Biomechanical Behavior of Tooth-Implant Supported Prostheses With Different Implant Connections: A Nonlinear Finite Element Analysis.

PURPOSE: Biomechanical behavior of tooth-implant-supported prostheses (TISPs) with external and internal implants was compared. MATERIALS AND METHODS: Two 3-D models of TISP were designed by varying the implant: external (Model EH) and internal hexagons (Model IH). After loading, von Mises stresses were obtained in implants, abutments, and screws. Principal maximum (σmax) and minimum (σmin) stresses were analyzed in periodontal ligament (PL), alveolar bone, and periimplant bone. RESULTS: Model IH showed lower stress peaks in axial loading in the implant and in the screw but higher in abutment. In oblique loading, Model IH had lower stresses in the implant, but higher in the abutment and in the screw. In the σmax analysis for axial and oblique loads, stress peaks in Model IH were lower in PL, alveolar bone, and periimplant bone. In the σmin analysis for axial load, stress peaks in Model IH were lower in PL, but higher in alveolar bone and in periimplant bone. In oblique load, Model IH showed lower stress peaks in PL and alveolar bone, but higher stress peaks in periimplant bone. CONCLUSIONS: TISPs with IH implants do present lower risk of biomechanical failure.

Effects of Screw- and Cement-Retained Implant-Supported Prostheses on Bone: A Nonlinear 3-D Finite Element Analysis.

PURPOSE: To compare the stresses and displacements on perimplant bone generated by screw- and cement-retained prostheses using the finite element method. MATERIALS AND METHODS: Two models were constructed: partial fixed implant-supported prostheses with three elements retained by screws (SFP) or cement (CFP). Vertical and oblique loads of 100 N were applied on the models. Bone was analyzed by the principal stresses σ1 and σ3. The displacement between the implant and the bone was identified by the penetration and gap. RESULTS: Results showed a similar pattern in the distribution of the principal stresses between both prostheses. Under the σ1 stresses, the SFP showed similar values in the bone compared with the CFP. The analysis of the σ3 showed stress peaks 28% higher in the SFP, considering vertical and oblique loads. Displacement analysis showed a similar pattern and similar values between the prostheses for penetration and gap under both loads. CONCLUSIONS: There were no important differences in the σ1 analysis and the displacement between the SFP and CFP. The differences in marginal bone level reported between SFP and CFP in some clinical studies may not be related to a mechanical factor.

Biomechanical evaluation of screw- and cement-retained implant-supported prostheses: a nonlinear finite element analysis.

STATEMENT OF PROBLEM: The mechanical stability of the prosthetic components in the implant-prosthesis complex is essential to the long-term success of the restorations. However, little is known about the differences in the biomechanical behavior of screw- and cement-retained prostheses. PURPOSE: The purpose of this study was to compare the preload maintenance, stresses, and displacements of prosthetic components of screw- and cement-retained implant-supported prostheses by using the finite element method in a nonlinear analysis. MATERIAL AND METHODS: Two 3-dimensional models were constructed: implant-supported fixed partial prostheses with 3 elements retained either by screws (SFP) or cement (CFP). After the simulation of screw tightening, the preload was calculated for both prostheses. Then vertical and oblique loads (100 N) were applied on the models. The preload was identified, the maximum von Mises equivalent stresses (SEQV) were obtained on the screws, and the displacement among the abutment, the implant, and screw was identified by observing the penetration and gap in the contact interfaces. RESULTS: Under vertical load, there was a higher decrease in the preload and in the SEQV on the screw in the SFP. Under oblique load, the SEQV was 24% higher on the screw of the SFP. In the displacement analysis under vertical load, penetration was concentrated in the threads of the screw in the SFP and between the abutment and implant in the CFP. The gap was 118% greater for the SFP and was concentrated on the abutment extension. Under oblique load, the displacement pattern was similar for both prostheses, but with values 66% higher for penetration and 96% higher for gap for the SFP. CONCLUSIONS: The SFP showed a higher biomechanical risk of failure than the CFP.

A method for obtaining a three-dimensional geometric model of dental implants for analysis via the finite element method.

PURPOSE: The aim of the study was to present a methodology of development of a virtual 3-dimensional dental implant model for analyses via the finite element method. MATERIALS AND METHODS: A set, consisting of a dental implant and abutment, was embedded in acrylic resin for subsequent metallographic grinding and polishing. After the evidentiation of the internal geometry of the implant, the specimen was treated in a sputter for observation using scanning electron microscopy (SEM). The SEM image was transported to computer-aided design software by which all details of the implant were measured. With the measures obtained, the geometry was reproduced with 3-dimensional modeling software. Finally, the model was imported into finite element method analysis software with which it was discretized, generating a mesh. RESULTS: A model with the accurate geometry of the implant was developed. A mesh of 297,600 elements and 490,045 nodes was generated. An aleatory acceleration simulation was performed to test the mesh, and no errors were identified. CONCLUSION: The developed methodology generated a precise dental implant model, which can be applied in different finite element method simulations.