A Study to Evaluate the Effect of Bone Density on Abutment Screw Loosening Using the Finite Element Method

The success of implant therapy is influenced by multiple factors that impact the bone-implant, implant-abutment, and abutment-prosthesis connections. The distribution of stress in the bone is a key determinant of whether dental implants succeed or fail. This study aimed to investigate the impact of bone density on the fatigue of abutment screws. This laboratory-based experimental study utilized a 3-dimensional bone model with 2 distinct densities, a Dentis OneQ implant, an inclined cyclic force of 100 N applied at a 30-degree angle, and positioned 4 mm above the implant platform. The analysis was conducted using the 3-dimensional finite element method in Abaqus software. The implant and abutment were of standard size, and stress measurements were taken at 5 locations on the abutment screw: Point A (beneath the screw head), Point B (middle of the screw neck), Point C (first thread), Point D (middle of the threads), and Point E (last thread), over time. The data underwent statistical analysis using Wilcoxon and Kruskal-Wallis tests. An increase (P < .001) in the mean von Mises stress was observed in low-density bone. The forces acting on the implant system were greater in dense bone, leading to increased deformation of the abutment screw and consequently a reduced fatigue life of the screw. Given that the total force applied to the implant system remains the same in both loose and dense bone, the greater transmission of force from the abutment to loose bone lessens the force impact within the implant-abutment system and the abutment screw.