Torque to Loosen Surface Treated Abutment Screws After Cyclic Loading

Introduction: Abutment screw loosening is the most common problem associated with single tooth implant restorations. Surface treatments have been applied to abutment screws in an attempt to increase the achieved preload and prevent screw loosening. Objectives: The aim of this study was to determine the torque required to loosen surface treated abutment screws before and after cyclic loading. Methods: Three groups of 5 screws each were divided as follows: 1-Unigrip (NobelBiocare); 2-Goldtite (Implant Innovations Inc.) and 3-Torqtite (Steri-Oss). The screws were used to tighten customized abutments to an external hex regular body implant. Groups 1 and 2 were torqued to 32Ncm and group 3 to 35Ncm using the manufacturers recommended torque equipment. All specimens were subjected to a cyclic loading test at 8Hz, load range of 0-200N for 10hrs. A Tohnichi torque gauge was used to record the torque required to loosen the abutment screws before and after cyclic loading. Results: The mean values, in Ncm, for the torque required to loosen the abutment screws before and after loading were respectively: Unigrip 34.8 ± 2.6/ 29.8 ± 4.6; Goldtite 36.6 ± 4.1/ 34.4 ± 3.2; Torqtite 44.4 ± 4.7/ 27.8 ± 1.6. Statistical analyses showed that Torqtite required a significantly lower torque to loosen after loading (P<0.05) compared to groups 1 and 2. Within each group, a paired t-test revealed that Unigrip (P=0.02) and Torqtite (P=0.001) required a statistically lower torque to loosen after loading. Conclusion: Unigrip and Torqtite screws required less torque to loosen after loading. The Torqtite screws required the lowest torque among the screws tested.