Finite element analysis of the effect of cantilever and implant orientation on stress distribution in a mandibular implant-supported bar overdenture

Park, Jun Soo; Lee, Sung Bok; Kwon, Kung Rock; Woo, Yi Hyung

Abstract

STATEMENT OF PROBLEM: Implant inclination and cantilever loading increse loads distributed to implants, potentially causing biomechanical complications. Controversy exists regarding the effect of the intentionally distal-inclined implant for the reduction of the cantilever length. PURPOSE: This study investigated the stress distribution at the bone/implant interface and prostheses with 3D finite element stress analysis by using four different cantilever lengths and implant inclinations in a mandibular implant-supported bar overdenture. MATERIAL AND METHODS: Four 3-D finite element models were created in which 4 implants were placed in the interforaminal area and had four different cantilver lengths(10, 6.9, 4 and 1.5mm) and distal implant inclinations(0degrees, 15degrees, 30degrees and 45degrees) respectively. Vertical forces of 120N and oblique forces of 45N were applied to the molar area. Stress distribution in the bone around the implant was analysed under different distal implant inclinations.
RESULTS
Analysis of the von Mises stresses for the bone/implant interfaces and prostheses revealed that the maximum stresses occurred at the most distal bone/implant interface and the joint of bar and abutment, located on the loaded side and significantiy incresed with the implant inclinations, especially over 45degrees.
CONCLUSION
Within the limitations of this study, it was suggested that too much distal inclination over 45 degrees can put the implant at risk of overload and within the dimension of the constant sum of a anterior-posterior spread and cantilever length, a distal implant inclination compared to cantilever length had the much larger effect on the stress distribution at the bone/implant interface.