Finite element stress analysis of dental prostheses supported by straight and angled implants.

PURPOSE: A three-dimensional finite element analysis was conducted to evaluate and compare the stress distribution around two prosthesis-implant systems, in which implants were arranged in either a straight-line or an intrabone offset configuration. MATERIALS AND METHODS: The systems were modeled with three titanium implants placed in the posterior mandible following a straight line along the bone. The straight system was built with three straight implants (no offset). The angled system was built as follows: the first implant (mesial) was an angled implant inclined lingually, the second (median) was straight, and the third (distal) was another angled implant inclined buccally. This buccal incline created an intrabone implant offset owing to the inclination of the angled implants' bodies. Each system received a metal-ceramic prosthesis with crowns that mimicked premolar anatomy. In both systems, an axial load of 100 N and a horizontal load of 20 N were applied on the center of the crown of the middle implant. RESULTS: In both systems, the major von Mises stresses occurred with vertical loading on the mesial and the distal neck area of the first and third implants, respectively: 6.304 MPa on the first implant of the straight system and 6.173 MPa on the third implant in the angled system. The peak stress occurred for the minimum principal stress (S3) on the neck of the first implant for both systems at the level of -8.835 MPa for the straight system and -8.511 MPa for the angled system. There was no stress concentration on the inner or outer angles of the angled implants, on the notches along the implant body, or on any apex. CONCLUSIONS: In this analysis, the angled system did not induce a stress concentration in any point around the implants that was different from that of the straight system. The stress distribution was very similar in both systems.

Finite element stress analysis of cuneiform and cylindrical threaded implant geometries.

Statement of problem. Different implant geometries present different biomechanical behaviors and in this context, one arising question is how cuneiform implant geometry compares to clinical successful cylindrical threaded implant geometry. Purpose. The purpose of this work was to study stress distribution around cuneiform and cylindrical threaded implant geometries using three-dimensional finite element stress analysis taking the latter as a reference. Material and methods. A model was generated from a computerized tomography of a human edentulous mandible with implants placed in the left first premolar region. The model was supported by the mastication muscles and by temporomandibular joint. A vertical load of 100N was applied at the top of each implant in the direction of their long axes. The mandibular boundary conditions were modeled considering the actual muscle supporting system. Taking muscle forces intensities and directions, balance moment equations were employed to assess the system equilibrium. Cortical and medullary bones were assumed to be homogeneous, isotropic and linearly elastic. Results. The analysis provided results for maximum (S1) and minimum (S2) principal stress and Von Mises (SEQV) stress field. For both geometries, the results showed concentration on one side of the neck, smooth stress distribution along the body and no considerable concentration at the apical area. Conclusion. Results showed similar stress distribution pattern for cuneiform and cylindrical threaded geometries. The stresses profiles along the implants length reproduced their morphology. In both occurred stress concentration at one side of the neck and no body or apical stress concentration.