopkinson Pressure Bar testing were rendered to a uniaxial true stress-strain behavior when simulated through iterative optimization of the finite element analysis of the biomaterial.

This study offers a combined experimental and finite element (FE) simulation approach for examining the mechanical behavior of soft biomaterials (e.g. ...

Design and Fabrication of an Elastomeric Unit for Soft Modular Robots in Minimally Invasive Surgery

In recent years, soft robotics technologies have aroused increasing interest in the medical field due to their intrinsically safe interaction in unstructured environments. At the same time, new procedures and techniques have been developed to reduce the invasiveness of surgical operations. Minimally Invasive Surgery (MIS) has been successfully employed for abdominal interventions, however standard MIS procedures are mainly based on rigid or semi-rigid tools that limit the dexterity of the clinician. This paper presents a soft and high dexterous manipulator for MIS. The manipulator was inspired by the biological capabilities of the octopus arm, and is designed with a modular approach. Each module presents the same functional characteristics, thus achieving high dexterity and versatility when more modules are integrated. The paper details the design, fabrication process and the materials necessary for the development of a single unit, which is fabricated by casting silicone inside specific molds. The result consists in an elastomeric cylinder including three flexible pneumatic actuators that enable elongation and omni-directional bending of the unit. An external braided sheath improves the motion of the module. In the center of each module a granular jamming-based mechanism varies the stiffness of the structure during the tasks. Tests demonstrate that the module is able to bend up to 120&#176; and to elongate up to 66% of the initial length. The module generates a maximum force of 47 N, and its stiffness can increase up to 36%.

This paper describes the design and fabrication of a soft unit for surgical manipulators. The base module includes three flexible fluidic actuators to achieve omnidirectional bending and elongation, and a granular jamming-based mechanism to enable stiffness control. A complete mechanical characterization is also reported.

In recent years, soft robotics technologies have aroused increasing interest in the medical field due to their intrinsically safe interaction in ...

Determination of the Mechanical Properties of Flexible Connectors for Use in Insulated Concrete Wall Panels

This document contains recommendations for performing a non-standard, double-shear test suitable for both continuous and discrete insulated concrete sandwich wall panels (ICSWPs). Such a standardized test does not exist, but several iterations of this and similar tests have been performed in the literature to varying degrees of success. Further, the tests in the literature are rarely-if ever-described in detail or discussed at length with respect to the testing, data analysis, or safety procedures. A test specimen configuration is recommended herein, and variations are discussed. Important mechanical properties are identified from the load versus displacement data, and their extraction is detailed. The use of test data for design, such as for determining the stiffness of the connectors, is briefly demonstrated to show how ICSWP deflection and cracking behavior may be calculated. The strength behavior of panels may be determined using the full load versus displacement curve or only the maximum connector strength. Shortcomings and unknowns are acknowledged, and significant future work is delineated.

We propose a testing protocol that can be combined with widely available analytical methods to assess the mechanical properties of shear connectors for use in the design of insulated concrete wall panels to predict full-scale insulated panel behavior.

This document contains recommendations for performing a non-standard, double-shear test suitable for both continuous and discrete insulated concrete ...

Engineering

A Millimeter Scale Flexural Testing System for Measuring the Mechanical Properties of Marine Sponge Spicules

Many load bearing biological structures (LBBSs)&#8212;such as feather rachises and spicules&#8212;are small (&#60;1 mm) but not microscopic. Measuring the flexural behavior of these LBBSs is important for understanding the origins of their remarkable mechanical functions.
We describe a protocol for performing three-point bending tests using a custom-built mechanical testing device that can measure forces ranging from 10-5 to 101 N and displacements ranging from 10-7 to 10-2 m. The primary advantage of this mechanical testing device is that the force and displacement capacities can be easily adjusted for different LBBSs. The device&#39;s operating principle is similar to that of an atomic force microscope. Namely, force is applied to the LBBS by a load point that is attached to the end of a cantilever. The load point displacement is measured by a fiber optic displacement sensor and converted into a force using the measured cantilever stiffness. The device&#39;s force range can be adjusted by using cantilevers of different stiffnesses.
The device&#39;s capabilities are demonstrated by performing three-point bending tests on the skeletal elements of the marine sponge Euplectella aspergillum. The skeletal elements&#8212;known as spicules&#8212;are silica fibers that are approximately 50 &#181;m in diameter. We describe the procedures for calibrating the mechanical testing device, mounting the spicules on a three-point bending fixture with a &#8776;1.3 mm span, and performing a bending test. The force applied to the spicule and its deflection at the location of the applied force are measured.

