Complications in implant dentistry are generally divided into biological and mechanical complications. Mechanical complications include fracture of the implant body or prosthetic components such as chipping of ceramic material as well as loosening or fracture of implant abutments or fixation screws. This has a documented prevalence of 6 to 13% and 0.4 to 2% respectively after 5 years [1-7].

With respect to the etiology of screw loosening, several causes are to be considered [8]. Screw-nut systems generally become unstable when the load that is applied to the system exceeds that of the preload of the screw that causes a clamping force preventing separation of the joint [9]. Preload is proportional to the tightening torque at placement. Hence, tightening torque on the one hand has a significant effect on screw loosening [10]. Embedment relaxation or settling can be overcome by retorquing abutment screws after a certain period of time, increasing joint stability [9,11]. On the other hand, the magnitude of forces applied to the system is of major influence. The transfer of high forces can be generated by bruxers, through non-occlusal loading or because of a non-passive fit of suprastructures [8,12-15]. Other factors that are of influence of a systems’ resistance to screw loosening include lubrication, screw design, screw material, and surface characteristics [16-20]. Especially implant designs with an external hex configuration are prone to abutment screw loosening [21].

Fracture of abutments or abutment screws can be contributed to acute trauma, chronic overload, production flaws, or errors in screw-nut design. If fractured screw components cannot be removed, it may render the implant unrestorable or forces the dentist to creative solutions, such as cementable components. Fortunately, fractured screw components will generally be loose because the preload has not been retained. In that case, they may be removed by manipulating them counter clockwise with a straight probing instrument. On occasion, screw remnants cannot be mobilized, and removal remains a clinical challenge. Careful instrumentation when attempting to remove them should prevent damage to the internal thread of the implant and its surrounding tissues. The use of a fine-tipped hand instrument, a round burr turning counter clockwise, or drilling a slot in the screw in order to get more grip can be attempted to loosen the fragment. Specific instrumentation to remove broken screws from implants is available from most implant suppliers.