The mechanical function of the periodontal ligament in the macaque mandible: a validation and sensitivity study using finite element analysis

Abstract

Whilst the periodontal ligament (PDL) acts as an attachment tissue between bone and tooth, hypotheses regarding the role of the PDL as a hydrodynamic damping mechanism during intraoral food processing have highlighted its potential importance in finite element (FE) analysis. Although experimental and constitutive models have correlated the mechanical function of the PDL tissue with its anisotropic, heterogeneous, viscoelastic and non-linear elastic nature, in many FE simulations the PDL is either present or absent, and when present is variably modelled. In addition, the small space the PDL occupies and the inability to visualize the PDL tissue using lCT scans poses issues during FE model construction and so protocols for the PDL thickness also vary. In this paper we initially test and validate the sensitivity of an FE model of a macaque mandible to variations in the Young's modulus and the thickness of the PDL tissue. We then tested the validity of the FE models by carrying out experimental strain measurements on the same mandible in the laboratory using laser speckle interferometry. These strain measurements matched the FE predictions very closely, providing confidence that material properties and PDL thickness were suitably defined. The FE strain results across the mandible are generally insensitive to the absence and variably modelled PDL tissue. Differences are only found in the alveolar region adjacent to the socket of the loaded tooth. The results indicate that the effect of the PDL on strain distribution and ⁄ or absorption is restricted locally to the alveolar bone surrounding the teeth and does not affect other regions of the mandible.

Multi-layered bird beaks: a finite-element approach towards the role of keratin in stress dissipation

“…To do so, the full field out-of-plane displacement in the FE model is compared with that measured using digital speckle pattern interferometry (DSPI). DSPI is an accurate tool allowing the measurement of small displacements in small and complex structures such as the upper beak of the Java finch [9][10][11][12][13]. The FE model contains the bony core of the upper beak and an outer 'keratin' layer, which is in fact an aggregation of the epidermal and dermal layer ( figure 1b-d).…”

The mechanical significance of morphological variation in the macaque mandibular symphysis during mastication

“…When voxels were located on the boundary of two structures with similar densities and the automatic threshold could not capture these density differences, manual segmentation was conducted (e.g., artifact connection between tooth crowns). Manual segmentation was also used to segment out the periodontal ligament (PDL) tissue as a three to four voxel structure between the tooth and the alveolar bone (Panagiotopoulou et al, 2011). Previous sensitivity studies have demonstrated that the pattern, magnitude, and orientation of strain across the adult macaque mandible are relatively insensitive to the presence of the PDL tissue (Panagiotopoulou et al, 2011).…”

“…Manual segmentation was also used to segment out the periodontal ligament (PDL) tissue as a three to four voxel structure between the tooth and the alveolar bone (Panagiotopoulou et al, 2011). Previous sensitivity studies have demonstrated that the pattern, magnitude, and orientation of strain across the adult macaque mandible are relatively insensitive to the presence of the PDL tissue (Panagiotopoulou et al, 2011). However, the PDL 1 Stress (r) is the force per unit area and the standard international unit for stress is Pa or N/m 2 .…”

“…In fact, a number of variations are found in the transverse tori of the mandibular symphysis including superior and inferior tori of equal proportions, a more prominent superior torus, a more prominent inferior torus and both tori being relatively reduced or even absent (Brown, 1997). A combination of factors, not necessarily mutually exclusive, have been proposed as determinants of variation in anterior mandibular morphology, including sexual dimorphism, facial orientation, dentition, and phylogenetic constraints (e.g., Shea, 1985Shea, , 1987 Brown, 1997;Plavcan and Daegling, 2006; Cobb and Baverstock, 2009a,b;Cobb and Panagiotopoulou, 2011). However, the greatest attention has been paid to adaptation of the mandible to resist loads during intraoral food processing (e.g., Hylander, 1984Hylander, , 1985Hylander and Johnson, 1994;Daegling and Hylander, 2000;Daegling, 2001).…”

A Sensitivity Analysis to the Role of the Fronto‐Parietal Suture in Lacerta Bilineata: A Preliminary Finite Element Study

“…The finite element (FE) method has recently gained popularity to analyze the role of sutures as modulators of the mechanical response of the skull to loading (Rayfield, 2005b;Jasinoski et al, 2009;Moazen et al, 2009b). Validity and sensitivity of these FE models is an important issue which needs to be addressed Kupczik et al, 2007;Gr€ oning et al, 2009;Bright and Rayfield, 2011;Panagiotopoulou et al, 2011Panagiotopoulou et al, , 2012Rayfield, 2011). While testing the validity of FE models is possible in the case of large living taxa, it is more challenging or impossible in the case of small animals or fossils.…”