Optimal mechanical design of anatomical post-systems for endodontic restoration

Abstract

This paper analyses the mechanical behaviour of a new reinforced anatomical post-systems (RAPS) for endodontic restoration. The composite restorative material (CRM) completely fills the root canal (as do the commonly used cast metal posts) and multiple prefabricated composite posts (PCPs) are employed as reinforcements. Numerical simulations based on 3D linearly elastic finite element models under parafunctional loads were performed in order to investigate the influence of the stiffness of the CRM and of the number of PCPs. Periodontal ligament effects were taken into account using a discretised anisotropic nonlinearly elastic spring system, and the full discrete model was validated by comparing the resulting stress fields with those obtained with conventional restorations (cast gold-alloy post, homogeneous anatomical post and cemented single PCP) and with the natural tooth. Analysis of the results shows that stresses at the cervical/middle region decrease as CRM stiffness increases and, for large and irregular root cavities that apical stress peaks disappear when multiple PCPs are used. Accordingly, from a mechanical point of view, an optimal RAPS will use multiple PCPs when CRM stiffness is equal to or at most twice that of the dentin. This restorative solution minimises stress differences with respect to the natural tooth, mechanical inhomogeneities, stress concentrations on healthy tissues, volumes subject to shrinkage phenomena, fatigue effects and risks of both root fracture and adhesive/cohesive interfacial failure.

Keywords:

• dental restorative material
• finite element analysis
• prefabricated composite post
• post-endodontic restoration
• anatomical post-systems
• periodontal-ligament discrete model

Acknowledgements

This work was developed within the framework of Lagrange Laboratory, a European research group comprising CNRS, CNR, the Universities of Rome ‘Tor Vergata’, Calabria, Cassino, Pavia and Salerno, Ecole Polytechnique, University of Montpellier II, ENPC, LCPC and ENTPE.

The cooperation of Riccardo Cottone and Michele Marino, graduate students at the School of Engineering, University of Rome ‘Tor Vergata’, offered for partial credit toward their Bachelor of Medical Engineering degrees, is gratefully acknowledged.