Implant-supported overdentures with different clinical configurations: Mechanical resistance using a numerical approach.

STATEMENT OF PROBLEM: Implant-supported overdentures (IODs) are a treatment option for patients with complete edentulism. However, this treatment increases the possibilities of peri-implant complications, characterized by inflammation or partial loss of surrounding hard and soft tissues.

PURPOSE: The purpose of this finite element analysis study was to evaluate the mechanical performance of different bar-IOD designs under different clinical configurations by comparing the stress and strain distribution on the bone during secondary stabilization.

MATERIAL AND METHODS: A finite element model of the mandible representing a patient with complete edentulism was developed. Different designs of bar-IODs were modeled and compared. The parameters studied were the material properties (cobalt-chromium, zirconium dioxide, titanium grade 5, and titanium grade 4), diameter and bar-IOD cross-sectional shape, tilt of the posterior implants (30 degrees), presence of a distal extension cantilever in the bar-IODs (12 mm), and number of implants (4 or 6). Two different mastication loading conditions were analyzed. One- and 2-way ANOVAs and the Tukey honestly significant differences post hoc test (α=.05) were used to determine the significant von Mises stress and strain values in the bone.

RESULTS: The 4 materials tested in the bar-IOD did not have a significant mechanical effect on the bone (P<.05). A smaller diameter and structure of the bar-IOD led to significantly higher bone stress (P<.001). A distal extension cantilever led to an increased stress concentration (model M1 versus model M3: P<.001), which reached 50% in the event of tilting of the posterior implants (model M2 versus model M4: P<.001). Tilting of the posterior implants alone, without extension, had a nonsignificant effect (model M3 versus model M4: P=.999). Model M5 supported with 6 implants reduces the stress transferred to the bone compared with model M3 supported with 4 implants (P<.05).

CONCLUSIONS: Distal extensions in bar-IODs, the tilt of the posterior implants, and the low amount of material in the cross-sectional area in the bar-IOD were the most influential parameters on the mechanical resistance of dental implants in the mandibular bone.