Name: in situ compressive loading and correlative noninvasive imaging of the bone-periodontal ligament-tooth fibrous joint
Uploaded: 2014-03-07T13:45:00
Description: Watch this Scientific Journal Video about In situ Compressive Loading and Correlative Noninvasive Imaging of the Bone-periodontal Ligament-tooth Fibrous Joint at JoVE.com

The authors acknowledge funding support NIH/NIDCR R00DE018212 (SPH), NIH/NIDCR-R01DE022032 (SPH), NIH/NIDCR T32 DE07306 (AJ, JDL), NIH/NCRR S10RR026645, (SPH) and Departments of Preventive and Restorative Dental Sciences and Orofacial Sciences, UCSF.&#160; In addition, the authors acknowledge Xradia Graduate Fellowship (AJ), Xradia Inc., Pleasanton, CA.&#160;
The authors thank Dr. Kathryn Grandfield, UCSF for her assistance with post processing of data; Drs. Stephen Weiner and Gili Naveh, Weizmann Institute of Science, Rehovot, Israel; Dr. Ron Shahar, The Hebrew University of Jerusalem, Israel for their insightful discussions specific to the in situ loading device.&#160; The authors would also like to thank Biomaterials and Bioengineering MicroCT Imaging Facility at UCSF for the use of Micro XCT and the in situ loading device.

Animal housing and euthanasia: All animals used in this demonstration were housed under pathogen-free conditions in accordance to the guidelines of the Institutional Animal Care and Use Committee (IACUC) and the National Institute of Health (NIH).
Provide animals with standard hard-pellet rat chow and water ad lib. Euthanize animals via a two-step method of carbon dioxide asphyxiation, bilateral thoracotomy in accordance with the standard protocol of UCSF as approved by IACUC. Perform...

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The first step in establishing this protocol involved evaluating the stiffness of the loading frame by using a rigid body. Based on the results, the stiffness was significantly higher enabling the use of the loading device for further testing of specimens with significantly lower stiffness values. The second step highlighted the ability of the instrument to distinguish different stiffness values by using two phases of the loading-unloading curve generated by using a rigid body, PDMS materials of different crosslink densi...

Several experimental methods continue to be used to investigate the biomechanics of diarthrodial and fibrous joints. Methods specific to the tooth organ biomechanics include the use of strain gauges1-3, photoelasticity methods4,5, Moir&#233; interferometry6,7, electronic speckle pattern interferometry8, and digital image correlation (DIC)9-14. In this study, the innovative approach includes noninvasive imaging using X-rays to expose the internal structures of a fibrous joint (mineralized tissues and their interfaces consisting of softer zones, and interfacing tissues such as ligaments) at loads equivalent to in vivo conditions. An in situ loading device coupled to a micro-X-ray microscope will be used. The load-time and load-displacement curves will be collected as the molar of interest within a freshly harvested rat hemi-mandible is loaded. The main goal of the approach presented in this study is to emphasize the effect of three-dimensional morphology of tooth-bone by comparing conditions at: 1) no load and when loaded, and when 2) concentrically and eccentrically loaded. Eliminating the need for cut specimens, and to perform experiments on whole intact organs under wet conditions will allow for maximum preservation of the 3D stress state. This opens a new area of investigation in understanding dynamic processes of the complex under various loading scenarios.
In this study, the methods for testing PDL biomechanics within an intact fibrous joint of a Sprague Dawley rat, a joint considered as an optimum bioengineering model system will be detailed. Experiments will include simulation of mastication loads under hydrated conditions in order to highlight three important features of the joint as they relate to organ level biomechanics. The three points will include: 1) reactionary force vs. displacement: tooth displacement within the alveolar socket and its reactionary response to loading, 2) three-dimensional (3D) spatial configuration and morphometrics: geometric relationship of the tooth with the alveolar socket, and 3) changes in readouts 1 and 2 due to a change in loading axis, i.e. from concentric to eccentric loads. The three fundamental readouts of the proposed technique can be applied to investigate the adaptive nature of joints in vertebrates either due to changes in functional demands, and/or disease. Changes in the aforementioned readouts, specifically the correlation between reactionary loads with displacement, and resulting reactionary load-time and load-displacement curves at different loading rates can be applied to highlight overall changes in joint biomechanics. Efficacy of the proposed protocol will be evaluated by coupling mechanical testing readouts to 3D morphometrics and overall biomechanics of the joint.

