The Effects of Different Base Materials on the Stress Distribution of the Endodontically Treated Teeth: 3D-FEA

Objectives: The aim this study was to analyze the stress formed by oblique forces in endodontically treated mandibular first molars that were restored with different base materials and direct composite restorations (3D-FEA).
Methods: The model of mandibular first molar tooth was obtained using a special software (Rhinoceros 4.0, USA). For the two different restorative approaches; an OM cavity design and a MOD cavity design was created. Then root canal obturation was modelled. On this two main designs to analyze the stresses caused by the use of various base materials, twelve different restoration models were prepared. Composite resin (CR) (Grandio, Voco), conventional glass ionomer cement (GIC) (Fuji IX, GC), fiber reinforced composite resin (FRCR) (EverX Posterior, GC), resin modified glass ionomer cement (RMGIC) (Vitrebond, 3M ESPE), flowable composite (FC) (TetricFlow, Ivoclar Vivadent), and bulk-fill composite resin (BF) (SDR, Dentsply) were used as base materials. All the restorations were finished with the use of one type of resin composite resin (Grandio, Voco). Oblique chewing forces of 240N were applied to all models and the resulting stresses in enamel, dentin, base materials and final restoration were analyzed using finite element stress analysis method.
Results: It was noted that MOD cavity design caused more stress than OM cavity design. Regarding the resulting stresses, CR caused highest stresses and RMGIC caused lowest stresses in enamel, base material, and final restoration. RMGIC caused highest stresses and CR caused lowest stresses in dentin.
Conclusions: To restore endodontically treated teeth with OM and MOD cavity, materials with elastic moduli similar to dentin; FRCR and GIC, may be better choice to avoid high stresses within the tooth and restoration.