We present a protocol for performing three-point bending tests on sub-millimeter scale fibers using a custom-built mechanical testing device. The device can measure forces ranging from 20 &#181;N up to 10 N and can therefore accommodate a variety of fiber sizes.

Many load bearing biological structures (LBBSs)&#8212;such as feather rachises and spicules&#8212;are small (&#60;1 mm) but not microscopic. Measuring the ...

Assessing Collagen and Elastin Pressure-dependent Microarchitectures in Live, Human Resistance Arteries by Label-free Fluorescence Microscopy

The pathogenic contribution of resistance artery remodeling is documented in essential hypertension, diabetes and the metabolic syndrome. Investigations and development of microstructurally motivated mathematical models for understanding the mechanical properties of human resistance arteries in health and disease have the potential to aid understanding how disease and medical treatments affect the human microcirculation. To develop these mathematical models, it is essential to decipher the relationship between the mechanical and microarchitectural properties of the microvascular wall. In this work, we describe an ex vivo method for passive mechanical testing and simultaneous label-free three-dimensional imaging of the microarchitecture of elastin and collagen in the arterial wall of isolated human resistance arteries. The imaging protocol can be applied to resistance arteries of any species of interest. Image analyses are described for quantifying i) pressure-induced changes in internal elastic lamina branching angles and adventitial collagen straightness using Fiji and ii) collagen and elastin volume densities determined using Ilastik software. Preferably all mechanical and imaging measurements are performed on live, perfused arteries, however, an alternative approach using standard video-microscopy pressure myography in combination with post-fixation imaging of re-pressurized vessels is discussed. This alternative method provides users with different options for analysis approaches. The inclusion of the mechanical and imaging data in mathematical models of the arterial wall mechanics is discussed, and future development and additions to the protocol are proposed.

We describe simultaneous mechanical testing and 3D-imaging of the arterial wall of isolated, live human resistance arteries, and Fiji and Ilastik image analyses for the quantification of elastin and collagen spatial organization and volume densities. We discuss the use of these data in mathematical models of arterial wall mechanics.

The pathogenic contribution of resistance artery remodeling is documented in essential hypertension, diabetes and the metabolic syndrome. Investigations ...

Biaxial Mechanical Characterizations of Atrioventricular Heart Valves

Extensive biaxial mechanical testing of the atrioventricular heart valve leaflets can be utilized to derive&#160;optimal parameters used in constitutive models, which provide a mathematical representation of the mechanical function of those structures. This presented biaxial mechanical testing protocol involves (i) tissue acquisition, (ii) the preparation of tissue specimens, (iii) biaxial mechanical testing, and (iv) postprocessing of the acquired data. First, tissue acquisition requires obtaining porcine or ovine hearts from a local Food and Drug Administration-approved abattoir for later dissection to retrieve the valve leaflets. Second, tissue preparation requires using tissue specimen cutters on the leaflet tissue to extract a clear zone for testing. Third, biaxial mechanical testing of the leaflet specimen requires the use of a commercial biaxial mechanical tester, which consists of force-controlled, displacement-controlled, and stress-relaxation testing protocols to characterize the leaflet tissue&#39;s mechanical properties. Finally, post-processing requires the use of data image correlation techniques and force and displacement readings to summarize the tissue&#39;s mechanical behaviors in response to external loading. In general, results from biaxial testing demonstrate that the leaflet tissues yield a nonlinear, anisotropic mechanical response. The presented biaxial testing procedure is advantageous to other methods since the method presented here allows for a more comprehensive characterization of the valve leaflet tissue under one unified testing scheme, as opposed to separate testing protocols on different tissue specimens. The proposed testing method has its limitations in that shear stress is potentially present in the tissue sample. However, any potential shear is presumed negligible.

This protocol involves characterizations of atrioventricular valve leaflets with force-controlled, displacement-controlled, and stress-relaxation biaxial mechanical testing procedures. Results acquired with this protocol can be used for constitutive model development to simulate the mechanical behavior of functioning valves under a finite element simulation framework.

