Influence of resin cement rigidity on the stress distribution of resin-bonded fixed partial dentures

The mechanical properties of the adhesive cement used in resin-bonded fixed partial dentures (RBFPD) can modify the clinical performance of the rehabilitation. The goal of this study was to evaluate the influence of the elastic modulus of different cements on the stress distribution in RBFPD using finite element analysis. For that an anterior 3-unit prosthesis was modeled based in a stereolithography file. The model was meshed with tetrahedral elements and materials considered isotropic, linearly elastic and homogeneous. The force applied to the palatal area of the lateral incisor (pontic) at 45° was 100 N. The cements used presented 7 different elastic modulus (E): 2, 6, 10, 14, 18, 22 or 26 GPa. The total deformation, von-Mises stress and maximum principal stress criteria were used to calculate the results. The lower tensile stress occurred in the cement layer with E = 2 GPa [25.6 (canine) and 16.32 MPa (incisor)]. For the prosthesis, the model with the lower tensile stress [287 (canine) and 248 MPa (incisor)] occurred when the cement presented E = 26 GPa. In this way, the stress concentration may have its magnitude modified depending on the stiffness of the cement. Since more flexible cements concentrate less tensile stress in its structure, but allow an increased displacement of the prosthesis, which is friable and rigid and ends up concentrating more tensile stress at its connector. In that way the clinician should avoid the use of adhesive cement with lower elastic modulus due to it increases the stress concentration in the ceramic

Short communication: Influence of retainer configuration and loading direction on the stress distribution of lithium disilicate resin-bonded fixed dental prostheses: 3D finite element analysis

The present study elucidates the mechanical performance of different designs of resin-bonded fixed dental prostheses made of lithium disilicate simulating masticatory loads of anterior or canine guidance. A three-dimensional model of maxilla was constructed containing central incisor and canine teeth, with edentulous space of the lateral incisor. Three designs of prosthesis were created: retained in central incisor (1-I), retained in canine (1-C) and fixed in both teeth (2-IC). The computational analysis was performed for load in canine and central incisor separately (100N, 45°). The tensile and shear stresses were calculated for the resin-bonded fixed dental prosthesis, bonding surface of each retainer and cement layer using 3D finite element analysis. The 20 highest stress values were analyzed using two-way ANOVA and post-hoc Tukey test, all with α = 5%. The computational analysis showed that 2-retainer resin-bonded fixed dental prosthesis presented the worst prognosis regardless of the mandibular movement. ANOVA showed that Mandibular movement*Retainer interaction influenced on the tensile and shear stresses values (p < 0.01). Higher stresses were observed in the connector region for all groups (13-82.2 MPa; 11-70.2 MPa). In order to reduce the stress concentration in the resin-bonded fixed dental prosthesis and the retainer made of lithium disilicate, the occlusion may serve as the selection criteria of the unitary abutment for better sustainability