Comparison of Dynamic Shear Properties of the Porcine Molar and Incisor Periodontal Ligament

Abstract

The role of the periodontal ligament (PDL) is to support the tooth during function and resist external forces applied to it. The dominant vertical component of these forces is associated with shear in the PDL. The mechanical response to vertical force may, however, be different between the molar and incisor as their loading regimen is different. The present study was designed to determine the viscoelastic behavior in shear of the PDL of the porcine molar and incisor (n = 10 for each). From dissected mandibles transverse sections including the mesial root of first molar and the incisal root were obtained and used for dynamic shear tests. Shear strain of 1.0% was applied in superoinferior direction parallel to the root axis with a wide range of frequencies (0.01-100 Hz). The viscoelastic behavior was characterized by the storage and loss modulus and loss tangent as a function of the frequency. For the incisor and molar, the complex and storage moduli increased significantly with the frequency. For the incisor, the loss modulus also increased with the frequency. The loss modulus and loss tangent were significantly (p < 0.05) larger in the incisor than in the molar. The present results suggest that the incisal PDL revealed more viscous behavior during dynamic shear than the molar one, which might have important implications for the principal role of the anterior teeth such as PDL sensation.

Mechanical Strength and Viscoelastic Response of the Periodontal Ligament in Relation to Structure

“…Tanaka et al (2006) [79] have measured dynamic shear properties of the porcine incisor and molar PDLs at an oscillation amplitude (Figure 17) of Δ γ = 1% with a wide range of frequencies (0.01–100 Hz). They found that storage modulus G ′ increased with frequency for both PDLs while loss modulus G ′′ did so only for the incisor PDL (Figure 18(a)).…”

“…Tan  δ ( = G ′′/ G ′) ranged between 0.1 and 0.2, which was greater in the incisor than in the molar PDL with frequencies between 1 and 100 Hz (Figure 18(b)). The incisor PDL may be considered to have better shock-absorbing characteristics for sudden loading [79]. …”

“…(b) Chucking device with a transverse section of a tooth root. (c) A schematic record of dynamic stress and strain during a sinusoidal oscillating strain, reproduced from Tanaka et al [79], by permission.…”

“…Data were obtained from incisor (white circle) and molar (black circle) periodontal ligaments. Vertical bars indicate 1 SD, reproduced from Tanaka et al [79], by permission.…”

Multiscale biomechanical responses of adapted bone–periodontal ligament–tooth fibrous joints

“…Early investigators isolated and performed biomechanical studies on transverse sectioned blocks of the bone-PDL-tooth complex and focused on the PDL’s intrusive, extrusive and related viscoelastic/viscoplastic characteristics [22–26]. Subsequently, by using an in situ mechanical loading device coupled to an x-ray microscope, biomechanical studies on intact bone-PDL-tooth fibrous joints, and geometric relationship of tooth with the alveolar socket in humans [27] and other mammalian models under normal [28–30] and diseased conditions [31] were performed.…”