Torque Removal Evaluation of One-piece and Two-piece Abutment Screws under Dry and Wet Conditions

Application of a lubricant material at the abutment screw interface has been proposed to reduce the possibility of screw loosening. The aim of this study was to compare removal torque values (RTVs) of one-piece and two-piece abutments tightened in three different conditions: dry, saliva impregnated and filled with saliva. 10 ITI implants were inserted in acrylic blocks. 10 one-piece abutments were connected on their corresponding implants and tightened with 10, 20 and 35 NCm torques. After each tightening, RTV of the abutment was measured. This experiment was conducted in three different conditions: dry environment, abutment screws impregnated with artificial saliva, and the fixture holes filled with artificial saliva. These procedures were repeated for two-piece abutments. Data were analyzed by repeated measure ANOVA and LSD tests. One-sample test was used to compare the RTVs with respective tightening torques (α=0.05). The RTVs of one- piece and two piece abutments increased continuously when the environment changed from dry to impregnated and filled with saliva respectively (P<0.001). The RTVs of one-piece abutments were higher than those of two-piece abutments in three applied torques (P<0.001). The RTVs of both one-piece and two-piece abutments increased when the abutment screw was impregnated with artificial saliva and the fixture hole was filled with artificial saliva, respectively.