Stress Distribution of Implant-Supported Fixed Partial Dentures with Cantilever Extension

Objectives: To evaluate the effects of cantilever length on load distribution surround the implants, according the cantilever length. The null hypothesis was that the cantilever length affects the load distribution around the implants. Methods: Two parallels implants with external hexagon (diameter: 4.0 mm; length: 11.5 mm), were positioned 10 mm between them, on a polyurethane model with dimensions of 10x4x4 cm. The abutments (Multi-Unit) were connected to the implants and impressions with an elastomeric material (Impregum) were made and them a stone model was obtained. For each model, was fabricated a superstructure with a 30 mm cantilevered section from the center of the most distal implant. The bar was casted in silver-palladium alloy. Three strain gauges (G1- mesial, G2- between implants, G3- distal) were positioned on the upper surface of the model around the implants. The model was loaded (10 N) using a universal testing machine (EMIC - DL1000 model) and the load was applied between the implants, 5 mm, 10 mm, 15 mm, 20 mm and 25 mm along the cantilever length. Each point of loading was measured five times. The data were submitted to ANOVA and Tukey test (p<0.05). Results: The mean of the data obtained in microstrain were: G1: between implants (1162.90), 5 (1460.86), 10 (1301.51), 15 (1821.85), 20 (0.00), 25 (0.00); G2: between implants (615.94), 5 (82.83), 10 (142.57), 15 (105.10), 20 (0.00), 25 (0.00); G3: between implants (30.68), 5 (505.14), 10 (530.84), 15 (574.71), 20 (0.00), 25 (0.00). The cantilever length affected negatively the load distribution around the implants around the implants (p<0.05). The null hypothesis was accepted. Conclusions: It can be concluded that longer cantilever causes higher stress around implants than a shorter cantilever.