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.