The article, “The mechanical function of the periodontal ligament in the macaque mandible: a validation and sensitivity study using finite element analysis,” by a group from the University of York, in the United Kingdom, purported to find that:
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 μCT 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.
But according to the Expression of Concern:
The above article from Journal of Anatomy, published in Volume 218, Issue 1, pages 75–86 (and first published online on 24 June 2010 in Wiley Online Library, www.onlinelibrary.wiley.com), is subject to an Expression of Concern by agreement between the authors, the Journal’s co-Editors-in-Chief, Julia Clarke, Thomas Gillingwater, Anthony Graham and Stefan Milz, and John Wiley & Sons Ltd.
The Expression of Concern has been agreed due to a potential error in the validation results of the experimental model published in a Journal of Biomechanics paper (Panagiotopoulou et al., 2010, 43: 1603–1611) and referenced in this paper.
The Journal of Anatomy paper has been cited 23 times, according to Thomson Scientific’s Web of Knowledge, while the Journal of Biomechanics article has been cited 20 times.
We notice that the earlier paper in the Journal of Biomechanics has not been corrected, nor is it the subject of its own expression of concern — which we find, um, concerning. We’ve emailed the editor of that journal for an explanation and will update this post if we learn more.