Mechanical Behavior of Different Restorative Materials and Onlay Preparation Designs in Endodontically Treated Molars

Abstract

This study evaluated the effect of the combination of three different onlay preparation designs and two restorative materials on the stress distribution, using 3D-finite element analysis. Six models of first lower molars were created according to three preparation designs: non-retentive (nRET), traditional with occlusal isthmus reduction (IST), and traditional without occlusal isthmus reduction (wIST); and according to two restorative materials: lithium-disilicate (LD) and nanoceramic resin (NR). A 600 N axial load was applied at the central fossa. All solids were considered isotropic, homogeneous, and linearly elastic. A static linear analysis was performed, and the Maximum Principal Stress (MPS) criteria were used to evaluate the results and compare the stress in MPa on the restoration, cement layer, and tooth structure (enamel and dentin). A novel statistical approach was used for quantitative analysis of the finite element analysis results. On restoration and cement layer, nRET showed a more homogeneous stress distribution, while the highest stress peaks were calculated for LD onlays (restoration: 69–110; cement layer: 10.2–13.3). On the tooth structure, the material had more influence, with better results for LD (27–38). It can be concluded that nRET design showed the best mechanical behavior compared to IST and wIST, with LD being more advantageous for tooth structure and NR for the restoration and cement layer.

Effect of Biologically Oriented Preparation Technique on the Stress Concentration of Endodontically Treated Upper Central Incisor Restored with Zirconia Crown: 3D-FEA

“…Even though the present study is not influenced by human interferences in marginal and internal misfits, as they are delimited and maintained in the CAD design and analysis software, it is important to emphasize that the cement layer influences the fracture resistance of fixed partial prostheses [ 31 ], as well as the bond strength of cement, can be influenced by the cement thickness [ 32 ]. These factors are corroborated by several studies in FEA that indicate that the failure risks are not precisely in the crown, but in the weakest part of the assembly (sometimes the cement) and the higher modulus of elasticity of the crown restorative material, would be better to protect the cement layer [ 33 , 34 , 35 ]. The use of zirconia crowns for BOPT and other types of preparation, as demonstrated in the results, can be seen as a positive factor for survival.…”

Influence of Cement Thickness on the Polymerization Shrinkage Stress of Adhesively Cemented Composite Inlays: Photoelastic and Finite Element Analysis

“…The adhesive factor is considered a critical point in the clinical success and long-term prognosis of minimally invasive restorations [28][29][30][31][32][33][34][35][36]. However, the present study demonstrates that the thickness of the resin cement layer affects the polymerization shrinkage and the cusp deflection.…”

Functional or Nonfunctional Cusps Preservation for Molars Restored with Indirect Composite or Glass-Ceramic Onlays: 3D FEA Study

“…A three-dimensional geometry was obtained with the aid of CAD (Computer Aided Design) software (Rhinoceros ® version 4.0; McNeel North America, Seattle, WA, USA). The 3D teeth were obtained from a scan of preparations made in resin models, in which the teeth presented anatomy based on the literature [15]. In this step, the models were generated from lines drawn over the image in STL, in which the main anatomical landmarks are chosen, with lines generated over them that referenced the surface.…”

“…Making use of a material that works well with the tooth structure would be an interesting alternative to circumventing the failures of restorations, since commercially there are blocks such as hybrid type ceramics or nanoresins with a greater number of fillers [15,16]. One of these types of blocks was launched in 2013 and is commercially distributed by VOCO under the name of Grandio Blocs.…”