Influence of Polymeric Restorative Materials on the Stress Distribution in Posterior Fixed Partial Dentures: 3D Finite Element Analysis

This study evaluated the effect of interim restorative materials (acrylic resin (AR), resin composite (RC) or polyetheretherketone (PEEK) for dental computer-aided design/computer-aided manufacturing (CAD/CAM)) on the stress distribution of a posterior three-unit fixed partial denture

Influence of the dental implant number and load direction on stress distribution in a 3-unit implant-supported fixed dental prosthesis

Background. The choice between 2 or 3 implants to support a 3-unit implant-supported fixed dental prosthesis (FDP) still generates doubt in clinical practice. Objectives. The aim of this study was to evaluate stress distribution in 3-unit implant-supported FDPs according to the implant number and load direction. Material and methods. A numerical simulation was performed to analyze stress and strain according to the implant number (2 or 3) and load direction (axial or oblique). A model of a jaw was created by means of the modeling software Rhinoceros, v. 5.0 SR8. External hexagon implants, micro-conical abutments and screws were also modeled. The final geometries were exported to the computer-aided engineering (CAE) software Ansys, v. 17.2, and all materials were considered homogeneous, isotropic and elastic. Different load directions were applied for each model (300 N) at the center of the prosthesis. Results. The von Mises stress and strain values were obtained for the titanium structures and the bone, respectively. The implant number influenced the prosthesis biomechanics, with higher stress and strain concentrations when 2 implants were simulated. The oblique load also affected the mechanical response, showing higher stress and strain in comparison with the axial load, regardless of the implant number. Conclusions. It was concluded that for a 3-unit implant-supported FDP, a greater number of implants associated with axial loads can result in a better mechanical response during chewing

Influence of occlusal anatomy on acrylic resin CAD/CAM crowns fracture load and stress distribution.

Objectives: This study compared the influence of occlusal anatomy on acrylic CAD/CAM crowns fracture load and stress distribution. The null hypothesis was that there would be no difference between the provisional crowns fracture load and stress according to different occlusal anatomy. Methods: A full-crown preparation was simulated using dentin analogue (G10, Protec, São Paulo, Brazil) totaling 20 identical preparations. Next, twenty acrylic crowns were milled using different occlusal design parameter (Young or Adult) available in the software database. The crowns were cemented (Temp-bond, NE Kerr Dental, Brea, CA, USA) and fractured using a compressive load (0.5 mm/min of cross-head speed). Data were analyzed by using one-way ANOVA and Tukey tests (p< 0.05). A similar geometry was modeled and exported to the analysis software to perform a static structural analysis. The maximum principal stress was calculated using the finite element method with 300 N chewing load simulation. Results: The occlusal anatomy significantly influenced the load-to-fracture (p<0.05). Young design showed lower fracture load (1139±132 N) than Adult design (2007±345 N). The tensile stress distribution showed a similar pattern for both groups however the highest stress peak was calculated for Young design (76 MPa) in the occlusal surface. Conclusion: The anatomy design with higher cusp angulation and occlusal sulcus more evident can increase the stress concentration and reduce the fracture load for acrylic resin CAD/CAM crowns

Loading stress distribution in posterior teeth restored by different core materials under fixed zirconia partial denture: A 3d-fea study

Purpose: To evaluate the effect of different substrate stiffness [sound dentin (SD), resin composite core (RC) or metal core (MC)] on the stress distribution of a zirconia posterior three-unit fixed partial denture (FPD). Methods: The abutment teeth (first molar and first premolar) were modeled, containing 1.5 mm of axial reduction, and converging axial walls. A static structural analysis was performed using a finite element method and the maximum principal stress criterion to analyze the fixed partial denture (FPD) and the cement layers of both abutment teeth. The materials were considered isotropic, linear, elastic, homogeneous and with bonded contacts. An axial load (300 N) was applied to the occlusal surface of the second premolar. Results: The region of the prosthetic connectors showed the highest tensile stress magnitude in the FPD structure depending on the substrate stiffness with different core materials. The highest stress peak was observed with the use of MC (116.4 MPa) compared to RC and SD. For the cement layer, RC showed the highest values in the molar abutment (14.7 MPa) and the highest values for the premolar abutment (14.4 MPa) compared to SD (14.1 and 13.4 MPa) and MC (13.8 and 13.3 MPa). Both metal core and resin composite core produced adequate stress concentration in the zirconia fixed partial denture during the load incidence. However, more flexible substrates, such as composite cores, can increase the tensile stress magnitude on the cement

Functional or nonfunctional cusps preservation for molars restored with indirect composite or Glass-ceramic Onlays: 3d FEA study

Evidence regarding the effect of the onlay preparation design for different CAD/CAM restorative materials considering the preservation of cusps is lacking. Molars were 3D-modeled in four preparation designs for onlay restoration: Traditional design with functional cusp coverage (TFC), non-retentive design with functional cusp coverage (NFC), traditional design with non-functional cusp coverage (TNFC) and non-retentive design with non-functional cusp coverage (NNFC). The restorations were simulated with two CAD/CAM restorative materials: LD—lithium disilicate (IPS e.max CAD) and RC—resin composite (GrandioBloc). A 100 N axial load was applied to the occlusal surface, simulating the centric contact point. Von Mises (VM) and maximum principal (Pmax) stress were evaluated for restorations, cement layer and dental substrate. The non-retentive preparation design reduced the stress concentration in the tooth structure in comparison to the conventional retentive design. For LD onlays, the stress distribution on the restoration intaglio surface showed that the preparation design, as well as the prepared cusp, influenced the stress magnitude. The non-retentive preparation design provided better load distribution in both restorative materials and more advantageous for molar structure. The resin composite restoration on thenon-functional cusp is recommended when the functional cusp is preserved in order to associate conservative dentistry and low-stress magnitude