Oscillatory Shear Loading of Bovine Periodontal Ligament—A Methodological Study

[+] Author and Article Information
Colin S. Sanctuary, John Botsis

Laboratory of Applied Mechanics and Reliability Analysis,  Swiss Federal Institute of Technology, Lausanne (EPFL), STI∕I2S∕LMAF, Switzerland

H. W. Wiskott

School of Dental Medicine,  University of Geneva, 19 rue Barthélemy-Menn, 1205 Geneva, SwitzerlandAnselm@Wiskott.com

Susanne S. Scherrer, Urs C. Belser

School of Dental Medicine,  University of Geneva, 19 rue Barthélemy-Menn, 1205 Geneva, Switzerland

J Biomech Eng 128(3), 443-448 (Dec 06, 2005) (6 pages) doi:10.1115/1.2187041 History: Received July 01, 2005; Revised December 06, 2005

This study examined the stress response of bovine periodontal ligament (PDL) under sinusoidal straining. The principle of the test consisted in subjecting transverse tooth, PDL and bone sections of known geometries to controlled oscillatory force application. The samples were secured to the actuator by support plates fabricated using a laser sintering technique to fit their contours to the tooth and the alveolar bone. The actuator was attached to the root slices located in the specimen’s center. Hence the machine was able to push or pull the root relative to its surrounding alveolar bone. After determining an optimal distraction amplitude, the samples were cyclically loaded first in ramps and then in sinusoidal oscillations at frequencies ranging from 0.2to5Hz. In the present study the following observations were made: (1) Imaging and the laser sintering technique can be used successfully to fabricate custom-made support plates for cross-sectional root-PDL-bone sections using a laser sintering technique, (2) the load-response curves were symmetric in the apical and the coronal directions, (3) both the stress response versus phase angle and the stress response versus. strain curves tended to “straighten” with increasing frequency, and (4) the phase lag between applied strain and resulting stress was small and did not differ in the intrusive and the extrusive directions. As no mechanical or time-dependent anisotropy was demonstrable in the intrusive and extrusive directions, such results may considerably simplify the development of constitutive laws for the PDL.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Specimen preparation and dimensions. Bovine mandibles were cut into blocks each comprising a molar tooth. Then the specimens were prepared by transverse cutting the roots (In most instances, only two levels were suitable for further processing). Finally, the dimensional specifications of the root were determined. Specifications are presented as means ±SD.

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Figure 2

(a) Overall view of the testing machine. (b) Schematics of the four laser-sintered components sandwiching the specimen. (c) Section of Fig. 2. Two lateral clamps were used to gently press the upper bone support plate, the sample and the lower support plate on the support table of the testing machine.

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Figure 3

Typical load responses under increasing triangular loads. The first detectable responses were observed at distractions of 300–400μm. Between 500 and 600μm fully formed response curves were obtained.

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Figure 4

Force system applied to the specimens. F is the vertical force applied onto the root section.

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Figure 5

Stress response (±SD) under triangular load application (rate: 20μms−1)

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Figure 6

Stress response (±SD) vs phase angle at frequencies of 0.2–5Hz. Note alteration in overall shape with increasing frequency (right).

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Figure 7

Stress response (±SD) vs strain at frequencies of 0.2–5Hz. Note alteration in overall shape with increasing frequency (right).

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Figure 8

Phase lags (±SD) in extrusive (i.e., coronal) and intrusive (i.e., apical) distractions



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