Scanning Electron Microscopic Analysis of the Screw Threads of Loosened and Fractured Abutments: A Case Report

Abstract

Fracture and loosening of the implant can pose a serious impact as the fractured segment remaining inside the implant may prevent it from functioning efficiently. The harmony between the implant supported prosthesis and implant could be disrupted, leading to failure of the upper structure. Fistula formation and soft tissue inflammation are frequently associated with loose abutment screws. This case report involved an evaluation of the screw threads of a loosened abutment compared with those of a fractured abutment removed from the same patient by Scanning Electron Microscopy (SEM). According to the results of the SEM analysis, deformities in the screw threads of the loosened abutment were evaluated, and whether a loosened abutment should be rescrewed was considered. In this case report an unused abutment screw, broken screw, and loosened abutment screw were analysed by SEM. In the loosened abutment screw, the thread was deformed in the concavities to a greater extent, than in the convexities. The metal structure appeared strained without any cracks. In the fractured abutment screw, the metal structure in the convexities appeared strained with small cracks present at grain boundaries. Crack growth appeared to be related to the high number of crack coalescence events. A significant difference was observed between screw threads with abutment loosening and screw threads without abutment loosening. Therefore, a loosened abutment should not be rescrewed because it increases the risk of abutment fracture.

Keywords

• dental implants
• fatigue
• fractography