Finite Element Analysis Comparison Between Invasive and Non-invasive Artificial Marginal Ridges on Endodontically Treated Teeth

Objectives: To compare the mechanical performance of invasive or non-invasive structures that could replace missing marginal ridges in MOD cavities on endodontically treated teeth.
Methods: An extracted human mandibular molar was scanned with a micro-CT scanner (SkyScan 1076 micro-CT, SkyScan, Aartselaar, Belgium), and virtual 3D models were then reconstructed to perform a finite element analysis (FEA). An endodontic access cavity and MOD cavities were simulated and two models were obtained after applying different designs for artificial marginal ridges. A fiber-reinforced composite ring wrapped around the remaining buccal and lingual walls was designed as the non-invasive artificial marginal ridge model (Ring) (Fig.1 a). An in vitro photograph of the Ring model was made to elaborate the design (Fig. 2). A zirconia transversal pin anchored in the remaining buccal and lingual walls was designed as the invasive artificial marginal ridge model (Pin) (Fig.1 b). Equal loads of 600N were applied on the same occlusal location of both models, and maximum principal stress and cuspal deformation values were examined.
Results: Analysis showed that the maximum principal stress at the cervical level of the tooth restored with the Pin as an invasive artificial marginal ridge (27 MPa) was higher than the stress observed in the tooth restored with the Ring as a non-invasive artificial marginal ridge (16 MPa). The measure of cuspal deformation also showed that the invasive Pin model had values higher by 52 micrometers than the non-invasive Ring model.
Conclusions: With the limitations of this study, a non-invasive approach using a ring to recreate the missing marginal ridges showed to be mechanically more advantageous than an invasive approach using a transversal pin.