Extensive biaxial mechanical testing of the atrioventricular heart valve leaflets can be utilized to derive&#160;optimal parameters used in constitutive ...

Cantilever Bending of Murine Femoral Necks

Fractures in the femoral neck are a common occurrence in individuals with osteoporosis. Many mouse models have been developed to assess disease states and therapies, with biomechanical testing as a primary outcome measure. However, traditional biomechanical testing focuses on torsion or bending tests applied to the midshaft of the long bones. This is not typically the site of high-risk fractures in osteoporotic individuals. Therefore, a biomechanical testing protocol was developed that tests the femoral necks of murine femurs in cantilever bending loading to replicate better the types of fractures experienced by osteoporosis patients. Since the biomechanical outcomes are highly dependent on the flexural loading direction relative to the femoral neck, 3D printed guides were created to maintain a femoral shaft at an angle of 20&#176; relative to the loading direction. The new protocol streamlined the testing by reducing variability in alignment (21.6&#176; &plusmn; 1.5&#176;, COV = 7.1%, n = 20) and improved reproducibility in the measured biomechanical outcomes (average COV = 26.7%). The new approach using the 3D printed guides for reliable specimen alignment improves rigor and reproducibility by reducing the measurement errors due to specimen misalignment, which should minimize sample sizes in mouse studies of osteoporosis.

The present protocol describes the development of a reproducible testing platform for murine femoral necks in a cantilever bending set-up. Custom 3D printed guides were used to consistently and rigidly fix the femurs in optimal alignment.

Fractures in the femoral neck are a common occurrence in individuals with osteoporosis. Many mouse models have been developed to assess disease states and ...

Principles and Protocols of Mechanical Testing for Bone Fracture Susceptibility

Practical Considerations for the Design, Execution, and Interpretation of Studies Involving Whole-Bone Bending Tests of Rodent Bones

Skeletal fragility leading to fracture is an American public health crisis resulting in 1.5 million fractures each year and $18 billion in direct care costs. The ability to understand the mechanisms underlying bone disease and the response to treatment is not only desired, but critical. Mechanical testing of bone serves as a valuable technique for understanding and quantifying a bone&#39;s susceptibility to fracture. While this method appears simple to perform, inappropriate and inaccurate conclusions may be reached if governing assumptions and key steps are disregarded by the user. This has been observed across disciplines as studies continue to be published with misuse of methods and incorrect interpretation of results. This protocol will serve as a primer for the principles associated with mechanical testing along with the application of these techniques-from considerations of sample size through tissue harvesting and storage, to data analysis and interpretation. With this in hand, valuable information regarding a bone&#39;s susceptibility to fracture may be obtained, furthering understanding for both academic research and clinical solutions.

Author Spotlight: Enhancing Accuracy and Reproducibility in Whole Bone Bending Tests 

Mechanical testing of rodent bones is a valuable method for extracting information regarding a bone's susceptibility to fracture. Lacking proper practical understanding, the results may be overinterpreted or lack validity. This protocol will serve as a guide to ensure mechanical tests are performed accurately to provide valid and functional data.

Skeletal fragility leading to fracture is an American public health crisis resulting in 1.5 million fractures each year and $18 billion in direct care ...

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a versatile analytical tool for characterizing viscoelastic mechanical properties for a variety of materials ranging from hard (plastic, glass, metal, etc.) surfaces to cells on any substrate. It has been widely used to measure the stiffness of cells, but less frequently used to measure the stiffness of aortas. In this paper, we will describe the procedures for using AFM in contact mode to measure the ex vivo elastic modulus of unloaded mouse arteries. We describe our procedure for isolation of mouse aortas, and then provide detailed information for the AFM analysis. This includes step-by-step instructions for alignment of the laser beam, calibration of the spring constant and deflection sensitivity of the AFM probe, and acquisition of force curves. We also provide a detailed protocol for data analysis of the force curves.

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

We present detailed protocols for isolation of aortas from mouse and measurement of their elastic modulus using atomic force microscopy.

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a ...

Force System with Vertical V-Bends: A 3D In Vitro Assessment of Elastic and Rigid Rectangular Archwires

Samenvatting

Meer video's verkennen