Nonlinear Finite Element Analysis Versus Ex Vivo Strain Gauge Measurements on Immediately Loaded Implants

Purpose: To evaluate the level of agreement between nonlinear finite element stress analysis (NL-FEA) and ex vivo strain gauge analysis (EV-SGA) on immediately loaded implants. Materials and Methods: Four 4.1-mm-diameter, 12-mm-long implants were placed bilaterally into the lateral and first premolar regions of completely edentulous maxillae of four human cadavers. Two-element 90-degree rosette strain gauges were bonded to the labial cortical bone around the implants, and 100 N maximal load was applied over two miniature load cells on bar-retained overdentures while simultaneous data acquisition from load cells and strain gauges was performed at a sample rate of 10 KHz. Individualized numeric models of the cadavers were constructed, and contact analysis with normal contact detection and separation behavior was performed between the implants and bone. Upon simulation of the loading regimen, axial and lateral strains were recorded. The NL-FEA data and EV-SGA data were compared. Results: There was a high level of agreement regarding the quality of strains, as determined by both techniques, although the mean values obtained with EV-SGA were higher than those found with NL-FEA. However, the strains recorded by NL-FEA did not differ significantly (P .05) from the strains recorded by EV-SGA. Conclusion: Considering the complex biomechanical behavior of human hard and soft tissues, EV-SGA and NL-FEA did not suggest inconsistency in the detection of the quality of strains. Further, the methods provided comparable values for the quantification of strains on implants supporting maxillary overdentures. Keywords: biomechanics, bone, finite element analyses, immediate loading, maxilla, overdenture, strain, strain gauge analysis