Effect of retorque on initial torque loss and preload maintenance

There is sufficient documentary evidence to prove that the dental implant treatment has predictable prognosis. In spite of the high rate of success, failures do occur with dental implants. The most commonly reported mechanical failure is related to abutment screw loosening. There are several factors attributed to screw loosening. One factor is the optimum preload applied which keeps the screw threads tightly adapted to the screw mating counterpart. Screw loosening appears to be a minor incident but the resultant complications should not be underestimated. Clinically, screw loosening is unpleasant for the patient, time consuming and expensive for the operating professional. The retrieval of these failing prosthesis is not easily achieved and occasionally it ends up with the sacrifice of the crown. Retightening of abutment screws after initial torque prevents initial torque loss due to friction between the screw mates and subsequent screw loosening by micro motion. This phenomenon is not fully explored. Hence the present study is designed to evaluate the initial torque loss and effect of retightening and mechanical cyclic loading on preload maintenance in titanium implant system.