<table border="0" cellpadding="0" cellspacing="0" width="652">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">Bard Parker Blade</td>
			<td style="width:101px;">BD</td>
			<td style="width:123px;">MEDC-001054</td>
			<td style="width:259px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">AFM metal disk</td>
			<td style="width:101px;">Ted Pella</td>
			<td style="width:123px;">16218</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">Polymethyl methacrylate&#160;</td>
			<td style="width:101px;">GC America</td>
			<td style="width:123px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">Uni-Etch</td>
			<td style="width:101px;">Bisco</td>
			<td style="width:123px;">E5502EBM</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">Optibond Solo Plus</td>
			<td style="width:101px;">Kerr Corp</td>
			<td style="width:123px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">Filtek Flow</td>
			<td style="width:101px;">3M</td>
			<td style="width:123px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">Hurculite Ultra</td>
			<td style="width:101px;">Kerr</td>
			<td style="width:123px;">34346</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">Tris buffer</td>
			<td style="width:101px;">Mediatech Inc.</td>
			<td style="width:123px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">Articulating paper</td>
			<td style="width:101px;"></td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:169px;">Phosphotungstic Acid</td>
			<td style="width:101px;">Sigma Aldrich</td>
			<td style="width:123px;">HT152</td>
			<td></td>
		</tr>
	</tbody>
</table>

in situ compressive loading and correlative noninvasive imaging of the bone-periodontal ligament-tooth fibrous joint

This study demonstrates a novel biomechanics testing protocol. The advantage of this protocol includes the use of an in situ loading device coupled to a high resolution X-ray microscope, thus enabling visualization of internal structural elements under simulated physiological loads and wet conditions. Experimental specimens will include intact bone-periodontal ligament (PDL)-tooth fibrous joints. Results will illustrate three important features of the protocol as they can be applied to organ level biomechanics: 1) reactionary force vs. displacement: tooth displacement within the alveolar socket and its reactionary response to loading, 2) three-dimensional (3D) spatial configuration and morphometrics: geometric relationship of the tooth with the alveolar socket, and 3) changes in readouts 1 and 2 due to a change in loading axis, i.e. from concentric to eccentric loads. Efficacy of the proposed protocol will be evaluated by coupling mechanical testing readouts to 3D morphometrics and overall biomechanics of the joint. In addition, this technique will emphasize on the need to equilibrate experimental conditions, specifically reactionary loads prior to acquiring tomograms of fibrous joints. It should be noted that the proposed protocol is limited to testing specimens under ex vivo conditions, and that use of contrast agents to visualize soft tissue mechanical response could lead to erroneous conclusions about tissue and organ-level biomechanics.

Estimation of loading device &#8220;backlash&#8221;, &#8220;pushback&#8221;, stiffness, and system drift under a constant load
Backlash: Between loading and unloading portions of the cycle, there exists a pause of 3 sec during which gears reverse within the motor before true unloading commences, i.e. as the specimen pulls away from the top jaw (Figure&#160;3). This period is referred to as a backlash in the system, which represents a ...

Watch this Scientific Journal Video about In situ Compressive Loading and Correlative Noninvasive Imaging of the Bone-periodontal Ligament-tooth Fibrous Joint at JoVE.com

In situ Compressive Loading and Correlative Noninvasive Imaging of the Bone-periodontal Ligament-tooth Fibrous Joint

In this study, the use of an in situ loading device coupled with micro-X-ray computed tomography for fibrous joint biomechanics will be discussed. Experimental readouts identifiable with an overall change in joint biomechanics will include: 1) reactionary force vs. displacement, i.e. tooth displacement within the alveolar socket and its reactionary response to loading, 2) three-dimensional (3D) spatial configuration and morphometrics, i.e.&#160;geometric relationship of the tooth with the alveolar socket, and 3) changes in readouts 1 and 2 due to a change in loading axis, i.e. concentric or eccentric loads.

In situ Compressive Loading and Correlative Noninvasive Imaging of the Bone-periodontal Ligament-tooth Fibrous Joint

This study demonstrates a novel biomechanics testing protocol. The advantage of this protocol includes the use of an in situ loading device coupled to a ...

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