Detorque and Wear of Dental Implant Joints After Immersion in a Biofilm Medium

Objectives: The aim of this in vitro study was to evaluate the torque loss of the abutment and wear morphological aspects of inner implant surfaces after contact with biofilms.
Methods: Abutment-implant assemblies were tightened by using a digital handheld torque meter (Lutron TQ8800, Lutron, Taiwan) coupled to a metallic holding device to avoid oblique loading during detorque measurement. The implant-abutment assemblies were placed into 24 well-plates containing 2 ml of BHI medium with cell suspensions and incubated for 72 h at 37 ^oC under microaerophilic conditions (5% CO₂). Before immersion in the biofilm medium, Afer 72 h, the detorque values of two groups of implant-abutment assemblies (n = 5) were recorded in artificial saliva containing or not biofilms. After detorque, the abutments were removed in order to evaluate morphologic aspects of the inner area of the implants. Abutments and the implant inner surfaces were analyzed by scanning electron microscopy (SEM). Also, the dental implants were cross-sectioned to assess the roughness of the implant inner surfaces by optical profilometry. The arithmetical roughness (Ra) and the maximum distance from peak to valley (Rt) were considered to evaluate the roughness of the inner implant surface.
Results: The mean values of abutment detorque without immersion in the biofilms medium and after immersion in biofilms grown for 72 h are shown in Image 1. The micrographs for the inner surfaces of the Morse taper implants are shown in Image 2. The results of the roughness analyses are shown in Image 3.
Conclusions: The roughness of Morse taper and external hexagon implant innersurfaces increased after abutment detorque. However, the presence of biofilms decreased the roughness values and wear of the implant inner surfaces.