2018 Volume 31 Issue 1 Pages 21-28
It is thought that loosening of the abutment influences fracture of the abutment and the implant body, and that this phenomenon influences bone resorption. Therefore, in this study, in a test piece without abutment loosening, an abutment was fitted to an implant body at 20 Ncm. In the test pieces with abutment loosening, the loosening was established by rotating it by 90°(1/4 rotating the abutment), 180°(1/2 rotating the abutment), and 360°(1 rotating the abutment). Each test piece with established loosening was set in a universal testing machine, the load until fracture of the tablet was measured, and strain occurring in the implant collar area was measured using a strain gauge. The relationship between abutment loosening and strain in the implant collar area was evaluated. Furthermore, the relationship between abutment loosening and the maximum bending load and amount of implant deformation was evaluated.
The following conclusions were obtained.
The fracture load of the tablet was 85.1±4.0 N, and the relationship between the fractured load and loosening of each abutment showed no significant difference.
When the tablet fractured, the strain in the collar area of test pieces with loosening of 1/2 and 1 rotation was more than 0.1%. This measurement value suggests the risk of bone resorption. Furthermore, the value of strain in the collar area of test pieces of loosened abutments was similar to that occurring when a load of 200-300 N was applied to the test piece fitted at 20 Ncm. Both the maximum bending load and the amount of deformation of the test piece with loosening of 1 rotation showed decreases of approximately 23% in comparison with those of the test piece without loosening. It is suggested that regular examination to detect the presence of abutment loosening is necessary after the setting of superstructures.
